Andres, Alyssa M., Emily Slesinger, Rachael E Young, Grace K Saba, and Vincent S Saba, et al., June 2024: Thermal sensitivity of metabolic performance in Squalus acanthias: efficacy of aerobic scope as a predictor of viable thermal habitat. Marine Ecology Progress Series, 738, DOI:10.3354/meps14586161-185. Abstract
Ocean warming due to climate change can affect the metabolism, performance, and survival of ectothermic marine species. On the US Northeast continental shelf (US NES), waters are warming faster than the global average, leading to elevated mean temperatures and an increased risk of marine heatwave exposure in the region. Thus, it is critical to understand the effects of warming on the region’s living marine resources. Here, we quantified the acute temperature sensitivity of metabolic traits to evaluate their role as possible drivers of acute thermal tolerance and viable habitat in the spiny dogfish shark Squalus acanthias on the US NES. From 10-23°C, the standard metabolic rate increased more rapidly than the maximum metabolic rate, resulting in a reduction in factorial aerobic scope at warmer temperatures. However, the oxygen supply capacity increased with temperature in proportion to maximum metabolic rate, and neither metric declined at the warmest temperatures, suggesting oxygen supply capacity does not limit performance within the tested range. Although behavioral observations revealed overt thermal stress via loss of equilibrium at ≥20°C and estimated lethal temperature at ∼24°C, sharks retained the ability to regulate their resting metabolic rate, achieve maximum activity, and peak absolute aerobic scope at warm temperatures. Results suggest that factors other than oxygen supply or aerobic scope are constraining thermal tolerance in S. acanthias and support the notion that aerobic scope cannot be universally applied to determine optimal or viable metabolic habitat.
Boyce, Daniel G., Derek P Tittensor, Susanna Fuller, Stephanie A Henson, Kristin Kaschner, Gabriel Reygondeau, Kathryn E Schleit, Vincent S Saba, Nancy L Shackell, Ryan R E Stanley, and Boris Worm, June 2024: Operationalizing climate risk in a global warming hotspot. npj Ocean Sustainability, 3, 33, DOI:10.1038/s44183-024-00067-5. Abstract
Climate change is a looming threat to marine life, creating an urgent need to develop climate-informed conservation strategies. The Climate Risk Index for Biodiversity was designed to assess the climate risk for marine species in a manner that supports decision-making. Yet, its regional application remains to be explored. Here, we use it to evaluate climate risk for ~2000 species in the northwest Atlantic Ocean, a marine warming hotspot, to explore its capacity to inform climate-considered fisheries management. Under high emissions, harvested species, especially those with the highest economic value, have a disproportionate risk of projected exposure to hazardous climate conditions but benefit the most from emission mitigation. By mapping critical risk areas for 90 fish stocks, we pinpoint locations likely to require additional intervention, such as in the southern Gulf of St. Lawrence for Atlantic cod. Finally, we demonstrate how evaluating climate risk geographically and understanding how it arises can support short- and long-term fisheries management and conservation objectives under climate change.
LeClaire, Alyssa M., Eric N Powell, Roger Mann, Kathleen M Hemeon, Sara M Pace, Vincent S Saba, Hubert du Pontavice, and Jillian R Sower, January 2024: Temporal and spatial comparisons of ocean quahog (Arctica islandica) growth and lifespan on the mid-Atlantic continental shelf during inshore transgressions of their range from the Neoglacial through the twentieth century. Continental Shelf Research, 272, 105143, DOI:10.1016/j.csr.2023.105143. Abstract
Arctica islandica provide long-term records of climate change on the U.S. northeast continental shelf transgressing and regressing across the shelf numerous times synchronously with cold and warm climatic periods. The availability of A. islandica in the death assemblage over a wide geographic and temporal range makes this species well suited for documenting both spatial and temporal influences of climate change in the Mid-Atlantic through the correlation of growth rates in response to changing water conditions. This study focuses on comparing regional growth of subfossil ocean quahogs obtained offshore of the Delmarva Peninsula (Delmarva), and living during the cold periods since the Holocene Climate Optimum, with living A. islandica from offshore New Jersey, offshore Long Island, and Georges Bank. These populations exhibited different growth rates, with subfossil individuals from Delmarva death assemblages, representing previous Holocene cold periods, having growth rates as greater than or equal the growth rates of living individuals. Moreover, the growth rates for subfossil A. islandica from Delmarva that were alive from 1740 to 1940 were more rapid than contemporaneous individuals of the same age alive today. Higher growth rates for A. islandica from off Delmarva suggest that conditions supported near maximum growth during the cold periods after the Holocene Climate Optimum, possibly due to increased food supply in water shallower than that inhabited today. Unlike many bivalves, evidence for range recession of A. islandica as bottom water temperatures warm is found first in juvenile abundance, suggesting that recruitment ceases long before the population's demise: range recession in this species is a 100+ year process determined by the survivorship of the oldest and largest individuals. This study is the largest spatial and temporal growth comparison of A. islandica ever recorded and the first record of the process by which this species' inshore range regresses as temperatures rise.
Slesinger, Emily, Hubert du Pontavice, Brad Seibel, Vincent S Saba, Josh Kohut, and Grace K Saba, April 2024: Climate-induced reduction in metabolically suitable habitat for U.S. northeast shelf marine species. PLOS Climate, 3(4), DOI:10.1371/journal.pclm.0000357. Abstract
The U.S. northeast shelf (USNES) has been experiencing rapid ocean warming, which is changing the thermal environment that marine species inhabit. To determine the effect of current and future ocean warming on the distribution of five important USNES fish species (Atlantic cod [Gadus morhua], black sea bass [Centropristis striata], cunner [Tautogolabrus adspersus], spiny dogfish [Squalus acanthias], summer flounder [Paralichthys dentatus]), we applied species-specific physiological parameters from laboratory studies to calculate the Metabolic Index (MI). The MI for each species was calculated across a historical (1972–2019) and contemporary (2010–2019) climatology for each season. Broadly, the oceanic conditions in the winter and spring seasons did not limit metabolically suitable habitat for all five species, while portions of the USNES in the summer and fall seasons were metabolically unsuitable for the cold water species (Atlantic cod, cunner, spiny dogfish). The warmer water species (black sea bass, summer flounder) experienced little metabolically suitable habitat loss, which was restricted to the most southern portion of the distribution. Under a doubling of atmospheric CO2, metabolically suitable habitat is projected to decrease substantially for Atlantic cod, restricting them to the Gulf of Maine. Cunner are projected to experience similar habitat loss as Atlantic cod, with some refugia in the New York Bight, and spiny dogfish may experience habitat loss in the Southern Shelf and portions of Georges Bank. In contrast, black sea bass and summer flounder are projected to experience minimal habitat loss restricted to the southern inshore portion of the USNES. The utility of using MI for co-occurring fish species in the USNES differed, likely driven by species-specific physiology and whether the southern edge of a population occurred within the USNES.
Amaya, Dillon J., Michael G Jacox, Melanie R Fewings, Vincent S Saba, Malte F Stuecker, Ryan R Rykaczewski, Andrew C Ross, and Charles A Stock, et al., April 2023: Marine heatwaves need clear definitions so coastal communities can adapt. Nature, 616, DOI:10.1038/d41586-023-00924-2.
Bi, Rujia, Chip Collier, Roger Mann, Katherine E Mills, Vincent S Saba, John Wiedenmann, and Olaf P Jensen, January 2023: How consistent is the advice from stock assessments? Empirical estimates of inter-assessment bias and uncertainty for marine fish and invertebrate stocks. Fish and Fisheries, 24(1), DOI:10.1111/faf.12714126-141. Abstract
Fishery management frequently involves precautionary buffering for scientific uncertainty. For example, a precautionary buffer that scales with scientific uncertainty is used to calculate the acceptable biological catch downward from the overfishing limit in the US federal fishery management system. However, there is little empirical guidance to suggest how large buffers for scientific uncertainty should be. One important component of uncertainty is variation among different assessments of the same stock in estimates of management-relevant quantities. We analysed commercially exploited marine fish and invertebrate stocks around the world and developed Bayesian hierarchical models to quantify inter-assessment variation in terminal year biomass and fishing mortality estimates, reference points, relative biomass and fishing mortality estimates, and overfishing limits. There was little evidence of inter-assessment bias; stock assessment estimates in the terminal year of the assessment were not consistently higher or lower than estimates of the same quantities in future years. However, there was a tendency for extreme values from the terminal year to be pulled closer to the mean in future years. Inter-assessment variation in all estimates differed across regions, and a longer inter-assessment interval generally resulted in greater variation. Inter-assessment uncertainty was greatest for estimates of the overfishing limit, with coefficients of variation ranging from 17% in Europe (non-EU) to 107% for Pacific Ocean pelagic stocks. Because inter-assessment variation is only one component of scientific uncertainty, we suggest that these uncertainty estimates may provide a basis for determining the minimum size of precautionary buffers.
Castillo-Trujillo, Alma C., Young-Oh Kwon, Paula Fratantoni, Ke Chen, Hyodae Seo, Michael A Alexander, and Vincent S Saba, December 2023: An evaluation of eight global ocean reanalyses for the Northeast U.S. Continental shelf. Progress in Oceanography, 219, 103126, DOI:10.1016/j.pocean.2023.103126. Abstract
The Northeast U.S. continental Shelf (NES) extending from the Gulf of Maine to Cape Hatteras, is a dynamic region supporting some of the most commercially valuable fisheries in the world. This study aims to provide a systematic assessment of eight widely used, intermediate-to-high spatial resolution global ocean reanalysis products (CFSR, ECCO, ORAS, SODA, BRAN, GLORYS, GOFS3.0, and GOFS3.1) against available in situ and satellite ocean observations. In situ observations include water level from tide gauges, and temperature and salinity from various sources including shipboard hydrographic data, and moorings on the NES. Overall, the coarser resolution products exhibit limited skill in the coastal environment, with the high-resolution products better representing the temperature and salinity on the NES. Common biases are found in all reanalyses and in some regions within the NES; for example, biases in temperature and salinity are larger in the southern Mid-Atlantic Bight than in the rest of the NES. There is no single reanalysis that performs well across all parameters in all regions within the NES, but GLORYS and BRAN stand out for their superior performance across the largest number of metrics, outperforming other products in 22 and 25 of the 65 metrics examined, respectively. SODA is the top performer among the coarser resolution products (CFSR, ECCO, ORAS and SODA). The Gulf Stream and local bathymetry are critical factors leading to differences between the reanalyses. Conditions in summer are less well represented than in winter. In particular, the Mid-Atlantic Bight Cold Pool is not reproduced in four (CFSR, ECCO, ORAS, BRAN) of the eight reanalyses.
du Pontavice, Hubert, Zhuomin Chen, and Vincent S Saba, January 2023: A high-resolution ocean bottom temperature product for the northeast U.S. continental shelf marine ecosystem. Progress in Oceanography, 210, 102948, DOI:10.1016/j.pocean.2022.102948. Abstract
The northeast U.S. continental shelf is a highly productive and socio-economically important marine ecosystem in which annual and seasonal variations of bottom temperature play a major role in the distribution, phenology, and productivity of its predominately demersal marine taxa. However, bottom temperature measurements are limited spatially and temporally and thus do not provide the required resolution to assess sub-seasonal variability and trends. Here we combined three ocean products, a regional ocean model (ROMS) and two global ocean data assimilated models (GLORYS12v1 and PSY4V3R1) to build a high-resolution, long-term bottom temperature product for the northeast U.S. continental shelf between 1959 and 2021. We bias-corrected ROMS using monthly decadal climatologies from ocean observations and analyzed long-term changes in the combined time series. Model skill was assessed using a large number of in situ observations. The combined bottom temperature product showed a long-term warming of the northeast U.S. continental shelf of + 0.36 °C decade-1 over the past 63 years, with notable variations among seasons and regions. The strongest long-term warming occurred during the summer months and in the Gulf of Maine. Although biases were observed, the bottom temperature product exhibited good performance reproducing seasonal and annual variability in observed temperature. This high-resolution product could be used in a wide range of applications from local to regional spatial scales, from long-term to near-term time scales, and from fisheries to marine ecology.
We present the development and evaluation of MOM6-COBALT-NWA12 version 1.0, a 1/12∘ model of ocean dynamics and biogeochemistry in the northwest Atlantic Ocean. This model is built using the new regional capabilities in the MOM6 ocean model and is coupled with the Carbon, Ocean Biogeochemistry and Lower Trophics (COBALT) biogeochemical model and Sea Ice Simulator version-2 (SIS2) sea ice model. Our goal was to develop a model to provide information to support living-marine-resource applications across management time horizons from seasons to decades. To do this, we struck a balance between a broad, coastwide domain to simulate basin-scale variability and capture cross-boundary issues expected under climate change; a high enough spatial resolution to accurately simulate features like the Gulf Stream separation and advection of water masses through finer-scale coastal features; and the computational economy required to run the long simulations of multiple ensemble members that are needed to quantify prediction uncertainties and produce actionable information. We assess whether MOM6-COBALT-NWA12 is capable of supporting the intended applications by evaluating the model with three categories of metrics: basin-wide indicators of the model's performance, indicators of coastal ecosystem variability and the regional ocean features that drive it, and model run times and computational efficiency. Overall, both the basin-wide and the regional ecosystem-relevant indicators are simulated well by the model. Where notable model biases and errors are present in both types of indicator, they are mainly consistent with the challenges of accurately simulating the Gulf Stream separation, path, and variability: for example, the coastal ocean and shelf north of Cape Hatteras are too warm and salty and have minor biogeochemical biases. During model development, we identified a few model parameters that exerted a notable influence on the model solution, including the horizontal viscosity, mixed-layer restratification, and tidal self-attraction and loading, which we discuss briefly. The computational performance of the model is adequate to support running numerous long simulations, even with the inclusion of coupled biogeochemistry with 40 additional tracers. Overall, these results show that this first version of a regional MOM6 model for the northwest Atlantic Ocean is capable of efficiently and accurately simulating historical basin-wide and regional mean conditions and variability, laying the groundwork for future studies to analyze this variability in detail, develop and improve parameterizations and model components to better capture local ocean features, and develop predictions and projections of future conditions to support living-marine-resource applications across timescales.
