DISTRIBUTION AND FILTRATION ACTIVITY OF THE ZEBRA MUSSEL, Dreissena polymorpha, IN THE GULF OF RIGA AND THE GULF OF FINLAND

Abstract

This paper gives an overview of the dispersion of the population of Dreissena polymorpha in the Gulf of Riga and the Gulf of Finland. The relationships between depth, sediment type, and biomass values of the species are described. Higher biomasses were found on stony bottoms at 5-7 m in the southeastern part of the Gulf of Riga. In order to estimate the impact of the species on the energy and matter flows the filtration rates of D. polymorpha were measured in the southern part of the Gulf of Riga. Higher filtration activity of D. polymorpha population coincides with the location of higher biomasses. Maximum population grazing rates reached 65 1 h-1 m-2 , the lowest values were around 0.005 1 h-1 m-2 .