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Determinations were made of the contents of heavy metals (Mn, Fe, Cu, Zn, Pb and Cd) in the soft tissues and shells of the mussels Anodonta woodiana and Dreissena polymorpha which inhabit the discharge channels of the Pątnów and Konin power plants and the heated Konin lakes. The studied mussels contained higher concentrations of metals, especially of Cu, Zn, and Pb, than did mussels of the family Unionidae and D. polymorpha which occur in fresh water reservoirs that are not polluted by dust fall-out from power plants. In the environments which were compared, the adult mussels of the genus Anodonta cumulate metals in greater concentrations than do D. polymorpha; this is due to their life span which is at least twice as long.
The bio-morphological (shells, weight) and genetic (izoenzymes) variations were studied in a new mussel species to Poland, Anodonta woodiana, which occurs in the heated Konin lakes system. The mussels were collected from three environments - the lenitic lake zones, the water flow-through channel and the lotic areas of a man-made reservoir. Significant bio-morphological differences between the shells of various populations were determined by environmental conditions. The high degree of genetic similarity of the mussels dictated their inclusion within the same species.
The individual growth rate of the Chinese mussel population of the genus Anodonta which inhabits the warm channels of the heated Konin lakes system was analysed. Four size and age groups were distinguished. The allometric growth of shells during early developmental stages and the isometric growth of 6 - 21 cm shells were ascertained. Three to five years old individuals were typical of the Anodonta woodiana found in the Konin channels. The theoretical maximal life span of the mussels is 10 years, while the maximal shell length is 21 cm.
The zebra mussel, Dreissena polymorpha (Pall.) inhabits various live and dead substrates of the lotic and lentic zones of the heated Konin lakes. Occurring at depths from 20 cm to 3.5 m, this species showed a preference for Unionidae mussels as a substrate. Aggregations of D. polymorpha varied in number from 2 000 to 2 million individuals per m², while the biomass reached more than 12 kg m⁻² . The most numerous were one year old mussels 5 mm in length, which comprised from 60 - 80% of the population. In the preliminary cooling reservoir, newly settled post-veligers comprised as much as 94% of the total of D. polymorpha numbers. The largest mussels did not exceed 35 mm. Aggregations of D. polymorpha contained 49 invertebrate taxa, and the most frequently occurring subdominants were from the Corophidae and Gammaridae families. The diel destruction of organic matter in the aggregations varied between 20 and 370 kJ m⁻² , depending on the number of animals and their biomass. The turnover coefficient (R/B) in the heated zones was 1.5 times higher, on average, than in the non-heated parts of the system.
The Chinese mussel Anodonta woodiana was accidentally introduced into the heated Konin lakes system in the mid 1980's. It inhabits the littoral of the five lakes of the complex, a preliminary cooling reservoir, and most of the discharge and inflow channels. It prefers habitats of an increased flow velocity and of rather high temperature. It has been found to be the dominant benthic species in most of the habitats. At times, its biomass exceeded 10 kg m⁻² , and it numbered more than 40 individuals per m².
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