While most attention surrounding climate change is the effect global warming is having on Earth’s atmosphere, recent research is revealing the devastating effects fossil fuel-based energy generation has on marine environments. An abundance of CO2 in our atmosphere is causing ocean acidification, an unpredictable—and harder to tackle side effect—of the Anthropocene.
There are several ways global warming impacts ocean water: rising sea temperatures contribute to loss of biodiversity and global impact on weather patterns due to thermohaline circulation; atmospheric and oceanic warming is causing glacial ice to melt, resulting in sea level rise and a shift in both the temperature and salinity of the water; and absorbed carbon is disturbing critical creatures’ ability to thrive. Combustion of fossil fuels for electricity is the biggest polluter of CO2, and in 2013 the US alone emitted 5,550 million metric tons of it. On average, it is estimated that the ocean absorbs anywhere between 30-50% of these anthropogenic pollutants, making the ocean’s phytoplankton the largest carbon sequestration system in the world.
When CO2 enters the ocean, the gas reacts with water to produce carbonic acid ions, decreasing the pH of the water. Since the Industrial Revolution, ocean pH has decreased 0.1% already. Some argue that this number is so small that it is a negligible decrease and nothing to worry about, but the catch is that pH measurements are logarithmic. This means that a 1% decrease in pH would be equivalent to a 10 fold increase in ocean acidity. This rapid acidification of ocean waters has already been wreaking havoc on sensitive corals and is expected to have much broader implications on marine ecosystems and species.
Acidification and Corals
Coral reefs are some of the most diverse ecosystems on Earth and are responsible for sheltering over 25% of all marine life. Corals are also extremely important for local economies and food sources due to the high density of life that they support. The people who rely on these environments, as well as the 6,000 species of fish that exclusively call coral reefs call their home, are threatened. When corals are stressed, due to warming, they expel their symbiotic algae, leaving them with a condition known as bleaching. A normally colorful coral will appear white when bleaching occurs, and due to the loss of their food-providing algae, bleached corals are left weak and even more vulnerable to changing acidity.
In addition, carbonic acid dissolves carbonate ions, which corals use to build their skeletons. As a result, corals are unable to build reefs fast enough to keep up with increasing dissolution and erosion rates. Without corals, many marine species could go extinct and fishing communities who rely on reefs for a food source, as well as protection from severe weather, will suffer.
Acidification, Plankton & other Calcifying Organisms
A much less obvious, but equally dangerous effect of an acidifying ocean is the toll it takes on phytoplankton and other marine species that use carbonate ions to form their shells. Phytoplankton is the foundation of the oceanic food chain and supports much of the life that inhabits ocean waters, acting as a keystone species. These essential species of phytoplankton and zooplankton, including Pterapods and Coccolithophores, also use carbonate ions to form a protective shell.
Acidic waters dissolve the shells of phytoplankton, and the carbonic acid prevents plankton from forming shells and reproducing, threatening their existence and ability to support entire marine ecosystems. Acidifying oceans also affect the nutrients that phytoplankton need to photosynthesize and produce energy. This phenomenon is doubly problematic due to the crucial role phytoplankton play in carbon sequestration. Plankton extinction will have major implications on global warming, marine cycles and ecosystems, and loss of marine biodiversity.
Shellfish, such as oysters and clams, are also gravely affected by increasingly corrosive waters. Like plankton, it is much more difficult for shellfish to build and maintain their shells for protection in acidic waters. With thinner shells, oysters and clams are more likely to die. In addition, oyster larvae often die off before they have the chance to build a shell, making it impossible to maintain oyster populations. This has already been devastating for fisheries that rely on shellfish in the Northwestern United States.
Reduction of ocean acidity directly relies on a reduction in greenhouse gas emissions. A group of scientists has proposed that human manipulation of the environment, known as geoengineering, could be the answer. Iron Fertilization, which involves dumping massive amounts of iron into areas of the ocean that are nutrient rich but are not experiencing phytoplankton blooms, could force plankton to photosynthesize at a higher rate and extract more CO2 from the atmosphere. However, tactics like this have unknown side effects that potentially exacerbate rising greenhouse gases rather than abating them–Iron Fertilization could actually have worse consequences than doing nothing at all.
The best solution for healing the oceans and allowing corals and phytoplankton populations to bounce back is to radically reduce, or eliminate, the burning of fossil fuels. Saving these crucial, fragile ecosystems is another powerful motivator to make the transition to renewable sources of energy as fast as possible before our oceans are lost.