Saba, Vincent S., et al., December 2023: NOAA fisheries research geared towards climate-ready living marine resource management in the northeast United States. PLOS Climate, 2(12), DOI:10.1371/journal.pclm.0000323. Abstract
Climate change can alter marine ecosystems through changes in ocean temperature, acidification, circulation, and productivity. Over the last decade, the United States northeast continental shelf (U.S. NES) has warmed faster than any other marine ecosystem in the country and is among the fastest warming regions of the global ocean. Many living marine resources in the U.S. NES ranging from recreational and commercial fish stocks to protected species have shifted their distribution in response to ocean warming. The National Oceanic and Atmospheric Administration’s National Marine Fisheries Service (NOAA Fisheries) is responsible for the assessment, protection, and sustainable use of the nation’s living marine resources. In the U.S. NES, NOAA Fisheries has made substantial progress on climate research related to fish, fisheries, and protected species. However, more research is needed to help inform tactical management decisions with the goal of climate-ready living marine resource management. This is a major challenge because the observed physical and biological changes are unprecedented, and the majority of marine species assessments and management decisions do not utilize environmental data. Here we review the research accomplishments and key needs for NOAA Fisheries in the U.S. NES in the context of climate change and living marine resource management. Key research needs and products are: 1) Infrastructure with continued and enhanced ocean surveys that includes cooperative research with the fishing industry and other NOAA line offices and partners; 2) Tracking and projecting change, and understanding mechanisms including state of the ecosystem reporting, improved regional ocean and ecosystem hindcasts, forecasts, and projections, and continued process-based laboratory and field studies, 3) climate-informed management, including stock assessments that account for climate where possible, translation of changing species distributions into spatial management, climate vulnerability assessment and scenario planning, ecosystem-based management, management strategy evaluations, and increased multidisciplinary science that includes economic and social indicators.
Santidrián Tomillo, Pilar, Francisca Pujol, Guillem Félix, Verónica Núñez-Reyes, Vincent S Saba, Jesús Tomás, and Adolfo Marco, August 2023: Colonization of new nesting areas could provide climate refuge to loggerhead turtles under climate change. Biological Conservation, 110146, DOI:10.1016/j.biocon.2023.110146. Abstract
Climate change can impact regional and global biodiversity for multiple reasons. In sea turtles, changes in local climate at nesting beaches can affect egg and hatchling survival and primary sex ratios. Sea turtles could respond to climate change by occupying new nesting areas. The recent increase in sporadic nesting in the western Mediterranean may indicate colonization of new nesting beaches. We assessed the suitability of a western area, the Balearic Islands (∼1500 km from current nesting grounds) as climate refuge for loggerhead turtles (Caretta caretta) under current (2015–2017) and climate change scenarios to the mid (+40 years) and end (+80 years) of the 21st century. Using a correlative approach based on air and sand temperatures, we predicted nest temperatures and sex ratios for 19 beaches. Most beaches could provide viable temperatures and predominantly produce male hatchlings under all scenarios. Sex ratio projections were male-biased but with an increasing female ratio throughout time. Although mean sex ratio under the +80 years scenario was still male-biased, the warmest beaches could provide female-biased ratios, which are similar to those estimated for current nesting sites. The Balearic Islands could function as climate refuge for loggerhead turtles in the Mediterranean because temperatures could favor embryo viability and a male sex ratio. However, a nesting population may not be established until the percentage of female hatchlings increases and turtles return to nest as adults. Conditions at sea should also favor survival of hatchlings and juveniles. Because western Mediterranean beaches are popular tourist destinations, active management may be needed to protect nesting populations.
Caracappa, Joseph C., Andrew Beet, Sarah K Gaichas, R J Gamble, Kimberly Hyde, S I Large, R E Morse, Charles A Stock, and Vincent S Saba, September 2022: A northeast United States Atlantis marine ecosystem model with ocean reanalysis and ocean color forcing. Ecological Modelling, 471, 110038, DOI:10.1016/j.ecolmodel.2022.110038. Abstract
The northeast United States Atlantis model (NEUSv2) is an end-to-end ecosystem model that can simulate biogeochemical, ecological, fishery, management, and socio-economic processes within marine ecosystems. As a major update to the original model, NEUSv2 includes changes to the model's functional group definitions and forcing data. NEUSv2 is the first Atlantis model to use a satellite-ocean-color-derived phytoplankton size class model that was tuned specifically for the region to force marine primary production. Additionally, physical ocean variables (currents, temperature, and salinity) were updated using a high-resolution global ocean reanalysis. Despite its coarse resolution, NEUSv2 was capable of reproducing the broad spatial patterns seen in the physical and biological forcing sources, with the exception of some circulation features. NEUSv2 produced plausible zooplankton and planktivore biomass, a stable lower trophic food web, and recent trends in zooplankton biomass. NEUSv2 meets calibration criteria for the persistence and long-term stability of functional group biomass. Given the success of this new Atlantis forcing approach, we detail the observations and challenges regarding spatial scale-related processes, data assimilation, and biological calibration. We also discuss possible tradeoffs with model scope, calibration, and the availability of feedback mechanisms. This NEUSv2 hindcast is well suited for exploring ecosystem-level sensitivity to lower trophic processes and for testing alternative biogeochemical forcing. Further developments will improve model performance for higher trophic levels.
du Pontavice, Hubert, Timothy J Miller, Brian C Stock, Zhuomin Chen, and Vincent S Saba, May 2022: Ocean model-based covariates improve a marine fish stock assessment when observations are limited. ICES Journal of Marine Science, 79(4), DOI:10.1093/icesjms/fsac0501259-1273. Abstract
The productivity of many fish populations is influenced by the environment, but developing environment-linked stock assessments remain challenging and current management of most commercial species assumes that stock productivity is time-invariant. In the Northeast United States, previous studies suggest that the recruitment of Southern New England-Mid Atlantic yellowtail flounder is closely related to the strength of the Cold Pool, a seasonally formed cold water mass on the continental shelf. Here, we developed three new indices that enhance the characterization of Cold Pool interannual variations using bottom temperature from a regional hindcast ocean model and a global ocean data assimilated hindcast. We associated these new indices to yellowtail flounder recruitment in a state–space, age-structured stock assessment framework using the Woods Hole Assessment Model. We demonstrate that incorporating Cold Pool effects on yellowtail flounder recruitment reduces the retrospective patterns and may improve the predictive skill of recruitment and, to a lesser extent, spawning stock biomass. We also show that the performance of the assessment models that incorporated ocean model-based indices is improved compared to the model using only the observation-based index. Instead of relying on limited subsurface observations, using validated ocean model products as environmental covariates in stock assessments may both improve predictions and facilitate operationalization.
Chen, Zhuomin, Young-Oh Kwon, Ke Chen, Paula Fratantoni, Glen Gawarkiewicz, Terrence M Joyce, Timothy J Miller, Janet A Nye, Vincent S Saba, and Brian C Stock, May 2021: Seasonal prediction of bottom temperature on the northeast U.S. continental shelf. Journal of Geophysical Research: Oceans, 126(5), DOI:10.1029/2021JC017187. Abstract
The Northeast U.S. shelf (NES) is an oceanographically dynamic marine ecosystem and supports some of the most valuable demersal fisheries in the world. A reliable prediction of NES environmental variables, particularly ocean bottom temperature, could lead to a significant improvement in demersal fisheries management. However, the current generation of climate model‐based seasonal‐to‐interannual predictions exhibits limited prediction skill in this continental shelf environment. Here, we have developed a hierarchy of statistical seasonal predictions for NES bottom temperatures using an eddy‐resolving ocean reanalysis data set. A simple, damped local persistence prediction model produces significant skill for lead times up to ∼5 months in the Mid‐Atlantic Bight and up to ∼10 months in the Gulf of Maine, although the prediction skill varies notably by season. Considering temperature from a nearby or upstream (i.e., more poleward) region as an additional predictor generally improves prediction skill, presumably as a result of advective processes. Large‐scale atmospheric and oceanic indices, such as Gulf Stream path indices (GSIs) and the North Atlantic Oscillation Index, are also tested as predictors for NES bottom temperatures. Only the GSI constructed from temperature observed at 200 m depth significantly improves the prediction skill relative to local persistence. However, the prediction skill from this GSI is not larger than that gained using models incorporating nearby or upstream shelf/slope temperatures. Based on these results, a simplified statistical model has been developed, which can be tailored to fisheries management for the NES.
Efforts to manage living marine resources (LMRs) under climate change need projections of future ocean conditions, yet most global climate models (GCMs) poorly represent critical coastal habitats. GCM utility for LMR applications will increase with higher spatial resolution but obstacles including computational and data storage costs, obstinate regional biases, and formulations prioritizing global robustness over regional skill will persist. Downscaling can help address GCM limitations, but significant improvements are needed to robustly support LMR science and management. We synthesize past ocean downscaling efforts to suggest a protocol to achieve this goal. The protocol emphasizes LMR-driven design to ensure delivery of decision-relevant information. It prioritizes ensembles of downscaled projections spanning the range of ocean futures with durations long enough to capture climate change signals. This demands judicious resolution refinement, with pragmatic consideration for LMR-essential ocean features superseding theoretical investigation. Statistical downscaling can complement dynamical approaches in building these ensembles. Inconsistent use of bias correction indicates a need for objective best practices. Application of the suggested protocol should yield regional ocean projections that, with effective dissemination and translation to decision-relevant analytics, can robustly support LMR science and management under climate change.
Mason, Julia G., Pamela J Woods, Magnús Thorlacius, Kristinn Guðnason, Vincent S Saba, Patrick J Sullivan, and Kristin M Kleisner, November 2021: Projecting climate-driven shifts in demersal fish thermal habitat in Iceland's waters. ICES Journal of Marine Science, fsab230, DOI:10.1093/icesjms/fsab230. Abstract
As climate change shifts marine species distribution and abundance worldwide, projecting local changes over decadal scales may be an adaptive strategy for managers and industry. In Iceland, one of the top fish-producing nations globally, long-term monitoring enables model simulations of groundfish species habitat distribution. We used generalized additive models to characterize suitable thermal habitat for 51 fish species in Iceland's waters. We projected changes in suitable thermal habitat by midcentury with an ensemble of five general circulation models from the Coupled Model Intercomparison Program 6 (CMIP6) and NOAA (CM2.6) and two scenarios (SSP 5-8.5 and SSP 2-4.5). We found a general northward shift in suitable thermal habitat distribution, with variable regional dynamics among species. Species thermal bias index was a weak predictor of projected thermal habitat change, with warmer-water species more likely to see increases in thermal habitat and southern warm-edge range expansions. While these results isolate the effects of future changes in temperature, providing an indication of suitable thermal habitat, low model explanatory power suggests that additional variables may improve distribution projections. Such projections might serve as guideposts to inform long-term management decisions about regional and species-specific suitability for Iceland's fisheries, infrastructure investment, and risk evaluation under climate change.
Nazzaro, Laura, Emily Slesinger, Josh Kohut, Grace K Saba, and Vincent S Saba, October 2021: Sensitivity of marine fish thermal habitat models to fishery data sources. Ecology and Evolution, 11(19), DOI:10.1002/ece3.781713001-13013. Abstract
Statistical models built using different data sources and methods can exhibit conflicting patterns. We used the northern stock of black sea bass (Centropristis striata) as a case study to assess the impacts of using different fisheries data sources and laboratory-derived physiological metrics in the development of thermal habitat models for marine fishes. We constructed thermal habitat models using generalized additive models (GAMs) based on various fisheries datasets as input, including the NOAA Northeast Fisheries Science Center (NEFSC) bottom trawl surveys, various inshore fisheries-independent trawl surveys (state waters), NEFSC fisheries-dependent observer data, and laboratory-based physiological metrics. We compared each model's GAM response curve and coupled them to historical ocean conditions in the U.S. Northeast Shelf using bias-corrected ocean temperature output from a regional ocean model. Thermal habitat models based on shelf-wide data (NEFSC fisheries-dependent observer data and fisheries-independent spring and fall surveys) explained the most variation in black sea bass presence/absence data at ~15% deviance explained. Models based on a narrower range of sampled thermal habitat from inshore survey data in the Northeast Area Monitoring and Assessment Program (NEAMAP) and the geographically isolated Long Island Sound data performed poorly. All models had similar lower thermal limits around 8.5℃, but thermal optima, when present, ranged from 16.7 to 24.8℃. The GAMs could reliably predict habitat from years excluded from model training, but due to strong seasonal temperature fluctuations in the region, could not be used to predict habitat in seasons excluded from training. We conclude that survey data source can greatly impact development and interpretation of thermal habitat models for marine fishes. We suggest that model development be based on data sources that sample the widest range of ocean temperature and physical habitat throughout multiple seasons when possible, and encourage thorough consideration of how data gaps may influence model uncertainty.
Patel, Samir H., Megan V Winton, Joshua M Hatch, Heather L Haas, Vincent S Saba, Gavin Fay, and Ronald J Smolowitz, April 2021: Projected shifts in loggerhead sea turtle thermal habitat in the Northwest Atlantic Ocean due to climate change. Scientific Reports, 11, 8850, DOI:10.1038/s41598-021-88290-9. Abstract
It is well established that sea turtles are vulnerable to atmospheric and oceanographic shifts associated with climate change. However, few studies have formally projected how their seasonal marine habitat may shift in response to warming ocean temperatures. Here we used a high-resolution global climate model and a large satellite tagging dataset to project changes in the future distribution of suitable thermal habitat for loggerheads along the northeastern continental shelf of the United States. Between 2009 and 2018, we deployed 196 satellite tags on loggerheads within the Middle Atlantic Bight (MAB) of the Northwest Atlantic continental shelf region, a seasonal foraging area. Tag location data combined with depth and remotely sensed sea surface temperature (SST) were used to characterize the species’ current thermal range in the MAB. The best-fitting model indicated that the habitat envelope for tagged loggerheads consisted of SST ranging from 11.0° to 29.7 °C and depths between 0 and 105.0 m. The calculated core bathythermal range consisted of SSTs between 15.0° and 28.0 °C and depths between 8.0 and 92.0 m, with the highest probability of presence occurred in regions with SST between 17.7° and 25.3 °C and at depths between 26.1 and 74.2 m. This model was then forced by a high-resolution global climate model under a doubling of atmospheric CO2 to project loggerhead probability of presence over the next 80 years. Our results suggest that loggerhead thermal habitat and seasonal duration will likely increase in northern regions of the NW Atlantic shelf. This change in spatiotemporal range for sea turtles in a region of high anthropogenic use may prompt adjustments to the localized protected species conservation measures.
