Diatoms as indicators of water pollution in the coast-al zone of the Gulf of Gdańsk (Southern Baltic Sea)

The subject of the study was microphytobenthos in the sediments of the coastal zone of the Sopot sea-resort (the Gulf of Gdask). Sediment samples were taken from 12 sites situated in the mouths of the streams and creeks and from the beach close to the sea, once a month from January to December 1998. The indicative groups of diatoms were the basis of the estimation of water quality, taking into consideration its salinity, trophic state and saprobity. The quality of water was classified according to Lange-Bertalot (1979). The results of the diatom studies indicate that the dominating groups were the oligo-halobous and mesohalobous taxa, chatacteristic of highly eutrophic waters. The most abundant groups were the resistant (poly-saprobic and '-mesosaprobic) and tolerant ($-mesosaprobic) diatoms, which are indicators of water quality class III in the coastal zone of the Sopot sea-resort.