Macroplankton communities in Antarctic surface waters: spatial changes related to hydrography

During the Anglo-German Antarctic expedition in February 1982 macroplankton was collected in the waters off the Antarctic Peninsula. Macroplankton compos~tions at 36 stations were compared and degrees of similarity submitted to hierarchical cluster analysis. Results demonstrate strong spatial heterogeneity, which could be attributed to the different water masses in this region. These dissimilarities demarcate 4 provinces, each characterized by a distinct macroplankton community: (l) The 'Oceanic Community' comprises the stations influenced by the Westwind Drift; oceanic forms are typical (e.g. the hyperiid amphipod Vibilia antarctica, and the polychaete Vanadis antarctica). (2) The 'Bellingshausen Water Community' is influenced by Bellingshausen Sea water and oceanic specles are scarce; large numbers of Antarctic krill Euphausja superba occur but shallow water forms are also abundant. (3) The 'Nentic Community' consists of stations in the shelf water of the southern Bransfield Strait; it is charactenzed by postlarvae of several fish species, and meroplanktonic larvae of benthic forms. Large krill concentrations, however, are also encountered. (4) A 'Transitional Community' exists in environments where various water masses mingle (e.g. at shelf slopes). This community lacks typical forms

Species composition and distribution patterns of early life stages of cephalopods at Great Meteor Seamount (subtropical NE Atlantic)

The distribution of early life stages of cephalopods was studied during a cruise of RV Meteor in September 1998 at Great Meteor Seamount, an isolated flat-topped seamount in the subtropical eastern North Atlantic. Zooplankton sampling was conducted with a multi-opening-closing net (modified MOCNESS, 1 m² net opening, 335 µm mesh size) in seven depth strata between 290 m depth and the surface. 1180 early life stages of cephalopods were collected, representing at least 18 families and 31 mainly oceanic species. Most of the identified cephalopods comprised mesopelagic species (e. g., representatives of the families Enoploteuthidae and Pyroteuthidae) that showed diel vertical migration patterns. Hydrographic measurements parallel to zooplankton sampling revealed slow anticyclonic recirculation around the seamount forming a Taylor column and, thus, some retention potential for passive particles. Nevertheless, multivariate statistical analysis revealed no differences in the cephalopod community between the area in the proximity of the summit and the adjacent oceanic region. This was partly related to the depth of the plateau (< 300 m), which resulted in only slightly enhanced primary production, as well as to the low retention potential for active vertical migrators. However, reduced numbers of cephalopods were observed over the summit in night-time sampling, indicating gap formation above the seamount

Research cruise data on the biology of the lesser flying suid, <em>Todaropsis eblanae</em> in the North Sea

A total of 324 specimens of the ommastrephid squid Todaropsis eblanae, collected from bottom trawl surveys in the North Sea was examined. Information on seasonal length frequency distributions and relationships of beak size to mantle length and wet body mass from the northernmost distribution of the species is supplied. The overall male: female ratio was 1: 0.78. Maturing males and females were found in winter and summer, while fully mature animals were observed only in summer. Sexual maturity in females occurred in bigger sizes than in males. Specimens were caught in water depths between 56 and 170 m throughout the whole investigated area except from the German Bight. This paper presents the first biological data on T. eblanae in the North Sea derived from scientific surveys

Distribution and lipid composition of early life stages of the cranchiid squid Galiteuthis glacialis (Chun) in the Weddell Sea, Antarctica

The relatively small numbers of pelagic cephalopods caught in the RMT-8 samples (0–300 m) in February/March 1983 in the Weddell Sea were dominated by early life stages of the cranchiid squid Galiteuthis glacialis. A total of 48 specimens were caught with dorsal mantle length (ML) ranging from 4–36 mm. They occurred with a mean density of 0.15 ind. × 1000 m−3 and were present in 38% of 33 RMT-8 samples. G. glacialis was the only cranchiid squid found in the Weddell Sea between 66° and 74°S. Its early life stages were concentrated in the layers below the summer thermocline (>50 m) and body sizes appeared to increase towards deeper water layers. For biochemical analyses, nine specimens of G. glacialis (ML 6–18 mm) were sampled in the eastern Weddell Sea between 185–520 m water depth in January/February 1985. Total lipid contents ranged from 8%–11% dry weight (DW) with phospholipids being the main lipid component (43–56% of total lipid). Storage lipids (triacylglycerols) made up 18–26% of total lipid. The relatively low lipid contents may reflect the early development stage of the specimens examined. The data presented give the first information on geographical and vertical distribution patterns of early life stages of G. glacialis in the high-Antarctic Weddell Sea, as well as on their lipid content and composition

Trophic signatures of marine organisms in the Mediterranean as compared with other ecosystems

We compared several large marine ecosystems in terms of species numbers of fishes, sea birds, marine mammals, and cephalopods. We examined how these numbers were distributed by trophic level, from herbivores to top predators. We created group-specific trophic signatures as plots of number of species by trophic level, and used these to identify similarities and discrepancies between taxonomic groups and ecosystems. Preliminary results suggested that trophic signatures are similar for ecosystems previously known to share major features, and different for dissimilar ecosystems. In the Mediterranean, as well as in the other large marine ecosystems, fish clearly dominate the predatory trophic levels above 3.0. Preliminary signatures for cephalopods, marine mammals, and sea birds in the Mediterranean and in the North Sea indicate that these groups are restricted to trophic levels above 3.0, and are represented by many fewer species than are predatory fish. Notably, cephalopods are the only invertebrates present at higher trophic levels (>= 4). Invertebrates other than cephalopods are restricted to trophic levels below 3, with very few exceptions. Trophic signatures appear to be useful tools for better understanding of the roles that different groups of organisms play in different ecosystems. We also applied free-scale network theory to analyse the food web created by trophic links of fishes. Our preliminary results indicated that Mediterranean fishes are, on average, only two trophic links away from each other