Woodworth-Jefcoats, Phoebe A., Ariel Jacobs, Anne B Hollowed, Ed Farley, Janet Duffy-Anderson, Martin Dorn, Thomas P Hurst, Jamal Moss, Lauren Rogers, Kalei Shotwell, Toby Garfield, Richard Zabel, Yvonne deReynier, Eric Shott, Lisa Crozier, Steven J Bograd, Nate Mantua, Jameal F Samhouri, John Quinlan, Karla Gore, Roldan Muñoz, Jennifer Leo, Lauren Waters, Michael Burton, Vincent S Saba, Diane L Borggaard, Marianne Ferguson, and Wendy Morrison, December 2021: NOAA Fisheries Climate Science Strategy Five Year Progress Report, NOAA Technical Memorandum: NMFS-F/SPO-228, 157pp.
Borggaard, Diane L., Dorothy M Dick, Jonathan Star, Barbara Zoodsma, Michael A Alexander, Michael J Asaro, Lynne Barre, Shannon Bettridge, Peter Burns, Julie Crocker, Quay Dortch, Lance Garrison, Frances Gulland, Ben Haskell, Sean Hayes, Allison Henry, Kimberly Hyde, Henry Milliken, John Quinlan, Teri Rowles, Vincent S Saba, Michelle Staudinger, and Harvey Walsh, December 2020: North Atlantic Right Whale (Eubalaena glacialis) Scenario Planning Summary Report, NOAA Technical Memorandum, NMFS-OPR-68, 88pp.
Crear, D P., B E Watkins, and Vincent S Saba, et al., August 2020: Contemporary and future distributions of cobia, Rachycentron canadum. Diversity and Distributions, 26(8), DOI:10.1111/ddi.13079. Abstract
Aim
Climate change has influenced the distribution and phenology of marine species, globally. However, knowledge of the impacts of climate change is lacking for many species that support valuable recreational fisheries. Cobia (Rachycentron canadum ) are the target of an important recreational fishery along the U.S. east coast that is currently the subject of a management controversy regarding allocation and stock structure. Further, the current and probable future distributions of this migratory species are unclear, further complicating decision‐making. The objectives of this study are to better define the contemporary distribution of cobia along the U.S. east coast and to project potential shifts in distribution and phenology under future climate change scenarios.
Location
Chesapeake Bay and the U.S. east coast.
Methods
We developed a depth‐integrated habitat suitability model using archival tagging data from cobia that were caught and tagged in Chesapeake Bay during summer months and coupled those data with high‐resolution ocean models to project the contemporary and future distributions of cobia along U.S. east coast.
Results
During the winter months, suitable cobia habitat currently occurs in offshore waters off North Carolina and further south, whereas during the summer months, suitable habitat occurs in waters from Florida to southern New England. In warmer years, the availability of suitable habitat increases in northern latitudes. Under continued climate change over the next 40–80 years, suitable habitat is projected to shift northward and decrease over the shelf.
Main conclusions
Habitat distributions suggest cobia overwinter offshore and could inhabit waters further north during warmer months, into state jurisdictions that do not have strict management regulations for cobia. When waters are warmer, distributions are projected to shift poleward and seasonal migrations may begin earlier. These results can inform resource allocation discussions between fishery managers and resource users.
Most present forecast systems for estuaries predict conditions for only a few days into the future. However, there are many reasons to expect that skillful estuarine forecasts are possible for longer time periods, including increasingly skillful extended atmospheric forecasts, the potential for lasting impacts of atmospheric forcing on estuarine conditions, and the predictability of tidal cycles. In this study, we test whether skillful estuarine forecasts are possible for up to 35 days into the future by combining an estuarine model of Chesapeake Bay with 35‐day atmospheric forecasts from an operational weather model. When compared with both a hindcast simulation from the same estuarine model and with observations, the estuarine forecasts for surface water temperature are skillful up to about two weeks into the future, and the forecasts for bottom temperature, surface and bottom salinity, and density stratification are skillful for all or the majority of the forecast period. Bottom oxygen forecasts are skillful when compared to the model hindcast, but not when compared with observations. We also find that skill for all variables in the estuary can be improved by taking the mean of multiple estuarine forecasts driven by an ensemble of atmospheric forecasts. Finally, we examine the forecasts in detail using two case studies of extreme events, and we discuss opportunities for improving the forecast skill.
Santidrián Tomillo, Pilar, L G Fonseca, M Ward, N Tankersley, N J Robinson, C M Orrego, F V Paladino, and Vincent S Saba, March 2020: The impacts of extreme El Niño events on sea turtle nesting populations. Climatic Change, 159(2), DOI:10.1007/s10584-020-02658-w. Abstract
The El Niño Southern Oscillation (ENSO) is the predominant interannual pattern of climate variability in the world and may become extreme approximately once every 20 years. Climate-forced interannual variability in fecundity rates of long-lived species are well-studied, but the effect of extreme events is less clear. Here, we analyzed the effect of the extreme 2015–16 El Niño event on three long-lived sea turtle species in a region highly influenced by ENSO. The effect of this extreme event varied considerably among species. While reproductive success dramatically declined in leatherback turtles (Dermochelys coriacea), the reduction was only marginal in green turtles (Chelonia mydas). Nevertheless, the number of nesting green turtles decreased following the extreme El Niño event, likely due to decreased ocean productivity. We used global climate models to project an increase in the decadal occurrence of extreme events from ~ 0.7 events (beginning of twentieth century) to ~ 2.9 events per decade (end of twenty-first century). This resulted in a projected decline in the reproductive success of leatherback turtles (~ 19%), a milder decline in olive ridley turtles (Lepidochelys olivacea) (~ 7%), and no decline in green turtles (~ 1%). Extreme El Niño events can have a strong detrimental effect on East Pacific leatherback turtles, a population that is already critically endangered due to other anthropogenic impacts. Our results highlight the importance of conducting species-specific and site-specific analyses of climatic impacts on sea turtles.
Tanaka, Kisei R., M P Torre, Vincent S Saba, Charles A Stock, and Yong Chen, August 2020: An ensemble high‐resolution projection of changes in the future habitat of American lobster and sea scallop in the Northeast US continental shelf. Diversity and Distributions, 26(8), DOI:10.1111/ddi.13069. Abstract
Aim
To address the uncertainty associated with climate‐driven biogeographical changes in commercial fisheries species through an ensemble species distribution modelling (SDM) approach.
Location
Northeast US Continental Shelf Large Marine Ecosystem (NEUS‐LME).
Methods
We combined an ensemble SDM platform (BIOMOD 2) and a high‐resolution global climate model (NOAA GFDL CM2.6) to quantify spatiotemporal changes in habitat of two commercially important species in the Northeast US Continental Shelf Large Marine Ecosystem (NEUS‐LME); American lobster (Homarus americanus); and sea scallop (Placopecten magellanicus). An ensemble SDM was calibrated using multi‐decadal fisheries‐independent surveys (1984–2016). Statistically weighted species‐specific ensemble SDM outputs were combined with 80 years of projected bottom temperature and salinity changes in response to a high greenhouse gas emissions scenario (an annual 1% increase in atmospheric CO2).
Results
Statistically significant changes (p < .05) in habitat suitability for both species were found over a large portion of the study area. Sea scallop undergoes a northward shift over the study period, while American lobster moves further offshore. The ensemble projections showed that several management zones were identified with increases and decreases in species‐specific habitat. Uncertainty due to variations in ensemble member models was also found in the direction of change within each management zone.
Main conclusions
This study provides ensemble estimates of climate‐driven changes and associated uncertainties in the biogeography of two economically important species in the United States. Projected climate change in the NEUS‐LME will pose management challenges, and our ensemble projections provide useful information for climate‐ready management of commercial fisheries.
Borggaard, Diane L., Dorothy M Dick, Jonathan Star, Michael A Alexander, M Bernier, M J Collins, K Damon-Randall, R. Dudley, R Griffis, Sean Hayes, M R Johnson, D Kircheis, J Kocik, B Letcher, Nate Mantua, Wendy Morrison, K Nislow, and Vincent S Saba, et al., December 2019: Atlantic Salmon Scenario Planning Pilot Report. Greater Atlantic Region Policy Series [19-05], Gloucester, MA: NOAA Fisheries Greater Atlantic Regional Fisheries Office - www.greateratlantic.fisheries.noaa.gov/policyseries., 89pp.
Capotondi, Antonietta, Michael G Jacox, C Bowler, M Kavanaugh, P Lehodey, D Barrie, Stephanie Brodie, S Chaffron, Wei Cheng, D Faggiani Dias, D Eveillard, L Guidi, D Iudicone, Nicole S Lovenduski, Janet A Nye, I Ortiz, D E Pirhalla, Mercedes Pozo Buil, and Vincent S Saba, et al., October 2019: Observational Needs Supporting Marine Ecosystems Modeling and Forecasting: Insights from U.S. Coastal Applications. Frontiers in Marine Science, 6(623), DOI:10.3389/fmars.2019.00623. Abstract
Many coastal areas host rich marine ecosystems and are also centers of economic activities, including fishing, shipping and recreation. Due to the socioeconomic and ecological importance of these areas, predicting relevant indicators of the ecosystem state on sub-seasonal to interannual timescales is gaining increasing attention. Depending on the application, forecasts may be sought for variables and indicators spanning physics (e.g., sea level, temperature, currents), chemistry (e.g., nutrients, oxygen, pH), and biology (from viruses to top predators). Many components of the marine ecosystem are known to be influenced by leading modes of climate variability, which provide a physical basis for predictability. However, prediction capabilities remain limited by the lack of a clear understanding of the physical and biological processes involved, as well as by insufficient observations for forecast initialization and verification. The situation is further complicated by the influence of climate change on ocean conditions along coastal areas, including sea level rise, increased stratification, and shoaling of oxygen minimum zones. Observations are thus vital to all aspects of marine forecasting: statistical and/or dynamical model development, forecast initialization, and forecast validation, each of which has different observational requirements, which may be also specific to the study region. Here, we use examples from United States (U.S.) coasts applications to identify and describe the key requirements for an observational network that is needed to facilitate improved process understanding, as well as for sustaining operational ecosystem forecasting. We also describe new holistic observational approaches, e.g., approaches based on acoustics, inspired by Tara Oceans or by landscape ecology, that have the potential to support and expand ecosystem modeling and forecasting activities by bridging global and local observations.
Greenan, B, Nancy L Shackell, K Ferguson, P Greyson, A Cogswell, D Brickman, Z Wang, A Cook, C E Brennan, and Vincent S Saba, September 2019: Climate Change Vulnerability of American Lobster Fishing Communities in Atlantic Canada. Frontiers in Marine Science, 6, 579, DOI:10.3389/fmars.2019.00579. Abstract
Climate change impacts on fisheries will undoubtedly have socio-economic impacts on coastal communities and the seafood market. However, it is a challenge to integrate climate change information in a form that can be used efficiently by adaptation planners, policy makers, and fishery managers. In this study, we frame a climate change impact assessment using a geographical perspective based on the management units of the dominant fishery, in this case, American lobster in Nova Scotia, Canada. The information considered here includes economic dependence on the fishery, population size, diversity of the fishery revenue, status of harbor infrastructure, total replacement cost of each harbor, increased relative sea level and flooding, and the vulnerability of offshore lobster to ocean warming and changes in zooplankton composition and anticipatory changes in fishery productivity across management borders. Using two ocean models to provide multi-decadal scale projections of bottom temperature, changes in offshore lobster distribution are projected to have a neutral, or positive impact on the region as a whole. However, when lobster vulnerability is combined with climate change related vulnerabilities of coastal fishing communities, it is evident that adaptation planning is needed for long-term sustainability. This impact assessment provides both a framework and information for further in-depth analyses by climate change adaptation planners and fishery managers.
McHenry, J, Heather Welch, S E Lester, and Vincent S Saba, December 2019: Projecting marine species range shifts from only temperature can mask climate vulnerability. Global Change Biology, 25(12), DOI:10.1111/gcb.14828. Abstract
Climate change is causing range shifts in many marine species, with implications for biodiversity and fisheries. Previous research has mainly focused on how species' ranges will respond to changing ocean temperatures, without accounting for other environmental covariates that could affect future distribution patterns. Here, we integrate habitat suitability modeling approaches, a high‐resolution global climate model projection, and detailed fishery‐independent and ‐dependent faunal datasets from one of the most extensively monitored marine ecosystems—the U.S. Northeast Shelf. We project the responses of 125 species in this region to climate‐driven changes in multiple oceanographic factors (e.g., ocean temperature, salinity, sea surface height) and seabed characteristics (i.e., rugosity and depth). Comparing model outputs based on ocean temperature and seabed characteristics to those that also incorporated salinity and sea surface height (proxies for primary productivity and ocean circulation features), we explored how an emphasis on ocean temperature in projecting species' range shifts can impact assessments of species' climate vulnerability. We found that multi‐factor habitat suitability models performed better in explaining and predicting species historical distribution patterns than temperature‐based models. We also found that multi‐factor models provided more concerning assessments of species' future distribution patterns than temperature‐based models, projecting that species' ranges will largely shift northward and become more contracted and fragmented over time. Our results suggest that using ocean temperature as a primary determinant of range shifts can significantly alter projections, masking species' climate vulnerability and potentially forestalling proactive management.
Montero, N, Pilar Santidrián Tomillo, and Vincent S Saba, et al., June 2019: Effects of local climate on loggerhead hatchling production in Brazil: Implications from climate change. Scientific Reports, 9, 8861, DOI:10.1038/s41598-019-45366-x. Abstract
Sea turtle eggs are heavily influenced by the environment in which they incubate, including effects on hatching success and hatchling viability (hatchling production). It is crucial to understand how the hatchling production of sea turtles is influenced by local climate and how potential changes in climate may impact future hatchling production. Generalized Additive Models were used to determine the relationship of six climatic variables at different temporal scales on loggerhead turtle (Caretta caretta) hatchling production at seventeen nesting beaches in Bahia, Espirito Santo, and Rio de Janeiro, Brazil. Using extreme and conservative climate change scenarios throughout the 21st century, potential impacts on future hatching success (the number of hatched eggs in a nest) were predicted using the climatic variable(s) that best described hatchling production at each nesting beach. Air temperature and precipitation were found to be the main drivers of hatchling production throughout Brazil. CMIP5 climate projections are for a warming of air temperature at all sites throughout the 21st century, while projections for precipitation vary regionally. The more tropical nesting beaches in Brazil, such as those in Bahia, are projected to experience declines in hatchling production, while the more temperate nesting beaches, such as those in Rio de Janeiro, are projected to experience increases in hatchling production by the end of the 21st century.
