Sea Cucumber Explosion

18 March 2004 (All day)

Holy holothurians! A surplus of carotenoid-laden food may have caused a thousand-fold jump in Amperima populations.

The abyss of the North Atlantic is crawling with them: wiggly pale pink sea cucumbers, here, there, everywhere. Their population has exploded, and deep-sea biologists suspect a sudden glut of food is the cause. The reasons for the sudden bounty aren't clear, but it could be a sign that even the darkness of the abyss has been touched by climate change.

The deep sea is mysterious--it's nearly as inaccessible as the moon, and some claim we know even less about it. But it's not lifeless. Sea cucumbers, or holothurians, are the dominant large animals. Crawling about on the sea floor, they feed off dead algae and other detritus that falls from above. For some reason, the population of Amperima rosea, a small pinkish sea cucumber in the North Atlantic, has skyrocketed.

Before 1996, dredged samples of the North Atlantic sea floor revealed just one or two Amperima rosea per hectare. By late 1997, this 5-centimeter-long sea cucumber was present in the thousands per hectare. In the most recent (December 2003) issue of Progress in Oceanography, researchers suggest this whopping increase was caused by a sudden influx of dead algae rich in carotenoids, pigments used by some plants for photosynthesis. Aquaculture farmers often use carotenoids to boost the reproduction of fish and sea urchins, and the compounds may have the same effect on Amperima. The researchers found higher levels of carotenoids in the guts and reproductive organs of Amperima than in other kinds of sea cucumbers that haven't boomed, suggesting that Amperima may have a distinct diet, says team member Ian Hudson of the Southampton Oceanography Centre in the United Kingdom.

Where the surfeit of carotenoids came from isn't clear. Climate change, or some other factor, might have caused an unusual bloom of phytoplankton with lots of carotenoids in 1996 in the north Atlantic, says Ron Kaufmann of the University of San Diego. But he cautions that with the limited knowledge of the deep sea, researchers can't really tell. Even so, he says, the Amperima explosion is noteworthy. “Changes in the food composition and population of these critters signal changes in the status of the deep sea as a whole.”

Related sites
Ian Hudson's site
The Southampton Oceanography Centre's holothurian site
Basic information about holothurians and their relatives

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