Heterotrophic activity associated with particulate size fractions in a Spartina alterniflora salt-marsh estuary, Sapelo Island, Georgia, USA, and the continental shelf waters

Abstract

An investigation was undertaken to determine the distribution and activity of the heterotrophic microplankton associated with particles from a Georgia salt marshestuarine ecosystem to the western edge of the Sargasso Sea. Heterotrophic activity was determined by the uptake of 14C-glucose. More than 80% of the activity was associated with detritus greater than 3 μm in creek, river and coastal (within 4 km of shore) waters. In the Gulf Stream, approximately 80% of the heterotrophic activity was in the fraction less than 3 μm. In the estuary, total heterotrophic activity fluctuated with the tides; the greatest activity occurred near low ebb tide at all locations. The lowest activity was measured at slack low and high tides. In creek water most of the heterotrophic activity was associated with particles between 14 and 180 μm, whereas in coastal waters (less than 4 km from shore) most of the activity was in the fraction greater than 180 μm.