James Clark Ross — Week 4, 14-20 March 200814-15 March 2008 — Census of Antarctic Marine Life diaryBy Jan StrugnellSea Mount trawling
Tonight we did some trawling on one of the Marie Byrd sea mounts in an attempt to sample some corals for the geologists on board. The geologists were hoping to collect some corals to look at past carbon dioxide levels held within the coral structure. Deep sea corals had been previously discovered in the Amundsen Sea region and initial analyses of them showed that some of them were alive during the last ice age! (between 12,000-24,000 years ago).
During the last ice age the concentration of carbon dioxide in the Earth's atmosphere was about 1/3 lower than at the start of the present warm period. Climate researchers do not know the location of the ‘sink’ for the carbon dioxide during this time. One explanation is that this carbon dioxide, which is in continuous exchange with the surface waters of the world‘s oceans, was locked up as dissolved carbon dioxide in the deep Southern Ocean during the last ice age. Therefore, deep sea corals represent a unique opportunity for investigating if the deep Southern Ocean was the world's carbon dioxide sink during the last ice age.
The biologists were also interested in any other fauna that we could collect from there as very little is known about sea mount biology and so anything we would collect would be of interest.
Trawling in potentially rocky conditions at depth is greatly increases the risk of getting the trawl stuck, damaging the trawl or even possibly losing it on the bottom! We were therefore a little worried about the condition that the trawl would come back in, if it would come back at all!
Firstly we trawled at 3000m water depth to sample the side of the sea mount. It took over an hour for the trawl to just reach the bottom at this depth and then another hour to be bought back up! The trawl came back in good condition, but unfortunately we did not manage to collect any corals for the geologists and in fact the catch was quite small; we caught brittlestars, an isopod and seacucumbers.
We then decided to trawl across the top of the sea mount at a depth of 2200m to sample the fauna there, and again, hope to collect some corals for the geologists work. Again the catch was very small, and this time contained a serolid isopod, a soft coral and an armoured seacucumber.
This is interesting because it is the first time that the biology of any Amundsen Sea seamounts have been sampled. Upon first inspection the animals seem very similar to those we found living at similar depths on the continental slope off Pine Island Bay.
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