The Solina–Myczkowce complex of reservoirs (SMCR) accounts about 15 % of the water storage in Poland. On the base of historical (2004–2006 years) data, the mass balance of nitrogen, phosphorus, total organic carbon and dissolved silicon were calculated. Large, natural affluents were the main source of the biogenic compounds in the studied ecosystem, delivering 90 % of TOC, 87 % of TN and 81 % of TP and DSi load. Moreover, results show that SMCR is an important sink for all the analysed biogenic elements. About 15–30 % of external loads were retained in the reservoir mainly in upper Solina. Due to the intensive processes of primary production, inorganic forms of nitrogen and phosphorus were mainly retained. Internal production of organic matter lead to an amount of the organic matter deposited in the sediments greater than was anticipated on the basis of the mass balance calculations. A constant load of dissolved silicon originating only from natural sources did not contribute to supplement deficits of Si present in the body of water in the reservoirs, promoting disturbances in N:C:P:Si ratios and another growth condition for other types of algae.

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There is a need to search for additional indicators allowing for more accurate identification of both the trophic status of waters as well as its chemical and biological consequences. The work detailed in this paper involved a preliminary analysis pertaining to the possibility of using an isotopic index in association with the values for trophic and saprobic indicators in describing a dam reservoir experiencing a far-reaching eutrophication. The water samples for the physicochemical analysis were collected from three sites along the axis of the dam reservoir in Rzeszów three times during the spring and summer of 2013. The results sustained the classification of the Reservoir's waters as hypertrophic, irrespective of the particular zone sampled. While phytoplankton blooms characterised by reference to the numbers of organisms per unit volume of water were also similar throughout the Reservoir, diversification in terms of taxonomic composition was to be noted, given the occurrence of cyanobacteria among the dominant diatoms in the area close to the dam. This presence was accompanied by enrichment of the Reservoir's suspended organic matter with carbon of the heavier 13 C isotope. On this basis, the δ 13 C isotopic index can be regarded as a potentially useful indicator allowing for more accurate identification of both the level and the nature of the ongoing trophic degradation in bodies of water.

The article reports the conducted analyses of certain chemical parameters characterising the sediments of Poland's Besko Reservoir. Specifically, determinations concerned the pH value, percentage organic matter (OM), total organic carbon (TOC), total nitrogen (TN), carbonates (CO 3 2-), total phosphorus (TP) and its fractions, as well as heavy metals (Fe, Al, Cr, Cu, Ni, Cd, Zn, Mn). The sediments have a slight alkaline reaction, with pH values correlating positively with the high content of carbonates. The sediments have low organic matter content, while organic carbon accounts for about 30% of OM. The values for the C:N ratio point to an allochthonous origin for organic matter. The analysis of phosphorus fractionation showed that inorganic phosphorus (IP) is predominant at every research station. The lowest percentage for a fraction was in turn obtained for NAIP. This testifies to a slight anthropogenic impact of the catchment area. The sediments can be classified as of the 2 nd purity class (according to PIG), due to their highest concentration of chromium. According to Müller's classification, the sediments can be classified as purity class 3 (i.e. with moderate contamination). The values noted for the EF coefficient confirm a very strong enrichment by chromium ions. In addition, chromium, copper, nickel and cadmium have a negative effect on aquatic organisms. The results show that the sediments can be used for example in building and maintaining hydraulic structures.

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