DISTRIBUTION OF COMMON BIVALVES IN THE POLISH COASTAL ZONE OF THE BALTIC SEA

Abstract

The populations of common Baltic bivalves Macoma balthica, Mytilus edulis and Cerastoderma glaucum were studied in the Polish coast (up to 4 Nm), both in estuary and open coastal zones of the Middle Pomerania as well as in the Puck Bay and the Gulf of Gdańsk (up to 2 Nm). The following parameters were investigated: density of the bivalves and environmental conditions (distance from the shore, substrate type, coast type, depth). Relationships between environmental conditions and abundance of the consecutive bivalve species were analysed with the help of ordination method (redundancy analysis RDA) and multivariate regression trees (MRT). RDA analysis indicated that C. glaucum density depended mainly on the localisation along the coast while M. edulis occurrence was governed by the distance from the shore and depth. Only density of M. balthica depended evenly on all the environmental parameters. MRT analysis revealed that the main factors influencing the distribution of bivalves were sediment granularity and depth.

Key words: Polish Baltic coastal zone, bivalves, density, MRT, RDA