The effects of bivalves (Mercenaria mercenaria, Mya arenaria, andGeukensia demissa) on zooplankton composition

摘要

To examine whether predation by hard clams, ribbed mussels, or soft clams alters the composition of the heterotrophic plankton community, we conducted experiments at two estuarine locations on Long Island, NY. Experimental treatments were created by placing locally collected M. mercenaria, M. arenaria or G. demissa in 57-1 buckets (n = 3 for each species) with ambient seawater. Nutrients (nitrate and phosphate) were added to all buckets to allow nutrient replete growth of phytoplankton in both control (n = 3) and experimental treatments. Water samples for chlorophyll a, brown tide, nanoplankton and bacteria, microplankton, and mesoplankton abundance were taken at the beginning and end (after 3 hours) of each experiment. Based on chlorophyll a disappearance, it was found that G. demissa had a clearance rate 4.7 times higher than the clearance rate for M. arenaria, and 3.9 times higher than the clearance rate for M. mercenaria. Preliminary data also suggest that there was a difference in susceptibility to bivalve predation among the various components of the heterotrophicplankton assemblage.