Nematoda, Tardigrada, Rotifera and Crustacea composition in different freshwater habitats on Spitsbergen (Arctic) and King George Island (Antarctic) was presented. In all surveyed groups more genera and species were recorded from Spitsbergen than from King George Island. Habitats richest in taxa were moss banks and thaw ponds, whereas streams were poorest in species. In all groups in both regions cosmopolitan species dominated, but higher number of endemic species was recorded on King George Island. Regarding species composition in surveyed groups it can be suggested that freshwater habitats on Spitsbergen are more similar to each other than those on King George Island.

Water bears (Tardigrada) are known as one of the most extremophile animals in the world. They inhabit environments from the deepest parts of the oceans up to the highest mountains. One of the most extreme and still poorly studied habitats which tardigrades inhabit are cryoconite holes. We analysed the relation between area, depth, elevation and tardigrades densities in cryoconite holes on four glaciers on Spitsbergen. The mean (±SD) of cryoconite area was 1287.21±2400.8 cm2, while the depth was on average 10.8±11.2 cm, the elevation 172.6±109.66 m a.s.l., and tardigrade density 24.9±33.0 individuals per gram of wet material (n = 38). The densities of tardigrades on Hans Glacier reached values of up to 168 ind. cm3, 104 ind. g-1 wet weight, and 275 ind. g-1 dry weight. The densities of tardigrades of the three glaciers in Billefjorden were up to 82 ind. cm2, 326 ind. g-1 wet weight and 624 ind. g-1 dry weight. Surprisingly, although the model included area, depth and elevation as independent variables, it cannot explain Tardigrada density in cryoconite holes. We propose that due to the rapid melting of the glacier surface in the Arctic, the constant flushing of cryoconite sediments, and inter-hole water-sediment mixing, the functioning of these ecosystems is disrupted. We conclude that cryoconite holes are dynamic ecosystems for microinvertebrates in the Arctic.

In polar regions, apart from tundra and glaciers, geothermally active areas

with elevated temperatures are important elements of ecosystems. One such geothermally

active region characterized by mosaic ecosystems and vast areas covered by recent lava

fields is Iceland. The aim of our study was to explore the diversity of invertebrates

inhabiting geothermally active lava fields in the Krafla area (Iceland). Eight bryophyte

samples were collected from a warm surface, mainly from the steaming areas. We have

found Nematoda, Rotifera, Tardigrada and Oribatida in the samples. Habitat analysis

demonstrated there to be 12 bryophyte species (five liverworts and seven mosses).

The diversity of bryophytes in a single sample ranged from one to six species. The

most common bryophyte was Racomitrium lanuginosum (Hedw.) Brid. Four species

of tardigrades were found, including one that was new. Pilatobius islandicus sp. nov.

is described herein by morphological, morphometric and molecular approaches (COI,

28S rRNA, 18S rRNA). Oribatida mites were identified as two species (Malaconothrus

monodactylus (Michael, 1888) and Camisia foveolata Hammer, 1955). The average density

of invertebrates was 13.1 ind./g with a maximum of 40.8 ind./g calculated per dry

material. The tardigrades found in our study belonged to herbivores, microbivores and

omnivores, whereas the mites belonged to saprophages, which indicates complex trophic

networks in geothermally active lava fields.

Studies of past vegetation from the inner fjords of the Svalbard archipelago have not previously been reported. This study assesses the potential of sediments retrieved from two sites in Petuniabukta, Billefjorden to track vegetation response to Quaternary climate change. The first sediment profile was retrieved from periodic lake on a 4 m a.s.l. marine terrace with a basal radiocarbon dated to 5 080 ± 30 BP, the second was retrieved from a depression in wet tundra on a 24 m a.s.l. marine terrace, which upper part was dated to 9 470 ± 30 BP. The study is primarily focused on macro- and micro−fossils. Pollen grains are present in very low concentrations. Macro−fossils were represented mostly by leafs and buds of Salix species and Dryas octopetala as well as the hybrid Salix herbacea x polaris . Fossil moss remains represent an important part of arctic ecosystems. Tardigrada remains were found in the sediments in high abundance whilst eggs and exuviae of at least six species were identified. The sediments are definitely suitable for the reconstruction of past conditions. However, it is necessary to take care not to focus at single type of analysis, as pollen analysis appeared uninformative and more information was obtained from plant macro − fossils (mosses, vascular plants). Little attention has been given to Tardigrada in the past, as they were overlooked and the preservation in sediments is usually very low.