Nitrogen dynamics in lower Narragansett Bay. II. Phytoplankton uptake, depletion rates of nitrogenous nutrient pools, and estimates of ecosystem remineralization

Phytoplankton nitrogen demand in lower Narragansett Bay, RhodeIsland, measured during the winter-spring of 1977–78 andsummers of 1978 and 1979, is compared with estimates of zooplanktonand the benthic nitrogen remineralization drawn from the resultsof ekperimental field studies. Measured uptake rates would generallylead to the depletion of available nitrogenous nutrient stockswithin hours, and usually exceeded estimates of benthic pluszooplankton remineralization. Additional estimates of nitrogeninputs from sewage and riverine sources appear insufficientto make up the difference. The discrepancy lends support tothe paradigm that water column remineralization by microheterotrophsmay supply much, if not most, of the nitrogen needs of coastalphytoplankton.