Controls on faunal microdistribution and reproductive development in deep-sea chemosynthetic environments in the Antarctic

Abstract

There is no longer any part of the ocean that is inaccessible, however, spanning 361 million km2 across the earth's surface and, with approximately 50% of its volume at a depth greater than 2000 m, it is the very sheer size and complex nature of the deep ocean, that means it still remains one of the least understood environments on earth. Deep-sea hydrothermal vents are insular and ephemeral sea oor habitats that host locally abundant populations of vent endemic taxa, supported by in situ primary production through chemolithoautotrophy. Since the initial discovery along the Galapagos rift in 1977, global vent communities have been shown to exhibit significant variation in the taxonomic composition of their assemblages and, as a result, a number of biogeographic provinces have been proposed. In 2009, the ChEsSO consortium (Chemosynthetic Ecosystem Science in the Southern Ocean) initiated a three-cruise program for the discovery and exploration of chemosynthetic environments south of the Polar front. One of the major findings was the discovery of the E2 and E9 vent fields on the East Scotia Ridge (ESR), revealing faunal assemblages distinct from those of other vent biogeographic provinces. Using precision high-definition ROV videography to create broad-extent mosaic images, this thesis examines the spatial dynamics and ecological processes that govern the zonation of the faunal assemblages associated with the Antarctic vent environment. Analysis of faunal microdistribution reveals a consistent pattern of zonation with increasing distance from vent fluid exits, which can be attributed to ecological processes such as nutritional mode and reproductive development. In addition, by examining the variation in microdistribution on chimneys with differing levels of activity, suggests a possible successional sequence for vent fauna in this new biogeographic province. Finally, with over three years of visual observations, this study reveals constancy in the broad taxonomic composition of assemblages, and stability in the spatial distribution in reproductive development of dominant motile vent fauna (Kiwa n. sp.) on an intermediate-spreading ridge, which challenges the widespread perception and understanding of deep-sea vent environments.

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ORCID for Jon Copley: orcid.org/0000-0003-3333-4325

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