Snow Crabs Snack at Methane Seeps

Tanner crabs, photo courtesy of Sara Seabrook.

A group of Oregon State University researchers studying the seafloor off the coast of British Columbia have made a surprising discovery. Tanner crabs, one of three species sold as “snow crabs,” were seen clustering around the methane seeps of the Clayoquot Slope. Some of the methane there is being eaten by archaea, an ancient prokaryote that still feeds off the same chemicals they did before Earth gained its modern oxygen atmosphere. Unexpectedly however, the crabs were found readily eating the methane-munching microorganisms.

This was surprising to marine ecologists like OSU’s Andrew Thurber and Sarah Seabrook, who are studying the crabs, and whose paper on them has just been published in the journal Frontiers in Marine Science. Previously, it had been thought that almost all food reached the seafloor by falling from above, therefore it had been expected that methane seeps would increase in number and intensity as the oceans warmed. Since methane is a much more potent greenhouse gas than carbon dioxide, this could be catastrophic, but we now know that much of it is being gobbled up by the archaea and, in turn, dispersed back into the food chain through crabs. This also helps fend off the deep-dwelling population crash that was expected due to the impact of climate change in the higher levels of the ocean. How much this helps remains to be seen, but discoveries like this are good news in a sea of bad news.

“It’s very exciting,” Seabrook says, “since methane seeps were first discovered, we’ve found many species of animals [besides] crabs. I’ve explored around [and marine geologists have] found over two thousand methane seeps.” Other species noticed near the seeps include Pacific sole and black cod.

“The Oregon economy depends on crabs caught off the coast,” Seabrook emphasized. Since it’s now known that crabs congregate around methane seeps, “we need to refine methods of finding that needle in a haystack.”

By John M. Burt