(Tables 1, 3) Details of Agassiz trawl stations and numbers of specimens per macro- and megazoobenthic taxon collected during POLARSTERN cruise ANT-XXII/3 (ANDEEP III)

The assemblages inhabiting the continental shelf around Antarctica are known to be very patchy, in large part due to deep iceberg impacts. The present study shows that richness and abundance of much deeper benthos, at slope and abyssal depths, also vary greatly in the Southern and South Atlantic oceans. On the ANDEEP III expedition, we deployed 16 Agassiz trawls to sample the zoobenthos at depths from 1055 to 4930 m across the northern Weddell Sea and two South Atlantic basins. A total of 5933 specimens, belonging to 44 higher taxonomic groups, were collected. Overall the most frequent taxa were Ophiuroidea, Bivalvia, Polychaeta and Asteroidea, and the most abundant taxa were Malacostraca, Polychaeta and Bivalvia. Species richness per station varied from 6 to 148. The taxonomic composition of assemblages, based on relative taxon richness, varied considerably between sites but showed no relation to depth. The former three most abundant taxa accounted for 10-30% each of all taxa present. Standardised abundances based on trawl catches varied between 1 and 252 individuals per 1000 m2. Abundance significantly decreased with increasing depth, and assemblages showed high patchiness in their distribution. Cluster analysis based on relative abundance showed changes of community structure that were not linked to depth, area, sediment grain size or temperature. Generally abundances of zoobenthos in the abyssal Weddell Sea are lower than shelf abundances by several orders of magnitude.

Response of A. aurita ephyrae to three stressors: high-temperature, high-CO2 and low-oxygen

Global change is affecting marine ecosystems through a combination of different stressors such as warming, ocean acidification and oxygen depletion. Very little is known about the interactions among these factors, especially with respect to gelatinous zooplankton. Therefore, in this study we investigated the direct effects of pH, temperature and oxygen availability on the moon jellyfish Aurelia aurita, concentrating on the ephyral life stage. Starved one-day-old ephyrae were exposed to a range of pCO2 (400-4000 ppm) and three different dissolved oxygen levels (from saturated to hypoxic conditions), in two different temperatures (5 and 15 °C) for 7 days. Carbon content and swimming activity were analysed at the end of the incubation period, and mortality noted. General linearized models were fitted through the data, with the best fitting models including two- and three-way interactions between pCO2, temperature and oxygen concentration. The combined effect of the stressors was small but significant, with the clearest negative effect on growth caused by the combination of all three stressors present (high temperature, high CO2, low oxygen). We conclude that A. aurita ephyrae are robust and that they are not likely to suffer from these environmental stressors in a near future.

The near-bottom plankton and benthic invertebrate fauna of Josephine and Great Meteor Seamounts (Table 2)

15 samples obtained with Beyer's epibenthic closing net were studied quantitatively. The numbers of epi- and endobenthic animals were found to be correlated with the volume of sediment in the samples. Among the planktonic components, calanoid copepodes were strongly predominant. In the samples obtained on the Great Meteor Seamount, very much larger numbers of these animals were caught in the daytime than at night. Possible explanations for this difference are suggested.