Graph credit: Seattle TImes
Even while they were eggs inside their moms Alaska crabs have been test subjects for how increasing ocean acidity will affect them as they grow.
“What we are finding is that amount of energy that goes into those eggs early in the process has something to do with how the mom was exposed to OA. She doesn’t see the impacts directly, but we do see impacts on her offspring two years later. So there’s an effect down the line.”
Bob Foy is NOAA’s Science and Research Director based at the Auke Bay lab in Juneau.
For more than a dozen years Alaska scientists at NOAA labs have run long term experiments on king and Tanner crabs exposed to levels of acidity the ocean is expected to reach from 30 or more years out. It’s referred to as pH –
“Why does pH matter? If you go to the doctor and he drew blood to look at your health – metabolism and how your chemistry is functioning internally. It’s the same thing for fish in the ocean. pH changes the ability of the genes to work properly. pH changes the ion balance in the blood. It changes the ability of chemicals to move, for instance, food and calcium to shells of a crab. So understanding that dynamic is super important.”
The pH also affects the ability to form shells. Results show that red king crab are more susceptible than Tanner crab and Tanner crab more than snow crab.
“We don’t show an effect of OA on snow crab – that’s pretty exciting because it’s the largest shellfish fishery in Alaska. But what we’re finding with red king crab, one of our most lucrative fisheries, is substantial impact.”
The mechanics of the claw in Tanners are affected, Foy says, but the carapace is not.
“Why does that matter? The claws are required for crushing that bivalve for food. If that’s more brittle, perhaps it will affect their ability to feed.”
Based on global estimates, the Bering Sea may reach a pH level of 7.5 to 7.8 in the next 75 to 100 years if not earlier.
Based on computer models, for red king crab that could mean a 25 percent decline in the number of larvae hatching.
“That means about a 50 percent decrease in catching and profits about 20 years after this onset of low pH or ocean acidification in Alaska. About 20 years, and that’s a buffer in there, the variability that we already see in the recruitment for these stocks. That equates to about $500 million to a billion dollars in total welfare lost to Alaska.”
Foy cautions what’s seen in the lab may be different in the wild. His presentation was hosted by the Alaska Ocean Acidification Network, an arm of the Alaska Ocean Observing System.