ABSTRACT
Food chain dynamics in waters off the southeast United States within the Southeast Shelf ecosystem are principally controlled by oceanographic processes occurring at the shelf break and at the coastal boundary. At the shelf break, upwelling along the Gulf Stream front is the dominant source of new plant nutrients sustaining plankton production. Upwelling dynamics determine the temporal and spatial attributes of plankton production on the outer shelf.
On the inner southeastern shelf, a coastal salinity front delineates the boundary between a 10-20-km wide zone of productive coastal waters from waters just seaward of the front which have very low productivity. Plankton dynamics of coastal waters shoreward of the front are unusual in that primary production is very high throughout the year, whereas concentrations of inorganic nitrogen (NH4, NO3 + NO2) are quite low. New N sources, such as rivers, provide only a small fraction of N required to sustain the observed rates of production. These observations imply that recycled N is the most important source on the inner shelf, and that photosynthesis and respiration are very tightly coupled throughout the year.
