Seasonal Changes in Biodeposition and Grazing Potential of the Suspension Feeding Bivalve Mytilus trossulus

Benthic suspension feeders are very important in coupling and energy transfer between benthos and plankton. Hence, it becomes essential to know which factors regulate the feeding activity of suspension feeders. In an in situ experiment seasonal variability in the biodeposition of Mytilus trossulus was related to temperature, salinity, current velocity, total chlorophyll a (Chl a equivalent), and the biomass of phytoplankton species in the northern Baltic Sea. The biodeposition was explained by current velocity interacting with ambient Chl a and temperature. The biodeposition increased curvilinearly with ambient concentration of Chl a eq suggesting that the saturation reduction occurred above 10 ¿g Chl a eq l^-1. The biomass of benthic diatoms (Pennales) better described the biodeposition of M. trossulus than the other studied variables. The result suggests that a significant part of its diet consists of benthic microalgae. The population of M. trossulus could remove on an average less than 3% of phytoplankton stock daily and, hence, had a minor effect on phytoplankton populations in the study area.