Benthic assemblages of mega epifauna on the Oregon continental margin

Lenaig G. Hemery; Sarah K. Henkel; Guy R. Cochrane

doi:10.1016/j.csr.2018.03.004

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Benthic assemblages of mega epifauna on the Oregon continental margin

Lenaig G. Hemery·Sarah K. Henkel·Guy R. Cochrane

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Abstract

Environmental assessment studies are usually required by a country's administration before issuing permits for any industrial activities. One of the goals of such environmental assessment studies is to highlight species assemblages and habitat composition that could make the targeted area unique. A section of the Oregon continental slope that had not been previously explored was targeted for the deployment of floating wind turbines. We carried out an underwater video survey, using a towed camera sled, to describe its benthic assemblages. Organisms were identified to the lowest taxonomic level possible and assemblages described related to the nature of the seafloor a nd the depth. We highlighted six invertebrate assemblages and three fish assemblages. For the invertebrates within flat soft sediments areas we defined three different assemblages based on primarily depth: a broad mid-depth (98–315 m) assemblage dominated by red octopus , sea pens and pink shrimps; a narrower mid-depth (250–270 m) assemblage dominated by box crabs and various other invertebrates; and a deeper (310–600 m) assemblage dominated by sea urchins, sea anemones, various snail s and zoroasterid sea stars. The invertebrates on mixed sediments also were divided into three different assemblages: a shallow (~100 m deep) assemblage dominated by plumose sea anemones, broad mid-depth (170–370 m) assemblage dominated by sea cucumbers and various other invertebrates; and, again, a narrower mid-depth (230–270 m) assemblage, dominated by crinoids and encr usting invertebrates. For the fish, we identified a rockfish assemblage on coarse mixed sediments at 170–370 m and another fish assemblage on smaller mixed sediments within that depth range (250–370 m) dominated by thornyheads, poachers and flatfishes; and we identified a wide depth-range (98–600 m) fish assemblage on flat soft sediments dominated by flatfishes, eelpouts and thornyheads. Three of these assemblages (the two broad fish assemblages and the deep flat soft sediments invertebrate assemblage) seem to represent deeper examples of assemblages already known on the Oregon continental shelf, especially on soft sediments, while the assemblages in the pockmarks habitat (the narrower depth ranges) might be unique to the area. This diversity of assemblages in a relatively small section of the Oregon continental upper slope and shelf shows the importance of environmental assessment studies in helping limit future impacts of industrial activities on benthic communities.

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Continental Shelf Research Article

Source-reported bounding extent: 43.3° to 43.5833° latitude; -124.8° to -124.4167° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeX RIS

Lenaig G. Hemery, Sarah K. Henkel, Guy R. Cochrane. 2018. Benthic assemblages of mega epifauna on the Oregon continental margin. https://doi.org/10.1016/j.csr.2018.03.004

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