NOAA Study: Snow Crab Likely Well Adapted to Projected Ocean pH Levels

A male snow crab embracing a mature female prior to mating. Photo: NOAA Fisheries/Chris Long.

Conclusions of a two-year federal study suggest that snow crabs are well adapted to face projected increases in ocean acidification within the next two centuries, with no detectible effects on embryo development, larval hatching or female calcification.

Authors of the study, which was published Oct. 18 in the open access online journal Plos One, said that given the number of strongly negative effects they have documented over the years it was refreshing to be able to report relatively good news in regard to how high the level of carbon dioxide needs to be to affect a commercial crab species.

In both years of the study, starvation-survival, morphology, condition and calcium/magnesium content were assessed for larvae.

The difference in response to high partial pressure of carbon dioxide between Tanner and snow crabs is striking, particularly regarding the response of embryos, the report said.

The two species are congenators, have overlapping distributions in the Bering Sea and are able to produce fertile hybrids, but ocean acidification reduces hatching success in Tanner crab by over 70%. It also reduces calcium content in larvae, increases mortality of both adults and juveniles, reduces juvenile growth, increases hemocyte mortality and causes both internal and external dissolution of the adult carapace, the report states.

Given current data, researchers said they were cautiously optimistic, though, that snow crab are likely to prove resistant in the face of changing oceanic carbonate chemistry. Future work, however, should still be conducted to see how different life stages respond to ocean acidification, they said.

Studies examining all larval stages, including the juvenile stage of snow crab, should be performed before it can be concluded that the species as a whole will be resistant to ocean acidification, they added.

Researchers also said that as the presence of partial pressure of carbon dioxide in oceans increases, temperatures are also projected to increase. They called for additional research on the impact of partial pressure of carbon dioxide, temperature and hypoxia on snow crab.

The work was conducted by Robert J. Foy, director of the Alaska Fisheries Science Center, along with center biologists Katherine M. Swiney and William Christopher Long.

The complete report is available online at