Friday February 14, 2014 | 11:51 AM
Posted by Mike Tetreault

Standing on Maine’s magnificent coast, looking out at the vast expanse of ocean, it’s easy to imagine that we stand alone, unaffected by the rest of the world and buffered by the sea’s immensity.

But big forces are at work, like a changing climate and its impacts on the ocean. The warming climate is not only raising sea levels – even measurably here in Maine – but also changing the ocean’s basic composition.

Scientists around the world have found that, as global temperatures rise, they impact everything from coral reefs to, possibly, shellfish and other marine life in the Gulf of Maine. In fact there’s been a fair amount of research on ocean acidification, thanks to Maine’s Island Institute, the Darling Marine Center and Bigelow Laboratory for Ocean Sciences.

The Maine Legislature is considering a bill (LD 1602) that would establish a commission to study the effects of ocean acidification on shellfish on our coast. If passed, the commission will ultimately recommend ways to mitigate ocean acidification, conduct research and take steps to protect commercially valuable shellfish. See North Cairn’s article on the bill.

Ocean acidification occurs when carbon dioxide dissolves in seawater and forms carbonic acid, causing a drop in the ocean’s pH levels and a corresponding increase in acidity. For our marine ecosystem, ocean acidification affects shellfish such as mussels, clams and oysters by slowing, stunting or stopping the growth of their calcium carbonate shells. It also affects the critical base of the food chain since many species of plankton also need calcium carbonate to grow.

Population reduction for these food species has the potential to disrupt a wide variety of species within the food chain that rely on these animals for survival, such as lobsters and the full suite of groundfish. Oceans have grown 30 percent more acid in the last two decades and clams are growing shells 30 percent slower, according to field work by Dr. Mark Green of St. Joseph’s College. The Gulf of Maine already has higher acidity than other parts of our coast and coastal waters are often twice or three times as acid as the open ocean.

The negative impacts to these species have significant economic consequences for Maine as well. For example, the soft-shelled clam fishery alone has an estimated economic value to the state of some $25 million.

The Nature Conservancy is undertaking ambitious oyster restoration efforts in Great Bay, along the New Hampshire-Maine border. And, many parts of Maine’s coast also once supported significant wild oyster populations. Recently there is evidence that wild oysters may be able to come back to some of those areas with a little help. But it would be foolish to invest in such efforts without knowing much more about the potential impacts of acidification and the ways those impacts can be mitigated.

The factors driving acidification of our coastal waters are not simple. Great differences in degree of acidification – and growth rate of clams – have been documented if different parts of Casco Bay. It is imperative to better understand what factors might be mitigating the acidification effects in some places and exacerbating them in others so that we can better protect our bays and estuaries from these changes.

Mainers need to be aware of the issue and its impacts of ocean acidification. Public information helps us all prepare for changes in our marine system and helps inform us how to be more flexible and adaptive as these changes occur. This is important for the Department of Marine Resources, fisherman, fisheries managers and others.

The Conservancy hopes that together we can learn what citizens, scientists, policymakers and others can do to not only mitigate and avoid disastrous impacts but also shed light on how NOT to exacerbate the issue.

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Mike Tetreault leads The Nature Conservancy in Maine, where he works with partners in conservation, government and community development to identify solutions which ensure that Maine's natural resources are available for people and for nature.

He holds a degree in environmental studies from Brown and a MS from the field naturalist program at the University of Vermont, and has studied resource management in Kenya, Mexico and throughout New England.

Tetreault started his career teaching wilderness leadership and environmental education, and has worked for The Nature Conservancy since 1998. He lives in Bath with his wife, their daughter and a menagerie of pets.

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