Since 2009 two segments of the East Scotia Ridge (ESR) in the Southern Ocean have been explored, using a remotely
operated vehicle. In each segment deep-sea hydrothermal vents were located, hosting high-temperature black smokers
up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new
yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star.
Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels,
and alvinocaridid shrimps, are absent from the ESR vents.
These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates,
suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa.
Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic
vent ecosystems represent a new vent biogeographic province.
However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate
that vent biogeography is more complex than previously recognised.
And to me that sounds more complex than I can understand, but let's look into it and see what we can find:
West of the ESR, the floor of the Scotia Sea forms part of the Scotia Plate (SCO). To the east of the ESR lies the small South Sandwich Plate (SAN), beneath which the South American Plate (SAM) is being subducted at the South Sandwich
Trench (SST). To the north, the Scotia Plate abuts the South American Plate at the North Scotia Ridge, while to the
south is the Antarctic Plate (ANT) boundary at the South Scotia Ridge.
The first evidence of hydrothermal activity along the ESR was from data obtained by a light-scattering sensor attached
to the Towed Ocean Bottom Instrument (TOBI), a deep-towed sonar system, during a geophysical mapping survey
along the ESR in 1999. The expedition covered here is from 2010-2011.
At E2 the expedition located black smoker chimneys, as well as observing associated fauna, and at E9 found considerable
evidence of diffuse hydrothermal venting, with anemones and stalked barnacles being the dominant megafauna.
Implications for Antarctic Biodiversity Recent investigations of the deep-sea ecosystems of the Southern Ocean have
revealed a high proportion of previously undescribed species, many of which are unknown from elsewhere.
Particularly notable in this respect are groups of the Isopoda, Ostracoda, Gastropoda, and Nematoda. It has been
suggested that Southern Ocean species of these groups are not found outside of the Southern Ocean because they
have life histories that are characterised by a low potential for dispersal.
Likewise, analyses of the fauna of the shelf and slopes of the islands of the Scotia Arc, as far north as Shag Rocks,
suggest that the fauna is largely composed of Antarctic endemics.
Implications for Hydrothermal Vent Biogeography The fauna observed at the vents along the ESR contains none of
the dominant vent species normally found at vents along the main mid-ocean ridge systems. The ESR sites are notable for the absence of siboglinid tubeworms, alvinellid polychaetes, vesicomyid clams, bathymodiolid mussels, and alvinocaridid
shrimp. In addition, there is an absence of typical predators such as bythograeid crabs. Species found at the ESR vents include anemones, lepetodrilid limpets, provannid gastropods, stalked barnacles, and at least three species of pycnogonids,
thus these vents share some faunal elements with communities found at vents associated with back-arc basins in the West
and South West Pacific, the mid-ocean ridge in the South East Pacific, and the Mid-Atlantic Ridge.
The dominant species at the ESR vents is an anomuran crab of the genus Kiwa, which has congeneric species
along the Pacific-Antarctic Ridge and at cold seeps off Costa Rica
Rogers AD, Tyler PA, Connelly DP, Copley JT, James R, et al. (2012) The Discovery of New Deep-Sea
Hydrothermal Vent Communities in the Southern Ocean and Implications for Biogeography.
PLoS Biol 10(1): e1001234. doi:10.1371/journal.pbio.1001234
downloaded January 6th, 2012.
Copyright: 2012 Rogers et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
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