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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.
Large-scale human-caused ecosystem disturbances may create new habitats. A good example may be long-lasting disturbances in five lakes (area from 148 to 379 ha, max. depth from 3 to 38 m) integrated into the cooling system of the power plants near Konin (52°17.8’– 52°23.3N, 18°14.4’–18°20.7’E, West Poland). In the middle of the 1990s Vallisneria spiralis began to colonize littoral zone of three of lakes and in 2002 it appeared also in fourth one. This species formed dense patches and almost completely displaced other submerged macrophytes. An aim of the study was to test a hypothesis that the appearance of rare and new for Polish fauna rotifer species might be a result of changes in littoral habitats of these lakes particularly caused by the invasion by Vallisneria spiralis. Studies were carried out in the years 2004–2006 on 3–6 littoral stations in each lake. Five-liter samples of water with macrophytes were collected from a center of macrophyte beds. Plankton (free-swimming) and epiphytic (connected with macrophyte surface) samples were elaborated separately. As many as 167 monogonont species were recorded during the three-years’ studies. From among them 6 species were new in Polish fauna. These were: Asplanchnopus hyalinus Harring, Beauchampia crucigera (Dutrochet). Lecane inopinata Harring & Myers, Lecane shieli Segers et Sanoamuang, Lecane undulata Hauer and Lepadella apsida Harring. The species are eurythermic or warm-stenothermic. Species new to the rotifer fauna of Poland were not numerous as they usually constituted less than 2% of the total density of rotifers. Thus, although the hypothesis that rare and new for Polish fauna rotifer species may appear in the littoral habitats of the heated Konin lakes was confirmed, it was also clear that the colonization of the habitats by rotifer invaders did not lead to their domination in the rotifer communities.
The aim of this paper was to identify the relationship between the degree of macrophyte cover on the lake bottom and the abundance and species richness of larva and juvenile stage assemblages. The analysis of the material verified the hypothesis that as the surface area of macrophyte cover increases so does the abundance, species richness, and diversity of fish aggregations. The investigations were conducted in the heated Lake Licheńskie in 2000-2003 during the period when underwater vegetation is at the height of development (June – September). The spatial differentiation of macrophyte occurrence had a significant impact on the occurrence and differentiation of the fry assemblages. It was confirmed that along with an increase in the macrophyte cover surface area there was also an increase in the species richness and diversity of juvenile fish assemblages. The locations that were most densely overgrown with vegetation had the highest fish biomass and individual weight. In littoral areas without macrophytes, abundant single-species concentrations of fish occurred. The bottom macrophyte cover did not have an impact on the numbers of fish.
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 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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