What Is Ocean Acidification?
Carbon dioxide is one of several factors influencing global warming. A good deal of it remains in the air after it is released by industrial processes, trapping solar radiation in the atmosphere. However, about 50 percent of it is absorbed by the ocean. As Christopher Sabine, a geophysicist with the National Oceanic and Atmospheric Administration in Seattle, Washington, explains, this process is “a great service to humankind.” Unfortunately, “this service has potential consequences for the biology and ecosystem structure of the oceans.”
When carbon dioxide is absorbed by seawater, the chemical composition of the seawater changes. The pH level drops (making the water more acidic) and the level of calcium carbonate minerals is subsequently reduced. That’s a problem because creatures such as oysters, clams, sea urchins, corals and calcareous plankton need calcium carbonate to build their shells. Corals and plankton especially form a foundation for the ocean’s biosphere, and a reduction in these essential minerals could result in a catastrophic blow to the food chain.
Since the Industrial Revolution, research shows that surface ocean waters have experienced a 30 percent increase in acidity.
Adaptation Has Its Limits
In her interview with Yale Environment 360’s Elizabeth Grossman, Gretchen Hofmann discussed how certain invertebrates appear to be adapting to this more acidic environment: “[W]hat we’ve found is that there are populations of sea urchins on the West Coast that appear to have the genetic diversity to, at least right now, respond to acidic conditions in the ocean.”
But this adaptability may have an upper threshold. Hofmann continues:
“We don’t know if this adaptive capacity can be sustained in low pH water for really long periods of time. Evolution can come to the rescue but probably can’t go on forever. You can say these organisms have responded to the changing environment because they’re used to a variable environment, but some of the biology they do, like calcification, is dependent on the chemistry of what’s in the water and it’s unlikely that they can adapt their way out of not having water that doesn’t support calcification anymore. I think evolution buys us time. How much, we don’t know.”
And just as West Antarctica’s glacial melt has passed the point of no return, so too has our chance of stopping acidification. “There are a lot of engineering solutions that people are looking at right now,” says Hofmann, “but geo-engineering solutions to change the pH of the ocean just are not going to apply. There’s not enough baking soda in the world to dump into the water to change things.”
Click here for the full interview on Yale Environment 360.