Distribution and composition of the epibenthic megafauna north of Svalbard (Arctic)

Abstract

Benthic communities north of Svalbard are less investigated than in other Arctic shelf regions, as this area was covered by sea-ice during most of the year. Improving our knowledge on this region is timely, however, since climate change is strongly evident there, particularly with regard to the extent of sea-ice decline and its huge ecological impact on all marine biota, including the benthos. Moreover, longer ice-free periods will certainly lead to an increase in human activity levels in the area, including bottom trawling. In two adjacent shelf and slope regions off northern Svalbard, we studied the composition of epibenthic megafauna and seafloor habitat structures by analyzing seabed images taken with both still and video cameras. In addition, we also used an Agassiz trawl to catch epibenthic organisms for ground-truthing seabedimage information. A wide variety of mostly sessile organisms 141 epibenthic taxa were identified in the images. The brittle star Ophiura sarsii and the soft coral Gersemia rubiformis were the most common species. At all stations [300 m in depth, evidence of trawling activities was detected at the seabed. The distribution of the benthic fauna in the study area exhibited a clear depth zonation, mainly reflecting depth-related differences in seabed composition. We conclude that natural factors determining the composition of the seafloor mostly affect the distribution and composition of epibenthic assemblages. Anthropogenic impact indicated by the trawl scours found is likely also important at smaller spatial scales.

Drivers of Megabenthic Community Structure in One of the World’s Deepest Silled-Fjords, Sognefjord (Western Norway)

“…In general, much of the same taxa composition was observed in both dives for depth zones below the sill depth. The largest difference in megabenthic community composition was found between the deepest and shallowest zones for both dives, and similar trends have been observed in other surveys (Starmans et al, 1999;Sswat et al, 2015;Molina et al, 2019). In the present study, the Basin Zone was characterized more by sessile fauna (e.g., P. squamatus, Acesta excavata, Hymenodiscus coronata, and sponges) and M. tenuimana, whereas the Above Sill Zone was more dominated by echinoderms and anemones.…”

Environmental factors structuring Arctic megabenthos—a case study from a shelf and two fjords

“…Lateral advection is also responsible for local-scale patterns of benthic food supply (Mayer and Piepenburg, 1996;Piepenburg, 2005). In a recent study, (Sswat et al, 2015) found that the north Svalbard shelf benthos was influenced by depth and substratum type, with higher diversity and abundance of sessile suspension feeders occurring at shallower stations. Station 14 in this case study had the highest abundance and diversity of suspension feeders and also the greatest availability of hard substrata (Figures 5, 9).…”

“…Despite recent research efforts (Sswat et al, 2015), our understanding of how abiotic factors influence the megabenthos around Svalbard remains limited. As future climatic changes are likely to be more dramatic in the Arctic than in other regions (ACIA, 2006;Mora et al, 2013), it is especially important to understand what factors influence these communities (Bergmann et al, 2011;Nephin et al, 2014).…”

Observations of floating anthropogenic litter in the Barents Sea and Fram Strait, Arctic

“…Their highest litter counts coincide with areas of intensive fishery and shipping. Indeed, Sswat et al (2015) reported evidence of trawling activities at all stations [300 m depth on the seabed northwest of Svalbard.…”