ALBERT

Description: The distribution of early life stages of cephalopods was studied during a cruise of the German research vessel RV Poseidon to the Sargasso Sea in March 1993, covering an area south-east of Bermuda from 24°N to 31°N and 61°W to 65°W. Hydrographic measurements were conducted by CTD and/ or XBT. The subtropical convergence zone was detected at a latitude of approximately 27°20’N and divided the Sargasso Sea into a northern and a southern area. Zooplankton sampling with a 6m² Isaac Kidd midwater trawl and Bongo nets yielded a total catch of 909 early life stages of cephalopods representing at least 14 families and 23 mainly oceanic species. Multivariate statistical analyses were performed in order to compare the species composition and abundance of cephalopods. Two different assemblages were clearly identified, north and south of the front. According to the position of the front an analysis of similarity (ANOSIM) was applied which confirmed the observed differences in species composition on a highly significant level. The Cranchiidae, mainly represented by the endemic species Leachia lemur, was the most abundant family especially in the northern part of the Sargasso Sea and was mainly responsible for the distinction between the cephalopod assemblages. In general, higher abundances of early life stages and a higher diversity was observed north of the subtropical convergence zone, which is assumed to form a faunal boundary

Description: Sprat Sprattus sprattus larvae were used as model organisms to evaluate whether larval lipids reflect in situ feeding conditions and can thus identify match-mismatch situations. In detail, we determined larval lipid content, growth rates based on RNA:DNA ratios, and fatty acid (FA) composition during the spawning season in the Central Baltic Sea, and evaluated these in light of feeding, mortality and recruitment (which were determined in parallel within the project ‘GLOBEC Germany’). Based on the opposing trend of RNA:DNA and lipid content, as well as on previous observations, we hypothesized that lipid content and current feeding conditions are largely uncoupled in the early life stages of sprat due to reduced lipid anabolism. However, lipids still provide information in several ways: (1) segmented generalised linear models proved to be a suitable tool for identifying phases of lipid catabolism during development, with the slope reflecting size-specific environmental starvation pressure. This method detected a previously identified mismatch situation with suitable prey in the early spawning season, which increased mortality of larger larvae. (2) Estimated starvation resistance, a proxy that accounts for temperature- and size-dependent metabolism, reflected the likelihood of near future starvation of individual larvae. (3) Principal component analyses on FAs identified monthly differences in diet composition. Biomarkers indicated a dinoflagellate and/or microbial loop based carbon flux to the larvae. (4) Regression analyses revealed lower docosahexaenoic acid (DHA) levels in spring, but no obvious effect on growth. Food quality was generally high, and its impact on larval survival was less evident than that of prey size suitability.

Description: Five cephalopods, all belonging to different species, were identified from deep-sea trawl samples conducted during the DIVA 1-expedition of RV “Meteor” in the Angola Basin in July 2000. These were the teuthoid squids Bathyteuthis abyssicola, Brachioteuthis riisei, Mastigoteuthis atlantica, Galiteuthis armata, and the finned deep-sea octopus Grimpoteuthis wuelkeri. The present study contributes information on size, morphometry, biology and distribution of the species form this unique cephalopod collection.

Description: The distribution of early life stages of cephalopods was studied during a cruise of the German R.V. "Poseidon" to the Sargasso Sea in March 1993, covering an area south-east of Bermuda from 24°N to 31°N and 61°W to 65°W. Hydrographic measurements were carried out by conductivity, temperature and depth casts and/or expendable bathythermographs. The subtropical convergence zone was detected at a latitude of approximately 27°20′N and divided the Sargasso Sea into a northern and a southern area. Zooplankton sampling with a 6 m2 Isaac–Kidd midwater trawl and Bongo nets yielded a total catch of 909 specimens of early life stages of cephalopods, representing at least 13 families and 20 mainly oceanic species. Multivariate statistical analyses were performed in order to compare the species composition and abundance of cephalopods. Two different assemblages were clearly identified, north and south of the front. According to the position of the front an analysis of similarity (ANOSIM) was applied, which confirmed the observed differences in species composition at a highly significant level. The Cranchiidae, mainly represented by the endemic species Leachia lemur, was the most abundant family, especially in the northern part of the Sargasso Sea, and was mainly responsible for the distinction between the cephalopod assemblages. In general, higher abundances of early life stages and a higher diversity was observed north of the subtropical convergence zone, which is assumed to form a faunal boundary.

Description: 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.

Description: We review current knowledge and understanding of the biology and ecology of the calanoid copepod Calanus helgolandicus in European waters, as well as provide a collaborative synthesis of data from 18 laboratories and 26 sampling stations in areas distributed from the northern North Sea to the Aegean and Levantine Seas. This network of zooplankton time-series stations has enabled us to collect and synthesise seasonal and multi-annual data on abundance, body size, fecundity, hatching success and vertical distribution of C. helgolandicus. An aim was to enable comparison with its congener Calanus finmarchicus, which has been studied intensively as a key component of European and north east Atlantic marine ecosystems. C. finmarchicus is known to over-winter at depth, whereas the life-cycle of C. helgolandicus is less well understood. Overwintering populations of C. helgolandicus have been observed off the Atlantic coast between 400 and 800 m, while in the Mediterranean there is evidence of significant deep-water populations at depths as great as 4200 m. The biogeographical distribution of C. helgolandicus in European coastal waters covers a wide range of habitats, from open ocean to coastal environments, and its contribution to mesozooplankton biomass ranges from 6% to 93%. Highest abundances were recorded in the Adriatic and off the west coast of Spain. C. helgolandicus is generally found in 9–20 °C water, with maximum abundances from 13–17 °C. In contrast, C. finmarchicus is found in cooler water between 0 and 15 °C, with peak abundances from 0 to 9 °C. As water has warmed in the North Atlantic over recent decades, the range of C. helgolandicus and its abundance on the fringes of its expanding range have increased. This review will facilitate development of population models of C. helgolandicus. This will not only help answer remaining questions but will improve our ability to forecast future changes, in response to a warming climate, in the abundance and distribution of this important species.

Description: Assemblage structures and distribution patterns of larval fishes and paralarval cephalopods were examined in September 1998 at Great Meteor Seamount, an isolated seamount located in the subtropical eastern North Atlantic. Early life stages of fish (n=18555) and cephalopods (n=1200) were collected at 23 stations with a multiple opening–closing net, in seven discrete depth strata from 290 m depth (close to the seamount plateau) to the surface. Oceanic species dominated in both taxonomic groups. A peak in diversity was observed at an intermediate depth, in the 100–150 m water layer. Direct and indirect gradient analyses showed distinct species assemblages in the upper and lower part of the water column, separated by approximately 150 m. The division was statistically significant, although a considerable overlap between species was also observed. Above the summit, vertical gaps were found in the distributions of the deeper assemblages, likely caused by increased predation pressure by benthopelagic fish. Horizontal distribution patterns of fish and cephalopods were similar and corresponded to the structure of closed circulation cells detected above the flanks and the flat plateau area. Fish assemblages were significantly different between the inner and outer seamount regime, which was approximately separated by the 1500 m depth contour. Differences in the taxonomic composition of cephalopods were less pronounced; for only one cephalopod species could a direct association with the seamount be assumed. The study indicates a significant retention potential at the seamount that facilitates local recruitment of resident stocks and generates self-sustainable populations isolated from the continental shelf and oceanic islands.