A group of researchers from the National Oceanography Center in Southampton has discovered a strange new deep-sea volcanic vent at Hook Ridge near the South Shetland Islands, Antarctica.
This image shows a 2 m-high chimney at a depth of ~1200 m, emanating hydrothermal fluid visible as shimmering water (Aquilina A et al)
Hydrothermal vents are like hot springs, spewing jets of water from the seafloor out into the ocean. The expelled water, if hot enough, is rich in dissolved metals and other chemicals that can nourish a host of strange-looking life, via a process called ‘chemosynthesis.’ The hot water, being more buoyant than the surrounding cold seawater, rises up like a fountain or ‘plume,’ spreading the chemical signature up and out from the source.
The newly discovered vent, named the Hook Ridge vent, however, was found to lack the high temperatures and alien-like creatures that scientists associate with hot hydrothermal vents. Instead there was a low-lying plume of shimmering water, caused by differences relative to the surrounding seawater in certain properties, such as salinity.
“Geochemical measurements of the water column provided evidence of slightly reducing, localized plumes close to the seafloor at Hook Ridge,” said Dr Alfred Aquilina, lead author of the study published in the journal PLoS ONE.
“We therefore went in with sled-mounted cameras towed behind the Royal Research Ship James Cook and saw shimmering water above the seafloor, evidence of hydrothermal fluid seeping through the sediment.”
So why were there no strange creatures around the vent? The team investigated this particular area of the deep-sea because prior measurements of the water column above Hook Ridge detected chemical changes consistent with a hydrothermal plume. On investigation, there was also a small relict ‘chimney’ of precipitated minerals on the seafloor, which suggests that the hydrothermal fluid flowing from the vent was once warmer.
This map shows the Bransfield Strait and the location of the Hook Ridge vent (Aquilina A et al)
The researchers therefore propose that hydrothermal activity at Hook Ridge is too irregular to provide the vital chemicals that support chemosynthetic life.
“This region was investigated because hydrothermal systems in this part of the Southern Ocean may potentially act as stepping stones for genetic material migrating between separate areas in the world ocean,” Dr Aquilina said. “The more hydrothermal vents we can find and investigate, the more we can understand about the evolution and dispersal of the creatures that live off the chemicals expelled in these dark, deep environments.”
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Bibliographic information: Aquilina A et al. 2013. Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica). PLoS ONE 8(1): e54686; doi: 10.1371/journal.pone.0054686
Source link: https://www.sci.news/geology/article00879.html
