February 7, 2013
Shimmering Water Leads Researchers To Rare Cold Volcanic Vent
April Flowers for redOrbit.com - Your Universe Online
Scientists at the National Oceanography Centre (NOC), Southampton have discovered the location of an underwater volcanic vent in the Southern Ocean. In a study published this week in the journal PLOS ONE, the researchers describe how this vent, marked by a low-lying plume of shimmering water, differs from "classic" hydrothermal vents.
The research group used the NOC´s high-resolution deep-towed camera platform SHRIMP to image the seafloor at Hook Ridge, which is more than half a mile deep. The original focus of the study, funded by the Natural Environment Research Council (NERC) was to expand scientific understanding of how deep-sea creatures associated with hydrothermal activity evolve and migrate between different regions.
Spewing jets of often boiling-hot water from beneath the seafloor into the ocean, hydrothermal vents are like hot springs. If the water is particularly hot, then it is typically rich in dissolved metals and other chemicals that nourish deep-sea life in a process known as "chemosynthesis." Because the hot water, like hot air, is more buoyant than the surrounding cold seawater, it rises like a plume towards the surface of the ocean. This spreads the chemical signature up and outwards from the source.
The vent at Hook Ridge was unusual, however, in that it did not have the typical high temperatures and alien-like sea creatures that scientists generally associate with hydrothermal vents. Instead, the Hook Ridge vent displayed a low-lying plume of shimmering water. This shimmer effect, the researchers say, is caused by differences in the water being spewed from the vent 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, former research fellow at University of Southampton Ocean and Earth Science.
"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."
The reason the team initially decided to investigate the Hook Ridge area was because prior-measurements of the water column above the ridge detected chemical changes most often associated with a hydrothermal plume. When they examined the area, they noticed that the unusual creatures typically found around hydrothermal vents were not there. They also found a small relict "chimney" of precipitated minerals on the seafloor, suggesting that the hydrothermal fluid coming from the vent was at one time much warmer.
The team suggests that the hydrothermal activity at Hook Ridge is irregular, too irregular to provide the vital chemicals that support chemosynthetic life. According to Dr. Aquilina, this is an important discovery.
"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," he explained.
"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."
This study is part of the on-going ChEsSO project to investigate chemosynthetic environments and their associated ecosystems south of the Polar Front.