Sea cucumbers dissolve coral reefs

Sea cucumbers release acidic gastric juices that break down coral reefs at night.
10 January 2012


A new study has uncovered the important role that humble sea cucumbers play in the balance of coral reefs, as it turns out their acidic gastric emissions cause coral reefs to dissolve.

Researchers at One Tree Island on Australia's Great Barrier Reef originally made measurements of seawater that showed that during the night, a significant portion of the coral reef dissolved away - and they didn't know why. But they did notice that there were a lot of sea cucumbers hanging out in the area, and they wondered if they perhaps were to blame.

sea cucumberIn the tropics these unprepossessing tubular relatives of starfish and sea urchins, spend much of their lives laying about on the seabed acting like living vacuum cleaners, slurping up mouthfuls of sand and coral rubble, and squirting out - from the other end - piles of cleaned up sediment.  In the process they release dissolved calcium carbonate into the water.

The team, led by Kenny Schneider from the Carnegie Institution for Science in California took some sea cucumbers into the lab and essentially measured what went in and what went out of them.

And they estimate that sea cucumbers are responsible for around half the carbonate dissolution every night on the coral reef. That might sound bad, but in fact sea cucumbers are doing a vital job of recycling nutrients back into the ecosystem to make them available to primary producers.

The dissolved calcium carbonate they release also helps to buffer against the rising levels of acidity in the oceans that's taking place because of increasing levels of carbon dioxide dissolving from the atmosphere.

It goes to show that there is still so much we need to learn about the complex interactions of species in ecosystems like coral reefs, and emphasizes the importance of maintaining all those different species - because even if they look like just harmless critters, lounging about on the seabed, they could be playing a very important role in the overall health of the ecosystem.

Find out more:

Kenny Schneider and Ken Caldiera
You Tube video discussing the study

Schneider et al. (2011). Potential influence of sea cucumbers on coral reef CaCO3 budget: A case study at One Tree Reef. Journal of Geophysical Research VOL. 116, G04032, 6 PP. doi:10.1029/2011JG001755


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