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Nine sites studied in the years 1997-1998 along the Upper Vistula course (from 10.9 to 336.7 km) were characterized based on the relative abundance of various net phytoseston (≥50 μm) predominant taxa. The prevalence of oligo-mesotraphentic diatoms (Fragilaria arcus (Ehr.) Cl.) and green alga Stichococcus sp. indicated generally pure waters at the montane sector of the river course. They were associated with betamesosaprobic taxa of chrysophytes (Kephyrion spp.) and rhodophytes (Audouinella sp.) characteristic for well oxygenated waters. Increased abundance of beta- and alpha-meso/polysaprobic indicators (Melosira varians Ag.) and those tolerant to organic pollution (Navicula lanceolata (Ag.) Ehr., Fragilaria ulna (Nitzsch) Lange-Bertalot) was noted on 36.6 km of the river indicating slight pollution. An increased trophic state, organic pollution and salinity level, expressed with the predominance of betamesosaprobic and eutraphentic diatoms (Aulacoseira granulata (Ehr.) Sim.) accompanied by desmids and euglenins (typical of beta-alpha-mesosaprobic zones) was observed on 45.7 km. The prevalence of Stichococcus sp. and Pediastrum spp. with increased share of alpha-meso/polysaprobic indicators (Stephanodiscus hantzschii Grun.) and polysaprobic (Nitzschia palea (Kütz.) W. Sm.) was found on 66.2 km. The sector between 117.6-185.2 km of the river course with strongly polluted waters of the worst quality, was characterized by augmented percentage share of cyanobacteria. Decreasing pollution level found on 248.2-336.7 km probably resulted from the dilution effect caused by montane Carpathian tributaries of the Vistula. The increase in beta-mesosaprobic and meso-eutraphentic indicators was related to Chlorococcales, which dominated over dense populations of cyanobacteria. Evaluation of water quality using net phytoseston groups with predominant indicator taxa, provides important information concerning the abundance of rapidly renewing Chlorococcales and potentially toxic cyanobacteria what is omitted in benthic diatom indices method.
Investigations on the Upper Vistula River course (from 11 to 337 km) in years 1997-1998 comprised: chemistry of water and sediments, indicators of water quality, such as bacteriological indices, metabolic activity of seston, phytoseston indicator taxa, algal growth test, zooseston assemblages, benthic diatom indices and occurrence of oligochaetes fauna. The pollution impact was reflected by distinct changes in chemistry of water and sediments, as well as by bacteriological indicators and alga growth test. No distinct changes have been noted in the structure of benthic diatom communities. Some improving tendency in the water quality was evident between 248-337 km of the river course, where the most tolerant to pollution taxa were partly replaced by less tolerant species. Some changes revealed an increase in numbers of beta-mesosaprobic and meso-eutraphentic Chlorococcales, which dominated over dense populations of cyanobacteria. Benthic animals assemblages indicated a decrease in pollution level between 248-337 km of the river course. In the case of zooseston no evident effect was observed. The sector of the river received on 95 km high load of chlorides from coalmines until last site on 337 km. Load of chlorides was constant, whereas their concentrations diminished. Nitrate concentration arose together with loadings. Phosphate concentrations were constant similarly to loadings, excluding site at 337 km of the rivercourse, where load arose. COD had similar pattern as chlorides. It seems to be better to operate on a greater number of specialised indices or parameters than mixed them into one, which might be confusing index.
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