A model has been developed to aid in understanding the effects of organic matter and nitrogen inputs from land on estuarine trophic flows and on the production of fisheries species. This model incorporates concepts of the structure of the trophic web and processing of allochthonous organic matter and inorganic nitrogen. The model predicts that differences in organic matter inputs among estuaries can have measurable effects on the amount and kinds of fish produced. For example, the model predicts a shift in the focus of fish production from the benthic to the pelagic zone as N inputs change from low quality organic matter to dissolved inorganic nitrogen. Total fish production predicted by the model is not a simple function of dissolved inorganic nitrogen input. Benthic-pelagic coupling an N recycling combine to make modeled fisheries production highest when there is an equal mixture of nutrients and organic matter.
This model illustrates how estuarine ecosystems may process nitrogen and has helped in the development of hypotheses about the ultimate fate of N. This model will be tested through a series of field measurements, and mesocosms and laboratory experiments in the next years.
Keywords: flow model, trophic web, organic matter, nutrients, fish production.