Polish Polar Research

The chlorophyll a content was measured at 62 oceanographic stations. At each station samples were collected from eight standard depths between the water surface and 150 m. Integrated values (chlorophyll α mg/m2) are used in the presentation of the results and discussion. The recorded quantities of chlorophyll α were rather high, amounting to as much as 634 mg/m2. The areas with high chlorophyll a content (> 200 mg/m2) were located in the region of the Anvers Island and Brabant Island, on the shelf around Joinville Island and opposite the Antarctic Sound, close to Clarence Island and beyond the regions recommended in the BIOMASS-SIBEX programme to the east and south of the South Orkney Islands. In the acetonie extracts of photosynthetizing pigments large quantities of phytoxanthin were found using the TLC method, what precludes the use of the Lorenzen method for determination of chlorophyll α and its degradation products.

On the basis of T/S measurements water masses were differentiated and geostrophic currents were drawn. It was stated, that the Weddell Sea waters filled a major part of Bransfield Strait from the southeast to Trinity Island on the west. Waters originating from Bellingshausen Sea occurred in the western and northern part of the research area and along the southern coasts of Shetlands. The direction of the geostrophic current is from the southwest to the northeast with a branch in the south at the top of the Antarctic Peninsula.

Water samples were collected at 12 oceanographic stations from six standard depths ranging from 0 to 100 and 150 m. The number of bacteria and concentration of organic components were expressed in adequate units per 1 litre of sea water and in the form of the integrated values for the whole water column under I m2 of sea of organic components were expressed in adequate units per 1 litre of sea water and in the form of the integrated values for the whole water column under 1 m2 of sea surface. Total numbers of bacteria (TC) ranged from 0.16 to 7.31 x 107/1 and 1.74 — 5.67 x 10, 2/m2 saprophytic bacteria (CFU) 0.10 — 46.85 x 103/1 and 0.62 — 27.7x 108/m2. contents of particulate organic carbon (РОС) 0.02 — 0.25 mg/1 and 3.5 — 20.0 g/m2 dissolved organic carbon (DOC) 0.07 — 3.02 mg/1 and 53.5 — 207.9 g/m2, dissolved free amino acids (DFAA) 0 — 1.8965 μmol/1 and 2.7 -151.5 mmol/m2, dissolved combined amino acids (DCAA) 0 2.9366 μmо1/1 and 16.5— 163.5 mmol/m2, particulate combined amino acids (PCAA) 0 — 3.0215 μmо1/1 and 3.7 — 249.0 mmol/m2. Total numbers of bacteria and РОС, DOC and DCAA concentrations, widely differentiated in the investigated area, were on the average much lower than the values obtaine in previous years. The saprophytic bacteria content and DFAA and PCAA concentrations were at a similar level to that in the past years. Higher TC and CFU values were observed in the areas with high concentrations of phytoioplankton to the NW of Anvers I. and around Clarence I.

Within the SIBEX study area greater concentrations of net-phytoplanklon biomass and numbers were found in waters with clearly defined physical characteristics of either Bellingshausen Sea (an area north and west of Anvers Island and northern part of the Bransfield Strait) or Weddell Sea (south eastern entrance to the Bransfield Strait). Low biomass and cell numbers occurred in the southern Drake Passage and in the south central Bransfield Strait, which in the latter case, appears to be a characteristic feature of ihsse waters during the entire phytoplankton growing season. Early summer blooms of Chaetoceros neglectus and C. tortissimum were mainly responsible for high values of phytoplankton biomass. Some diatoms, such as C. socialis were exclusively associated with Weddell Sea water; a replacement of one water type by another in the Bransfield Strait may considerably modify phytoplankton populations which are present there.

Planktonie material was collected at 63 samling stations during the BIOMASS-SIBEX cruise of the r/v "Profesor Siedlecki". Samples were collected with a Bango-505 net in the water column from the sea surface downwards to a depth of about 200 m. Throughout the research area most numerous were the following typically Antarctic species: Calanoides acutus, Calanus propinquus, Rhincalanus gigas, and Metridia gerlachei. The abundance of the last one was several times higher that of other species. At the time of the investigations the animals were in the final stage of invidual development and in readiness for reproduction.

Macrozooplankton was collected at 63 stations by means of a Bongo sampler in the layer from the surface to a depth of 200 m. Wet formalin volume of siphonophors, polychaetes, pteropods, copepods, amphipods, euphausiids, chaetognaths, salps, and the remaining animals was determined; the distribution of major species was presented. Low diversity in macrozooplankton composition was observed in the study area. As far as biomass was concerned, salps predominated in the whole area; they occurred in exceptionally large quantities Large amounts of krill were also observed in some areas. Besides salps and krill, other euphausiids had the greatest share in the zooplankton; they were more abundant than copepods. Macrozooplankton biomass without salps and krill was low when compared with the values known from literature.

In the plankton samples, collected with a Nansen net in three water layers downwards to a depth of 500 m, larvae and eggs of Euphausia superba were found as well as the larvae of E. crystallorophias and E. frigida. Eggs of the species E. superba predominated and among the larvae most numerous were calyptopis I and metanauplius stages. Eggs and larvae of E. superba occurred in small quantities, mainly in Bransfield Strait. Larvae of E. crystallorophias were found in the southeastern part of Bransfield Strait. Metanauplius, calyptopis I and II stages were predominant. Larvae of E. frigida, mostly calyptopis I stage, were very scarce and occurred only at the stations located in Drake Passage.

In the plankton samples collected with a Bongo net besides Euphausia superba the following species of the Euphausiacea were found:. £. frigida, crystallorophias, E. triacantha and T. macrura. The most aboundant and most frequently caught species was T. macrura equally distributed throughout the research area. The species E. frigida also occurred regularly though in much smaller numbers. E. triacantha occurred sporadically, mainly in the western part of the research region, and E. crystallorophias only at two stations in the Bransfield Strait. Some aspects of the biology and ecology of the mentioned above species are presented in this study.

During SIBEX the acoustically evaluated amount of krill in the Bransfield Strait and Drake Passage was very low with the mean density 3.24 individuals/m2 and 4.29 individuals/m2 accordingly. Any substantial quantities of krill were found North-West from the Elephant Island and North from the King George Island, where the density of krill exceeded 1000 individuals/m2 (about 100 t/nM2]). The total biomass was estimated at 70590 ton in the Bransfield Strait and at 122470 ton in the Drake Passage, which was many times less than during FIBEX 81, especially in the Bransfield Strait.

During the SIBEX1' programme in December 1983/January 1984, 27 hauls were made from the "Profesor Siedlecki" with a 368 — mesh midwater sampling trwal. A total of 13 fish species at postlarval or juvenile stages was found in the catches. The greatest aboundance and species diversity of juvenile ichthyofauna was observed within shelf waters of the Peninsula. Postlarval and juvenile Pleuragramma antarcticum was the most common and most aboundant species there.

The presence of 31 species of birds was observed at sea sout of 50°S, out of this number 26 species were present also south of 60°S. The most numerous aggregations of birds were recorded in the regions of: Elephant Island, the South Orkneys and NE part of Bransfield Strait. The average number of birds during 10-minute observation was 74.5. In the areas under observations Daption capense predominated quantitatively. The following species were subdominant: Pygoscelidae, Oceanites oceanicus, Diomedea melanophris, Fulmarus glacialoides and Macronectes giganieus. In the total number of the birds observed krill-eaters contributed in 80.1% plankton-eaters — 7.8%, squid-eaters — 6.2% omnivores — 5.9% and fish-eaters — 0.1%. In comparison with the autumnal observations more than twice as many birds at sea were observed in the same area.