Ocean Acidification
Over the years, atmospheric carbon dioxide levels have increased significantly due to human activities like industrialization, burning fossil fuels, and deforestation, which increase carbon dioxide. As opposed to contrary belief, all carbon dioxide in the atmosphere is not completely utilized by land vegetation. Some of it is absorbed by ocean water (Melzner, 2020). Consequently, the pH of surface ocean water has decreased by an average of 0.1 pH units (Intergovernmental Oceanographic Commission, 2019). This scale represents about 30% of the increase in acidity of the ocean because of absorbing up to 30% of the atmospheric carbon dioxide. In turn, the carbon dioxide absorbed in ocean water will undergo several chemical reactions causing an increase in the concentration of hydrogen ions, a process called ocean acidification. This process affects not only the oceanic environment but also organisms found in this environment. The purpose of this essay is to succinctly discuss ocean acidification, its chemistry, and impacts on organisms and marine ecosystem.
Chemistry of Ocean Acidification
Once CO2 is absorbed by ocean water, the initial reaction results in the formation of carbonic acid (H2CO3) (Hurd, 2020). The carbonic acid then dissociates, forming hydrogen ions (H+) and bicarbonate ions (HCO3-). Continued reactions will increase H+, making the water more acidic as the pH lowers. Hurd (2020) explains that some hydrogen reactions usually react with carbonate ions forming bicarbonate.
Scientists rely on pH, a measure of the concentration of hydrogen ions, to check the acidity of water. However, the Intergovernmental Oceanographic Commission (2019) adds that scientists will employ a negative logarithmic scale, which corresponds with the pH findings. Usually, a decrease of the pH unit by one shows an increase in acidity by a 10-fold.
Impact on Marine Organisms
According to Baumann (2019), many marine creatures rely on calcium carbonate ions for calcification. However, acidification produces hydrogen ions which react with carbonate ions forming bicarbonate. This reaction reduces the concentration of carbonate ions in the water. The reduction in carbonate ions caused by this reaction presents a problem to various species in the ocean, which rely on the ocean water to provide carbonate ions for calcification, the process of making skeletons, and calcium carbonate shells. Thus, as the carbonate ions reduce in concentration, these organisms, like clams and corals, will experience difficulties in carrying out calcification and maintaining the process.
Acidification interferes with the metabolism of sea creatures Baumann (2019). The majority of sea creatures’ metabolic processes are set such that they optimally function within a narrow range of pH. Beyond the limits of this range, metabolic processes may either be inefficient or too slow to keep the organism alive within the environment. Although some organisms can withstand external changes in pH by adjusting their internal environment, some organisms may be unable to adjust because of a significant expenditure of energy. More developed and old animals may have the required energy, however, less developed and young creatures cannot meet this new energy requirement, eventually causing death (Melzner, 2020).
Oceanic acidification also causes difficulty for marine animals to absorb iron, nitrogen, phosphorus, and other essential elements and minerals for growth and development (Melzner, 2020). In an acidic sea environment, these elements, like iron will chemically combine with organic compounds. Thus, marine animals fail to obtain these essential elements.
Impacts on Ecosystems
The effects on individual marine organisms scale up to populations and marine ecosystems. According to Hall-Spencer (2019), ecosystems represent a complex network of organisms and how they interact with the environment. Hence, a disturbance at one point of the ecosystem has the potential to affect the entire ecosystem. The marine ecosystem support fish population, marine features and human beings through commerce, recreation and protection from sea storm surges.
Some of the marine species which are critical to marine ecosystem but prone to oceanic acidification include corals and seagrasses. These species also act as the natural habitat for a diverse number of organisms within the ocean. Acidification will trigger a subtle change the performance of these species, which in turn affect the communities of organisms that they host, scaling up to the change in the population size and potentially the larger ecosystem (Hall-Spencer, 2019). For example, the open ocean ecosystem, composed of planktons and animals living in the surface waters, make up the base of the marine food chain. Planktons require carbonate ions to make their shells. However, due to acidification, the planktons cannot make their shells, hence, animals relying on planktons as source of food lose their source.
Conclusion
Ocean acidification is significantly caused by industrialization over the years which caused a significant increase in atmospheric carbon dioxide levels. About 30% of the carbon dioxide in the atmosphere is absorbed by the ocean, directly causing an increase in ocean acidity by approximately 30%. The carbon dioxide will immediately react with the water forming bicarbonate ions and hydrogen ions. Hydrogen ions are responsible for the acidity. Hydrogen ions will also react with carbonate ions in the water, forming bicarbonate ions. This reaction makes carbonate ions less available for the process of calcification. Acidification also affects the metabolism of sea creatures, mostly those who fail to adjust to changing external conditions. This form of interference at one part of the marine ecosystem can potentially threaten the survival of other organisms within the ecosystem.
References
Baumann, H. (2019). Experimental assessments of marine species sensitivities to ocean acidification and co-stressors: how far have we come?. Canadian Journal of Zoology, 97(5), 399-408.
Hall-Spencer, J. M., & Harvey, B. P. (2019). Ocean acidification impacts on coastal ecosystem services due to habitat degradation. Emerging Topics in Life Sciences, 3(2), 197-206.
Hurd, C. L., Beardall, J., Comeau, S., Cornwall, C. E., Havenhand, J. N., Munday, P. L., … & McGraw, C. M. (2020). Ocean acidification as a multiple driver: how interactions between changing seawater carbonate parameters affect marine life. Marine and Freshwater Research, 71(3), 263-274.
Intergovernmental Oceanographic Commission. (2019). Indicator Methodology for SDG 14.3. 1: Indicator Description 14.3. 1–Average marine acidity (pH) measured at agreed suite of representative sampling stations.
Melzner, F., Mark, F. C., Seibel, B. A., & Tomanek, L. (2020). Ocean acidification and coastal marine invertebrates: tracking CO2 effects from seawater to the cell. Annual Review of Marine Science, 12, 499-523.