Relationships between host phylogeny, host type and bacterial community diversity in cold-water coral reef sponges.

Cold-water coral reefs are known to locally enhance the diversity of deep-sea fauna as well as of microbes. Sponges are among the most diverse faunal groups in these ecosystems, and many of them host large abundances of microbes in their tissues. In this study, twelve sponge species from three cold-water coral reefs off Norway were investigated for the relationship between sponge phylogenetic classification (species and family level), as well as sponge type (high versus low microbial abundance), and the diversity of sponge-associated bacterial communities, taking also geographic location and water depth into account. Community analysis by Automated Ribosomal Intergenic Spacer Analysis (ARISA) showed that as many as 345 (79%) of the 437 different bacterial operational taxonomic units (OTUs) detected in the dataset were shared between sponges and sediments, while only 70 (16%) appeared purely sponge-associated. Furthermore, changes in bacterial community structure were significantly related to sponge species (63% of explained community variation), sponge family (52%) or sponge type (30%), whereas mesoscale geographic distances and water depth showed comparatively small effects (<5% each). In addition, a highly significant, positive relationship between bacterial community dissimilarity and sponge phylogenetic distance was observed within the ancient family of the Geodiidae. Overall, the high diversity of sponges in cold-water coral reefs, combined with the observed sponge-related variation in bacterial community structure, support the idea that sponges represent heterogeneous, yet structured microbial habitats that contribute significantly to enhancing bacterial diversity in deep-sea ecosystems

Spatial patterns in the distribution of benthic assemblages across a large depth gradient in the Coral Sea, Australia

The Queensland Plateau in the Coral Sea off north-eastern Australia supports numerous submerged and emergent reefs. Osprey Reef is an emergent reef at the northern tip of the plateau ~1500 m in elevation. Over such a large depth gradient, a wide range of abiotic factors (e.g. light, temperature, substratum etc.) are likely to influence benthic zonation. Despite the importance of understanding the biodiversity of Australia's Coral Sea, there is a lack of biological information on deep-water habitats below diving depths. Here we used a deep-water ROV transect to capture video, still photos and live samples over a depth range spanning 92 to 787 m at North Horn on Osprey Reef. Video analysis, combined with bathymetry data, was used to identify the zones of geomorphology and the benthic assemblages along the depth gradient. There were marked changes in the geomorphology and the substrate along this depth gradient which likely influence the associated benthos. Cluster analysis indicated five benthic assemblage groups, which showed clear zonation patterns and were generally predictable based on the depth and sedimentary environment. These results are the first quantitative observations to such depths and confirm that the waters of the Coral Sea support diverse benthic assemblages, ranging from shallow-water coral reefs to mesophotic coral ecosystems, to deep-water azooxanthellate corals and sponge gardens. The knowledge provided by our study can inform management plans for the Coral Sea Commonwealth Marine Reserve that incorporate the deeper reef habitats and help to minimise future damage to these marine ecosystems

Timing of retreat of the Reuss Glacier (Switzerland) at the end of the Last Glacial Maximum

We used cosmogenic 10Be and 36Cl to establish the timing of the onset of deglaciation after the Last Glacial Maximum of the Reuss Glacier, one of the piedmont lobes of the Alpine ice cap that reached the northern Alpine foreland in Switzerland. In this study, we sampled erratic boulders both at the frontal position in the foreland (Lenzburg and Wohlen, canton Aargau) and at the lateral Alpine border position (Seeboden moraine, Rigi, canton Schwyz). The minimum age for the beginning of retreat is 22.2 ± 1.0 ka at the frontal (terminal) position and 20.4 ± 1.0 ka at the lateral position. These ages are directly comparable with exposure ages from the other piedmont lobes in the northern Alpine foreland. Our data from the mountain called Rigi, do not support the hypothesis that boulders located external to the Seeboden moraine were deposited prior to the last glacial cycle. We present a first exposure age from an erratic boulder in a retreat position in the Alpine foreland. The Reuss Glacier was approximately 12 km behind the maximal extent no later than at 18.6 ± 0.9 ka