photo: michelle's blue planet via flickr.
Though it's a small percentage of the total 5.5 gigatonnes of carbon emissions released annually from human activities, it appears that echinoderms such as starfish, sea urchins and sea lilies are greater carbon sinks than anticipated. They store about 0.1 gigatonnes to be exact, or slightly under 2% human's emissions:Less Than Plankton, but Still Significant
This figure is less than that of organisms like plankton which store carbon as they sink to the bottom of the ocean--these store 0.4-1.8 gigatonnes per year, depending on which studies are used--but still represents "a sizable carbon pump."
Echinoderms' bodies are made of up to 80% calcium carbonate, which led Mario Lebrato, PhD student at the Leibniz Institute of Marine Science, to wonder how much carbon actually was stored by them.
Figure May Be Higher - More Study Needed
Quoted by Nature.com the University of Hawaii's Craig Smith says that these figures may actually be low as "this project had to extrapolate over large areas [and] no doubt hot spots that were glossed over and not included in the global average." Smith pointed out that there are vast areas of the Equatorial Pacific that have large numbers of echinoderms but are not well studied.
Another question that remains: How's ocean acidification going to impact this?
More: Nature News
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