Tonnacypris glacialis (G.O. Sars, 1890) is a meiobenthic species widely distributed in Arctic freshwater lakes. Field study of its life cycle as well as the laboratory experiments showed clearly that only one generation of this ostracod species occurs during the vegetation season, and that the condition necessary for the next generation to appear is eggs freezing.

Genetic variability of two populations of Arctic freshwater crustacean Lepidurus arcticus (Crustacea, Notostraca) occuring in small tundra reservoirs near the Polish Polar Sta− tion in Hornsund (Spitsbergen) was studied. The allozyme polimorphism analysis of 11 en− zyme systems indicates a considerable distinctness and genetically heterogeneous character of the populations of L. arcticus inhabiting freshwater reservoirs of similar hydrological con− ditions situated close to each other (2 km). Our research revealed a complicated and geneti− cally heterogeneous character of the populations. Three hypotheses about genetic structure and type of reproduction were tested: hypothesis M – the free transfer without assigning a clone for particular reservoir and the lack of doublemutations; hypothesis I – separation of in− dividuals between reservoirs and the possibility of doublemutations; hypothesis S – presence of partial sexual reproduction in the population, probably with males. In conclusion participa− tion ofmales in reproduction is probable, despite their presence was not recorded in our study. Males usually occur in low numbers or not every year. The populations' clonal structure as well as the genetic diversity typical of species reproducing sexually was observed. The Hardy−Weinberg genetic equilibrium is maintained as new clonal lines appear due to the ge− netic diversity increasing incidentally as a result of sexual reproduction.

Candona rectangulata is an ostracod species common in cold (<15 ° C ) shallow freshwater Arctic water bodies. This species is useful in palaeolimnological studies because only few known autecological data can be applied in reconstructions of palaeoclimate. Particular attention was paid to the temperature, which is the basic factor determining the geo− graphic range of a species. In this study a wide tolerance of C. rectangulata to the temperature was demonstrated for the first time. Its high tolerance to the temperature changes seems to be based on induction of set of proteins belonging to the family of heat shock proteins. Using PAGE−SDS electrophoresis variation in the protein profile of non−model organism undergoing stress in the field (South Spitsbergen, near Stanisław Siedlecki Polish Polar Station) and in laboratory cultures was presented. These results could explain the eurythermic range of C. rectangulata and its good adaptation to the environmental conditions which normally do not exist in Arctic freshwater ponds.

The aim of this study was to examine the pollution level of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and selected chloroorganic pesticides (HCH isomers, DDT and its metabolites, aldrin, dieldrin, endrin, heptachlor, endosulfan I and II, and methoxychlor) in surface sediments from selected fjords, tidal plains and lakes from the North Svalbard area. The sediments were collected from 34 sampling stations in July 2005. Only endosulfan I and methoxychlor, among selected chloroorganic pesticides, were measured in concentrations near detection limit (LoD) in fourteen sediment samples. The sum of seven PCB congeners varied from < 0.9 to 5.6 ng g-1 d.w. in sediments from fjords and tidal plains and from < 0.1 to 14.6 ng g-1 d.w. in sediments from lakes. The concentrations of analysed PAH compounds in surface sediments from lakes were over ten times higher (Ʃ16PAHs to 429 ng g-1 d.w.) than in sediments from fjords and tidal plains (Ʃ16PAHs to 36 ng g-1 d.w.).

Identification of discrete stocks of Greenland halibut is an important aspect of proper fisheries exploitation. Available literature data indicated a lack of significant inter‑area differences between Greenland halibut populations from the Northeast Atlantic. To define the population diversity, two aspects were taken into account: enzyme‑genetic diversity and the concentration of heavy metals in tissues. Seven allozyme loci variations were used to characterize the genetic structure of four populations of Greenland halibut from the Western Barents Sea region. The samples were collected from the spawning area in the period when this species took migration to spawn. The sample RH4 was significantly different from the other samples collected from the same location (RH2 and RH3) and depth for over two days. Another sample (RH8), collected from the nearby area 6 days later was similar to the samples RH2, RH3. We noticed a significant divergence between the sample RH4 and the three remaining samples, where the value of the index FST fluctuated about 0.40 and approximately 0.01 between three similar populations. This genetic fluctuation negates the thesis of a panmictic character of the Western Atlantic population. Feeding groups of Greenland halibut are moving along the Barents Sea shelf and they are exposed to different heavy metals concentrations according to the food preferences or the exact place of feeding. We identified similar concentrations of heavy metals, i.e., Zn, Cu, Cd, and Pb in all samples. Trace metal analysis of aquatic organisms from the Barents Sea can provide important information on the degree of environmental contamination, and the potential impact of seafood consumption.

The specific activity of natural gamma emitters like actinium (228Ac), bismuth (212Bi, 214Bi), lead (212Pb, 214Pb), potassium (40K), radium (224Ra), thallium (208Tl) and artificial radioisotope caesium (137Cs) was measured in 2005 in the surface layer of marine sediments in the northern Svalbard: Wijdefjorden, Woodfjorden, Vestfjorden and Bockfjorden as well as in the freshwater reservoirs in Andre Land. Nonuniform spatial distribution of these radionuclides was found. Sediment sample from Bockfjorden had the highest specific activities of all natural radionuclides. The specific radioactivity of 137Cs was much lower than specific radioactivities of natural radionuclides but there were differences between investigated locations. The distribution of 137Cs is similar to persistent organic pollutants of the lake sediments in the area.

The paper presents the first physicochemical and microbiological studies conducted in the northern area of Svalbard (Spitsbergen). Ten sediment samples were collected from the bottom of the longest fjord in the region, Wijdef jorden. Bottom sediments from ten lakes located along the shores of Wijdefjorden and Woodfjorden were also sampled. Organic matter content (LOI), water content, temperature, pH, and salinity of the sediments were determined. The quantity of aerobic bacteria cultured on various growth media at 4 ° C, 14 ° C, and 37 ° C ranged from 10 2 to 10 6 cfu/g of wet sediment mass, depending on the type of sampling station (fjord or lake). The number of bacteria did not co rrelate with organic matter content. Out of the 37 bacterial strains isolated from Wijdefjorden, 48% and 70% revealed ureolytic and proteolytic activity, respectively. The proportion of freshwater strains with ureolytic and proteolytic activity was 32% and 55%, respectively. Antibiotic resistance testing indicated that bacterial strains from the bottom sediments of the lakes were resistant to 8 antibiotics (out of the 18 investigated). Possible sources of this resistance are discussed. Using 16S DNA analysis, bacterial isolates from the lakes were identified as Pseudomonas sp., whereas frequently occurring strains in bottom sediment of the fjord were Pseudoalteromonas sp.