Vertical distribution of megafauna on the Bering Sea slope based on ROV survey

Abstract

Video surveys were carried out during the 75th cruise of the RV Akademik M.A. Lavrentyev (June 2016) along the northern slope of the Volcanologists Massif, in the south-western Bering Sea. The seafloor was explored using the ROV Comanche 18. Seven dives were performed in the depth range from 4,278 m to 349 m. Overall, about 180 species of megafauna were recognised. Fifteen types of megafauna communities corresponding to certain depth ranges were distinguished based on the most abundant taxa. Dominance changed with depth in the following order: the holothurian Kolga kamchatica at the maximum depth (4,277–4,278 m); the holothurian Scotoplanes kurilensis at 3,610–2,790 m; the ophiuroid Ophiura bathybia at 3,030–2,910 m; benthic shrimps of the family Crangonidae at 2,910–2,290 m; the holothurian Paelopatides solea at 2,650–2,290 m; benthic jellyfish from the family Rhopalonematidae at 2,470–2,130 m; the enteropneust Torquaratoridae at 2,290–1,830 m; the holothurian Synallactes chuni and the ophiuroid of the genera Ophiura and Ophiocantha at 1,830–1,750 m. At depths 1,750–720 m most of the megafauna was associated with live or dead colonies of the sponge Farrea spp. Depths 720–390 m were dominated by the coral Heteropolypus ritteri and/or Corallimorphus pilatus. At 390–350 m depth, the shallowest depth range, the dominant taxon was the zoantharian Epizoanthus sp. Soft sediment megafauna communities dominated by torquaratorid enteropneusts to our knowledge have not been observed before in the deep-sea, the same as communities with a dominance of benthopelagic rhopalonematid jellyfish. The depths of the largest community changes, or the largest turnover of dominant species, were revealed at ∼2,790 m between the bathyal and abyssal zones and ∼1,750 m and ∼720 m within the bathyal zone.

A synoptic review of the family Dendronotidae (Mollusca: Nudibranchia): a multilevel organismal diversity approach

“…Bathymetry. A deep-sea (bathyal) species, so far recorded at 670-761 m depth (for discussion of the different usage of the term "bathyal", see Rybakova et al, 2020).…”

New and Poorly Known Species of Peniagone (Holothuroidea, Elpidiidae) from the Northwest Pacific Ocean with Discussion on Phylogeny of the Genus

“…It can be explained by possible interspecies interactions. Rybakova et al [44] showed the abyssal community in the Bering Sea being dominated by another elpidiid species, Kolga kamchatica Rogacheva. The latter may occupy the same trophic niche as Peniagone replacing Peniagone species in the Bering Sea.…”

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“…The species has been reported from eastern Russia at depths of 64-145 m off the island of Paramushir (Naumov 1960;Antsulevich 1987Antsulevich , 2015, from 8-24 m in Avacha Bay on the east coast of the Kamtchatka Peninsula (Schuchert et al 2016), and from Matua Island . Meanwhile, Rybakova et al (2020) reported Candelabrum sp. from video surveys of the northern slope of Volcanologists Massif, southwest Bering Sea, at bathyal and abyssal depths (3450-3610 m; 4277-4278 m).…”