Benthic-pelagic coupling in northern Gulf of Mexico estuaries: do benthos feed directly on phytoplankton?

Abstract

Few of the dominant benthic taxa of the northern Gulf of Mexico feed directly on phytoplankton. Rather, most of them feed on near-bottom seston and detritus. This is in contrast to models for Chesapeake Bay and San Francisco Bay. We found that detfitivores represented over 80% of the macrobenthic organisms and over 90% of the biomass in Gulf of Mexico estuaries. The paucity of benthos that consumed phytoplankton led us to hypothesize that macrobenthos in Gulf of Mexico estuaries had less effect on plankton communities than was documented in U.S. east coast and west coast estuaries, where benthic communities consumed much of the watercolumn production. We provided as evidence gut-contents analyses of dominant taxa, the feeding morphology of suspension feeders (especially clams), and the lack of vertical mixing or strong turbulent flow that is necessary for benthos to remove substantial portions of the phytoplankton.