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Acidification: The Ocean's Changing Climate

Ocean Acidification

Scientists overwhelmingly agree that carbon dioxide (CO2) emissions in the atmosphere cause global temperatures to rise.  This has detrimental impacts for the environment due to changes in climate patterns.  The increase in ocean temperatures, particularly within the last 50 years, is assumed to contribute to stronger hurricanes and tropical storms, as well as changes in ocean currents.  Marine ecosystems face other damaging aspects of human-caused carbon emissions as well.  A chemical change is taking place in our oceans, and it is making waters more and more acidic.  Ocean acidification occurs due to several effects of CO2 in the atmosphere.  Excess amounts of CO2 are entering our oceans and creating a high concentration of carbonic acid: a product of the chemical reaction between water and carbon dioxide.

Oceans on Acid            

Scientists have been studying the acidification of oceans for years.  In 2007, Scott Doney, a senior scientist with the Marine Chemistry & Geochemistry Department of the Woods Hole Oceanographic Institution testified before a U.S. Senate Subcommittee about the effects of climate change on the ocean.  Dr. Doney mentioned then that ocean life was facing an almost unprecedented environmental challenge.  He stated in his testimony:

[m]arine life has survived large climate and acidification variations in the past, but the
projected rates of climate change and ocean acidification over the next century are much
faster than experienced by the planet in the past.

The ocean has always absorbed CO2 from the air.  An article published in Nature August 2012 explains that about half of all human-generated CO2 is absorbed by the ocean.  This chemical reaction is naturally occurring, but at the rate carbon is being absorbed, the concentration of carbonic acid is rising.  This has devastating consequences, especially for shelled creatures.  Animals such as clams, crabs, and corals need calcium carbonate to build their shells.  Carbonic acid dissolves calcium carbonate, and that means these animals are unable to maintain calcium casings.  Additional studies, such as one published in Biogeosciences in 2010, suggest that carbon sequestration by oceans and land is decreasing, which has the potential to further worsen the impact of carbon emissions.

Ecosystem Damage

Without calcium carbonate, shellfish and coral cannot survive.  The ocean’s ecosystem depends on these organisms because they provide a large source of food at the bottom of the food chain.  They need to be plentiful in order to feed higher predators, who in turn are the food for even larger predators.  Without a sufficient supply of feeder organisms at the bottom of the food chain, other animals go without food and their numbers diminish.  This collapses the marine ecosystem due to lack of sufficient food for marine animals to survive.

Recent information about the increasingly acidic ocean is suggesting that unless there is some mitigation of anthropogenic warming, corals and other calcifying organisms will simply dissolve into the ocean.  Acidification is also exacerbated by warming ocean temperatures.  Coral bleaching is a phenomenon already observed in several places in the world where warming waters have made habitats unsuitable for coral polyps and the symbionts that give coral reefs brilliant colors.  Coral polyps are tiny creatures that tend to live in colonies and secrete the calcium carbonate that eventually becomes a coral skeleton.  Over time, these organisms build massive colonies that become reefs.  Symbiotic algae live inside coral polyps and supply them with oxygen and essential nutrients in return for carbon dioxide and other nutrients secreted by the coral.  Bleaching occurs when waters become too warm for the polyps and symbiotic algae to survive.  They die off, and only the calcium coral skeleton remains.

Impact for Economy and Sustainability

Coral reefs are often called “rainforests of the sea” because of their biodiversity and beauty.  Together with other calcifying organisms, these creatures support an estimated 25 percent of all marine species known to science.  They provide a large portion of the base of the ocean’s food web and are necessary for the survival of marine ecosystems.

Preserving coral reefs and other calcifying sea creatures has an ecological importance that impacts the everyday lives of most humans.  Commercial fishing contributes to the world economy, manufacturing industry, and feeds millions of people.  Feeder organisms not only provide stability for species like whales, dolphins, and sharks – they also provide the food commercial fish need to maintain sustainable populations.

Not all fish caught are used as food for humans.  Chemicals derived from commercially caught fish are literally everywhere.  Omega-3 fish supplements are popular.  Everyday products such as fertilizers, gelatins, cosmetic ingredients, vitamins and even pigments can all be made from byproducts of commercially caught fish.

Ocean acidity will destroy marine ecosystems if it continues unabated.  Maintaining sustainable fishing industries will become impossible if the carbon dioxide absorbed by the world’s oceans is not drastically reduced.

Photo Credit: Acidification and Climate Change/shutterstock

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