COMPOSITION, PRODUCTIVITY AND NUTRIENT CHEMISTRY OF A COASTAL OCEAN PLANKTONIC FOOD-WEB

A 3 year field study was conducted to investigate patterns, magnitude and variability of primary production; the abundance, biomass and comp osition of producers and consumers; and the relative importance of phy sical and chemical variables associated with these parameters, in inne r shelf waters of the South Atlantic Bight. Discrete interval, time se ries and continuous measurements were made along a transect and at two process-oriented stations during summer and winter 1985-88. A quasi-p ermanent density front constrains low salinity (<34 parts per thousand ) waters to within ca 10 km of the coast. These waters contain abundan t autotrophic and heterotrophic communities. Primary production is hig h, 6-7 x 10(2) gC m-2 year-1, and is apparently subsidized by rapid nu trient recycling in the water column, sediments and adjacent salt mars hes. Silicate is notable for its excess concentrations year-round and supports substantial diatom productivity. Correlation analyses suggest that Si strongly influences phytoplankton biomass, whereas growth rat es are coupled to availability of light and NH4. Despite evidence of c onsiderable variability in primary production over daily to interannua l scales, plankton biomass is relatively constant. Experimental studie s suggest a tight coupling between primary producers and microconsumer s, and support the hypothesis that substantial fractions of primary an d secondary production are recycled within the water column.