The chemistry showing that our oceans are becoming more acidic can’t be denied. So how does all that absorption of increasing carbon dioxide affect some key Alaska fisheries?
“The direct effect of carbon dioxide increase may be the pH effect on the ability of a pollock or cod to grow or to have gas exchange across the gill membranes. It may be carbonate availability for a crab to build a shell directly.”
Bob Foy is director of the NOAA Fisheries lab at Kodiak. Other impacts, he says, affect fish behavior and senses.
“ A number of studies have shown that some species of fish lose the olfactory ability to find prey with lower pH. That’s going to be a problem, obviously.”
Then there are the food web effects –
“Pteropods are known to be severely affected by ocean acidification they also are one of the most important prey items for pink salmon.”
Ocean acidification impacts are a research focus of at the Kodiak NOAA lab. At a Sea Grant marine science symposium, Foy revealed years of test results on key Alaska species.
“Initial work on northern rock sole found they are sensitive to increases in cO2 , found not much effect at the hatch of the egg stage but reduced growth and higher mortality in high cO2 levels.”
It’s a different story for Alaska’s biggest catch: pollock.
“No results have suggested that OA is an issue for walleye pollock. Again, remembering that this is just physiological effects in the lab so we are moving on to see if there are any behavioral effects.”
It’s the opposite for Bering Sea Tanner and king crab.
“We have found they are very affected especially at the younger life stages, when embryos are exposed to acidified water that negatively affects all the rest of the life stages to the point where we’re seeing substantial mortality at the larval stage and juvenile stage. “
Unless the trend is reversed, a tipping point could be reached in 50 to 75 years .
“This is an extreme, a worst possible scenario based on our laboratory experiments and considering no acclimation of the organism. But it is important to take the information to communities to explain the potential about where we are going or where OA might take us relative to our commercial fisheries.”
Based on global estimates of ocean acidification, the Bering Sea may reach a pH level of 7.5 to 7.8 in the next 75 to 100 years if not earlier.
“Once the Bering Sea reaches those pH levels, Foy said, “there will be significant decreases in survival and subsequent fishery yields and profits within 20 years.”
Laine Welch, Alaska Fish Radio, 24 August 2017. Audio and text.