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. © 2007 Elsevier Ltd. All rights reserved.
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Beta-diversity measures have been used to understand patterns of community distribution in natural ecosystems. Recent studies included different facets of beta-diversity analyses, e.g. trait- and phylogeny-based. Here, we used ostracod communities to evaluate the influence of environmental and spatial factors structuring different facets of beta-diversity and their components (Beta-total, replacement and richness-difference) of ostracod communities associated with different macrophyte life forms. We test the hypotheses (1) that the influence of environmental factors is higher for ostracod beta-diversity facets of communities associated with submerged plants compared to emergent and floating plants and (2) that the influence of spatial factors is higher in communities associated with rooted, compared to non-rooted plants. Ostracods were sampled from five life forms of macrophytes, including emergent, rooted floating, rooted submerged, free submerged and free floating in 25 floodplain lakes. Our results showed that the environmental factors turned out to be important for all beta-diversity facets of ostracod communities, mainly for those associated with submerged macrophytes, thus corroborating the first hypothesis. We also found that spatial factors’ influence on ostracod beta-diversity was not related to whether the plant is rooted or not, thus refuting our second hypothesis. We also found differences in factors structuring each of the beta-diversity facets, showing the importance to include these three approaches (species-, traits- and phylogeny-based) in ecological surveys. Finally, we highlight the importance of considering different macrophyte life forms in biodiversity surveys for the preservation and management of the diversity of these plants and their associated communities.
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RBINS Staff Publications 2021
