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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.
Polychlorinated hydrocarbons are convenient indicators of environmental pollution. The aim of this study was to determine the presence of p,p′-DDT and its metabolites (p,p′-DDE and p,p′-DDD) and γ-HCH and PCBs in: the dorsal muscles of 3 most important fish species (cod, herring, and flounder), in blue mussel, and in the bottom sediments off the coast of the south-western Baltic Sea. The analyses were carried out using the method of gas chromatography. The presence of all analysed compounds was detected in the samples studied. The highest concentrations of polychlorinated hydrocarbons in the bottom sediments were stated at the coast of Kiel, while the lowest-in the Świnoujście area. In blue mussels no such significant differences in the content levels of the analysed compounds were observed. The muscles of herring demonstrated the highest content of ΣDDT and PCBs. The present results will constitute a contribution to the knowledge on the presence of polychlorinated hydrocarbons in the marine environment of the south-western Baltic Sea.
A population of Mya arenaria was studied in the Polish coastal zone (up to 3 nautical miles) of the Baltic Sea in the open coast of Polish Middle Pomerania. Abundance, wet biomass, and the frequency of Mya were determined in the coastal waters, including estuaries of the Parseta, Wieprza, Słupia, Łupawa, and Łeba rivers and Władysławowo. The frequency (F) of Mya in the open coast of the Middle Pomerania amounted to 19.5%. The abundance of Mya, in the coastal zone surveyed, ranged from 0 to 265 specimens per m2 of the bottom (x¯ = 10.4 spec. m–2). Wet biomass of this bivalve ranged from 0 to 25.52 gww m-2 (x¯ = 1.56 gww m-2). Apparently Mya arenaria has found better conditions for living and development in the central of the Middle Pomerania coast. The abundance of this mollusc in the estuary of Słupia (Ustka) was 100-fold higher than in the estuary of Wieprza (Darłowo) and Łupawa (Rowy) and the wet weight was 11-fold higher, respectively. Mya arenaria plays an important role in the monitoring of benthos of the Baltic Sea, constitutes a food base of animals (fish), and takes part in the process of purification of waters of the coast stretch studied (biofiltration, biosedimentation).
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