Slesinger, Emily, Alyssa M Andres, Rachael E Young, Brad Seibel, and Vincent S Saba, et al., June 2019: The effect of ocean warming on black sea bass (Centropristis striata) aerobic scope and hypoxia tolerance. PLoS-ONE, 14(6), DOI:10.1371/journal.pone.0218390. Abstract
Over the last decade, ocean temperature on the U.S. Northeast Continental Shelf (U.S.
NES) has warmed faster than the global average and is associated with observed distribution
changes of the northern stock of black sea bass (Centropristis striata). Mechanistic
models based on physiological responses to environmental conditions can improve future
habitat suitability projections. We measured maximum, standard metabolic rate, and hypoxia
tolerance (Scrit) of the northern adult black sea bass stock to assess performance
across the known temperature range of the species. Two methods, chase and swim-flume,
were employed to obtain maximum metabolic rate to examine whether the methods varied,
and if so, the impact on absolute aerobic scope. A subset of individuals was held at 30˚C for
one month (30chronic˚C) prior to experiments to test acclimation potential. Absolute aerobic
scope (maximum–standard metabolic rate) reached a maximum of 367.21 mgO2 kg-1 hr-1 at
24.4˚C while Scrit continued to increase in proportion to standard metabolic rate up to 30˚C.
The 30chronic˚C group exhibited a significantly lower maximum metabolic rate and absolute
aerobic scope in relation to the short-term acclimated group, but standard metabolic rate or
Scrit were not affected. This suggests a decline in performance of oxygen demand processes
(e.g. muscle contraction) beyond 24˚C despite maintenance of oxygen supply. The
Metabolic Index, calculated from Scrit as an estimate of potential aerobic scope, closely
matched the measured factorial aerobic scope (maximum / standard metabolic rate) and
declined with increasing temperature to a minimum below 3. This may represent a critical
threshold value for the species. With temperatures on the U.S. NES projected to increase
above 24˚C in the next 80-years in the southern portion of the northern stock’s range, it is
likely black sea bass range will continue to shift poleward as the ocean continues to warm.
Caesar, L, S Rahmstorf, A Robinson, G Feulner, and Vincent S Saba, April 2018: Observed fingerprint of a weakening Atlantic Ocean overturning circulation. Nature, 556(7700), DOI:10.1038/s41586-018-0006-5. Abstract
The Atlantic meridional overturning circulation (AMOC)—a system of ocean currents in the North Atlantic—has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature ‘fingerprint’—consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region—and is calibrated through an ensemble of model simulations from the CMIP5 project. We find this fingerprint both in a high-resolution climate model in response to increasing atmospheric carbon dioxide concentrations, and in the temperature trends observed since the late nineteenth century. The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Comparisons with recent direct measurements from the RAPID project and several other studies provide a consistent depiction of record-low AMOC values in recent years.
Muhling, Barbara A., Carlos F Gaitán, Charles A Stock, Vincent S Saba, Desiree Tommasi, and Keith W Dixon, March 2018: Potential Salinity and Temperature Futures for the Chesapeake Bay Using a Statistical Downscaling Spatial Disaggregation Framework. Estuaries and Coasts, 41(2), DOI:10.1007/s12237-017-0280-8. Abstract
Estuaries are productive and ecologically important ecosystems, incorporating environmental drivers from watersheds, rivers, and the coastal ocean. Climate change has potential to modify the physical properties of estuaries, with impacts on resident organisms. However, projections from general circulation models (GCMs) are generally too coarse to resolve important estuarine processes. Here, we statistically downscaled near-surface air temperature and precipitation projections to the scale of the Chesapeake Bay watershed and estuary. These variables were linked to Susquehanna River streamflow using a water balance model and finally to spatially resolved Chesapeake Bay surface temperature and salinity using statistical model trees. The low computational cost of this approach allowed rapid assessment of projected changes from four GCMs spanning a range of potential futures under a high CO2 emission scenario, for four different downscaling methods. Choice of GCM contributed strongly to the spread in projections, but choice of downscaling method was also influential in the warmest models. Models projected a ~2–5.5 °C increase in surface water temperatures in the Chesapeake Bay by the end of the century. Projections of salinity were more uncertain and spatially complex. Models showing increases in winter-spring streamflow generated freshening in the Upper Bay and tributaries, while models with decreased streamflow produced salinity increases. Changes to the Chesapeake Bay environment have implications for fish and invertebrate habitats, as well as migration, spawning phenology, recruitment, and occurrence of pathogens. Our results underline a potentially expanded role of statistical downscaling to complement dynamical approaches in assessing climate change impacts in dynamically challenging estuaries.
Schulte, J A., N Georgas, Vincent S Saba, and P Howell, April 2018: North Pacific Influences on Long Island Sound Temperature Variability. Journal of Climate, 31(7), DOI:10.1175/JCLI-D-17-0135.1. Abstract
Climate indicators related to Long Island Sound (LIS) water and air temperature variability were investigated. The Pacific Decadal Oscillation (PDO) and East Pacific/North Pacific (EP/NP) patterns are found to be strongly correlated with LIS air temperature anomalies during most seasons, especially during the winter. Additionally, the winter EP/NP index is strongly correlated with subsequent spring and summer LIS water temperature anomalies, potentially rendering the EP/NP index useful in extended LIS water temperature outlooks. Such a lagged relationship is found to be related largely to the decorrelation time scale of seasonal water temperature anomalies. The atmospheric circulation pattern associated with anomalous LIS water temperature conditions is consistent with atmospheric Rossby wave trains emanating from the western equatorial Pacific. The EP/NP index has a characteristic time-scale of approximately 5 to 10 years and such fluctuations are termed the quasi-decadal mode, the mode identified as varying coherently with LIS air and water temperature anomalies. Apparent PDO and EP/NP regime shifts in 1997 are found to coincide with a LIS water temperature regime shift. This result suggests that not all LIS warming experienced during recent decades is solely due to anthropogenic causes but to some extent a result of natural variability. The results from this study provide a useful framework for both seasonal and decadal prediction of LIS water temperature variability.
Selden, Rebecca L., R D Batt, Vincent S Saba, and Malin L Pinsky, January 2018: Diversity in thermal affinity among key piscivores buffers impacts of ocean warming on predator-prey interactions. Global Change Biology, 24(1), DOI:10.1111/gcb.13838. Abstract
Asymmetries in responses to climate change have the potential to alter important predator-prey interactions, in part by altering the location and size of spatial refugia for prey. We evaluated the effect of ocean warming on interactions between four important piscivores and four of their prey in the U.S. Northeast Shelf by examining species overlap under historical conditions (1968-2014) and with a doubling in CO2. Because both predator and prey shift their distributions in response to changing ocean conditions, the net impact of warming or cooling on predator-prey interactions was not determined a priori from the range extent of either predator or prey alone. For Atlantic cod, an historically dominant piscivore in the region, we found that both historical and future warming led to a decline in the proportion of prey species’ range it occupied and caused a potential reduction in its ability to exert top-down control on these prey. In contrast, the potential for overlap of spiny dogfish with prey species was enhanced by warming, expanding their importance as predators in this system. In sum, the decline in the ecological role for cod that began with overfishing in this ecosystem will likely be exacerbated by warming, but this loss may be counteracted by the rise in dominance of other piscivores with contrasting thermal preferences. Functional diversity in thermal affinity within the piscivore guild may therefore buffer against the impact of warming on marine ecosystems, suggesting a novel mechanism by which diversity confers resilience.
Bjorndal, K A., A B Bolten, M Chaloupka, and Vincent S Saba, et al., November 2017: Ecological regime shift drives declining growth rates of sea turtles throughout the West Atlantic. Global Change Biology, 23(11), DOI:10.1111/gcb.13712. Abstract
Somatic growth is an integrated, individual-based response to environmental conditions, especially in ectotherms. Growth dynamics of large, mobile animals are particularly useful as bio-indicators of environmental change at regional scales. We assembled growth rate data from throughout the West Atlantic for green turtles, Chelonia mydas, which are long-lived, highly migratory, primarily herbivorous mega-consumers that may migrate over hundreds to thousands of kilometers. Our dataset, the largest ever compiled for sea turtles, has 9690 growth increments from 30 sites from Bermuda to Uruguay from 1973 to 2015. Using generalized additive mixed models, we evaluated covariates that could affect growth rates; body size, diet, and year have significant effects on growth. Growth increases in early years until 1999, then declines by 26% to 2015. The temporal (year) effect is of particular interest because two carnivorous species of sea turtles – hawksbills, Eretmochelys imbricata, and loggerheads, Caretta caretta – exhibited similar significant declines in growth rates starting in 1997 in the West Atlantic, based on previous studies. These synchronous declines in productivity among three sea turtle species across a trophic spectrum provide strong evidence that an ecological regime shift (ERS) in the Atlantic is driving growth dynamics. The ERS resulted from a synergy of the 1997/1998 El Niño Southern Oscillation (ENSO) – the strongest on record – combined with an unprecedented warming rate over the last two to three decades. Further support is provided by the strong correlations between annualized mean growth rates of green turtles and both sea surface temperatures (SST) in the West Atlantic for years of declining growth rates (r = -0.94) and the Multivariate ENSO Index (MEI) for all years (r = 0.74). Granger-causality analysis also supports the latter finding. We discuss multiple stressors that could reinforce and prolong the effect of the ERS. This study demonstrates the importance of region-wide collaborations.
DePiper, G S., Sarah K Gaichas, S M Lucey, P Pinto da Silva, M R Anderson, H Breeze, A Bundy, P M Clay, Gavin Fay, R J Gamble, R S Gregory, Paula Fratantoni, C L Johnson, M Koen-Alonso, Kristin M Kleisner, J Olson, C T Perretti, P Pepin, F Phelan, and Vincent S Saba, et al., October 2017: Operationalizing integrated ecosystem assessments within a multidisciplinary team: lessons learned from a worked example. ICES Journal of Marine Science, 74(8), DOI:10.1093/icesjms/fsx038. Abstract
Between 2014 and 2016, an interdisciplinary team of researchers including physical oceanographers, biologists, economists and anthropologists developed a working example of an Integrated Ecosystem Assessment (IEA) for three ecologically distinct regions of the Northwest Atlantic; Georges Bank, the Gulf of Maine and the Grand Banks, as part of the International Council for the Exploration of the Sea (ICES) Working Group on the Northwest Atlantic Regional Sea (WGNARS). In this paper, we review the transdisciplinary and collaborative process by which the IEA was developed, with a particular focus on the decision points arising from the IEA construct itself. The aim is to identify key issues faced in developing any IEA, practical decisions made to address these issues within the working group and lessons learned from the process.
Grieve, B D., J A Hare, and Vincent S Saba, July 2017: Projecting the effects of climate change on Calanus finmarchicus distribution within the U.S. Northeast Continental Shelf. Scientific Reports, 7, 6264, DOI:10.1038/s41598-017-06524-1. Abstract
Calanus finmarchicus is vital to pelagic ecosystems in the North Atlantic Ocean. Previous studies suggest the species is vulnerable to the effects of global warming, particularly on the Northeast U.S. Shelf, which is in the southern portion of its range. In this study, we evaluate an ensemble of six different downscaled climate models and a high-resolution global climate model, and create a generalized additive model (GAM) to examine how future changes in temperature and salinity could affect the distribution and density of C. finmarchicus. By 2081–2100, we project average C. finmarchicus density will decrease by as much as 50% under a high greenhouse gas emissions scenario. These decreases are particularly pronounced in the spring and summer in the Gulf of Maine and Georges Bank. When compared to a high-resolution global climate model, the ensemble showed a more uniform change throughout the Northeast U.S. Shelf, while the high-resolution model showed larger decreases in the Northeast Channel, Shelf Break, and Central Gulf of Maine. C. finmarchicus is an important link between primary production and higher trophic levels, and the decrease projected here could be detrimental to the North Atlantic Right Whale and a host of important fishery species.
Kleisner, Kristin M., Michael J Fogarty, S McGee, S Moret, C T Perretti, and Vincent S Saba, April 2017: Marine species distribution shifts on the U.S. Northeast Continental Shelf under continued ocean warming. Progress in Oceanography, 153, DOI:10.1016/j.pocean.2017.04.001. Abstract
The U.S. Northeast Continental Shelf marine ecosystem has warmed much faster than the global ocean and it is expected that this enhanced warming will continue through this century. Complex bathymetry and ocean circulation in this region have contributed to biases in global climate model simulations of the Shelf waters. Increasing the resolution of these models results in reductions in the bias of future climate change projections and indicates greater warming than suggested by coarse resolution climate projections. Here, we used a high-resolution global climate model and historical observations of species distributions from a trawl survey to examine changes in the future distribution of suitable thermal habitat for various demersal and pelagic species on the Shelf. Along the southern portion of the shelf (Mid-Atlantic Bight and Georges Bank), a projected 4.1°C (surface) to 5.0°C (bottom) warming of ocean temperature from current conditions results in a northward shift of the thermal habitat for the majority of species. While some southern species like butterfish and black sea bass are projected to have moderate losses in suitable thermal habitat, there are potentially significant increases for many species including summer flounder, striped bass, and Atlantic croaker. In the north, in the Gulf of Maine, a projected 3.7°C (surface) to 3.9°C (bottom) warming from current conditions results in substantial reductions in suitable thermal habitat such that species currently inhabiting this region may not remain in these waters under continued warming. We project a loss in suitable thermal habitat for key northern species including Acadian redfish, American plaice, Atlantic cod, haddock, and thorney skate, but potential gains for some species including spiny dogfish and American lobster. We illustrate how changes in suitable thermal habitat of important commercially fished species may impact local fishing communities and potentially impact major fishing ports along the U.S. Northeast Shelf. Given the complications of multiple drivers including species interactions and fishing pressure, it is difficult to predict exactly how species will shift. However, observations of species distribution shifts in the historical record under ocean warming suggest that temperature will play a primary role in influencing how species fare. Our results provide critical information on the potential for suitable thermal habitat on the U.S. Northeast Shelf for demersal species in the region, and may contribute to the development of ecosystem-based fisheries management strategies in response to climate change.
