Ocean acidification – not so basic…

Marine pollution may take place in the form of ocean acidification. Ocean acidification has become an urgent issue in recent years, especially since the Industrial Revolution began (NOAA, n.d.). Since then, the pH level of ocean surface waters has dropped by 0.1 (NOAA, n.d.). As the pH scale is logarithmic, a 0.1 drop in pH level actually corresponds to a 30% increase in acidity (NOAA, n.d.). The rapid reduction in the ocean’s pH level over a short period of time has “serious consequences for the marine food chain” (Lee, 2019) and also the lives of calcifying organisms that depend on carbonate ions in the ocean (NOAA, n.d.).

Ocean acidification is essentially caused by the “absorption of large amounts of carbon dioxide” from the atmosphere (Lee, 2019). These carbon dioxide are produced and released into the atmosphere from the burning of fossil fuels and also deforestation (Lee, 2019), and possibly other land use changes. The dissolved carbon dioxide sets off a series of chemical reactions which increases the amount of hydrogen ions in the ocean (NOAA, n.d.). As the amount of dissolved hydrogen ions in the ocean increases, the ocean’s pH level decreases.

The series of chemical reactions have negative impacts on calcifying organisms living in the ocean. As carbon dioxide dissolves into the seawater, water combines with it to form carbonic acid (Figure 1), a weak acid that dissociates to form hydrogen ions and hydrogen carbonate ions (NOAA, n.d.), as shown in Figure 2. The hydrogen carbonate ions exists in an equilibrium with hydrogen ions and carbonate ions. When the concentration of hydrogen ions increase, the equilibrium shifts left to favour the formation of hydrogen carbonate ions, causing a drop in the concentration of carbonate ions and hydrogen ions. This drop in carbonate ions affects the calcifying organisms, which require carbonate ions to build their shells and skeletons. As less carbonate ions become available for these organisms’ usage, the shells or even skeletons of these organisms may begin to dissolve and become less defined (NOAA, n.d.).

Overall, air pollution and greenhouse gas emissions, which results from burning of fossil fuels, deforestation and other land use changes, have a negative impact on the ocean as it causes acidification. This acidification affects our biodiversity such as calcifying organisms. There is a rising urgency of this issue as we dive into water pollution.

References:

Lee, A. E. (2019, January 31). Marine Pollution: Ocean Acidification. International Marine Mammal Project. https://savedolphins.eii.org/news/marine-pollution-ocean-acidification

NOAA. (n.d.). Ocean Acidification. National Oceanic and Atmospheric Administration. https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-acidification

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