One of the species of plankton that fish depend on is already being threatened by ocean acidification. That’s from data presented at the Alaska Marine Science Symposium in Anchorage this week.
Nina Bednarsek with the Southern California Coastal Research Center is studying pterapods, a kind of tiny oceangoing snail which many fish, including salmon, eat. She has been looking into ocean acidification data for the Gulf of Alaska, the Bering Sea, and the Canadian Beaufort Sea. She’s using the tiny snails as an indicator of the water’s acidity level. Highly corrosive water can literally dissolve its shell.
“Pterapods are already dissolving in the Gulf of Alaska, and that’s mostly in the western part of the Gulf of Alaska in the spring time.”
That could be bad news for salmon that eat these tiny snails. Ocean acidity varies from place to place. For instance, Bednarsek says that the snails are doing a bit better in the Bering Sea, but not that much better.
“We start seeing some presence of shell dissolution in the inner to mid shelf, but less so in the mid to outer shelf.”
Again, the situation is worse closer to shore. The data indicates that the situation is especially bad in the spring. Much of this is due to the spring meltwater, and Claudine Hauri at the University of Alaska Fairbanks says that climate change means that there is more of that fresh water runoff each year.
“So that means there is already an effect of climate change that enhances ocean acidification as well.”
The scenarios laid out by Bednarsek for pterapods look a bit like horror movies. One possibility is a crash, with the pterapods being at their most vulnerable in the kinds of conditions that have become increasingly more common: when high acidic levels coincide with their spring spawn.
“And so there is a real danger if you’re going to have those mismatch be the spawning and the worse conditions," she said. "We also know that these conditions are changing here with one of the fastest rates globally.”
As bad as it is in Alaskan waters, all we have to do to find even more acidic conditions is look next door to Canada’s Beaufort Sea.
“Inner fiords are really severely affected,” says Bednarsek. We can find upwards to 70 percent of pterapods being severely affected by shell dissolution already.”
Scientists are studying to see if these snails and other ocean creatures can find ways to adapt to these changing ocean conditions.