Muhling, Barbara A., John Jacobs, Charles A Stock, Carlos F Gaitán, and Vincent S Saba, September 2017: Projections of the future occurrence, distribution, and seasonality of three Vibrio species in the Chesapeake Bay under a high-emission climate change scenario. GeoHealth, 1(7), DOI:10.1002/2017GH000089. Abstract
Illness caused by pathogenic strains of Vibrio bacteria incurs significant economic and health care costs in many areas around the world. In the Chesapeake Bay, the two most problematic species are V. vulnificus and V. parahaemolyticus, which cause infection both from exposure to contaminated water and consumption of contaminated seafood. We used existing Vibrio habitat models, four global climate models, and a recently developed statistical downscaling framework to project the spatiotemporal probability of occurrence of V. vulnificus and V. cholerae in the estuarine environment, and the mean concentration of V. parahaemolyticus in oysters in the Chesapeake Bay by the end of the 21st century. Results showed substantial future increases in season length and spatial habitat for V. vulnificus and V. parahaemolyticus, while projected increase in V. cholerae habitat was less marked and more spatially heterogeneous. Our findings underscore the need for spatially variable inputs into models of climate impacts on Vibrios in estuarine environments. Overall, economic costs associated with Vibrios in the Chesapeake Bay, such as incidence of illness and management measures on the shellfish industry, may increase under climate change, with implications for recreational and commercial uses of the ecosystem.
Schulte, J A., N Georgas, Vincent S Saba, and P Howell, July 2017: Meteorological Aspects of the Eastern North American Pattern with Impacts on Long Island Sound Salinity. Journal of Marine Science and Engineering, 5(3), 26, DOI:10.3390/jmse5030026. Abstract
The eastern North American sea level pressure dipole (ENA) pattern is a recently identified teleconnection pattern that has been shown to influence mid-Atlantic United States (U.S) streamflow variability. Because the pattern was only recently identified, its impacts on U.S. precipitation and estuaries on daily to seasonal timescales is unknown. Thus, this paper presents the first seasonal investigation of ENA relationships with global atmospheric fields, U.S. precipitation, and mid-Atlantic estuarine salinity. We show that the ENA pattern explains up to 25–36% of precipitation variability across Texas and the western U.S. We also show that, for the Northeast U.S, the ENA pattern explains up to 65% of precipitation variability, contrasting with previous work showing how well-known climate indices can only explain a modest amount of precipitation variability. The strongest ENA-precipitation relationships are in the spring and fall. The relationships between the ENA pattern and precipitation across remote regions reflect the upper-atmospheric Rossby wave pattern associated with the ENA pattern that varies seasonally. The El-Nino/Southern Oscillation (ENSO) is related to the spring ENA pattern, indicating that extended outlooks of the ENA pattern may be possible. We also show that the ENA index is strongly correlated with salinity and vertical haline stratification across coastal portions of the mid-Atlantic Bight so that hypoxia forecasts based on the ENA index may be possible. Statistical connections between vertical salinity gradient and ENSO were identified at lags of up two years, further highlighting the potential for extended hypoxia outlooks. The strong connection between anomalies for precipitation and mid-Atlantic Bight salinity suggests that the ENA pattern may be useful at an interdisciplinary level for better understanding historical regional climate variability and future impacts of climate change on regional precipitation and the health of estuaries.
Tommasi, Desiree, Charles A Stock, A J Hobday, R Methot, Isaac C Kaplan, J P Eveson, Kirstin Holsman, Timothy J Miller, Sarah K Gaichas, Marion Gehlen, A Pershing, Gabriel A Vecchi, Rym Msadek, Thomas L Delworth, C M Eakin, Melissa A Haltuch, Roland Séférian, C M Spillman, J R Hartog, Samantha A Siedlecki, Jameal F Samhouri, Barbara A Muhling, R G Asch, Malin L Pinsky, Vincent S Saba, Sarah B Kapnick, and Carlos F Gaitán, et al., March 2017: Managing living marine resources in a dynamic environment: The role of seasonal to decadal climate forecasts. Progress in Oceanography, 152, DOI:10.1016/j.pocean.2016.12.011. Abstract
Recent developments in global dynamical climate prediction systems have allowed for skillful predictions of climate variables relevant to living marine resources (LMRs) at a scale useful to understanding and managing LMRs. Such predictions present opportunities for improved LMR management and industry operations, as well as new research avenues in fisheries science. LMRs respond to climate variability via changes in physiology and behavior. For species and systems where climate-fisheries links are well established, forecasted LMR responses can lead to anticipatory and more effective decisions, benefitting both managers and stakeholders. Here, we provide an overview of climate prediction systems and advances in seasonal to decadal prediction of marine-resource relevant environmental variables. We then describe a range of climate-sensitive LMR decisions that can be taken at lead-times of months to decades, before highlighting a range of pioneering case studies using climate predictions to inform LMR decisions. The success of these case studies suggests that many additional applications are possible. Progress, however, is limited by observational and modeling challenges. Priority developments include strengthening of the mechanistic linkages between climate and marine resource responses, development of LMR models able to explicitly represent such responses, integration of climate driven LMR dynamics in the multi-driver context within which marine resources exist, and improved prediction of ecosystem-relevant variables at the fine regional scales at which most marine resource decisions are made. While there are fundamental limits to predictability, continued advances in these areas have considerable potential to make LMR managers and industry decision more resilient to climate variability and help sustain valuable resources. Concerted dialog between scientists, LMR managers and industry is essential to realizing this potential.
Bjorndal, K A., M Chaloupka, and Vincent S Saba, et al., May 2016: Somatic growth dynamics of West Atlantic hawksbill sea turtles: a spatio-temporal perspective. Ecosphere, 7(5), e01279, DOI:10.1002/ecs2.1279. Abstract
Somatic growth dynamics are an integrated response to environmental conditions. Hawksbill sea turtles (Eretmochelys imbricata) are long-lived, major consumers in coral reef habitats that move over broad geographic areas (hundreds to thousands of kilometers). We evaluated spatio-temporal effects on hawksbill growth dynamics over a 33-yr period and 24 study sites throughout the West Atlantic and explored relationships between growth dynamics and climate indices. We compiled the largest ever data set on somatic growth rates for hawksbills – 3541 growth increments from 1980 to 2013. Using generalized additive mixed model analyses, we evaluated 10 covariates, including spatial and temporal variation, that could affect growth rates. Growth rates throughout the region responded similarly over space and time. The lack of a spatial effect or spatio-temporal interaction and the very strong temporal effect reveal that growth rates in West Atlantic hawksbills are likely driven by region-wide forces. Between 1997 and 2013, mean growth rates declined significantly and steadily by 18%. Regional climate indices have significant relationships with annual growth rates with 0- or 1-yr lags: positive with the Multivariate El Niño Southern Oscillation Index (correlation = 0.99) and negative with Caribbean sea surface temperature (correlation = −0.85). Declines in growth rates between 1997 and 2013 throughout the West Atlantic most likely resulted from warming waters through indirect negative effects on foraging resources of hawksbills. These climatic influences are complex. With increasing temperatures, trajectories of decline of coral cover and availability in reef habitats of major prey species of hawksbills are not parallel. Knowledge of how choice of foraging habitats, prey selection, and prey abundance are affected by warming water temperatures is needed to understand how climate change will affect productivity of consumers that live in association with coral reefs.
Busch, D S., R Griffis, Jason S Link, K Abrams, J Baker, R Brainard, M Ford, J A Hare, Amber Himes-Cornell, Anne B Hollowed, Nate Mantua, S McClatchie, M McClure, M Nelson, K Osgood, Jay O Peterson, M Rust, and Vincent S Saba, et al., December 2016: Climate science strategy of the US National Marine Fisheries Service. Marine Policy, 74, DOI:10.1016/j.marpol.2016.09.001. Abstract
Changes to our climate and oceans are already affecting living marine resources (LMRs) and the people, businesses, and economies that depend on them. As a result, the U.S. National Marine Fisheries Service (NMFS) has developed a Climate Science Strategy (CSS) to increase the production and use of the climate-related information necessary to fulfill its LMR stewardship mission for fisheries management and protected species conservation. The CSS establishes seven objectives: (1) determine appropriate, climate-informed reference points; (2) identify robust strategies for managing LMRs under changing climate conditions; (3) design decision processes that are robust to climate-change scenarios; (4) predict future states of ecosystems, LMRs, and LMR-dependent human communities; (5) determine the mechanisms of climate-change related effects on ecosystems, LMRs, and LMR-dependent human communities; (6) track trends in ecosystems, LMRs, and LMR-dependent human communities and provide early warning of change; and (7) build and maintain the science infrastructure required to fulfill NMFS mandates under changing climate conditions. These objectives provide a nationally consistent approach to addressing climate-LMR science needs that supports informed decision-making and effective implementation of the NMFS legislative mandates in each region. Near term actions that will address all objectives include: (1) conducting climate vulnerability analyses in each region for all LMRs; (2) establishing and strengthening ecosystem indicators and status reports in all regions; and (3) developing a capacity to conduct management strategy evaluations of climate-related impacts on management targets, priorities, and goals. Implementation of the Strategy over the next few years and beyond is critical for effective fulfillment of the NMFS mission and mandates in a changing climate.
Cimino, M A., H J Lynch, Vincent S Saba, and M J Oliver, June 2016: Projected asymmetric response of Adélie penguins to Antarctic climate change. Scientific Reports, 6, 28785, DOI:10.1038/srep28785. Abstract
The contribution of climate change to shifts in a species’ geographic distribution is a critical and often unresolved ecological question. Climate change in Antarctica is asymmetric, with cooling in parts of the continent and warming along the West Antarctic Peninsula (WAP). The Adélie penguin (Pygoscelis adeliae) is a circumpolar meso-predator exposed to the full range of Antarctic climate and is undergoing dramatic population shifts coincident with climate change. We used true presence-absence data on Adélie penguin breeding colonies to estimate past and future changes in habitat suitability during the chick-rearing period based on historic satellite observations and future climate model projections. During the contemporary period, declining Adélie penguin populations experienced more years with warm sea surface temperature compared to populations that are increasing. Based on this relationship, we project that one-third of current Adélie penguin colonies, representing ~20% of their current population, may be in decline by 2060. However, climate model projections suggest refugia may exist in continental Antarctica beyond 2099, buffering species-wide declines. Climate change impacts on penguins in the Antarctic will likely be highly site specific based on regional climate trends, and a southward contraction in the range of Adélie penguins is likely over the next century.
Friedland, K D., Nicholas R Record, R G Asch, T Kristiansen, and Vincent S Saba, et al., April 2016: Seasonal phytoplankton blooms in the North Atlantic linked to the overwintering strategies of copepods. Elementa: Science of the Anthropocene, (4), 000099, DOI:10.12952/journal.elementa.000099. Abstract
The North Atlantic Ocean contains diverse patterns of seasonal phytoplankton blooms with distinct internal dynamics. We analyzed blooms using
remotelysensed
chlorophyll a concentration data and change point statistics. The first bloom of the year began during spring at low latitudes and later
in summer at higher latitudes. In regions where spring blooms occurred at high frequency (i.e., proportion of years that a bloom was detected), there
was a negative correlation between bloom timing and duration, indicating that early blooms last longer. In much of the Northeast Atlantic, bloom
development extended over multiple seasons resulting in peak chlorophyll concentrations in summer. Spring bloom start day was found to be positively
correlated with a spring phenology index and showed both positive and negative correlations to sea surface temperature and the North Atlantic
Oscillation in different regions. Based on the characteristics of spring and summer blooms, the North Atlantic can be classified into two regions: a
seasonal bloom region, with a welldefined
bloom limited to a single season; and a multiseasonal
bloom region, with blooms extending over multiple
seasons. These regions differed in the correlation between bloom start and duration with only the seasonal bloom region showing a significant,
negative correlation. We tested the hypothesis that the nearsurface
springtime distribution of copepods that undergo diapause (Calanus finmarchicus,
C. helgolandicus, C. glacialis, and C. hyperboreus) may contribute to the contrast in bloom development between the two regions. Peak nearsurface
spring abundance of the late stages of these Calanoid copepods was generally associated with areas having a welldefined
seasonal bloom, implying a
link between bloom shape and their abundance. We suggest that either grazing is a factor in shaping the seasonal bloom or bloom shape determines
whether a habitat is conducive to diapause, while recognizing that both factors can reenforce
each other.
Fuentes, M P., and Vincent S Saba, September 2016: Impacts and effects of ocean warming on marine turtles In Explaining ocean warming: Causes, scale, effects and consequences, Laffoley, D., & Baxter, J.M. (editors), Gland, Switzerland, IUCN, 289-302.
Georgas, N, Lun Yin, Yu Jiang, Yifan Wang, P Howell, and Vincent S Saba, et al., September 2016: An Open-Access, Multi-Decadal, Three-Dimensional, Hydrodynamic Hindcast Dataset for the Long Island Sound and New York/New Jersey Harbor Estuaries. Journal of Marine Science and Engineering, 4, 48, DOI:10.3390/jmse4030048. Abstract
This article presents the results and validation of a comprehensive, multi-decadal, hindcast
simulation performed using the New York Harbor Observing and Prediction System´s (NYHOPS)
three-dimensional hydrodynamic model. Meteorological forcing was based on three-hourly gridded
data from the North American Regional Reanalysis of the US National Centers for Environmental
Prediction. Distributed hydrologic forcing was based on daily United States Geologic Survey records.
Offshore boundary conditions for NYHOPS at the Mid-Atlantic Bight shelf break included hourly
subtidal water levels from a larger-scale model ran for the same period, tides, and temperature
and salinity profiles based on the Simple Ocean Data Assimilation datasets. The NYHOPS model’s
application to hindcast total water level and 3D water temperature and salinity conditions in its
region over three decades was validated against observations from multiple agencies. Average indices
of agreement were: 0.93 for storm surge (9 cm RMSE, 90% of errors less than 15 cm), 0.99 for water
temperature (1.1 ◦C RMSE, 99% of errors less than 3 ◦C), and 0.86 for salinity (1.8 psu RMSE, 96% of
errors less than 3.5 psu). The model’s skill in simulating bottom water temperature, validated
against historic data from the Long Island Sound bottom trawl survey, did not drift over the years,
a significant and encouraging finding for multi-decadal model applications used to identify climatic
trends, such as the warming presented here. However, the validation reveals residual biases in
some areas such as small tributaries that receive urban discharges from the NYC drainage network.
With regard to the validation of storm surge at coastal stations, both the considerable strengths
and remaining limitations of the use of North American Regional Reanalysis (NARR) to force such
a model application are discussed.
