R. Herman

QUANTITATIVE INVESTIGATIONS ON MACROBENTHOS COMMUNITIES OF THE SOUTHEASTERN WEDDELL SEA SHELF BASED ON MULTIBOX CORER SAMPLES.

A total of 233 multibox corer samples from 36 stations along the southeastern Weddell Sea shelf and upper continental slope between Atka Bay (70°S) and Gould Bay (78° S), covering a depth range from 170 to 2,037 m, provided biomass and abundance data for analysis of faunal communities. Twenty-eight major taxa were distinguished. Based on these data, 3 different macrobenthos communities could be identified by means of cluster analysis. Hexactinellid sponges, polychaetes and echinoderms were most abundant. Biomass values have been found to be in the range of 94 mg up to 1.6 kg wet weight per sqm. According to TWINSPAN, the sampled stations can be divided into two groups each consisting of two major subgroups. Peracarid crustaceans, polychaetes and bivalves are commonly distributed in the area of investigation whereas others such as sponges, brachiopods, pantopods and asteroids are more confined to Kapp Norvegia and Halley Bay. Biomass values of these latter taxa off Kapp Norvegia were generally higher than in the Halley Bay area.

Meiobenthos of the central Arctic Ocean with special emphasis on the nematode community structure.

We investigated the abundance of the meiobenthos and the biomass and community structure of the nematodes in the central Arctic Ocean along two separate transects during 1991 and 1994. Meiobenthos abundances ranged from (100 to 600 individuals per 10 cm2, in the same order of magnitude as in other oligotrophic areas of the world’s deep ocean. Nematodes were the numerically dominant meiofaunal group at every station. Nematode biomass ranged from ( 1t o 48lg dry weight per 10 cm2. A combination of water depth and latitude explained 55% of the variability among stations in nematode biomass and 67% of the variability of total abundance, implying that both vertical and advective #uxes are important sources of food to the meiofaunal communities.The dominant nematode genus was Monhystera, a detrivorous/bacterivorous deposit feeder, suggesting that bacteria may play an important role in the food web of the meiobenthos in the Central Arctic. Multivariate analysis of genera abundances revealed di!erences among stations in the Eurasian and Amerasian Basins. During 1994, however, the deep stations in the Eurasian Basin were more similar to the other Amerasian stations, while the single deep station in the Makarov Basin was most similar to the other Eurasian Basin stations. The structure of meiofaunal communities in the central Arctic may provide insight into spatial variability in the Arctic Ocean. ( 2000 Elsevier Science Ltd. All rights reserved.

Meiofauna communities along a depth transect off Halley Bay (Weddell Sea-Antarctica)

Meiofauna communities from 10 stations along a depth transect from approximately 500 to 2,000 m off the Halley Bay Station (Weddell Sea) are investigated. Representatives of about 30 smallsized taxa of higher category are found, most of them belonging to the meiofauna. Loricifera are recorded for the first time for the Southern Ocean. At one of the stations a maximum of 22 taxa occur, the mean number of taxa ranges from 7 to 16. Nematoda, Harpacticoida, Ostracoda, Polychaeta and Bivalvia are present at all sampling sites. Nematodes are always dominant representing more than 90% of the individuals per sample, followed by harpacticoids (3%) and kinorhynchs (1.2%). Important fractions of the meiofauna (an average of more than 50%) occur in strata below the top 0–1 cm layer. Maximal density is 3,800 individuals (10 cm−2), the mean abundance per station ranges from 790 to 3,720 individuals (10 cm−2) and the overall mean is 1,700 individuals (10 cm−2). Multivariate analysis (TWINSPAN, Cluster analysis, DCA) discriminates between three communities which are correlated with depth and sediment characteristics: the near shelf-ice, the slope and the deep-sea communities.

Macrofaunal communities on the continental shelf and slope of the southeastern Weddell Sea, Antarctica

During the third leg of the “European Polarstern Study” (EPOS leg 3) in the austral summer season 1989, benthic macrofaunal communities were sampled from the Elephant Island area (61° southern latitude) and from Kapp Norvegia (71° southern latitude) to Halley Bay (75°30′ southern latitude) using a commercial bottom trawl and an Agassiz trawl. Thirty-six trawl samples from a depth range of about 200–2,000 m were considered, with most of the samples being from the shelf and upper slope. Multivariate analysis techniques (clustering and TWIN-SPAN) discriminated between an eastern and a southern community in which parallel subgroups can be distinguished at increasing distance from the ice shelf.

Composition, distribution, biomass and production of North Sea meiofauna

The distribution and composition of meiofaunal assemblages in the North Sea is described. Only the coastal areas of Belgium, the Netherlands and Germany are relatively well known, especially for nematodes and copepods. Characteristic assemblages may be described which are closely linked to sediment composition. Knowledge on other groups is scarce everywhere. Temporal distribution data are even scarcer. One study on copepods shows large specific variation. Direct production measurements of North Sea meiofauna do not exist but indirect information based on respiration, body weight and life-history may be used to estimate an energy consumption in the order of magnitude of 10 g C.m−2.a−1.

Seasonal fluctuations in vertical distribution and breeding activity of a subtidal harpacticoid community in the southern bight, North sea

Seasonal changes in vertical distribution and breeding activity of 14 dominant harpacticoid species from a sandy station in the Southern Bight of the North Sea are described over a period of 1 year, from January 1983 to January 1984. It is clear that the bulk of the meiofauna penetrates deeper than expected from the literature. The need for long cores for quantitative work in subtidal sandy areas is stressed. The factors affecting vertical distribution in the sediment are discussed. Except for the winter breeder Interleptomesochra eulittoralis, all other species bred at least partially in summer when temperature is high. In these species migratory behaviour and reproductive activity were interrelated, and as a result egg development took place in the surface layers of the sand. Only Microarthridion littorale bred continuously throughout the year. In all other species the breeding season, as defined by the simultaneous presence of juveniles and ovigerous females in the population, was either restricted or protracted: distinct maxima occurred at different times in different species, but the majority reached maximum breeding activity in the summer. The observed breeding patterns of the dominant species are compared with those reported from other localities. Most of them are so-called “plastic species”, which show a latitudinally related alteration in breeding periodicity.