The influence of the geomorphological and sedimentological settings on the distribution of epibenthic assemblages on a flat topped hill on the over-deepened shelf of the western Weddell Sea (Southern Ocean)

Abstract

Abstract. Epibenthos communities play an important role in the marine ecosystems of the Weddell Sea. Information on the factors controlling their structure and distribution are, however, still rare. In particular, the interactions between environmental factors and biotic assemblages are not fully understood. Nachtigaller Hill, a newly discovered seabed structure on the over-deepened shelf of the northwest Weddell Sea (Southern Ocean), offers a unique site to study these interactions in a high-latitude Antarctic setting. Based on highresolution bathymetry and georeferenced biological data, the effect of the terrain and related environmental parameters on the epibenthos was assessed. At Nachtigaller Hill, both geomorphological and biological data showed complex distribution patterns, reflecting local processes such as iceberg scouring and locally amplified bottom currents. This variability was also generally reflected in the variable epibenthos distribution patterns although statistical analyses did not show strong correlations between the selected environmental parameters and species abundances. By analysing the interactions between environmental and biological patterns, this study provides crucial information towards a better understanding of the factors and processes that drive epibenthos communities on the shelves of the Weddell Sea and probably also on other Antarctic shelves.

Organic carbon and biogenic silica in marine sediments in the vicinities of the Antarctic Peninsula: spatial patterns across a climatic gradient

“…Local-scale conditions were also distinct for the case for the station 190 in the WS, where the lowest biogenic matter contents were found. This station was in the shadow of a prominent sea floor structure (e.g., submarine hill), the Nachtigaller Hill, which apparently exerts influence on the near-bottom water current and consequently on the benthos (Dorschel et al 2014) and based on our results, and also on the arrival of biogenic matter to the seabed. Nevertheless, the low inventories calculated for this station did not change the regional differences.…”

Seabed images from Southern Ocean shelf regions off the northern Antarctic Peninsula and in the southeastern Weddell Sea

“…In the northern Weddell Sea, stations were selected to cover a range of habitats that are as comparable as possible to those sampled in the Bransfield Strait. Four stations were situated at the northeastern side of the Nachtigaller Shoal on the western Weddell Sea shelf (Dorschel et al, 2014). Figure 3 is an example of a seabed photo taken at station PS81/110, showing rich megabenthic epifauna (e.g., abundant ascidians and a swarm of demersal nototheniid fish) on the shelf off Joinville Island in the eastern Bransfield Strait at 212 m of water depth on 26 January 2013.…”

“…The supplementary information used in this study, including environmental data, is also available from PANGAEA (SegelkenVoigt et al, 2016a). A second example is the investigation of the influence of geomorphological and sedimentological settings on the distribution of epibenthic assemblages on the Nachtigaller Shoal, a flat-topped submarine hill at the over-deepened shelf of the western Weddell Sea discovered during the PS81 cruise in 2013 (Dorschel et al, 2014).…”

Your comment on Ms “Seabed images from Southern Ocean shelf regions off the northern Antarctic Peninsula and in the southeastern Weddell Sea” by Dieter Piepenburg et al.

“…These regions are well suited for a comparative ecological study with a biogeographical and ecological background, since they are characterized by different environmental conditions in terms of sea-ice coverage, current regime, and food supply to the benthos. Within these regions, regional habitat blocks were selected that were comprised of bathymetric intermediate-scale shelf-slope gradients Dorschel et al, 2016). In the Bransfield Strait, such bottom topography structures were most obvious, and three distinct habitat blocks were sampled.…”

“…It is a contribution to the international scientific research program Antarctic Thresholds -Ecosystem Resilience and Adaptation (AnT-ERA) of the Scientific Committee on Antarctic Research (SCAR). By applying a comparative field study approach, the geographical focus of Dy-nAMo was on an area with above-average warming of surface waters and sea-ice reduction around the tip of the Antarctic Peninsula (Gutt, 2013;Gutt et al, 2016) and a stable high-Antarctic marine environment that is not (yet) affected by climate change in the southeastern Weddell Sea (Schröder, 2016).…”