Warmer, More Acidic Seas Spell Doom for West Coast Abalone

inside abalone shell photo

Migrated Image / Rojer / Flickr

As the temperature and acidity of the ocean hike up, shellfish are having a harder time battling the shift. This includes the abalone that lives up and down the west coast of North America. Considered a delicacy, the sea snail is struggling with overfishing -- and now it must also deal with conditions that are stunting growth and killing off the next generations. According to a new study by the University of British Columbia, as ocean acidity increases, the chances of survival of larvae, and the size of those that do survive, decrease dramatically.

In an experiment to replicate possible levels of CO2 in the ocean in the coming years, the researchers tested the effects of hiking up CO2 levels from 400 parts per million to 1,800 ppm. They found that such an increase killed 40% of larvae and increased shell abnormalities. Granted, that kind of increase is very dramatic. Current CO2 levels in the ocean are around 380 ppm and that is expected to continue to rise as the ocean absorbs more of the carbon dioxide already released into the atmosphere. However, it would take centuries to reach 1,800 ppm. Still, the experiment shows that increased CO2 levels are not something the abalone easily deals with.

Not only does this create concern over the future of wild abalone, but it also means that aquaculture may not be an option as well.

"This is quite bad news, not only in terms of the endangered populations of abalone in the wild but also the impact it might have on the prospects for aquaculture and coastal economics," says Christopher Harley, Full Professor with the Department of Zoology and one of the authors of the study. "And because the species is already thought to be limited by reproductive output and recruitment, these effects are likely to scale up to the population level, creating greater limits on population growth."

Similar findings were uncovered by Australian researchers earlier this year, showing that sea urchins and abalone can't grow shells in warmer temperatures, with the team noting, "The results of a new study show that abalone and sea urchins born into ocean conditions 100 years from now will be unable to calcify their shells or grow their spines - suggesting that key sources of protein will be lost due to climate change in the future. "

Researchers have also uncovered difficulties for other crustaceans as CO2 levels rise. For some creatures, the response is thickened shells, which is bad news for both the species itself and those who feed off it. For the animal, a thickened shell equates to wasted energy as its body uses nutrients to build up an excess shell, which can then become a burden to carry. And for predators, it means a harder time getting at prey. On the flip side, heightened CO2 levels cause shells of other species to dissolve, making them too weak to be a protective cover.

No matter what, warmer and more acidic oceans are problematic for shellfish, and could signal a pending mass extinction of shellfish species.