BENTHIC MICROALGAL PRODUCTION AT STELLWAGEN BANK, MASSACHUSETTS BAY, USA

Benthic microalgal chlorophyll a and production were measured at 3 sit es at Stellwagen Bank, a cold temperate continental shelf habitat in M assachusetts Bay, USA, during August 1991. Benthic microalgal chloroph yll a averaged 39.8 Mg M-2, vs average integrated phytoplankton chloro phyll a of 25.9 mg m-2. Gross benthic microalgal production, measured by oxygen exchange in clear and opaque benthic chambers, averaged 20.9 mg C m-2 h-1. This production was supported by average daily light fl uxes to the bottom that never exceeded 1 % of surface incident radiati on and were as low as 4.7 muE M-2 s-1. These results indicate that ben thic microalgal production can be spatially extensive and quantitative ly important in continental shelf ecosystems.