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Abstract

The study included mesotrophic Lake Piaseczno, located in the Łęczna-Włodawa Lake District. The aim of the study was to evaluate changes of water vegetation of a mesotrophic lake subjected to strong recreational pressure. Specifically we sought to better understand which natu-ral landscapes and anthropogenic developments stimulate or impede macrophyte development and spread. The study was conducted in July in 1997, 2007 and 2017 in three transects: the peat-bog (northern part of the lake), the recreational area (southeast part) and the agricultural area (east). The phytolittoral zone was analyzed from the shoreline to the maximum range of macrophytes occurrence. The study included all groups of macrophytes. Macrophytes in the mesotrophic Lake Piaseczno are still subjected to successive changes. Clearly increased diversity among emergent macrophytes, while a group of submerged macrophytes decreased. The largest changes among analyzed groups of macrophytes occurred in recreational and agricultural transects. Macrophytes have increased the range of occurrence, which may be due to hydrological changes associated with raising the overall water level, thus with increasing the area of the littoral. Impoverishment of diversity among elodeids shows the processes associated with the increase in Lake trophy.
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Abstract

The aim of this study was to assess the anisakid nematode distribution pattern in the fish collected from the South Shetland Islands . A total of 32 fish species were examined for the presence of nematodes in 1978, 1979, 1981 and 2007/2008. The fish were caught off the South Shetland Islands ( Elephant Island , Shishkov Island and in Admiralty Bay – King George Island ). Three genera of L3 larval nematodes were identified: Anisakis sp., Contracaecum spp. and Pseudoterranova decipiens. The infection level was higher on the shelf around the islands than in Admiralty Bay . This is explained by a higher abundance of the final hosts in the region. A comparison of the infection data from 1978/79 and 2007/2008 with data from 1994/96 (Palm et al. 1998, 2007) was done. The parameters of infection of Notothenia coriiceps and Lepidonotothen nudifrons by Pseudoterranova decipiens were decreasing within the 30 years period.
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