Planktonic Ecosystem Models: Perplexing Parameterizations and a Failure to Fail
Chapman Lecture Series
Dr. Peter Franks
Scripps Institution of Oceanography
Almost every planktonic ecosystem model being used today is based upon
the same fundamental processes: Michaelis-Menten uptake of nutrients by
the phytoplankton, and a saturating grazing response by the
zooplankton. In tracing the history of the use of Michaelis-Menten
kinetics in ecosystem models, the question arises whether this is the
most appropriate way to represent nutrient uptake of a diverse
phytoplanktonic community. While this nonlinear form may be a good
representation of an enzyme, it is not clear that a changing community
would necessarily show such a relationship of uptake rate with nutrient
concentration. Furthermore, the way we have been using ecosystem models
may be limiting our ability to understand the dynamics of marine
ecosystems. Given that models are hypotheses, we should spend more time
trying to reject them than trying to make them fit our data. Testing a
suite of distinct models - hypotheses - may lead to stronger inferences
about ecosystem structure and function. This testing requires
sufficient data, particularly measurements of rates (e.g., nutrient
uptake, grazing). Future research would benefit from a more intimate
interaction and iteration between modeler and field scientist, models
and data.
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