Hare, J A., Diane L Borggaard, K D Friedland, J Anderson, Peter Burns, K Chu, P M Clay, M J Collins, P Cooper, Paula Fratantoni, M R Johnson, L Milke, Timothy J Miller, C D Orphanides, and Vincent S Saba, December 2016: Northeast Regional Action Plan – NOAA Fisheries Climate Science Strategy , U.S. Dept. of Commerce, NOAA Technical Memorandum NMFS-NE-239, 100pp. Abstract
Kleisner, Kristin M., Michael J Fogarty, S McGee, A Barnett, Paula Fratantoni, J Greene, J A Hare, S M Lucey, C McGuire, J Odell, and Vincent S Saba, et al., February 2016: The Effects of Sub-Regional Climate Velocity on the Distribution and Spatial Extent of Marine Species Assemblages. PLoS-ONE, 11(2), DOI:10.1371/journal.pone.0149220. Abstract
Many studies illustrate variable patterns in individual species distribution shifts in response to changing temperature. However, an assemblage, a group of species that shares a common environmental niche, will likely exhibit similar responses to climate changes, and these community-level responses may have significant implications for ecosystem function. Therefore, we examine the relationship between observed shifts of species in assemblages and regional climate velocity (i.e., the rate and direction of change of temperature isotherms). The assemblages are defined in two sub-regions of the U.S. Northeast Shelf that have heterogeneous oceanography and bathymetry using four decades of bottom trawl survey data and we explore temporal changes in distribution, spatial range extent, thermal habitat area, and biomass, within assemblages. These sub-regional analyses allow the dissection of the relative roles of regional climate velocity and local physiography in shaping observed distribution shifts. We find that assemblages of species associated with shallower, warmer waters tend to shift west-southwest and to shallower waters over time, possibly towards cooler temperatures in the semi-enclosed Gulf of Maine, while species assemblages associated with relatively cooler and deeper waters shift deeper, but with little latitudinal change. Conversely, species assemblages associated with warmer and shallower water on the broad, shallow continental shelf from the Mid-Atlantic Bight to Georges Bank shift strongly northeast along latitudinal gradients with little change in depth. Shifts in depth among the southern species associated with deeper and cooler waters are more variable, although predominantly shifts are toward deeper waters. In addition, spatial expansion and contraction of species assemblages in each region corresponds to the area of suitable thermal habitat, but is inversely related to assemblage biomass. This suggests that assemblage distribution shifts in conjunction with expansion or contraction of thermal habitat acts to compress or stretch marine species assemblages, which may respectively amplify or dilute species interactions to an extent that is rarely considered. Overall, regional differences in climate change effects on the movement and extent of species assemblages hold important implications for management, mitigation, and adaptation on the U.S. Northeast Shelf.
Lee, Y J., P A Matrai, Marjorie A M Friedrichs, Vincent S Saba, Olivier Aumont, M Babin, Erik T Buitenhuis, M Chevallier, L de Mora, M Dessert, John P Dunne, I H Ellingsen, Daniel Feldman, R Frouin, Marion Gehlen, T Gorgues, Tatiana Ilyina, M Jin, Jasmin G John, J Lawrence, Manfredi Manizza, C Menkes, C Perruche, V Le Fouest, E E Popova, Anastasia Romanou, A Samuelsen, Jörg Schwinger, Roland Séférian, and Charles A Stock, et al., December 2016: Net primary productivity estimates and environmental variables in the Arctic Ocean: An assessment of coupled physical-biogeochemical models. Journal of Geophysical Research: Oceans, 121(12), DOI:10.1002/2016JC011993. Abstract
The relative skill of 21 regional and global biogeochemical models was assessed in terms of how well the models reproduced observed net primary productivity (NPP) and environmental variables such as nitrate concentration (NO3), mixed layer depth (MLD), euphotic layer depth (Zeu), and sea ice concentration, by comparing results against a newly updated, quality-controlled in situ NPP database for the Arctic Ocean (1959–2011). The models broadly captured the spatial features of integrated NPP (iNPP) on a pan-Arctic scale. Most models underestimated iNPP by varying degrees in spite of overestimating surface NO3, MLD, and Zeu throughout the regions. Among the models, iNPP exhibited little difference over sea ice condition (ice-free versus ice-influenced) and bottom depth (shelf versus deep ocean). The models performed relatively well for the most recent decade and toward the end of Arctic summer. In the Barents and Greenland Seas, regional model skill of surface NO3 was best associated with how well MLD was reproduced. Regionally, iNPP was relatively well simulated in the Beaufort Sea and the central Arctic Basin, where in situ NPP is low and nutrients are mostly depleted. Models performed less well at simulating iNPP in the Greenland and Chukchi Seas, despite the higher model skill in MLD and sea ice concentration, respectively. iNPP model skill was constrained by different factors in different Arctic Ocean regions. Our study suggests that better parameterization of biological and ecological microbial rates (phytoplankton growth and zooplankton grazing) are needed for improved Arctic Ocean biogeochemical modeling.
Patel, Samir H., S J Morreale, and Vincent S Saba, et al., June 2016: Climate impacts on sea turtle breeding phenology in Greece and associated foraging habitats in the wider Mediterranean Region. PLoS-ONE, 11(6), e0157170, DOI:10.1371/journal.pone.0157170. Abstract
Sea turtles are vulnerable to climate change impacts in both their terrestrial (nesting beach) and oceanic habitats. From 1982 to 2012, air and sea surface temperatures at major high use foraging and nesting regions (n = 5) of loggerhead turtles (Caretta caretta) nesting in Greece have steadily increased. Here, we update the established relationships between sea surface temperature and nesting data from Zakynthos (latitude: 37.7°N), a major nesting beach, while also expanding these analyses to include precipitation and air temperature and additional nesting data from two other key beaches in Greece: Kyparissia Bay (latitude: 37.3°N) and Rethymno, Crete (latitude: 35.4°N). We confirmed that nesting phenology at Zakynthos has continued to be impacted by breeding season temperature; however, temperature has no consistent relationship with nest numbers, which are declining on Zakynthos and Crete but increasing at Kyparissia. Then using statistically downscaled outputs of 14 climate models assessed by the Intergovernmental Panel on Climate Change (IPCC), we projected future shifts in nesting for these populations. Based on the climate models, we projected that temperature at the key foraging and breeding sites (Adriatic Sea, Aegean Sea, Crete, Gulf of Gabès and Zakynthos/Kyparissia Bay; overall latitudinal range: 33.0°—45.8°N) for loggerhead turtles nesting in Greece will rise by 3–5°C by 2100. Our calculations indicate that the projected rise in air and ocean temperature at Zakynthos could cause the nesting season in this major rookery to shift to an earlier date by as much as 50–74 days by 2100. Although an earlier onset of the nesting season may provide minor relief for nest success as temperatures rise, the overall climatic changes to the various important habitats will most likely have an overall negative impact on this population.
The Intergovernmental Panel on Climate Change (IPCC) fifth assessment of projected global and regional ocean temperature change is based on global climate models that have coarse (∼100-km) ocean and atmosphere resolutions. In the Northwest Atlantic, the ensemble of global climate models has a warm bias in sea surface temperature due to a misrepresentation of the Gulf Stream position; thus, existing climate change projections are based on unrealistic regional ocean circulation. Here we compare simulations and an atmospheric CO2 doubling response from four global climate models of varying ocean and atmosphere resolution. We find that the highest resolution climate model (∼10-km ocean, ∼50-km atmosphere) resolves Northwest Atlantic circulation and water mass distribution most accurately. The CO2 doubling response from this model shows that upper-ocean (0-300 m) temperature in the Northwest Atlantic Shelf warms at a rate nearly twice as fast as the coarser models and nearly three times faster than the global average. This enhanced warming is accompanied by an increase in salinity due to a change in water mass distribution that is related to a retreat of the Labrador Current and a northerly shift of the Gulf Stream. Both observations and the climate model demonstrate a robust relationship between a weakening Atlantic Meridional Overturning Circulation (AMOC) and an increase in the proportion of Warm-Temperate Slope Water entering the Northwest Atlantic Shelf. Therefore, prior climate change projections for the Northwest Atlantic may be far too conservative. These results point to the need to improve simulations of basin and regional-scale ocean circulation.
Friedland, K D., R T Leaf, J Kane, Desiree Tommasi, R G Asch, N Rebuck, R Ji, S I Large, Charles A Stock, and Vincent S Saba, July 2015: Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf. Continental Shelf Research, 102, DOI:10.1016/j.csr.2015.04.005. Abstract
The spring phytoplankton bloom on the US Northeast Continental Shelf is a feature of the ecosystem production cycle that varies annually in timing, spatial extent, and magnitude. To quantify this variability, we analyzed remotely-sensed ocean color data at two spatial scales, one based on ecologically defined sub-units of the ecosystem (production units) and the other on a regular grid (0.5°). Five units were defined: Gulf of Maine East and West, Georges Bank, and Middle Atlantic Bight North and South. The units averaged 47×103 km2 in size. The initiation and termination of the spring bloom were determined using change-point analysis with constraints on what was identified as a bloom based on climatological bloom patterns. A discrete spring bloom was detected in most years over much of the western Gulf of Maine production unit. However, bloom frequency declined in the eastern Gulf of Maine and transitioned to frequencies as low as 50% along the southern flank of the Georges Bank production unit. Detectable spring blooms were episodic in the Middle Atlantic Bight production units. In the western Gulf of Maine, bloom duration was inversely related to bloom start day; thus, early blooms tended to be longer lasting and larger magnitude blooms. We view this as a phenological mismatch between bloom timing and the “top-down” grazing pressure that terminates a bloom. Estimates of secondary production were available from plankton surveys that provided spring indices of zooplankton biovolume. Winter chlorophyll biomass had little effect on spring zooplankton biovolume, whereas spring chlorophyll biomass had mixed effects on biovolume. There was evidence of a “bottom up” response seen on Georges Bank where spring zooplankton biovolume was positively correlated with the concentration of chlorophyll. However, in the western Gulf of Maine, biovolume was uncorrelated with chlorophyll concentration, but was positively correlated with bloom start and negatively correlated with magnitude. This observation is consistent with both a “top-down” mechanism of control of the bloom and a “bottom-up” effect of bloom timing on zooplankton grazing. Our inability to form a consistent model of these relationships across adjacent systems underscores the need for further research.
Lee, Y J., P A Matrai, Marjorie A M Friedrichs, and Vincent S Saba, et al., September 2015: An assessment of phytoplankton primary productivity in the Arctic Ocean from satellite ocean color/in situ chlorophyll-a-based models. Journal of Geophysical Research: Oceans, 120(9), DOI:10.1002/2015JC011018. Abstract
We investigated 32 net primary productivity (NPP) models by assessing skills to reproduce integrated NPP in the Arctic Ocean. The models were provided with two sources each of surface chlorophyll-a concentration (chlorophyll), photosynthetically available radiation (PAR), sea surface temperature (SST), and mixed-layer depth (MLD). The models were most sensitive to uncertainties in surface chlorophyll, generally performing better with in situ chlorophyll than with satellite-derived values. They were much less sensitive to uncertainties in PAR, SST, and MLD, possibly due to relatively narrow ranges of input data and/or relatively little difference between input data sources. Regardless of type or complexity, most of the models were not able to fully reproduce the variability of in situ NPP, whereas some of them exhibited almost no bias (i.e., reproduced the mean of in situ NPP). The models performed relatively well in low-productivity seasons as well as in sea ice-covered/deep-water regions. Depth-resolved models correlated more with in situ NPP than other model types, but had a greater tendency to overestimate mean NPP whereas absorption-based models exhibited the lowest bias associated with weaker correlation. The models performed better when a subsurface chlorophyll-a maximum (SCM) was absent. As a group, the models overestimated mean NPP, however this was partly offset by some models underestimating NPP when a SCM was present. Our study suggests that NPP models need to be carefully tuned for the Arctic Ocean because most of the models performing relatively well were those that used Arctic-relevant parameters. This article is protected by copyright. All rights reserved.
Link, Jason S., J S Griffis, S Busch, K Abrams, J Baker, R Brainard, M Ford, J A Hare, Amber Himes-Cornell, Anne B Hollowed, K Osgood, Nate Mantua, S McClatchie, M McClure, M Nelson, M Rust, and Vincent S Saba, et al., August 2015: NOAA Fisheries Climate Science Strategy, Washington, DC: U.S. Dept. of Commerce, NOAA Technical Memorandum NMFS-F/SPO-155, 82pp. Abstract
Saba, Vincent S., et al., February 2015: Physical associations to spring phytoplankton biomass interannual variability in the U.S. Northeast Continental Shelf. Journal of Geophysical Research: Biogeosciences, 120(2), DOI:10.1002/2014JG002770. Abstract
The continental shelf of the Northeast United States and Nova Scotia is a productive marine ecosystem that supports a robust biomass of living marine resources. Understanding marine ecosystem sensitivity to changes in the physical environment can start with the first order response of phytoplankton (i.e. chlorophyll-a), the base of the marine food web. However, the primary physical associations to the interannual variability of chlorophyll-a in these waters are unclear. Here we used ocean color satellite measurements and identified the local and remote physical associations to interannual variability of spring surface chlorophyll-a from 1998 to 2013. The highest interannual variability of chlorophyll-a occurred in March and April on the northern flank of Georges Bank, the western Gulf of Maine, and Nantucket Shoals. Complex interactions between winter wind speed over the Shelf, local winter water levels, and the relative proportions of Atlantic versus Labrador Sea source waters entering the Gulf of Maine from the previous summer/fall were associated with the variability of March/April chlorophyll-a in Georges Bank and the Gulf of Maine. Sea surface temperature and sea surface salinity were not robust correlates to spring chlorophyll-a. Surface nitrate in the winter was not a robust correlate to chlorophyll-a or the physical variables in every case suggesting that nitrate limitation may not be the primary constraint on the interannual variability of the spring bloom throughout all regions. Generalized linear models suggest that we can resolve 88% of April chlorophyll-a interannual variability in Georges Bank using lagged physical data.
Saba, Vincent S., Charles A Stock, and John P Dunne, October 2015: Relation of Marine Primary Productivity to Leatherback Biology and Behavior In The Leatherback Turtle: Biology and Conservation, Baltimore, MD, John Hopkins University Press, 173-184.
