Polish Polar Research

On the basis of observations and topographic surveys carried out mainly in the northern part of Linnedalen on Spitsbergen, geological structure of the valley was described and determination of the forms of relief by the means of lithology was demonstrated. The relief of the valley was characterized with particular regard to periglacial processes. A geomorphological map of the northern part of Linnédalen was made and a part of a cataloque of polygonal and structural soils was prepared.

The radar device for measurement of thickness and structure of "warm" glaciers was used in this work. The measurement of thickness of dielectric is based here on the examination of transit time of hight frequency electromagnetic pulse throught the measured stratum. A total ice volume of "warm" glaciers is in the melting temperature here. Such glaciers are characterized by a large number of internal structure defects. The electromagnetic wave reflections are caused not only b the glacier base but, additionally by ice crevasses, more imbided water layers and by all other defects of the internal glacier structure, too. The simple statistical method was elaborated for differentiation of essential layers reflections from random reglections caused by less extented objects. This method was used to obtain the two transversal profiles of the Hans Glacier (South Spitsbergen).

Measurements of water temperatures, salinity, oxygen, suspended matter, nutrients and some metals contents were determined in the waters of the Hornsund Fjord. The investigations were carried out at the end of June and July and in mid-September 1979.

During austral summer 1978/1979 the content of dissolved oxygen, phosphates, nitrates and nitrites was determined in the waters of Admiralty Bay. Environmental conditions prevailing in Admiralty Bay are compared with the conditions in the open Antarctic waters.

Studies on the quantity and distribution of organic carbon (DOC and РОС) in the water of the Admiralty Bay were conducted between 20 December 1978 and 15 February 1979. The С org. content ranged from 1.62 to 3.22 mg 1-1 for DOC and from 0.22 to 0.65 mg x 1-1 for РОС. Maximal DOC amounts were observed at the depth 25—50 m (on average about 2.50 mg x 1-1 ) and in chosen regions of surface waters of the Admiralty Bay, among others, in the vicinity of a large penguin colony. Mean content of DOC in waters of the Admiralty Bay (about 2.26 mg x 1-1 ) is lower as compared to mean DOC content in waters of the Bransfield Strait (about 4.12 mg x 1-1).

Vertical distribution and quantitative and qualitative phytoplankton composition were studied in Ezcurra Inlet, Admiralty Bay, South Shetland Islands in the austral summer 1977/78. Nannoplankton flagellates, 12—15 μm in diameter and 4—6 μm "monads" were the principal algae of the plankton. Diatoms, present in a low abundance, were dominated by Thalassiosira antarctica and several species of the genera Nitzschia and Chaetoceros. Peaks of cell numbers within the 1—10 m surface stratum and at the bottom of the euphotic zone were characteristic of the vertical distribution of phytoplankton. Light, water movements and density micro-gradients were the likely factors controlling the vertical distribution of algae.

Distribution and population age structure of krill Euphausia superba larvae is presented for four consequent years on the basis of the summer materials from 1976 to 1979. An approximate rate of growth of krill larvae was calculated on the basis of the above observations and the literature data on the occurrence of particular larval stages. This allowed to determine the main period of krill breeding in particular years. Intense breeding of krill took place from January to middle of March in summers 1976/1977 and 1977/1978, but much earlier — mid November to mid January in 1975/1976. In summer of 1978/1979 the breeding of krill was poor till March.

The presence of Euphausia superba, E. crystallorophias and Thysanoessa macrura was observed in Admiralty Bay (King George Island, South Shetland Islands) and the size of individuals of particular species are diverse and varying during the summer season. E. superba population is older and specimens larger than in analogous season in 1979. The maximum number of females with eggs was noted in the first half of January 1980, i.e. earlier than in 1979. In E, crystallorophias population the presence of females with eggs was observed in the second half of December 1979.

On the basis of measurements of the depth of occurrence of 11000 krill aggregations and the biological analyses of these animals and measurements of some environmental factors the diurnal vertical distribution of aggregations is presented against the background of various environmental conditions. Vertical distribution of aggregations is closely related to the feeding rhythm of krill. Active vertical migrations have been recorded at civil twilight. The increasing and decreasing rate of aggregations in those periods is described.

The method of target strength measurement adopted for the krill's target strength determination is proposed. The relation between the length of krill's individual and its target strength, obtained at the laboratory conditions, is presented.

Observations indicate a constantly decreasing mean age of shoal. In consecutive years of investigations a loss of older individuals was recorded. At present the catches consist of 3—14 years old fishes; 9—10 years old dominate. During the austral summer the fish most probably do not migrate. The shoal of the shelf maintains approximately constant frequency and dominance in classes of length.

The material obtained between 1977 and 1979 has allowed to compare body length, age and sex of South Georgia fish caught in the region of South Georgia Island. The growth rate of body length and weight of individuals have been determined. According to results the South Georgia icefish at the time of investigations did not form a homogenous, stable stock in the region of South Georgia Island.

The shelf fishing grounds of Kerguelen Islands and of some neighbouring ocean shallows were studied in April 1975. The occurrence of 15 species representing 9 families was found in the catches. Detailed study of the following five species was performed: Champsocephalus gunnari, Channichthys rhinoceratus, Notothenia rossi rossi, N. squamifrons and Dissostichus eleginoides, all of potential commercial importance. The boundaries of regions with concentrations of Ch. gunnari and N. squamifrons were determined, the productive and suitable for trawling fishing grounds were localized.