ANOXIC MARINE BASINS -
ENVIRONMENT
News: Anoxic marine basins are among
the best candidates for deep-sea carbon sequestration, say scientists
What's in the news?
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Anoxic marine basins may be among the most viable
places to conduct large-scale carbon sequestration in the deep ocean, while
minimizing negative impacts on marine life.
Anoxic Marine Basins:
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An anoxic basin is a body of water without oxygen.
Formation:
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Permanent anoxic basins form when there is a strong
layering of the water column created in a cup-like formation on the ocean
floor.
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The layering is caused by density differences due to salt concentration or temperature.
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Once stratification occurs, circulation with the
rest of the ocean is minimised, and microorganisms consume the oxygen in the
water.
Features:
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In most anoxic basins, the water is extremely stagnant and can have mixing times of
many thousand years.
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They range
from a few hundred metres to several kilometres across and from 10 metres to
500 metres deeper than the surrounding seafloor.
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They can’t
support animal life and are populated primarily by microbes and some very
specialised fungi with different metabolisms than creatures in oxygen-rich
environments.
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Some of them rely
on molecules such as nitrate for respiration, and some get their carbon
from gases like carbon dioxide (CO2) and methane (CH4) instead of eating other
organisms or particles of organic matter.
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Many anoxic basins also contain toxic chemicals, which are produced by
geothermal activity or by microbes living in the basins.
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Some also contain salt domes, big mounds of hardened salt.
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In some anoxic basins, methane and other gases collect in reservoirs beneath the seafloor.
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The gases can percolate upward, pushing up domes of
sediment on the seafloor that are called mud volcanoes.
● The gases can burst through the soft sediments, creating "mini-eruptions" of the wispy column.