Ocean Acidification

Pickling or prodding life in an acidifying ocean

As greenhouse gas levels rise, the amount of carbon dioxide in the air and in the ocean increases. When carbon dioxide dissolves in water, it leads to a chemical reaction that increases acidity. Increasing greenhouse gases are leading to ocean acidification and global warming. The pH of the ocean is already dropping, and scientists predict a decrease of 0.3 pH units in the next 100 years. That may not seem like much, but it equates to 3 times more acidity, as the pH scale is logarithmic. In comparison, if the pH of a person’s blood (which has a salinity close to that of seawater) dropped by 0.1 units, he or she would end up in the emergency room with acidosis. This increase in acidity will impact shelled organisms the most, such as clams, oysters, scallops, and sea snails by reducing their ability to make protective shells.

If the ph of a person’s blood dropped as much as predicted will happen in the ocean, he or she would end up in the emergency room with acidosis

A team of Bigelow Laboratory scientists Drs. Steve Archer, Pete Countway, and Paty Matrai and postdoctoral researcher Dr. Kerstin Suffrian are looking at the interaction of ocean acidification and the microbial release of trace gases that may bring about cloud formation. Cloud formation and its cooling effects can help to mitigate climate change, while reduced cloud formation can amplify warming. The team has quantified these interactions in both Arctic waters and in tropical waters off the Canary Islands. This year the team brought the experiment in house, where they used mesocosms—large tanks where environmental conditions can be controlled and manipulated—in the Laboratory’s Seawater Suite to test what might occur if the ocean continues to acidify over the next 100 years. The team has noted a relationship between increased ocean acidity and decreased trace gas emissions in the surface ocean, and predicts that these effects could potentially amplify man-made warming by diminishing cloud cover. They are examining if increasing ocean acidity leads to changes in gene expression among marine bacteria. Using high-throughput DNA sequencing, a technique that makes it possible to identify DNA by processing massive amounts of data quickly, they are able to decipher millions of DNA sequences. By exploring the connections between genes in microbial communities and ocean acidification, they hope to better understand the processes leading to changes in trace gas emissions, and subsequently to improve prediction capabilities. Clearly, the changing activity of tiny marine microbes could have a giant impact on global warming.

Dr. Nichole Price is looking at ocean acidification from other angles. She is working with a team of international collaborators to study the impacts of ocean acidification on highly sensitive seaweeds, known as red encrusting coralline algae. Coralline algae are distributed from the equator to the polar regions. In the tropics, certain coralline algae attract corals, helping to re-establish depleted reefs. Ocean acidity is especially problematic for these highly sensitive seaweeds, making them another ‘canary in the coal mine’ for rising seawater acidity. Price and her team are using mineralogy techniques gathering data from sites in the Atlantic and Pacific Oceans. Their goal is to determine the physiological response of coralline algae species to natural variations in acidity, temperature, and disease over space and time. The team hopes to find instances of resilience to these changing ocean impacts of ocean acidification on Maine’s commercial fisheries.

The Balch and Fields laboratories are examining how ocean acidification affects a simple two-member food chain involving marine plants (coccolithophores) and their zooplankton predators. They are investigating how ocean acidification affects each organism independently and how it might be influencing their relationship with one another — the predator-prey relationship. Such interactive effects are the most difficult to tease-out, but are potentially the most relevant to understanding the overall effects of an increasingly acidic ocean on the marine food web. The Balch lab measures ocean acidification as part of its ongoing long-term sampling of the Gulf of Maine.

Researchers at Bigelow Laboratory are not only studying the consequences of ocean acidification in different ecosystems, but also contributing solutions to help mitigate its impacts. Dr. Meredith White, a postdoctoral researcher in the Balch laboratory, was named to the study commission established by the Maine legislature to investigate and report on the impacts of ocean acidification on Maine’s commercial fisheries. Maine was one of the first states to take steps to study this important issue, and Bigelow Laboratory scientists have played a key role in informing lawmakers of the impacts ocean acidification is having here in Maine, and around the world.