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

Abstract

From photographic samples, we describe the benthic megafaunal communities in two north Svalbard fjords and on the adjacent continental shelf. We analyze the fauna in relation to abiotic factors of depth, bottom water temperature, percent cover of hard substrata, heterogeneity of stone size, and bottom-water turbidity to explore how these factors might affect the fauna and how they are related to the functional traits (size, morphology, mobility, colonial/solitary, and feeding type) of the megabenthos. Depth and bottom water temperature were consistently the strongest correlates with faunal composition and functional traits of the constituent species. A greater proportion of the variability in the functional traits of the megabenthos could be explained by abiotic factors rather than faunal composition, indicating that the abiotic factors of depth and temperature were strongly related to the functional traits of the megabenthos. On a local scale, stone size heterogeneity explained most variation in the functional traits of the megabenthos in one fjord. The results of this case study show a significant relationship between bottom water temperature and the functioning of north Svalbard megabenthic communities. If our results are representative for other areas, warming temperatures in the Arctic may decrease the variety of functional traits represented in Svalbard megabenthos, resulting in scavenger-dominated communities. A reduction in megabenthic biomass may also result, reducing energy availability to higher trophic levels.

Glacial dropstones: islands enhancing seafloor species richness of benthic megafauna in West Antarctic Peninsula fjords

“…This could contribute to poor connectivity between fjords as well as between fjord and shelf sites, leading to community differences on scales of 10−100 km. Similar results were observed in the Arctic as well, where variability in functional traits of dropstone fauna was best correlated with bottomwater temperature (Meyer et al 2015).…”

“…iceberg scour, burial from glacial sedimentation), sea-ice duration, productivity, and habitat heterogeneity (Gutt 2001, Gutt & Piepenburg 2003, Cummings et al 2006, Thrush et al 2010. In Svalbard fjords and in the Weddell Sea, heterogeneity provided by dropstones enhances functional and taxonomic diversity (Meyer et al 2015, Post et al 2017, and similar patterns may exist for other soft-sediment habitats containing dropstones, including within Antarctic glaciomarine fjords.…”

“…The addition of hard substrata, in the form of dropstones, to soft-sediment dominated benthic landscapes at fjord and shelf floors enhances habitat heterogeneity, potentially influencing biodiversity. Habitat heterogeneity has been shown to increase diversity in many ecosystems, ranging from forests to abyssal plains (MacArthur & Wilson 1967, Simberloff 1974, Huston 1979, McClintock et al 2005, Schön-berg & Fromont 2012, Amon et al 2016), but the contribution of glacial debris to habitat heterogeneity has been assessed at only a few locations on continental shelves (Oschmann 1990, Starmans et al 1999, Schulz et al 2010, Meyer et al 2015, Lacharité & Metaxas 2017. On the Antarctic shelf, the most influential factors affecting benthic biodiversity are postulated to be disturbance (e.g.…”

Major impacts of climate change on deep-sea benthic ecosystems

“…This disturbance leads to scale-dependent recolonization of scoured areas and an increased input of dropstones (Smale and Barnes, 2008). These processes will enhance seafloor heterogeneity and create hard substrates for sessile megafauna (Schulz et al, 2010;Meyer et al 2015Meyer et al , 2016. Dropstones also create diverse microhabitats for meiofauna, allowing for greater trophic and functional diversity around stones (Hasemann et al, 2013;Gooday et al, 2015).…”

First records of Lacydonia eliasoni Hartmann-Schröder, 1996 (Polychaeta: Phyllodocida) in the European Arctic

“…As is the influence of this increase on the composition, productivity and diversity of functional traits of both planktonic and benthic communities (Drinkwater 2006;Weydmann et al 2014;Meyer et al 2015). Organisms with pelagic life stages have better dispersal potential and should be the first to react to changing environments with range expansions (e.g.…”