The oceans do a lot of the Earth’s dirty work. On a given day, they will absorb 22 million tons of carbon dioxide (CO2), a third of the global output. In doing so they help to keep climate change in check, but they also pay a heavy toll as a result.
Increasing levels of carbon in the ocean are making the water more acidic, and that’s beginning to have an impact on shellfish, corals and some of the tiniest shell-making marine organisms that are essential to the ocean food web. The June 2012 issue of E – The Environmental Magazine (now posted at www.emagazine.com) takes a closer look at the phenomenon of “ocean acidification,” the process by which levels of CO2 are rising, changing the chemistry of the ocean, and the ways this is impacting sea creatures on which mankind depends.
Shellfish farmers in Washington and Oregon were some of the first to sound the alarm about ocean acidification. In 2006, hatchery-produced oyster larvae began to die off, despite their controlled and monitored environments. The two largest oyster hatcheries — which supply seedling to the majority of West Coast oyster farmers — lost between 60% and 80% of their larvae. Through ocean monitoring, the farmers discovered that the pH had fallen enough to make the water too corrosive for the oysters to form shells.
Once the problem was identified, shellfish farmers were able to take precautions — such as waiting to fill tanks following a north wind when upwelling causes corrosive water to rise to the surface. But in the open ocean, there are no quick fixes for ocean acidification.
“A lot of things we like to eat have these calcium carbonate shells and they’re very sensitive to acidification,” says Richard Feely, Ph.D., a senior scientist with the National Oceanic and Atmospheric Administration (NOAA) and its Pacific Marine Environmental Laboratory (PMEL). “Just a small drop in pH can cause the shells to begin to dissolve. It turns out that for many of these species, the larval and juvenile stages are much more sensitive than the adults. And we’re finding that they can die off quite rapidly even with the kinds of changes that we’re seeing right now.”
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