Imagine a future swarming with jellyfish but lacking in oysters, where algal mats smother coral reefs and salmon stocks plummet – a future in which the ocean is more than 100 percent more acidic than today.
The scientific predictions of the impacts of ocean acidification are still evolving, but whatever the future outcome, policymakers struggle to find solutions to these changes.
Since the Industrial Revolution, the ocean has functioned as a carbon sink, extracting at least a quarter of the anthropogenic carbon emitted into the atmosphere. However, this carbon sequestration has come with a price: a marked reduction of ocean pH levels. Scientists at the National Oceanic and Atmospheric Administration (NOAA) anticipate that by 2100, the global ocean pH will have decreased by .5 and be at least 100 percent more acidic than it is today.
More acidic oceans will affect the security of our food supplies, but scientists and policymakers are considering ways to mitigate the impacts.
Ocean acidification has a major impact on food networks because it changes the chemistry of ocean water and the availability of carbonate ions. Shell-based marine organisms rely on carbonate ions to build their calcium carbonate shells; however, as ocean chemistry becomes more acidic, fewer carbonate ions are available to make those shells. A study conducted by NOAA’s Northwest Fisheries Science Center has shown that increased acidity can dissolve the small, carbonate-reliant creatures that form the base of much of the ocean food chain.
While ripple effects from depletion of these small creatures have yet to be acutely felt, ocean acidification has already affected the shellfish industry, which is worth $1 billion dollars a year in the United States according to the Natural Resources Defense Council.
Oyster larvae have recently experienced sudden die-offs and production has “plummeted by as much as 80 percent between 2005 and 2009” according to the NOAA Pacific Marine Environmental Laboratory (PMEL).
As George Waldbusser of Oregon State University College of Earth, Ocean and Atmospheric sciences explained, oyster larvae “precipitate roughly 90 percent of their body weight as a calcium carbonate shell within 48 hours.”
Because young oysters have not yet developed feeding organs at this stage, they “rely solely on the energy they derive from the egg,” he said.
Lower pH means there are fewer carbonate ions available in the water, so more energy is needed for the oyster to build a shell, and as a result many oysters die within their first two days. PMEL projects that “acidification could reduce U.S. shellfish harvests by as much as 25 percent over the next 50 years.”
Possible Long-Term Solutions
To tackle the issue of ocean acidification in the state of Washington, Gov. Christine Gregoire convened the Blue Ribbon Panel in February 2012 to address ocean acidification at a regional level. Many of the panel’s recommendations–increased monitoring, creating forecasting models, researching the effects on marine organisms and ecosystem impact, providing education, and raising awareness–echoed the Federal Ocean Acidification Research and Monitoring Act (FOARAM), which Congress passed 2009.
An Interagency Working Group on Ocean Acidification (IWG-OA), set up under the provisions of FOARAM, fosters collaboration among U.S. federal agencies, including NOAA, the National Science Foundation, the Bureau of Ocean Energy Management, the Bureau of Safety and Environmental Enforcement, Department of State, Environmental Protection Agency, NASA, U.S. Fish and Wildlife Service, U.S. Geological Survey and the U.S. Navy.
The IWG-OA produced a Strategic Plan for Federal Research and Monitoring of Acidification, and member agencies have spent an average $22 million annually on activities related to ocean acidification, including monitoring and research aimed at understanding its biological impacts. However, a 2014 Government Accountability Office report found that several of FOARAM’s requirements have yet to be met, including outlining budget requirements, and generating adaptation and mitigation strategies.
Members of the scientific community have been researching adaptive strategies.
The most direct and frequently suggested adaptive strategy is to reduce emissions from, and use of, fossil fuels. Another involves increasing the natural uptake of carbon from the air by planting trees and conserving forests, mangroves, seagrass beds, and salt marshes.
While a shift to renewable or greener energy and additional carbon sequestration from natural sources or carbon capture would positively impact the future ocean, any adaptive strategy will still entail years of mitigation while the ocean’s carbon cycle buffers and rebalances: NOAA research shows that current upwelling of deep water off the West Coast reflects the carbon emissions of 30 to 50 years ago.
Possible Short-Term Solutions
Some researchers have proposed strategies with more immediate effect. One such strategy is to seed the oceans with iron; iron dust triggers plankton blooms, which quickly take up carbon dioxide as they grow.
However, out of 12 small-scale tests thus far of the iron seeding theory, only three have shown carbon reduction, though it is still unclear at what exact level of effectiveness. Also, the iron seeding theory has many potential drawbacks, including unforeseen impacts on the food chain and potential depletion of nutrients and oxygen caused by the bloom.
Engineered weathering is another potential strategy, proposed by researchers at Harvard and Penn State. The process would involve extracting hydrochloric acid from the ocean, then exposing it to silicate material for a net alkaline affect. This treated solution would be poured back into the ocean, resulting in increased ocean alkalinity. As a result, the ocean could hold more dissolved carbon in bicarbonate form – the type of carbon used by shell-forming creatures. However, the cost of creating facilities to carry out this process would be prohibitively expensive. The study’s researchers also note that more studies to assess the process’s environmental impact would have to be done before any implementation.
Bioengineering offers a potential answer for the shellfish industry. While oyster growers have dealt with the threat of acidification through monitoring water acidity and closing intakes to prevent corrosive water from reaching oyster larvae, and adding sodium carbonate to their tanks to help with shell growth, a long-range solution via breeding oysters for specific traits, namely resistance to acidity, is a frequent suggestion in studies on the issue.
Ocean acidification directly impacts food security and the U.S. economy. Through bills like the FOARAM Act, and regional work like the Washington State Blue Ribbon Panel, policymakers are working to address these issues. However, our understanding of ocean processes and the impacts of ocean acidification are limited, necessitating further research and monitoring to better understand these systems. Moving forward, scientists will focus on generating adaptive strategies for preventing long-range impacts, and on mitigation strategies to cover the lag time between implementing those adaptive strategies and when they take effect.