SEASONAL-VARIATION IN THE FILTRATION-RATES OF A SEMINATURAL MUSSEL BED IN RELATION TO SESTON COMPOSITION

In September 1988 a mussel bed, with a biomass of 1362 g ash-free dry weight.m2, was created in a concrete tank with a continuous supply of natural seawater. Measurements of particulate matter uptake by the mus sel bed were carried out monthly from December 1988 till December 1989 . Fluxes of suspended particulate matter, particulate organic carbon ( POC), particulate organic nitrogen (PON), particulate-organic phosphor us (POP) and chlorophyll-a, were significantly correlated with water c olumn concentrations. A control experiment showed that sedimentation d id not affect observed fluxes. Clearance rates of the mussel bed varie d between 0.4 and 2.7 m3.m-2.h-1. Seasonal variation in the filtration activity of the mussel bed could be attributed to changes in the comp osition of the suspended particulate matter: individual clearance rate s of the mussels were reduced in the period April-June, which coincide d with a bloom of Phaeocystis sp. Moreover, clearance rates decreased with increasing SPM concentrations, and showed a positive correlation with chlorophyll-a.