SPATIAL VARIATION IN GROWTH OF MACOMA-BALTHICA AND MYA ARENARIA (MOLLUSCA, BIVALVIA) IN RELATION TO ENVIRONMENTAL GRADIENTS IN THE POMERANIAN BAY (SOUTHERN BALTIC SEA)

This paper deals with spatial variations in individual growth rates of Macoma balthica L. and Mya arenaria L. in the shallow sublittoral zon e of the Southern Baltic Sea. Field sampling was carried out in the Po meranian Bay between 6 and 30 m depth in 1993 and 1994. Growth of M. b althica and M. arenaria was studied by the analysis of annual growth c hecks. Compared to full marine environments, growth rates were conside rably lower in this brackish area (salinity about 8 PSU). Growth of M. balthica correlated significantly with phytoplankton concentration. G rowth of M. arenaria was assumed to be negatively affected by intensiv e physical disturbances. It is supposed that reduced salinities affect the growth of M, arenaria more than that of M balthica.