Active volcanoes / Aktive vulkaner:

Scotia-vents. South Atlantic Ocean.   ikke ferdig enda

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:

The following are the results of an expedition to the Scotia sea, which is located between
Argentine, The Sandwich Islands and Antarctic.

The presence of black smokers, diffuse venting, and associated chemosynthetically driven ecosystems
along the ESR, a geographically isolated back-arc spreading centre in the Atlantic sector of the
Southern Ocean, Antarctica

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.

(D). Dog’s Head vent site is indicated. White arrows indicate vent sites not mentioned in text.

Chimneys of variable morphology were up to 15 m tall and venting
clear fluid with a maximum measured temperature of
352.6°C, which formed focused black smokers on contact with cold
seawater (Figure A).

At E2 and E9, the fauna is visually dominated by extensive
dense aggregations of a new species of yeti crab, Kiwa n. sp.
(Figure E).

This is the original Kiwa Hirsuta.
(The hairy limbs seems to be missing on the Scotia species???)
Yeti crabs were apparently first observed in 2001 near Easter Island in the Pacific Ocean,
and then again in 2005.

Perhaps the most notable facet of the Kiwa hirsuta's anatomy is its hairy limbs. These "hairs" are
in fact a dense collection of setae. Currently, the actual use of these setae are unknown, however,
under microscopic inspection many filamentous bacteria has been found living among this dense
group of setae.

Kiwa hirsuta was discovered 900 miles south of Easter Island on the floor of the Pacific Ocean at a
depth of 7,540 feet (2,300 meters). Its natural habitat seems to be around hydrothermal vents along
the ocean floor. Because the Kiwa hirsua somewhat newly discovered, little is known specific about
the dietary habitats of this species.

Additional common fauna at the sites includes at least five morphospecies of sea anemone,
three of which are found in diffuse flow associated with chimneys or sheet and pillow lavas in
densities of up to ,70 m22 (Figure 3A–3D).
One is a red anemone that is similar in appearance to Chondrophellia sp. or Hormathia spinosa

Actinostolid sea anemones surrounded by cf. Vulcanolepas on a chimney with diffuse
hydrothermal venting at E9 (Dive 138, 2,396 m depth).

Anemone field at E9 with juvenile Kiwa n. sp. interspersed (Dive 139, 2,398 m depth).
Scale bar: 10 cm upper right.

A second common gastropod is a limpet of the genus Lepetodrilus (Figure 3D).
Lepetodrilus is a genus of sea snails, marine gastropod mollusks in the family Lepetodrilidae.
Undescribed peltospiroid gastropod at E2 surrounding single Kiwa n. sp. and partially covered by
Lepetodrilus n. sp. The pycnogonid cf. Sericosura is at the bottom right of the image
(Dive 132, 2,608 m depth). Scale bar: 10 cm for foreground.

An undescribed seven-arm sea star predatory on the stalked barnacles cf. Vulcanolepas at E9
(Dive 139, 2,402 m depth). Scale bar: 10 cm for foreground.

Unidentified octopus at E9 (Dive 144, 2,394 m depth). Scale bar: 10 cm for foreground.

Collage of frame grabs of high-definition video to show fauna dispersion on the E9 vent site Ivory Tower.
The vertical chimneys are covered with the anomuran Kiwa n. sp., and the area between the chimneys is
occupied primarily by an undescribed peltospiroid gastropod (Dive 142, 2,398 m depth, ROV heading 090u).
Scale bar: 1 m upper right.
Collage created by L. M. doi:10.1371/journal.pbio.1001234.g004

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
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.



over 250


over 500


over 300

    alfabetisk liste
    alphabetic list

Denne siden er laget ved hjelp av Macromedia Dreamweaver