The past of oceans told by sponges and corals
25 September 2011
Although our main objectives are to explore the New Caledonia deep-sea biodiversity and to better understand the biogeography of the fauna, our trawls bring back a large variety of samples that can be of interest to our chemist, geologist, and paleoceanographer colleagues like Kate Hendry (Woods Hole Oceanographic Institution / Cardiff University) and Laura Robinson (Woods Hole Oceanographic Institution).
Kate and Laura explain how the corals and sponges collected during ExBoDi will advance their work on the chemical composition of the oceans in the past and the factors that control coral populations:
“My name is Kate Hendry, and I’m a paleoceanographer, and I use sedimentary archives to unravel how changes in ocean circulation are linked with climate change. Although I’m not lucky enough to have taken part in the cruise to New Caledonia, I’m benefiting from the science on board nonetheless.
I specialize in the chemistry of deep-sea sponges.
Sponges are very simple animals that live on the seafloor and make their living from eating detritus. They make their skeletons from glassy needle-like “spicules”, and it’s the chemical composition of these spicules that can give us information about the nutrients in the seawater in which they grow. This means that by analyzing fossil spicules that are found in deep-sea sediment cores, we can figure out how the circulation of nutrients, which are essential for the growth of algae that take up carbon from the atmosphere, has changed in the past.
Although I’ve investigated modern sponges, and the chemistry of their skeletons, from various places such as the Southern Ocean and the Pacific, I have never investigated sponges from New Caledonia. I’m so grateful to the scientists on the cruise for collecting samples for me, and I wish them all the luck for their science projects too.”
“I too am a paleoceanographer, and I have been using the chemical composition of the fossil remains of deep-sea corals to look at oceanographic change over time. Since some deep-sea corals can live for hundreds to thousands of years they form a truly unique archive of the history of deep water.
We can also use the radioactive decay of either carbon or uranium to find out how long it has been since the coral died, so by dating the skeletons of the corals collected off New Caledonia we will be able to find out how long corals have populated this part of the ocean.
These chemical tools give a historic perspective when thinking about the major controls on coral populations today, and I look forward to collaborating with the biology team to think about how and why coral populations may thrive or die out.”
For further information
Robinson LF, Adkins JF, Scheirer DS, Fernandez DP, Gagnon A, Waller RG (2007) Deep-sea scleractinian coral age and depth distributions in the Northwest Atlantic for the last 225,000 years. Bulletin of Marine Science 81(3): 371-391
The blog of the NBP11-03 expedition lead by Laura this summer: http://antarcticcorals.blogspot.com