The Acid Test

Posted on Oct 20, 2012

Clam flat monitoring in Casco Bay shows a disturbing trend

This past summer, Bowdoin College intern Jessie Turner assisted Friends of Casco Bay on a project to see if ocean acidification, a worldwide phenomenon, is having an effect here in Casco Bay. Jessie spent much of her time in the field, or more precisely, in the mud, measuring levels of acidity at 30 clam flats between South Portland and Phippsburg.

Jessie says of the experience, “I got the chance to see some of Casco Bay’s secret coves and essentially play in the mud. The field work presented some challenges, like fighting off swarms

of gnats while slogging through smelly, thigh-deep mud. But it taught me to appreciate the quiet beauty of the clam flats, with their spectacular sunrises and their silent orchestras of spurting animals living just under the surface. Being able to explore these places has inspired me to pursue environmental research in the future, to better understand the natural world I hope to protect.”

Her work added more data to a project that Research Associate Mike Doan launched last summer, when we sampled the mud on 14 clam flats. He found that the clam flats that were still being actively harvested by shellfishermen tended to be less acidic than those areas where clammers no longer find enough clams to make it worthwhile to work those flats.

Mike explains why this may be happening. “The ocean absorbs nearly a third of all carbon dioxide pumped into the atmosphere by burning fossil fuels. When carbon dioxide is absorbed by the ocean, it reacts with water to form carbonic acid. This is making the world’s oceans more acidic. Closer to shore, nitrogen pollution – from fertilizers, sewage discharges, cars and factories – adds to the problem. This excess nitrogen promotes algae blooms in bays and coves. When these plants die and decompose, carbon dioxide is released into coastal sediments. We are calling this coastal acidification.”

This acidification is hampering the ability of clams and oysters to build and maintain their shells. Newly-settled clams may dissolve completely at acidity levels found in some parts of Casco Bay today.

Cathy Ramsdell, Friends of Casco Bay’s Executive Director, says, “This project is a great example of how key scientific investigation is to our approach to advocacy in this organization. We don’t collect data for publication in scientific journals; we use data to tell us where conditions in the Bay are trending in the wrong direction and then work to change behavior to improve the health of the Bay. By establishing the link between nitrogen pollution and our coastal economy, we hope to persuade residents, businesses, municipalities, and the Maine Department of Environmental Protection that we must reduce nitrogen runoff.”

What can you do?

Limit fertilizer — Practice BayScaping.

• Fertilize your lawn only if a soil test shows it’s needed

• Don’t apply fertilizer when rain is predicted

Keep water on your property

• Leave undergrowth, duff, and shredded leaves

• Install rain barrels, rain gardens, and permeable pavement

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