Santidrián Tomillo, Pilar, and Vincent S Saba, et al., November 2015: Global analysis of the effect of local climate on the hatchling output of leatherback turtles. Scientific Reports, 5, 16789, DOI:10.1038/srep16789. Abstract
The most recent climate change projections show a global increase in temperatures along with
precipitation changes throughout the 21st century. However, regional projections do not always
match global projections and species with global distributions may exhibit varying regional
susceptibility to climate change. Here we show the effect of local climatic conditions on the hatchling
output of leatherback turtles (Dermochelys coriacea) at four nesting sites encompassing the Pacific,
Atlantic and Indian Oceans. We found a heterogeneous effect of climate. Hatchling output increased
with long-term precipitation in areas with dry climatic conditions (Playa Grande, Pacific Ocean and
Sandy Point, Caribbean Sea), but the effect varied in areas where precipitation was high (Pacuare,
Caribbean Sea) and was not detected at the temperate site (Maputaland, Indian Ocean). High air
temperature reduced hatchling output only at the area experiencing seasonal droughts (Playa
Grande). Climatic projections showed a drastic increase in air temperature and a mild decrease
in precipitation at all sites by 2100. The most unfavorable conditions were projected for Sandy
Point where hatching success has already declined over time along with precipitation levels. The
heterogeneous effect of climate may lead to local extinctions of leatherback turtles in some areas
but survival in others by 2100.
Spotila, J R., Vincent S Saba, Samir H Patel, and Pilar Santidrián Tomillo, October 2015: Warming Climate: A New Threat to the Leatherback Turtle In The Leatherback Turtle: Biology and Conservation, Baltimore, MD, Johns Hopkins University Press, 185-195.
Cimino, M A., W R Fraser, D L Patterson-Fraser, Vincent S Saba, and M J Oliver, October 2014: Large-scale climate and local weather drive interannual variability in Adelie penguin chick fledging mass. Marine Ecology Progress Series, 513, DOI:10.3354/meps10928. Abstract
The fledging mass of penguin chicks can be an indicator of food availability and environmental conditions at a penguin colony. For the period 1989 to 2011, we analyzed predictor variables of environmental and food resource factors acting on multiple spatial scales near Palmer Station, Antarctica, that may influence the interannual variability in Adélie penguin chick fledging mass (CFM). To understand the influence of parental Adélie penguin diet on CFM, we modeled the energy density and krill demographics of penguin diet samples. We found a weak but significant positive relationship between the proportion of immature krill in adult penguin diets and CFM, which may indicate that krill recruitment and prey availability to adults influences CFM. However, the impact of large-scale climate and local weather outweighed the impact of parental diet characteristics on CFM. CFM was negatively associated with a positive Antarctic Oscillation (or Southern Annular Mode) and increased westerly winds and was positively associated with increased air temperature. The mechanistic relationship between climate, local weather, and CFM could include direct and indirect impacts, such as increased thermo-regulative costs for unattended chicks, decreased chick feeding frequency, and smaller meal mass for chicks driven by the geophysical transport of krill by climate and wind events.
Polovina, J J., A J Hobday, J A Koslow, and Vincent S Saba, 2014: Open Ocean Systems In The Sea, Volume 16: Maine Ecosystem-Based Management, Cambridge, MA, Harvard University Press, 429-473.
Robinson, N J., S E Valentine, Pilar Santidrián Tomillo, and Vincent S Saba, et al., June 2014: Multidecadal trends in the nesting phenology of Pacific and Atlantic leatherback turtles are associated with population demography. Endangered Species Research, 24(3), DOI:10.3354/esr00604. Abstract
Knowledge of the mechanisms influencing phenology can provide insights into the adaptability of species to climate change. Here, we investigated the factors influencing multidecadal trends in the nesting phenology of the leatherback turtle Dermochelys coriacea at Playa Grande, Costa Rica, in the eastern Pacific Ocean and at Sandy Point, US Virgin Islands, in the western Atlantic Ocean. Between 1993 and 2013, the median nesting date (MND) at Playa Grande occurred later, at a rate of ~0.3 d yr-1. In contrast, between 1982 and 2010, the MND at Sandy Point occurred earlier, at a rate of ~0.17 d yr-1. The opposing trends in the MND of each population were not explained by variation in the multivariate El Niño-Southern Oscillation index, North Atlantic Oscillation index, or Atlantic Multidecadal Oscillation index; however, the MND at Playa Grande was significantly correlated with nesting population size. We propose that changes in demography, linked to the population decline at Playa Grande, and the population recovery at Sandy Point may explain the contrasting trends in MNDs. If the observed trends in MND continue into the future, the nesting season at Playa Grande will coincide with increasingly adverse conditions for hatching success, exacerbating the already detrimental effects of climate change. Alternatively, shifts in the nesting phenology may make the Atlantic populations more resilient to climate change. Our findings highlight the increasing need for conservation efforts for eastern Pacific leatherback turtles to consider climate change mitigation practices.
Saba, Grace K., W R Fraser, and Vincent S Saba, et al., July 2014: Winter and spring controls on the summer food web of the coastal West Antarctic Peninsula. Nature Communications, 5(4318), DOI:10.1038/ncomms5318. Abstract
Understanding the mechanisms by which climate variability affects multiple trophic levels in food webs is essential for determining ecosystem responses to climate change. Here we use over two decades of data collected by the Palmer Long Term Ecological Research program (PAL-LTER) to determine how large-scale climate and local physical forcing affect phytoplankton, zooplankton and an apex predator along the West Antarctic Peninsula (WAP). We show that positive anomalies in chlorophyll-a (chl-a) at Palmer Station, occurring every 4-6 years, are constrained by physical processes in the preceding winter/spring and a negative phase of the Southern Annular Mode (SAM). Favorable conditions for phytoplankton included increased winter ice extent and duration, reduced spring/summer winds, and increased water column stability via enhanced salinity-driven density gradients. Years of positive chl-a anomalies are associated with the initiation of a robust krill cohort the following summer, which is evident in Adelie penguin diets, thus demonstrating tight trophic coupling. Projected climate change in this region may have a significant, negative impact on phytoplankton biomass, krill recruitment and upper trophic level predators in this coastal Antarctic ecosystem.
Arendt, M D., J A Schwenter, B E Witherington, A B Meylan, and Vincent S Saba, December 2013: Historical versus Contemporary Climate Forcing on the Annual Nesting Variability of Loggerhead Sea Turtles in the Northwest Atlantic Ocean. PLoS-ONE, 8(12), DOI:10.1371/journal.pone.0081097. Abstract
A recent analysis suggested that historical climate forcing on the oceanic habitat of neonate sea turtles explained two-thirds of interannual variability in contemporary loggerhead (Caretta caretta) sea turtle nest counts in Florida, where nearly 90% of all nesting by this species in the Northwest Atlantic Ocean occurs. Here, we show that associations between annual nest counts and climate conditions decades prior to nest counts and those conditions one year prior to nest counts were not significantly different. Examination of annual nest count and climate data revealed that statistical artifacts influenced the reported 31-year lag association with nest counts. The projected importance of age 31 neophytes to annual nest counts between 2020 and 2043 was modeled using observed nest counts between 1989 and 2012. Assuming consistent survival rates among cohorts for a 5% population growth trajectory and that one third of the mature female population nests annually, the 41% decline in annual nest counts observed during 1998–2007 was not projected for 2029–2038. This finding suggests that annual nest count trends are more influenced by remigrants than neophytes. Projections under the 5% population growth scenario also suggest that the Peninsular Recovery Unit could attain the demographic recovery criteria of 106,100 annual nests by 2027 if nest counts in 2019 are at least comparable to 2012. Because the first year of life represents only 4% of the time elapsed through age 31, cumulative survival at sea across decades explains most cohort variability, and thus, remigrant population size. Pursuant to the U.S. Endangered Species Act, staggered implementation of protection measures for all loggerhead life stages has taken place since the 1970s. We suggest that the 1998–2007 nesting decline represented a lagged perturbation response to historical anthropogenic impacts, and that subsequent nest count increases since 2008 reflect a potential recovery response.
Saba, Vincent S., 2013: Oceanic Habits and Habitats: Dermochelys coriacea In The Biology of Sea Turtles Volume III, Boca Raton, FL, CRC Press, 163-188.
Assessing the potential impacts of climate change on individual species and populations is essential for the stewardship of ecosystems and biodiversity. Critically endangered leatherback turtles in the eastern Pacific Ocean are excellent candidates for such an assessment because their sensitivity to contemporary climate variability has been substantially studied1, 2, 3, 4. If incidental fisheries mortality is eliminated, this population still faces the challenge of recovery in a rapidly changing climate. Here we combined an Earth system model5, climate model projections assessed by the Intergovernmental Panel on Climate Change6 and a population dynamics model to estimate a 7% per decade decline in the Costa Rica nesting population over the twenty-first century. Whereas changes in ocean conditions had a small effect on the population, the ~2.5 °C warming of the nesting beach was the primary driver of the decline through reduced hatching success and hatchling emergence rate. Hatchling sex ratio did not substantially change. Adjusting nesting phenology or changing nesting sites may not entirely prevent the decline, but could offset the decline rate. However, if future observations show a long-term decline in hatching success and emergence rate, anthropogenic climate mitigation of nests (for example, shading, irrigation)7, 8 may be able to preserve the nesting population.
Saba, Vincent S., 2012: Sea Turtles in the Tropical High Seas: Climate Variability, Oceanography, and Ecosystem Responses In Sea Turtles of the Eastern Pacific: Advances in Research and Conservation, Tucson, AZ, University of Arizona Press, 39-62.
Santidrián Tomillo, Pilar, Vincent S Saba, G S Blanco, Charles A Stock, F V Paladino, and J R Spotila, May 2012: Climate Driven Egg and Hatchling Mortality Threatens Survival of Eastern Pacific Leatherback Turtles. PLoS-ONE, 7(5), DOI:10.1371/journal.pone.0037602. Abstract
Egg-burying reptiles need relatively stable temperature and humidity in the substrate surrounding their eggs for successful
development and hatchling emergence. Here we show that egg and hatchling mortality of leatherback turtles (Dermochelys
coriacea) in northwest Costa Rica were affected by climatic variability (precipitation and air temperature) driven by the El
Nin˜o Southern Oscillation (ENSO). Drier and warmer conditions associated with El Nin˜o increased egg and hatchling
mortality. The fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC) projects a warming and
drying in Central America and other regions of the World, under the SRES A2 development scenario. Using projections from
an ensemble of global climate models contributed to the IPCC report, we project that egg and hatchling survival will rapidly
decline in the region over the next 100 years by ,50–60%, due to warming and drying in northwestern Costa Rica,
threatening the survival of leatherback turtles. Warming and drying trends may also threaten the survival of sea turtles in
other areas affected by similar climate changes.
Saba, Vincent S., et al., February 2011: An evaluation of ocean color model estimates of marine primary productivity in coastal and pelagic regions across the globe. Biogeosciences, 8(2), DOI:10.5194/bg-8-489-2011. Abstract
Nearly half of the earth's photosynthetically fixed carbon derives from the oceans. To determine global and region specific rates, we rely on models that estimate marine net primary productivity (NPP) thus it is essential that these models are evaluated to determine their accuracy. Here we assessed the skill of 21 ocean color models by comparing their estimates of depth-integrated NPP to 1156 in situ 14C measurements encompassing ten marine regions including the Sargasso Sea, pelagic North Atlantic, coastal Northeast Atlantic, Black Sea, Mediterranean Sea, Arabian Sea, subtropical North Pacific, Ross Sea, West Antarctic Peninsula, and the Antarctic Polar Frontal Zone. Average model skill, as determined by root-mean square difference calculations, was lowest in the Black and Mediterranean Seas, highest in the pelagic North Atlantic and the Antarctic Polar Frontal Zone, and intermediate in the other six regions. The maximum fraction of model skill that may be attributable to uncertainties in both the input variables and in situ NPP measurements was nearly 72%. On average, the simplest depth/wavelength integrated models performed no worse than the more complex depth/wavelength resolved models. Ocean color models were not highly challenged in extreme conditions of surface chlorophyll-a and sea surface temperature, nor in high-nitrate low-chlorophyll waters. Water column depth was the primary influence on ocean color model performance such that average skill was significantly higher at depths greater than 250 m, suggesting that ocean color models are more challenged in Case-2 waters (coastal) than in Case-1 (pelagic) waters. Given that in situ chlorophyll-a data was used as input data, algorithm improvement is required to eliminate the poor performance of ocean color NPP models in Case-2 waters that are close to coastlines. Finally, ocean color chlorophyll-a algorithms are challenged by optically complex Case-2 waters, thus using satellite-derived chlorophyll-a to estimate NPP in coastal areas would likely further reduce the skill of ocean color models.
Saba, Vincent S., and John P Dunne, et al., September 2010: Challenges of modeling depth-integrated marine primary productivity over multiple decades: A case study at BATS and HOT. Global Biogeochemical Cycles, 24, GB3020, DOI:10.1029/2009GB003655. Abstract
The performance of 36 models (22 ocean color models and 14 biogeochemical ocean circulation models (BOGCMs)) that estimate depth-integrated marine net primary productivity (NPP) was assessed by comparing their output to in situ 14C data at the Bermuda Atlantic Time series Study (BATS) and the Hawaii Ocean Time series (HOT) over nearly two decades. Specifically, skill was assessed based on the models' ability to estimate the observed mean, variability, and trends of NPP. At both sites, more than 90% of the models underestimated mean NPP, with the average bias of the BOGCMs being nearly twice that of the ocean color models. However, the difference in overall skill between the best BOGCM and the best ocean color model at each site was not significant. Between 1989 and 2007, in situ NPP at BATS and HOT increased by an average of nearly 2% per year and was positively correlated to the North Pacific Gyre Oscillation index. The majority of ocean color models produced in situ NPP trends that were closer to the observed trends when chlorophyll-a was derived from high-performance liquid chromatography (HPLC), rather than fluorometric or SeaWiFS data. However, this was a function of time such that average trend magnitude was more accurately estimated over longer time periods. Among BOGCMs, only two individual models successfully produced an increasing NPP trend (one model at each site). We caution against the use of models to assess multiannual changes in NPP over short time periods. Ocean color model estimates of NPP trends could improve if more high quality HPLC chlorophyll-a time series were available.
