Researchers discover crab feeding on methane seeps

The researchers say the implications are many and surprisingly, most of them are good. The human consumption of tanning crabs, one of the three species sold as snow crab, which feed on methane-eating and archaic bacteria should not pose any health problems, as methane seeps do not are not toxic environments.

This discovery could actually mean that methane seepage could provide some species living on the seabed with important protection against climate change, as almost all models predict that less food will fall to the depths of the oceans in the years to come. to come up.

The results of the study have just been published in the journal Frontiers in Marine Science.

"Previously, it was thought that the marine food chain relied almost solely on phytoplankton that went down the water column and fertilized the depths," said Andrew Thurber, marine ecologist at Oregon State University and co-author of the # 39; study. "We now know that this point of view is not complete and that it could have many more facets.

"The tanning crabs are probably not the only species to derive energy from methane seeps, which have not yet been much studied." We used to think it was There may have been five off the northwest Pacific coast and research now shows that there are at least 1,500 infiltration sites – and probably many more.

"Methane can be a very important and underestimated source of energy for marine organisms, unlike plankton, it does not change much with the seasons and it is thought that seepage will last for hundreds of years. "

Researchers first observed a dense conglomeration of tanning crabs (Chionoecetes tanneri) in 2012, inhabiting Clayoquot Slope, a methane fault off the coast of British Columbia. The crabs were actively feeding, sifting through the sediment in areas with lots of bubbles, feeding both on and around the bacterial mats that had formed near the point of infiltration.

Another dense group was observed in microbes that consume methane in 2014 around the nearby Barkley Canyon Dam, suggesting that crabs could use seepage as a source of "trophic support," said Sarah Seabrook, lead author of the 39, study, Sarah Oregon, author of the study. Ph.D. candidate at the College of Earth Sciences, Ocean and Atmosphere.

"Despite observing tanners crabs feeding at the sites over and over, there was not much evidence that animals were eating methane using established methods," Seabrook said. "So we looked at it more closely and found chemical evidence of methane tracers in the intestines and biogeochemical evidence in their tissues.

"This raises the question of whether we can apply these new techniques to other species and find out if the use of oozed methane as a food source is more prevalent than tanning crabs."

Other fish caught for commercial purposes, especially in deeper waters, have often been observed near methane seeps. This includes the long-thorn spine, a species of commercial importance for export to Japan; Patagonian toothfish, also known as the Chilean bar; and the strange orange off New Zealand. Sole and black cod (sablefish) have also been observed off the coast of Oregon near methane seeps.

"There are hundreds of methane infiltrating on the east coast of the United States, thousands in the Gulf of Mexico, and there are probably thousands in the Arctic who have not seen it. not yet discovered, "said Thurber. "They are all over the world, so the idea that they can provide a source of energy is quite intriguing."

OSU and NOAA researchers have mapped methane infiltration sites off the northwest coast in the past two years. Although many of them have depths of several hundred meters, they have also been documented in much shallower waters, which would make them available for a wider range of sites. Marine animals.

Thurber also notes that "deep-sea discoveries are not just new discoveries, but that they can often change our understanding of the importance of the deep seabed." This project was born from our observation of a crab raised by methane above the seabed. This entertaining footage was the genesis of this project and led us to add to our understanding of the connection between depths and society. "

Fabio De Leo, co-author of the document and marine ecologist with Ocean Networks Canada (ONC) at the University of Victoria (UVic), adds: "For us, the collection of wildlife specimens from the seabed is d & # 39; great value for understanding how different species respond to long-term changes in the ocean environment. "

The study took place at the ONC Observatory, which has been collecting data on the deep seabed since 2009. "We hope to continue studying the deep sea fauna of the northeastern Pacific in order to to understand how it adapts to changing climate change, "said De Leo.

Thurber said that Oregon, Washington, and California are all starting to include the distribution and importance of methane leakage in management decisions off their respective coasts. This work can help inform these decisions by providing a previously undocumented link between the species harvested and the energy released during methane seeps.

Explore further:
Biodiversity surprises when the Cascadia Fault infiltrates the icy waters of the deep sea

More information:
Sarah Seabrook et al, Flipping for Food: The use of a methane seepage by tanning crabs (Chionoecetes tanneri), Frontiers in Marine Science (2019). DOI: 10.3389 / fmars.2019.00043