Purple Sea Urchin Combats Ocean Acidification with 'Evolutionary' Weapon

First Posted: Jun 13, 2013 11:47 AM EDT

Ocean acidification is one of the huge issues of climate change. It could drastically affect creatures with a calcium carbonate shell, such as hard corals, mussels and clams. Yet at least one species is fighting back. It turns out that a certain purple sea urchin is learning how to adapt to combat climate change with its own weapon--evolution

Sea urchins can be found everywhere--from the Caribbean to the Pacific. With their spines and spherical symmetry, these creatures live on the ocean floor, feeding off of algae. It's this taste preference in particular that makes them such a valuable species. Many places have had most of their algae-eating species taken through fishing, which means that sea urchins keep reefs clean and healthy.

Ocean acidification, though, presents a huge risk to sea urchins and the future of our seas. Rising carbon dioxide in the Earth's atmosphere is dissolved into the oceans, which slowly acidify due to the increased concentrations of gas.

Essentially, the acidity causes the levels of calcium carbonate to decrease in the water. This would, in turn, result in smaller animals, thinner shells and perhaps shorter spines for the urchins. "It gives them osteoporosis," said Morgan Kelly, one of the researchers, in a news release

In order to see exactly how quickly this acidity would affect sea urchins, the researchers exposed the larvae of these animals to 1,100 parts per million of carbon dioxide. Current CO2 levels are about 400 parts per million and are expected to increase to 700 parts per million by the end of the century.

It was perhaps not surprising that the larvae reared under these future conditions were, on average, smaller. What was unusual, though, was that sizes varied greatly. In fact, the differing sizes seemed to indicate that some of the larvae had inherited tolerance for higher CO2 levels. This indicated that the sea urchins were highly adaptable and could potentially survive as a species when the ocean acidifies.

Needless to say, this is good news for the sea urchin--and the world's oceans. Without the spiny creature, it's likely that conditions would deteriorate rapidly as algae overtook certain areas. Yet that doesn't mean that the sea urchin escapes scot-free.

"We don't expect evolution to completely erase the effects of ocean acidification, but we do expect evolution to mitigate these effects," said Kelly in a news release.

The findings are published in the journal Global Change Biology.

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