As climate change moves to the forefront of our agenda, we are getting more concerned about what effect the increasing levels of carbon in the atmosphere are having on the planet’s biggest carbon sink; the ocean.
Atmospheric carbon dioxide is rising to levels unprecedented in modern geological history, and as a result our ocean is experiencing changes to its chemistry that may significantly alter habitats and affect marine organisms. Collectively, these changes are referred to as ocean acidification, or a lowering of global ocean water pH due to the absorption of excess carbon dioxide. Scientists have only begun to investigate this process, but it is likely to have a profound impact on New England waters and the species that coastal communities rely upon.
Ocean acidification is a relatively new term for most of us, as a large percentage of the research on this subject has been conducted within the past decade. Scientists have identified a number of changes that occur when CO₂ is dissolved in water. The primary outcomes include an increase in the concentration of hydrogen ions, lowering pH and ‘acidifying’ ocean waters, and the consumption of carbonate, an important component for shell-building organisms. These changes could place stress on marine-dwellers, particularly the critters that require carbonate, like oysters, mussels, clams, and corals, to build their shells or skeletons.
But the ocean is huge! How do we know that these changes are occurring on a scale large enough to affect global ocean chemistry? Scientists have information about past atmospheric and oceanic conditions from clues in the geological record. They can compare these records to projections about how much carbon is likely to be in our atmosphere- and subsequently our oceans- in 20, 50 or even 100 years. The ocean’s pH has dropped from 8.2 to 8.1 since the Industrial era- that’s a 30% increase in acidity- and is projected to fall another 0.3-0.5 units by 2100. Researchers claim that this drop in pH is unlike anything the ocean has undergone in the last 300 million years!
One recent study has shown that the waters of the Gulf of Maine are particularly susceptible to acidification due to already low pH and carbonate levels relative to other regions along the Atlantic coast. This means that we New Englanders could end up with a front row seat to the impacts of ocean acidification!
What does this mean for ocean-dwelling animals? It’s impossible to know how every species will react to changes in ocean chemistry. Some studies have shown that rapid changes in water chemistry can place heightened stress on shellfish, affecting growth, development rates, and even survival. Another study has shown that acidified waters impair organ development in our already-depleted Atlantic cod. “Adapt or die!” –says Darwin, but these human-made changes may be happening too fast for nature to keep up.
The ocean is so important to us, and it’s difficult to imagine how these changes might affect our daily lives. Many fish and shellfish species are critical to our economy, and are relied upon as integral parts of people’s livelihoods. Seafood lovers can’t deny the importance of the ocean as a food source. Beyond our stomachs, the ocean also appeals to our emotions. CLF’s Keren Bitan recently discussed how learning about sea critters can foster a strong personal connection to the ocean and its ecosystems. And anyone who’s explored the tiny world of a tidal pool, or taken a morning walk on a sandy beach, can appreciate the beauty and complexity of the ocean and its habitats. These connections are often what compel us to realize just how important it is that we continue to protect ocean habitat and do what we can to prevent climate change from taking its toll on the world’s oceans.
We have explored less than 5% of our ocean, and yet we may be changing it in ways we are only beginning to understand. We will continue to work to protect the ocean’s resources, animals and habitats, even as the uncertain effects of climate change become apparent.
Ellie Milano is a current Masters student at Tufts University studying Conservation Medicine, an innovative program that seeks solutions to global environmental and health issues. Her thesis work focuses on public opinion of global climate change, and understanding how extreme weather events affect attitudes toward climate change. She is a recent graduate of Hobart and William Smith Colleges in Geneva, NY, where she double majored in Biology and Environmental Studies. During college, she spent two summers at Cornell University studying aquatic ecology. She grew up in the Berkshires of Massachusetts, and her interests include horseback riding, recreational hiking and rock climbing.