Variability of Salpa thompsoni population structure in the Drake Passage in summer season 2010

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 decrease in the number of this crustacean has been recorded, followed by an increase in the population of the gelatinous zooplankterSalpa thompsoni. In the research presented herein, population and morphometric analyses ofSalpa thompsonihave 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 theSalpa thompsonipopulation 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.