NOAA scientists develop simple model to predict global patterns in the energy available to marine resources
On November 24, 2009 scientists from NOAA’s Geophysical Fluid Dynamics
Laboratory (GFDL) published a study on global patterns in the transfer
of energy from phytoplankton to mesozooplankton. The production of
organic matter from light and nutrients by phytoplankton, referred to as
primary production, supports nearly all ocean life. Mesozooplankton
consume phytoplankton and smaller zooplankton and act as a conduit
within the marine food web for primary production to reach critical
living marine resource (e.g., harvested fish and endangered species).
The study combined a marine ecosystem model with a broad synthesis of
published in-situ, laboratory, and satellite data to reveal and explain
global-scale relationships between primary production and
Figure: The top-panel shows global estimates of the ratio of
mesozooplankton production to primary production (referred to as the
z-ratio) estimated from a combination of in-situ and laboratory
mesozooplankton data, and satellite-derived primary production.
Critical zooplankton biomass data for this compilation was provided by NOAA’s global plankton database “COPEPOD”.
The bottom panel shows model-derived z-ratios. Both the estimates in
the top panel and the model-derived estimates have uncertainties and the
observed zooplankton biomass can be highly patchy. However, the
critical similarity is the order-of-magnitude shift between unproductive
sub-tropical gyres (large blue patches), and highly productive regions
near the coast and in upwelling regions along the equator.
It was found that, on average, only 1-4% of primary production by
phytoplankton is translated to mesozooplankton production in relatively
unproductive marine ecosystems such as sub-tropical gyres. This compares
with 10-20% in highly productive marine ecosystems such as coastal
upwelling systems (see figure). An important implication of this
finding is that climate-driven fractional changes in primary production
may yield larger fractional changes in mesozooplankton production.
Since mesozooplankton are important food items for fish, these changes
may also have pronounced impacts on fisheries production.
The simple model developed in this study represents a first step in
directly linking climate models of the physical climate system to models
that predict long term changes in fish stocks resulting from climate
change. The simple model is presently being integrated into GFDL’s Earth
System Model, where it will provide a means of predicting the impacts
of climate variability and change on the energy available to marine
Stock, Charles A., and John P Dunne, January 2010: Controls on the ratio of
mesozooplankton production to primary production in marine ecosystems.
Deep-Sea Research, Part I, 57(1), doi:10.1016/j.dsr.2009.10.006.
Click here to access the manuscript that is in press.
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