Alaska’s oceans are becoming increasingly acidic, which could damage Alaska’s king crab and salmon fisheries, according to new findings by a University of Alaska Fairbanks scientist.
This spring, chemical oceanographer Jeremy Mathis returned from a cruise armed with seawater samples collected from the depths of the Gulf of Alaska. When he tested the samples’ acidity in his lab, the results were more acidic than expected. They show that ocean acidification is likely more severe and is happening more rapidly in Alaska than in tropical waters. The results also matched his recent findings in the Chukchi and Bering Seas.
It seems like everywhere we look in Alaska’s coastal oceans, we see signs of increased ocean acidification. The increasing acidification of Alaska waters could have a destructive effect on all of our commercial fisheries. This is a problem that we have to think about in terms of the next decade instead of the next century.—Jeremy Mathis
The ocean absorbs carbon dioxide from the air. As the ocean absorbs more carbon dioxide, seawater becomes more acidic. Scientists estimate that the ocean is 25% more acidic today than it was 300 years ago.
Mathis’ recent research in the Gulf of Alaska uncovered multiple sites where the concentrations of shell-building minerals were so low that shellfish and other organisms in the region would be unable to build strong shells.
We’re not saying that crab shells are going to start dissolving, but these organisms have adapted their physiology to a certain range of acidity. Early results have shown that when some species of crabs and fish are exposed to more acidic water, certain stress hormones increase and their metabolism slows down. If they are spending energy responding to acidity changes, then that energy is diverted away from growth, foraging and reproduction.—Jeremy Mathis
Another organism that could be affected by ocean acidification is the tiny pteropod, also known as a sea butterfly or swimming sea snail. The pteropod is at the base of the food chain and makes up nearly half of the pink salmon’s diet. A 10% decrease in the population of pteropods could mean a 20% decrease in an adult salmon’s body weight.
The cold waters and broad, shallow continental shelves around Alaska’s coast could be accelerating the process of ocean acidification in the North, Mathis said. Cold water can hold more gas than warmer water, which means that the frigid waters off Alaska’s coasts can absorb more carbon dioxide. The shallow waters of Alaska’s continental shelves also retain more carbon dioxide because there is less mixing of seawater from deeper ocean waters.
Mathis said that it is still unclear what the full range of effects of ocean acidification will be, but that it is a clear threat to Alaska’s commercial fisheries and subsistence communities.