If you're a clam chowder fan, be alarmed: The carbon dioxide we are pumping into the atmosphere is also turning our oceans into clam-shell-eating acid, with consequences that have already hit coastal shellfishing towns hard. Now, researchers have come up with some ideas of how—and where—to make the biggest difference, at least in the short run.
"Ocean acidification has already cost the oyster industry in the US Pacific Northwest nearly US $110 million, and directly or indirectly jeopardized about 3,200 jobs," write Natural Resources Defense Council researcher Julia Ekstrom and 16 other scientists in Nature Climate Change. That's sparked efforts to find regional solutions that can be put in place now, but not much has been done to understand which communities will need help or what could be done to combat the effects of ocean acidification.
Combining the environmental and social factors, the Pacific Northwest and northern California in the West, and Maine in the East are likely to feel the harshest effects of ocean acidification.
Roughly speaking, ocean acidification works like this: absorbed into the ocean, carbon dioxide combines with water to form carbonic acid. Carbonic acid in turn binds together with materials like calcium carbonate, the stuff mollusk shells are made of, to form bicarbonates that are of no use to mollusks. The effects are nasty. Oyster larvae build their shells from a form of calcium carbonate called aragonite, for example, but in acidic water there isn't enough aragonite for young oysters to grow properly. Meanwhile, carbonic acid in high enough concentration can eat away at adult mollusks' existing shells.
To examine how growing CO2 levels in the atmosphere will affect shellfish—and with them, regional economies—the team first broke U.S. coastal waters into parts corresponding to National Estuarine Research Reserve regions. Within each, they looked at projections for ocean acidification and its effects on aragonite, the particular calcium carbonate form mollusks use to build their shells, as well as local effects that could amplify the process. The researchers combined that with data on how dependent clusters of coastal communities are on shellfish to identify the regions most likely to be threatened by ocean acidification.
The waters off Alaska, Washington, and Oregon, the team found, will probably cross the threshold into shellfish-lethal acidity first, likely within the next 35 years. On the other hand, East and Gulf Coast regions are most vulnerable economically—in Massachusetts, for example, shellfishing accounts for a great deal of revenue and makes up a higher portion of fishing revenue than most other locales. Combining the environmental and social factors, the Pacific Northwest and northern California in the West, and Maine in the East are likely to feel the harshest effects of ocean acidification.
Though it's a grim outlook, the study does offer some suggestions to reduce the risk. Reducing the amount of acid-boosting fertilizers that end up in oceans, and improving the diversity of harvested shellfish species are just two specific examples given. Alternatively, programs already underway suggest that water monitoring combined with acid buffering, changes in the production timing, and selectively breeding for more acid-tolerant shellfish appear to have averted the collapse of the Pacific Northwest's oyster industry.