Sublittoral and bathyal Harpacticoida (Crustacea: Copepoda) of the Magellan region

Two expeditions, undertaken in 1994 and 1996, provided quantitatively sampled material of sublittoral and bathyal meiobenthos from the Paso Ancho of the Straits of Magellan, the Beagle Channel, and the Patagonian continental slope (Chile). To investigate whether these distinct geographic areas might also be characterised by different harpacticoid assemblages, qualitative and quantitative analyses of Copepoda Harpacticoida were carried out. At supraspecific level 25 harpacticoid families were found, as well as several species that could not yet be assigned to any major harpacticoid taxon. Due to the high amount of collected Harpacticoida, detailed investigations at species level had to be restricted to six taxa, namely the Ancorabolidae, Argestidae, Cletodidae, Diosaccinae, Paramesochridae, and Paranannopinae. The corresponding specimens were assigned to 122 species in 52 genera. More than 80% of them are new to science. Qualitative comparisons of both species composition and species distribution allow the three areas to be distinguished in terms of species richness. However, statistical analyses confirm these results only partly. Similarity analyses applying non-metrical multidimensional scaling, as well as diversity analyses using the rarefaction method, suggest that the observed differences in distribution and diversity patterns are due to small-scale, local conditions, which may overlay possible large-scale ones.

Abundance and biomass of in- and epibenthic invertebrate macrofauna in the German Bight from 1969 to 2000

In order to examine the long-term development of offshore macrozoobenthic soft-bottom communities of the German Bight, four representative permanent stations (MZB-SSd, -FSd, -Slt, -WB) have been sampled continuously since 1969. Inter-annual variability and possible long-term trends were analysed based on spring-time samples from 1969 until 2000. This is part of the ecological long-term series of the AWI and is supplemented by periodic large-scale mapping of the benthos. The main factors influencing the development of the benthic communities are biological interactions, climate, food supply (eutrophication) and the disturbance regime. The most frequent disturbances are sediment relocations during strong storms or by bottom trawling, while occasional oxygen deficiencies and extremely cold winters are important disturbance events working on a much larger scale. Benthic communities at the sampling stations show a large inter-annual variability combined with a variation on a roughly decadal scale. In accordance with large-scale system shifts reported for the North Sea, benthic community transitions occurred between roughly the 1970ies, 80ies and 90ies. The transitions between periods are not distinctly marked by strong changes but rather reflected in gradual changes of the species composition and dominance structure.

Seawater carbonate chemistry and biological processes during experiments with calcifiing organisms, 2009

Anthropogenic elevation of atmospheric carbon dioxide (pCO2) is making the oceans more acidic, thereby reducing their degree of saturation with respect to calcium carbonate (CaCO3). There is mounting concern over the impact that future CO2-induced reductions in the CaCO3 saturation state of seawater will have on marine organisms that construct their shells and skeletons from this mineral. Here, we present the results of 60 d laboratory experiments in which we investigated the effects of CO2-induced ocean acidification on calcification in 18 benthic marine organisms. Species were selected to span a broad taxonomic range (crustacea, cnidaria, echinoidea, rhodophyta, chlorophyta, gastropoda, bivalvia, annelida) and included organisms producing aragonite, low-Mg calcite, and high-Mg calcite forms of CaCO3. We show that 10 of the 18 species studied exhibited reduced rates of net calcification and, in some cases, net dissolution under elevated pCO2. However, in seven species, net calcification increased under the intermediate and/or highest levels of pCO2, and one species showed no response at all. These varied responses may reflect differences amongst organisms in their ability to regulate pH at the site of calcification, in the extent to which their outer shell layer is protected by an organic covering, in the solubility of their shell or skeletal mineral, and whether they utilize photosynthesis. Whatever the specific mechanism(s) involved, our results suggest that the impact of elevated atmospheric pCO2 on marine calcification is more varied than previously thought.

Macrofauna abundance and sediment characteristics during R/V Senckenberg cruise west of Sylt in september 2010

The continuously influence of human impacts on the seafloor and benthic habitats demands the knowledge of clearly defined habitats to assess recent conditions and to monitor future changes. In this study, a benthic habitat dominated by sorted bedforms was mapped in 2010 using biological, sedimentological and acoustic data. This approach reveals the first interdisciplinary analysis of macrofauna communities in sorted bedforms in the German Bight. The study area covered 4 km², and was located ca. 3.5 km west of island of Sylt. Sorted bedforms formed as sinuous depressions with an east west orientation. Inside these depressions coarse sand covers the seafloor, while outside predominantly fine to medium sand was found. Based on the hydroacoustic data, two seafloor classes were identified. Acoustic class 1 was linked to coarse sand (type A) found inside these sorted bedforms, whereas acoustic class 2 was related to mainly fine to medium sands (type B). The two acoustic classes and sediment types corresponded with the macrofauna communities 1 and 2. The Aoinides paucibranchiata-Goniadella bobretzkii community on coarse sand and the Spiophanes bombyx - Magelona johnstonii community on fine sand. A transitional community 3 (Scoloplos armiger - Ophelia community), with species found in communities 1 and 2, could not be detected by hydroacoustic methods. This study showed the limits of the used acoustic methods, which were unable to detect insignificant differences in the fauna composition of sandy areas.