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Abstract

The paper aimed to get the analysis of spatial horizontal distribution of summer phyto-plankton in a small and shallow lake (Głębokie, Western Polesie, CE Poland) in relation to wind conditions occurring during the research period. The study was conducted in 2011 from 5th of July to 5th of September with eight sampling dates between. Water was sampled in the littoral zone from the depth of 0.5 m in four sites situated in different and opposite to one another lake shores. We analyzed the phytoplankton abundance by the way of chlorophyll a determination as well as the community taxonomic structure. Our research revealed that: a) the direction of the wind, which occurred during sampling might have an important role in the horizontal distribution of planktonic algal biomass within the lake; b) the geomorphology of lake surroundings probably mitigated the influence of wind on phytoplankton distribution; c) even weak or mild wind may influence phytoplankton horizontal differentiation.
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Abstract

Dynamic climate changes have become noticeable in recent decades, especially in the vulnerable region of the West Antarctic. The relatively simple food web of this area relies on krill – Euphausia superba . Presumably, as a result of climatic fluctuations, a de− crease in the number of this crustacean has been recorded, followed by an increase in the population of the gelatinous zooplankter Salpa thompsoni . In the research presented herein, population and morphometric analyses of Salpa thompsoni have been conducted. Specimens for this research were collected from the Drake Passage, using a Bongo net in the summer season of 2010. It has been found that the horizontal distribution of this gelatinous zooplankter was significantly irregular (Kruskal−Wallis test, p < 0.001). In the northern part of the investigated area, both blastozooids and oozooids were recorded, which confirms the dynamic development of this species. The central part of the Drake Passage was characterized by the dominance of blastozooids, with embryos found at different stages of the development. Only in the region of the South Shetland Islands, the salpid population was characterized by reduced or even stopped reproduction. The immense reproductive efficiency observed in the Salpa thompsoni population was mostly induced by the favourable thermal conditions. These observations may suggest that the ongoing climat changes in the West Antarctic will promote the population expansion of this species.
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