Rapid Adaptation Is Purple Sea Urchins' Weapon Against Ocean Acidification

June 12, 2013 — In the race against climate change and ocean acidification, some sea urchins may still have a few tricks up their spiny sleeves, suggesting that adaptation will likely play a large role for the sea creatures as the carbon content of the ocean increases.

"What we want to know is, given that this is a process that happens over time, can marine animals adapt? Could evolution come to the rescue?" said postdoctoral researcher Morgan Kelly, from UC Santa Barbara's Department of Ecology, Evolution and Marine Biology. She is a co-author of the paper "Natural variation, and the capacity to adapt to ocean acidification in the keystone sea urchinStrongylocentrotus purpuratus." The paper was published in the latest edition of the journal Global Change Biology.

Easily identified by their spherical symmetry and prickly barbs, sea urchins are found on the sea floor all over the world. They are considered a keystone species, meaning their population has an important impact on the rest of the undersea ecosystem. Too many of them and their habitat becomes barren and other algae-eating species disappear; too few and their predators -- including sea mammals, seabirds, and fish -- lose an important food source.

Due to rising carbon dioxide in Earth's atmosphere, the oceans of the future are projected to absorb more carbon dioxide, leading to acidification of the water. The change in the ocean chemistry is expected to negatively affect the way urchins and other calcifying creatures create and maintain their shells and exoskeletons.

"It gives them osteoporosis," said Kelly. Increased water acidity would cause the levels of calcium carbonate -- which the sea urchins require -- to decrease. This, in turn, would result in smaller animals, thinner shells and perhaps shorter spines for the urchins.

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