Rybakova E et al. (2019), Deep-sea megabenthos communities of the Eurasia...

ECB-ART-47312

PLoS One 2019 Jan 01;147:e0211009. doi: 10.1371/journal.pone.0211009.

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Deep-sea megabenthos communities of the Eurasian Central Arctic are influenced by ice-cover and sea-ice algal falls.

Rybakova E , Kremenetskaia A , Vedenin A , Boetius A , Gebruk A .

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Quantitative camera surveys of benthic megafauna were carried out during the expedition ARK-XXVII/3 to the Eastern Central Arctic Basins with the research icebreaker Polarstern in summer 2012 (2 August-29 September). Nine transects were performed for the first time in deep-sea areas previously fully covered by ice, four of them in the Nansen Basin (3571-4066m) and five in the Amundsen Basin (4041-4384m). At seven of these stations benthic Agassiz trawls were taken near the camera tracks for species identification. Observed Arctic deep-sea megafauna was largely endemic. Several taxa showed a substantially greater depth or geographical range than previously assumed. Variations in the composition and structure of megabenthic communities were analysed and linked to several environmental variables, including state of the sea ice and phytodetritus supply to the seafloor. Three different types of communities were identified based on species dominating the biomass. Among these species were the actiniarian Bathyphellia margaritacea and the holothurians Elpidia heckeri and Kolga hyalina. Variations in megafaunal abundance were first of all related to the proximity to the marginal ice zone. Stations located closer to this zone were characterized by relatively high densities and biomass of B. margaritacea. Food supply was higher at these stations, as suggested by enhanced concentrations of pigments, organic carbon, bacterial cell abundances and nutrients in the sediments. Fully ice-covered stations closer to the North Pole and partially under multi-year ice were characterized by lower concentrations of the same biogeochemical indicators for food supply. These stations nevertheless hosted relatively high density and biomass of the holothurians E. heckeri or K. hyalina, which were observed to feed on large food falls of the sea-ice colonial diatom Melosira arctica. The link between the community structure of megafauna and the extent and condition of the Central Arctic sea-ice cover suggests that future climate changes may substantially affect deep ocean biodiversity.

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Genes referenced: LOC100887844 LOC100893907 LOC115919910 LOC115925415 pole

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References [+] :

Bienhold, The energy-diversity relationship of complex bacterial communities in Arctic deep-sea sediments. 2012, Pubmed

	Fig 1. Location of stations performed during the expedition ARK-XXVII/3 in summer 2012 (August-September) to the Arctic Ocean.Ice margin in 2012 (black line) and the marginal ice zone integrated over previous 5 years (dotted area) where sea ice data were available are shown. 2012 represented a new sea-ice minimum except for the area around Gakkel Ridge (140–180°E) that showed a minimum already in 2007. Stations 1–5 were situated closer to the marginal ice zone and were characterized by the first-year sea ice. Stations 7–9 were situated at some distance from the ice edge and/or were characterized by multi-year ice (6).
	Fig 2. Images of the most abundant taxa.(a) Bathyphellia margaritace (Actiniaria), (b) Hyalopomatus claparedii (Polychaeta), (c) Macellicephalinae gen.sp.5 (Polychaeta), (d) Elpidia heckeri (Holothuroidea), (e) Eurycope inermis (Isopoda), (f) Ascorhynchus abyssi (Pycnogonida), (g) Kolga hyalina (Holothuroidea), (h) Onisimus leucopis (Amphipoda), (i) Ophiostriatus striatus (Ophiuroidea). Scale bar 1 cm.
	Fig 3. Contribution to abundance (in %) per station of six most abundant taxa.
	Fig 4. Multidimensional scaling plot for stations based on multivariate Bray-Curtis similarity coefficients for taxa abundance data.Abundance data were standardized to densities and square-root transformed. Similarity (%) is indicated by the coloured lines.
	Fig 5. Contribution to biomass (in %) per station of four most abundant taxa.
	Fig 6. Degree of freshness of ice algae in aggregations at seafloor: (a) greenish-brownish, freshly deposited, (b) whitish-yellowish, mostly degraded diatom falls.
	Fig 7. Canonical correspondence analysis (CCA).Explained variance on the first axis—41% and second axis—33%.