Cladocera species composition in lakes in the area of the Hornsund Fjord (Southern Spitsbergen) – preliminary results

Abstract

Key-words: Cladocera species composition, Spitsbergen, lakes, Hornsund Fjord Species composition of benthic and planktonic Cladocera was analysed in four lakes and ponds located in the southern part of the SpitsbergenIsland near the Fjord Hornsund. This is the first study to provide information on the species composition of the contemporary and subfossil Cladocera in this region. A total of eight Cladocera taxa were found in the sediments and waters of the lakes that have been chosen for the study. The sediments included remains of only five species, while seven Cladocera species were found in the zooplankton samples. The results imply that the lakes are subject to natural transformations driven by the fluctuating climate which was reflected by increasing the number of species, and in particular in the appearance of Bosmina longirostris. Absence of some littoral Cladocera species in the sediments (e.g. ,s mallAlona, Ophyroxus gracilis), with simultaneous occurrence of these species in the water, may be a result of physical and chemical processes influencing the destruction and lack of preservation of the remains in the sediments.