Poland has been active in Antarctica for 41 years and modernizes its infrastructure and research program in accordance with the recommendations of the Antarctic Treaty, SCAR, and international recommendations.
The environments of inlets, coves and lagoons varies widely. Climate warming has lead to retreat of glaciers directly entering the sea. In lagoons this is accompanied by exposure of an uncolonized substratum. Colonization processes in these lagoon appear to describe processes which have previously occurred in bays and fjords of glacial origin in the South Shetlands.
Comparison of T and S values in areas 1, 2, and 3 in the Bransfield Strait and Admiralty Bay (Fig. 1) shows that the warmest waters are found in area 1, while the coldest in area 3. Surface salinity is the lowest in area 2 as a result of water outflow from land. In area 3 vertical salinity variations are the lowest, with the maximum occurring at the surface. At 500 m depth the highest salinity is recorded in area 1. The most homogeneous distribution of temperature and salinity is observed in area 3. In Admiralty Bay, in the annual cycle of 1995 water temperatures at 4 m, 10 m and 100 m are similar to those in 1979 except in the winter, when they are lower.
In the examined area three types of waters have been recorded: Surface Waters of winter modification, Warm Deep Waters and East Bransfield Strait Waters. Geographical location of Scotia Front is similar to that observed in previous years. The dynamics of waters within the examined area is high. It is reflected not only in physical and chemical parameters but also in the distribution of chlorophyll α. In the Front its total amount in a water column is greater than outside.
The length of crystalline cones (cc) is proportional to krill body length and this proportion can be described by the equation L cc = L krill x 1.679 + 52.032 ( cc — μm; L krill - mm). By measuring cc one can determine the size of krill with the precision of 2—3 mm. The structure of crystalline cones is not crystal, and the elemental composition includes much of S and Ca. Crystalline cones are often found in the stomach and feces of animals feeding on krill.
Krill population structure was studied in Western Antarctic in austral spring and summer 1986/87. At the end of October and the beginning of November in the waters around Elephant Island the mean krill length was 44 mm and sexually mature specimens dominated. Juveniles were absent. In the Bransfield Strait the mean E. superba length was 43 mm. and males slightly overdominated females. The share of females with spermatophores and of immature females was higher than in the Elephant Island area. Juveniles were also not recorded. Krill was most diversified around Elephant Island in January; juveniles and females with ovaries filled with eggs were recorded. It was found that 84% of krill population was infested by ciliate protozoans (Apostomatida).
Pinnipeds were monitored in Admiralty Bay between 1988 and 1992. No particular trends during this period were found, but seasonal changes in each are distinct. It is suggested that the phenology of pinnipeds and that of penguins ensures low competition for food between these groups.
On the basis of about 12500 depth measurements of which 6700 were taken from r/v Profesor Siedlecki, 1300 from r/v Polarstern and the remainder from British navigation charts, a bathymetric chart of the Bransfield Strait in the scale 1:500 000 has been prepared. Within the assumed boundaries the total area of the Bransfield Strait covers 65308.6 square kilometres, of which the Western Basin covers 23.5%, Central Basin — 47.3%, and Eastern Basin 29.2%. Capacity of the whole Bransfield Strait amounts to 38451 km3 . The average depth of the Bransfield Strait is 592 m.
The paper provides information on oceanobiological expeditions to the Antarctic organized by Polish Academy of Sciences. The scope of research of five expeditions is described and main achievements of Polish Antarctic studies are summarized.
The highest infestation by phoronts (resting stages) of Apostoma ciliates forms 1, 2, is restricted to the 3-th and 4-th pairs of E. superba thoracic limbs. They occur mostly on meropodites of endopodite and plumose setae of exopodite. The trophonts (trophic stage) of those Apostoma are present in large numbers in krill's tissue. The life cycle of those histophagous Apostoma include also free-living stage - tomit. Swarm formed by krill seems to be a reason for the common and extensive infestation by protozoans.
The authors describe the scope of Polish studies in the field of biology and ecology carried on during 20 years of activity of Polish Antarctic Station. Principal results are briefly summarized and ample literature is presented.