Acidification Threatens Viability of Pacific Mussels
California mussels may be in danger from climate change
Rising carbon dioxide levels acidify oceans, weaken shells
TheAggie.org (California), Aug. 8, 2011
A recent study has found that the declining pH of oceans, a phenomenon called ocean acidification, could result in diminishing numbers of mussels throughout the northeastern Pacific.
"Mussels are a foundation species," said Eric Sanford, a co-author of the study and associate professor at the UC Davis department of evolution and ecology. "They live on the outer coast of California and create habitat for other small organisms like a coral reef," he explained.
Brian Gaylord, main co-author and professor of evolution and ecology at UC Davis added, "They are a conspicuous band of organisms living on rocks. Some organisms do consume mussels but most small organisms crawl within the matrix of the mussel bed for shelter."
These animals dependent on mussels for their home and food include crabs, worms and snails - a complex web that is now threatened because of the rising amounts of carbon dioxide in the atmosphere.
The report claims that carbon dioxide absorbed by seawater results in lowered pH levels and loss of carbonate ions. This changed seawater chemistry can "impair the ability of marine organisms to construct calcium carbonate shells and skeletons," leaving them vulnerable to predation.
The report was published in The Journal of Experimental Biology. It was based largely on lab studies conducted at the Bodega Marine Lab that tested effects of ocean acidification on mussels.
Mussel larvae spend between a week to six months swimming freely. Larvae shells increase in strength over time before the larvae eventually settle on a rocky surface to grow into adulthood.
The larvae used in the study were raised by the scientists in elevated carbon dioxide seawater cultures.
"Carbon dioxide levels were selected to match predictions for the end of this century," according to the report.
The scientists then measured shell strength and area midway through the larval period. The second measurement was taken prior to the settlement of the organisms.
According to the report, the results were far from optimistic, as the acidic seawater strongly impacted shell strength. The shell area measurements were also discouraging, as the acidic environment resulted in a subtle change in shell area.
Scientists also measured shell thickness where the most devastating effect of ocean acidification could be seen. The report noted that, "shell thickness was significantly altered under [ocean acidification], leading to larval shells … that were approximately 15 percent thinner in elevated carbon dioxide."
The report says that although most climate change research in the past has centered on global warming, scientists are now faced with the realization that similarly drastic changes have resulted from the absorption of carbon dioxide in seawater.
In fact, the report claims that "between 25 and 40 percent of ... carbon emissions have entered the marine realm since the advent of the industrial age."
When asked what short term steps can be taken to prevent this phenomenon, Gaylord said, "Nothing."
"It is a pessimistic response," he said, later adding that "we are committed to climate change and change in seawater chemistry globally now, but there is no quick fix and it is advantageous that people are aware of the situation."
Gaylord said there are skeptics of climate change, but their arguments are flawed.
Sanford agreed, "There is overwhelming consensus among the scientific community that climate change is very real, and they agree that it is because of human activity."