A research paper published this week reveals that large die-offs of algae locally magnify ocean acidification. As the cells die and sinks to the bottom, the bacteria population that feeds on them swells in response, consuming more oxygen and releasing more carbon dioxide (CO2). The CO2 reacts in seawater to form acidic compounds that lower the pH, challenging shellfish larvae, coral polyps, and fish that thrive in more alkaline conditions favorable for forming their calcium-rich protective shells and bones.
The researchers developed a new chemical model to predict this increase in acidity over a range of salinities, temperatures and atmospheric CO2 concentrations. It showed that the process of eutrophication—the production of excess algae from increased nutrients such as nitrogen and phosphorus—is a large, often overlooked source of CO2 in coastal waters. When combined with increasing CO2 in the atmosphere, the release of CO2 from decaying organic matter is accelerating the acidification of coastal seawater.
The researchers validated their model against historic records on algae blooms and known pH levels in the Gulf of Mexico and Europe's Baltic Sea.This computer model will help local officials adapt their management of vulnerable coastal resources, such as the placement of shellfish farms, based on future conditions of their water.
The study is available online in the American Chemical Society's journal Environmental Science and Technology.