Friedrichs, Marjorie A., M-E Carr, R T Barber, M Scardi, D Antoine, R A Armstrong, I Asanuma, M J Behrenfeld, Erik T Buitenhuis, Fei Chai, James R Christian, A M Ciotti, Scott C Doney, M Dowell, John P Dunne, B Gentili, W Gregg, N Hoepffner, J Ishizaka, T Kameda, Ivan D Lima, J Marra, F Melin, J Keith Moore, A Morel, R T O'Malley, J E O'Reilly, and Vincent S Saba, et al., February 2009: Assessing the uncertainties of model estimates of primary productivity in the tropical Pacific Ocean. Journal of Marine Systems, 76(1-2), DOI:10.1016/j.jmarsys.2008.05.010. Abstract
Depth-integrated primary productivity (PP) estimates obtained from satellite
ocean color-based
models (SatPPMs) and those generated from biogeochemical ocean general
circulation models
(BOGCMs) represent a key resource for biogeochemical and ecological studies
at global as well as
regional scales. Calibration and validation of these PP models are not
straightforward, however,
and comparative studies show large differences between model estimates. The
goal of this paper is
to compare PP estimates obtained from 30 different models (21 SatPPMs and 9
BOGCMs) to a
tropical Paci fic PP database consisting of ~1000
14C
measurements spanning more than a decade
(1983–1996). Primary findings include: skill varied significantly
between models, but performance
was not a function of model complexity or type (i.e. SatPPM vs. BOGCM);
nearly all models underestimated the observed variance of PP, specifically yielding too
few low PP (<0.2 g Cm-2
d-1)
values; more than half of the total root-mean-squared model–data differences
associated with the
satellite-based PP models might be accounted for by uncertainties in the
input variables and/or the
PP data; and the tropical Pacific database captures a broad scale shift from
low biomass normalized
productivity in the 1980s to higher biomass-normalized productivity in the
1990s,
which was not successfully captured by any of the models. This latter result
suggests that
interdecadal and global changes will be a significant challenge for both
SatPPMs and BOGCMs.
Finally, average root-mean-squared differences between in situ PP data on
the equator at 140°W and PP estimates from the satellite-based productivity models were 58% lower
than analogous
values computed in a previous PP model comparison 6 years ago. The success
of these types of
comparison exercises is illustrated by the continual modification and
improvement of the
participating models and the resulting increase in model skill.
Mansfield, K L., and Vincent S Saba, et al., November 2009: Satellite tracking reveals a dichotomy in migration strategies among juvenile loggerhead turtles in the Northwest Atlantic. Marine Biology, 156(12), DOI:10.1007/s00227-009-1279-x. Abstract
Few data are available on the movements and behavior of immature Atlantic loggerhead sea turtles (Caretta caretta) from their seasonal neritic foraging grounds within the western north Atlantic. These waters provide developmental habitat for loggerheads originating from several western Atlantic nesting stocks. We examined the long-term movements of 23 immature loggerheads (16 wild-caught and seven headstart turtles) characterizing their seasonal distribution, habitat use, site fidelity, and the oceanographic conditions encountered during their migrations. We identified two movement strategies: (1) a seasonal shelf-constrained north–south migratory pattern; and (2) a year-round oceanic dispersal strategy where turtles travel in the Gulf Stream to the North Atlantic and their northern dispersal is limited by the 10–15°C isotherm. When sea surface temperatures dropped below 20°C, neritic turtles began a migration south of Cape Hatteras, North Carolina (USA) where they established fidelity to the waters between North Carolina’s Outer Banks and the western edge of the Gulf Stream along outer continental shelf. Two turtles traveled as far south as Florida. Several turtles returned to their seasonal foraging grounds during subsequent summers. Northern movements were associated with both increased sea surface temperature (>21°C) and increased primary productivity. Our results indicate strong seasonal and interannual philopatry to the waters of Virginia (summer foraging habitat) and North Carolina (winter habitat). We suggest that the waters of Virginia and North Carolina provide important seasonal habitat and serve as a seasonal migratory pathway for immature loggerhead sea turtles. North Carolina’s Cape Hatteras acts as a seasonal “migratory bottleneck” for this species; special management consideration should be given to this region. Six turtles spent time farther from the continental shelf. Three entered the Gulf Stream near Cape Hatteras, traveling in the current to the northwest Atlantic. Two of these turtles remained within an oceanic habitat from 1 to 3 years and were associated with mesoscale features and frontal systems. The ability of large benthic subadults to resume an oceanic lifestyle for extended periods indicates plasticity in habitat use and migratory strategies. Therefore, traditional life history models for loggerhead sea turtles should be reevaluated.
Suryan, R M., and Vincent S Saba, et al., April 2009: Environmental forcing on life history strategies: Evidence for multi-trophic level responses at ocean basin scales. Progress in Oceanography, 81(1-4), DOI:10.1016/j.pocean.2009.04.012. Abstract
Variation in life history traits of organisms is thought to reflect adaptations to environmental forcing occurring from bottom-up and top-down processes. Such variation occurs not only among, but also within species, indicating demographic plasticity in response to environmental conditions. From a broad literature review, we present evidence for ocean basin- and large marine ecosystem-scale variation in intra-specific life history traits, with similar responses occurring among trophic levels from relatively short-lived secondary producers to very long-lived apex predators. Between North Atlantic and North Pacific Ocean basins, for example, species in the Eastern Pacific exhibited either later maturation, lower fecundity, and/or greater annual survival than conspecifics in the Western Atlantic. Parallel variations in life histories among trophic levels also occur in adjacent seas and between eastern vs. western ocean boundaries. For example, zooplankton and seabird species in cooler Barents Sea waters exhibit lower fecundity or greater annual survival than conspecifics in the Northeast Atlantic. Sea turtles exhibit a larger size and a greater reproductive output in the Western Pacific vs. Eastern Pacific. These examples provide evidence for food-web-wide modifications in life history strategies in response to environmental forcing. We hypothesize that such dichotomies result from frequency and amplitude shifts in resource availability over varying temporal and spatial scales. We review data that supports three primary mechanisms by which environmental forcing affects life history strategies: (1) food-web structure; (2) climate variability affecting the quantity and seasonality of primary productivity; (3) bottom-up vs. top-down forcing. These proposed mechanisms provide a framework for comparisons of ecosystem function among oceanic regions (or regimes) and are essential in modeling ecosystem response to climate change, as well as for creating dynamic ecosystem-based marine conservation strategies.
Wallace, B P., and Vincent S Saba, March 2009: Environmental and anthropogenic impacts on intra-specific variation in life history traits and population trends of leatherback turtles: Opportunities for targeted research and conservation. Endangered Species Research, 7(1), DOI:10.3354/esr00177. Abstract
Intra-specific variation in life history traits and/or population trends provides ‘natural experiments’ to identify causes of observable differences among populations of organisms. Geographically widespread marine species, for example, can experience variation in both environmental and anthropogenic impacts across their ranges that can differentially influence expression of life history traits and population dynamics in separate populations. For example, body size and reproductive output differences among geographically separate, conspecific populations of leatherback turtles Dermochelys coriacea have been linked to variations in environmentally driven resource availability, which differentially affect the resilience of leatherback populations to anthropogenic pressures. Specifically, differences in life history traits and population trends among breeding populations of leatherbacks that forage in the eastern Pacific versus Atlantic Ocean reflect the variable nature of resource availability in the eastern Pacific. These environmentally driven life history differences have contributed to divergent population responses to anthropogenic sources of mortality. In this review, we provide a synoptic view of this body of research and conclude with strategic recommendations for future research and conservation initiatives. This approach has implications for other widely distributed marine species with variations in life history traits that make them more susceptible to human-driven population declines.
Nesting populations of leatherback turtles (Dermochelys coriacea) in the Atlantic and western Indian Oceans are increasing or stable while those in the Pacific are declining. It has been suggested that leatherbacks in the eastern Pacific may be resource limited due to environmental variability derived from the El Niño Southern Oscillation (ENSO), but this has yet to be tested. Here we explored bottom-up forcing and the responding reproductive output of nesting leatherbacks worldwide. We achieved this through an extensive review of leatherback nesting and migration data and by analyzing the spatial, temporal, and quantitative nature of resources as indicated by net primary production at post-nesting female migration and foraging areas. Leatherbacks in the eastern Pacific were the smallest in body size and had the lowest reproductive output due to less productive and inconsistent resources within their migration and foraging areas. This derived from natural interannual and multidecadal climate variability together with an influence of anthropogenic climate warming that is possibly affecting these natural cycles. The reproductive output of leatherbacks in the Atlantic and western Indian Oceans was nearly twice that of turtles in the eastern Pacific. The inconsistent nature of the Pacific Ocean may also render western Pacific leatherbacks susceptible to a more variable reproductive output; however, it appears that egg harvesting on nesting beaches is their major threat. We suggest that the eastern Pacific leatherback population is more sensitive to anthropogenic mortality due to recruitment rates that are lower and more variable, thus accounting for much of the population differences compared to Atlantic and western Indian turtles.
Read More: http://www.esajournals.org/doi/abs/10.1890/07-0364.1
Saba, Vincent S., et al., May 2008: An oceanographic context for the foraging ecology of eastern Pacific leatherback turtles: Consequences of ENSO. Deep-Sea Research, Part I, 55(5), DOI:10.1016/j.dsr.2008.02.006. Abstract
We analyzed some of the primary biological and physical dynamics within the eastern Pacific leatherback turtle (Dermochelys coriacea) migration area in relation to ENSO and leatherback nesting ecology at Parque Nacional Marino Las Baulas (PNMB), Costa Rica. We used data from remote sensing to calculate resource availability via a net primary production (NPP) model, and to analyze the physical dynamics of the migration area via sea surface temperature fronts. Within the migration area, NPP north of 15°S was highly governed by interannual variability as indicated by the Multivariate ENSO Index while south of 15°S, production had a more seasonal signal. Nesting peaks of leatherbacks at PNMB were associated with cool, highly productive La Niña events and with large-scale equatorial phytoplankton blooms encompassing 110°W that were induced by iron enrichment following the termination of El Niño events. Resource availability in the northern migration area (eastern equatorial Pacific) appeared to determine the nesting response for the population at PNMB, Costa Rica. We suggest that ENSO significantly influences the nesting ecology of leatherbacks at PNMB because the majority of the population consists of pelagic foragers that strictly rely on the eastern equatorial Pacific for prey consumption prior to the nesting season. Coastal foragers may be a minority in the population because of high mortality rates associated with coastal gillnet fisheries along Central and South America.
Santidrián Tomillo, Pilar, and Vincent S Saba, et al., October 2008: Effects of Illegal Harvest of Eggs on the Population Decline of Leatherback Turtles in Las Baulas Marine National Park, Costa Rica. Conservation Biology, 22(5), DOI:10.1111/j.1523-1739.2008.00987.x. Abstract
Within 19 years the nesting population of leatherback turtles (Dermochelys coriacea) at Parque Nacional Marino Las Baulas declined from 1500 turtles nesting per year to about 100. We analyzed the effects of fishery bycatch and illegal harvesting (poaching) of eggs on this population. We modeled the population response to different levels of egg harvest (90, 75, 50, and 25%) and the effect of eradicating poaching at different times during the population decline. We compared effects of 90% poaching with those of 20% adult mortality because both of these processes were present in the population at Las Baulas. There was a stepwise decline in number of nesting turtles at all levels of egg harvest. Extirpation times for different levels of poaching ranged from 45 to 282 years. The nesting population declined more slowly and survived longer with 20% adult mortality (146 years) than it did with 90% poaching (45 years). Time that elapsed until poaching stopped determined the average population size at which the population stabilized, ranging from 90 to 420 nesting turtles. Our model predicted that saving clutches lost naturally would restore the population when adult mortality rates were low and would contribute more to population recovery when there were short remigration intervals between nesting seasons and a large proportion of natural loss of clutches. Because the model indicated that poaching was the most important cause of the leatherback decline at Las Baulas, protecting nests on the beach and protecting the beach from development are critical for survival of this population. Nevertheless, the model predicted that current high mortality rates of adults will prevent population recovery. Therefore, protection of the beach habitat and nests must be continued and fishery bycatch must be reduced to save this population.
Saba, Vincent S., et al., April 2007: The effect of the El Niño Southern Oscillation on the reproductive frequency of eastern Pacific leatherback turtles. Journal of Applied Ecology, 44(2), DOI:10.1111/j.1365-2664.2007.01276.x. Abstract
1) Pacific leatherback turtle Dermochelys coriacea populations have been declining precipitously. It has been suggested that fishery-associated mortality is the leading factor causing the decline; however, the sensitivity of leatherbacks to climate variability relative to their population ecology is unknown.
2) We investigated the effects of interannual climate variability, as governed by the El Niño Southern Oscillation (ENSO), on leatherback nesting ecology. We used equatorial Pacific sea surface temperature (SST) anomaly data over various time scales derived from both moored buoys and remote satellites as signals of ENSO. We then incorporated these data into a remigration probability model for the largest nesting population of eastern Pacific leatherbacks at Parque Nacional Marino Las Baulas (PNMB), Costa Rica.
3) Our results showed that nesting females of PNMB exhibited a strong sensitivity to ENSO, as reflected in their nesting remigration probabilities. Cool La Niña events corresponded with a higher remigration probability and warm El Niño events corresponded with a lower remigration probability.
4) We suggest that productivity transitions at leatherback foraging areas in the eastern equatorial and south-eastern Pacific in response to El Niño/La Niña events result in variable remigration intervals and thus variable annual egg production. This phenomenon may render the eastern Pacific leatherback population more vulnerable to anthropogenic mortality than other populations.
5) Synthesis and applications. Physical indices of environmental variation can be used to estimate the probability of leatherbacks remigrating to nest at PNMB. This type of modelling approach can be extremely useful for understanding the effects of climatic variation on the population dynamics of sea turtles. Our remigration probability model can be applied to any monitored sea turtle nesting population where nesting site fidelity and beach monitoring coverage remains high. This modelling approach can help nesting beach monitoring programmes forecast remigrant numbers based on prior climate data, and can further quantify anthropogenic mortality by validating survival estimates.
An oil spill in February 2000 at the John Heinz National Wildlife Refuge in southeastern Pennsylvania affected four species of freshwater turtles including painted turtles (Chrysemys picta), snapping turtles (Chelydra serpentina), red-eared slider turtles (Trachemys scripta), and red-bellied turtles (Pseudemys rubriventris). In the summer and fall of 2000, there were no differences in survival, home range, and temperature preference of 16 oil exposed/rehabilitated (OER) turtles, 18 possibly exposed (PE) turtles, and 32 non-exposed (NE) turtles as measured with temperature sensitive radio transmitters. Post-release mortality or transmitter loss was not correlated to oil exposure (OER=25%, PE=22%, NE=31%). There were no statistically significant differences in home range minimum convex polygon area, (0.28
