ClimateWire's Morello examines impact of rising ocean acidity on crab development

According to the Intergovernmental Panel on Climate Change, ocean acidity is expected to dramatically rise by the end of the century. This drop in pH could cause major problems for certain species of fish, and hurt the commercial fishing industry. In this ClimateWire Special Report, Lauren Morello reports on research being conducted at the National Oceanic and Atmospheric Administration's (NOAA) Fisheries Science Center in Kodiak, Alaska. Morello talks to Bob Foy, director of the Center, about the impact of ocean acidification on crab growth.


Lauren Morello: Carbon dioxide is changing the ocean. The world seas absorb about 2 million tons of CO2 each day. Ocean water is now 30 percent more acidic than it was in the early 19th century, before humans began burning unprecedented amounts of fossil fuels. Scientists are scrambling to understand how the drop in pH will affect life under water. If ocean water becomes too acidic it can hinder shellfish, corals, and plankton from building their shells. At extreme levels of acidity the shells could even begin to dissolve. That's a big concern in the state of Alaska where commercial fishing pulled in over $1 billion worth of fish in 2006. Bob Foy, director of the National Oceanic and Atmospheric Administration's laboratory in Kodiak, Alaska, is one scientist examining how ocean acidification might affect Alaskan waters.

Bob Foy: I would say that the ocean acidification has hit the radar screen of fishermen and scientists and legislators and managers like a rock in the last couple of years.

Lauren Morello: Foy and his colleagues have been trying to figure out how more acidic waters will affect Alaska's famed king crabs, one of the most valuable species harvested in state waters.

Bob Foy: The pH has only changed 0.1 to 0.2 pH units and one might think that that's minor, but pH is on a logarithm scale, meaning that that's quite a large change in pH units. Biologically that's a very large change. Biological organisms tend to live in a fairly consistent pH range, so even a small change like that is fairly large.

Lauren Morello: Foy's first experiments showed that growing in low pH water makes it harder for young crabs to survive. Now, he and his colleagues are beginning a more sophisticated set of experiments. They're using a special set of tanks and tubes that allow them to pipe in precise amounts of carbon dioxide simulating future atmosphere and surface ocean conditions predicted by climate models. According to the Intergovernmental Panel on Climate Change the ocean pH could fall another 0.14 to 0.35 units by the end of this century, equaling or even doubling the change of observed over the last 200 years.

Bob Foy: Our initial results are that, in fact, higher carbon dioxide does cause a lower pH and does impact the growth of the crab.

Lauren Morello: The next step for the researchers is to determine how the lower pH interferes with crab growth.

Bob Foy: The question is does the low pH situation affect their physiological ability to build the shell or is the low pH literally dissolving the shell on their back? And that's a question we don't have an answer to yet.

Lauren Morello: A broader issue facing scientists, how might changes caused by ocean acidification rippled through entire ocean ecosystems? In Alaska, for example, there are concerns that tiny marine snails called pteropods might be especially vulnerable to more acidic waters. These creatures are a staple food for young salmon, a major commercial fish.

Bob Foy: For the first time you're starting to hear people say that ocean acidification may be even more important than some other aspects of just temperature change.

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