No abstract

Changes in the higher plant populations of the Argentine Islands over the last four to five decades have been central to developing an understanding of the likely biological responses to the globally exceptional rates of regional climate change, in particular warming, experienced along the western Antarctic Peninsula over the same period. In this study, we reassessed local populations and distribution of the two indigenous flowering plants on two islands in this archipelago, the grass Deschampsia antarctica and the pearlwort Colobanthus quitensis, in order to compare with previous partial and detailed surveys carried out by the British Antarctic Survey between 1963 and 1990. Our major finding was that the strong trend of recent increase in population size documented in 1990 has not continued, with current population sizes of both higher plants now being slightly lower than but still comparable with those recorded in the last survey in 1990. We discuss reasons underlying this, including possible limits imposed by the suitability of available habitat, and a recent plateauing of the local climate warming trend in comparison with that seen before the 1990 survey, with no significant short-term warming apparent in annual or seasonal meteorological data since 1990.

Current meta-community theories postulate that the structure of local communities depends on dispersal, environmental filtering, and biotic interactions. However, disentangling the relative effects of these factors in the field and for diverse assemblages is a major challenge. A solution is to address natural but simple communities (i.e. with low numbers of species in few trophic levels), wherein one of these factors is predominant. Here, we analyse the micro-arthropod community of a moss-turf habitat typical of the Antarctic Peninsula region, and test the widely accepted hypothesis that this system is abiotically driven. In the austral summers 2006/7 and 2007/8, we sampled nearly 80 units of moss from four islands in the Argentine Islands. Using variance partitioning, we quantified the relative contribution of: (1) multiple scale spatio-temporal autocorrelation; (2) environmental effects; (3) the island effect. Little variance (1 %) was accounted for by sources 1 (1 %, significant) and 2 (<1 %, not significant). The island effect significantly accounted for the largest amount of variation (8 %). There was a relatively large effect of spatially structured environmental variation (7 %). Null models demonstrated that species co-occurred less frequently than expected by chance, suggesting the prevalence of negative interactions. Our data support the novel hypothesis that negative biotic interactions are the most important structuring force of this micro-arthropod community. The analysed system is a good proxy for more complex communities in terms of taxonomic composition and the functional groups present. Thus, biotic interaction might be a predominant factor in soil meta-community dynamics.

Results of the investigation of the littoral zooplankton's structural and faunistic organization of the Uday river are presented. The research was conducted in the National Nature Park "Pyriatynskiy" in summer 2015. As the result of research 58 zooplankton's species were established. Their density, biomass, ecological spectrum of the community, type and way of the feeding were analyzed.

Black rockcod Notothenia coriiceps (Nototheniidae) is one of the common fish species of the Argentine Islands Archipelago region, and it is very common in the Southern Ocean waters. So, objective of the original research was to study the seasonal changes of biological characteristics of N. coriiceps individuals. The material was collected during the XII Ukrainian Antarctic Expedition in 2007-2008 using classical methods, specifically by the bottom gear in the ice-free water places from the boat and from the shore, and in winter also from the ice. Pieces of fresh meat and fish were used as bait for gear. The catches were carried out at the depths from 10 to 50 m (mainly at depths of 20-30 m). Result The majority of black rockcod has a standard length of 26,0-30,0 cm (45,3%) and the age of 4-5 full years (84,5%). During the year, the majority of individuals has II stage of development of the gonads (82,9%), however the number of individuals whitch have III and over stage of development has gradually increased from October to January. It was detected that the main diet components of N. coriiceps in the Argentine Islands Archipelago region were fish and crustaceans rarely-mollusks. Two size groups (>25 cm and <25 cm) of black rockod had the same feeding components ratios. In the majority of individuals (67,7%), the gastrointestinal tract was filled poorly (0-1 point). Fat content during the year was predominantly 2-3 points (94,3%). The value of cardiosomatic index during the year has gradually increased from 0,181±0,008 in April to 0,283±0,005 in September and has again decreased to 0,182±0,003 in December. The value of hepatosomatic index has decreased from 2,11±0,10 in April to 1,58±0,06 in November. In December and January the index has increased to 2,66±0,57. The value of fatness by Fulton has decreased from 1,89±0,06 in April to 1,60±0,03 in September, in January it has increased to 1,86±0,52. Conclusions: the character of feeding and development stage of N. coriiceps in the region of the material collection has matched with data from the other researches of the other Antarctic Peninsula regions. In the majority of representatives (66,7%), the gastrointestinal tract was poorly filled (0-1 point), and fat content during the year was predominantly 2-3 points (94,3%). The biological features of N. coriiceps were characterized by the seasonal dynamics, that was associated with the feeding in summer and small amount of food in winter.