R-18-05 From paleoceanography to policy: Applying historical coastal pH baselines from long-lived shells and skeletons to contemporary shellfish aquaculture

Michele LaVigne
Bowdoin College

Branwen Williams
Claremont Colleges

Alan Wanamaker
Iowa State University

David Carlon
Bowdoin College

Aaron Strong
University of Maine

Increasing concentrations of carbon dioxide in the atmosphere are causing ocean waters to become more acidic, the result of gas exchange at the air-sea interface and chemical reactions in seawater. A more acidic environment (measured as lower pH) could create problems for marine animals, especially those that rely on acid-sensitive minerals to build shells. Lobsters, clams, oysters, mussels, urchins, and microscopic crustaceans are all believed to be at risk. Despite the potential magnitude of the impact of ocean acidification, actual pH data are scarce, especially data for historical conditions. Without a baseline, scientists will have a hard time demonstrating changing ocean chemistry. Is the Gulf of Maine more acidic today than it was hundreds of years ago? Has pH changed over the last century?

LaVigne and her colleagues will use existing monitoring data (collected as part of the Maine Coastal and Ocean Acidification Partnership) to quantify current pH in a range of locations. To determine pH of the deep past, before human production of excess carbon dioxide, they will use “paleoceanographic proxies.” Coralline algae (Clathromorphum compactum) and Arctic surf clam (Arctica islandica) are long-lived species that incorporate calcium carbonate and boron into rigid structures--the algae building a skeleton and the clam making its shell. These structures are built in regular increments, annual growth bands that contain an archive of ocean chemistry, circulation, and temperature. Williams and Wanamaker are experts in reading these geochemical fingerprints (primarily isotopes of boron) and establishing historical records of ocean conditions.

Finally, using the established levels of acidity, the researchers will conduct laboratory experiments to study how past, present, and future pH changes affect shellfish species.

Two-year project, 2018-2020
Sea Grant funds: $149,971