Breaking Point

Previous research has shown that ocean acidification will thin the shells of some marine organisms. Now a new study suggests that mussels will suffer another side effect: The threads that attach them to rocks will weaken.

Higher carbon dioxide levels in the atmosphere mean higher CO2 levels near the surface of the ocean as well. That increase in CO2 causes the pH of the water to drop, making it more acidic. Some mussels use stiff, stretchy structures called byssal threads to latch onto surfaces, and the researchers wanted to know whether ocean acidification would loosen the organisms’ grip.

The team collected mussels from San Juan Island, Washington and exposed them to different pH levels. The byssal threads of mussels at a pH of 7.5 broke more easily than mussel threads at a pH of 8.0, the researchers report in Nature Climate Change. The threads also couldn’t stretch as far in low-pH conditions. Overall, a mussel’s ability to hang on drops by 35 to 41 percent in more acidic water, the authors estimate.

Weakened mussels could be bad news for ocean ecosystems and seafood producers. Acidification will “increase dislodgement risk in natural habitats and commercial suspension cultures,” the team writes. Roberta Kwok | 11 March 2013

Source: O’Donnell, M.J., M.N. George, and E. Carrington. 2013. Mussel byssus attachment weakened by ocean acidification. Nature Climate Change doi: 10.1038/nclimate1846.

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