The Swelinia Stream is one of several streams discharging into the Gulf of Gdansk in the Sopot coastal zone. The stream is inhabited by a great variety of benthic diatom flora, among which freshwater alkaliphilous diatoms, typical of eutrophic waters, are predominant. The $-meso- and $/'-mesosaprobic diatoms typical of waters moderately polluted by organic matter prevail within the saprobic groups. Xenosaprobic diatoms occur only occasionally. Quantitative analysis of diatoms, classified according to their saprobic requirements into taxa sensitive, tolerant and resistant to organic pollution, has shown that the water quality is deteriorating downstream. Evidence for this was the absence of class I water in the stream's lower course; the usual quality level is class II, which may even drop to class III in the summer and autumn.
This aim of this study was to test the applicability of diatom indices developed in Europe for monitoring coastal stream waters in northern Poland. Water, sediment, and diatom samples were taken from streams in the resort town of Sopot that discharge into the Gulf of Gdansk. The physical and chemical measurements taken during the sampling period indicated that the purity of the stream waters had improved, and recently they were classified as I class water purity. This is contrasted by the studied waters? diatom communities, which were dominated by eutraphentic taxa. High abundances of -mesosaprobic and -mesosaprobic taxa were recorded at most of the sites. Diatom indices developed for water quality surveillance were calculated with the Omnidia3 database software. Redundancy analyses (RDA), an ordination technique, was used to determine the indices that best correspond to water pollution in coastal streams. The results of the present study indicate that the pollution indices that follow can be applied successfully to monitor flowing freshwaters in the Gulf of Gdansk area in northern Poland: IDAP (Indice Diatomique Artois-Picardie); SPI (Specific Polluosensivity Index); EPI-D (Eutrophication/Pollution Index based on Diatoms), which integrates organic pollution, eutrophication, and mineralization.
The subject of the study were the benthic diatom communities of the Puck Bay littoral zone. Samples of the sediments were taken from sites situated near the sewage treatment plant at Swarzewo from June 1998 to May 1999. The analysis of the species composition and the relative percentages of the diatom indicative groups were used to evaluate water quality. The following ecological factors were taken into consideration: salinity, trophic status and saprobity. Following Lange?Bertalot (1979), water quality was classified based on a 5-degree scale of saprobity. It was correlated to the percentages of the sensitive, tolerant and resistant diatoms taxa and their reaction to organic matter content. The water quality evaluation was tested with the diatom indices using Omnidia 3 software. The results of the diatom studies indicate that the dominating groups were the oligohalobous and mesohalobous taxa, which are characteristic of eutrophic waters and contain biogenic compounds, mainly nitrogen and phosphorus. The most abundant groups in the saprobic spectrum were the resistant (-mesosaprobic, polysaprobic) and tolerant (-mesosaprobic, /-mesosaprobic) diatoms, which are indicators of water purity class II (III), and in summer, predominantly class III. The comparison of the results of diatom analysis of the Puck Bay microphytobenthos obtained with the Lange?Bertalot (1979) method and the those acquired with Omnidia 3 software demonstrates the possibility of applying it to evaluate environmental status and assess polluted brackish waters.
The subject of the study was microphytobenthos in the sediments of the coastal zone of the Sopot sea-resort (the Gulf of Gdansk). 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.
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