for National Geographic News
When it comes to climate change, polar bears and sharks may grab the bulk of the headlines—but it's the threat to the sea's tiniest creatures that has some marine scientists most concerned.
Malformed seashells show that climate change is affecting even the most basic rungs of the marine food chain—a hint of looming disaster for all ocean creatures—experts say.
Climate change could drastically reduce sea urchin populations in particular, according to Gretchen Hofmann, a marine biologist at the University of California, Santa Barbara.
The purple sea urchin is commonly found off the coast of Australia and Antarctica. It is an essential food source for many marine animals such as cod or lobster, as well as a common ingredient in sushi.
Hofmann is concerned because increasing amounts of atmospheric carbon dioxide are also raising the amount of the gas dissolved in ocean water. This makes the seas more acidic, decreasing the available amount of shell-forming calcium carbonate.
Future Ocean in a Box
To test the theory, Hofmann tested sea urchins in highly acidic water similar to what is predicted for the oceans.
"We checked if they can make the skeleton that forms their bodies, and yes it is formed," Hofmann said. "But it was shorter and stumpier—not the same shape—so they swim and move differently. Plus it comes at a cost, which is they are more sensitive to temperature."
Hofmann refers to this malformed skeleton and sensitivity to heat as "double jeopardy."
She went further than any previous research by analyzing the recently sequenced sea urchin genome to find out what genes were turning off and on under this new environmental stress.
"We wanted to ask them how they were doing and get a sense of their health and physiology," Hofmann said. "We found it caused their shell-forming genes to go up threefold, so their developing system was having to put more energy into making the skeleton and less into other things."
Hofmann presented her findings at the recent meeting of the American Association for the Advancement of Science in Boston, Massachusetts.
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