Causes and Impacts of Ocean Acidification

2475 words (10 pages) Essay in Environmental Studies

23/09/19 Environmental Studies Reference this

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Causes and Impacts of Ocean Acidification



What impacts will this have?

Co2 absorbed into ocean

Ocean Acidification

1                    Overview

1.1 What is ocean acidification?       

2                How it affects marine animals……………………………

2.1             Calcification

2.2             Olfaction

3               How it affects marine plants   

 Bleaching of coral reefs                             

4                  Conclusion

5                  References

1         Overview

In this essay I will be discussing the impacts of ocean acidification, along with its various effects upon changing the oceans chemistry and the problems that a changing pH can cause. Additionally, discussing how this is affecting various Marine animalsand plant species.

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1.1 What is ocean acidification

Ocean acidification can be caused by the burning of fossil fuels. These fossil fuels will release carbon dioxide when they are burnt thus increasing the levels in the atmosphere. However the earths oceans act as a carbon sink- which allows the ocean to store amounts of carbon dioxide that are in the atmosphere and can help to reduce this,additionally the ocean is regarded as the largest carbon sink .In relation to this the carbon dioxide is often used in the ocean by plants and animals for photosynthesis and can also dissolve into the sea water.(Block, 2018).It is estimated that over the past 200 years the ocean has absorbed atleast one third of the total carbon dioxide emissions.(Committee on the Development of an Integrated Science Strategy for Ocean Acidification Monitoring., 2010)

As seen in figure 1 when the carbon dioxide is absorbed into the ocean it reacts with the H20 molecules which forms Carbonic acid. The carbonic acid is then broken down into smaller molecules such as Bicarbonate and carbonate ions. However, the more carbonate ions that are formed the more hydrogen atoms are left in the water to freely move around and this is how the ocean can become more acidic.

Figure 1-The process of the ocean absorbing CO2 from the atmosphere and the processes it goes through. (University of Maryland, 2018)

However even though the ocean is absorbing some of the carbon dioxide which benefits society it is causing changes to our oceans. These changes include the pH of the sea water to change.In relation to this the average pH of the ocean has dropped by 0.1 unit, although the number may seem small this can have huge changes upon the ecosystem and the organisms in the ocean may struggle to cope and adapt the changes as the ocean becomes more acidic over time.(Committee on the Development of an Integrated Science Strategy for Ocean Acidification Monitoring., 2010).

This can then lead to a reduction of marine life as the smallest organisms such as Phytoplankton and this can affect the whole food chain. Furthermore, as global warming increases this also raises the oceans temperature, due to the water being warmed it cannot store as much carbon dioxide.

2.The affect on marine animals

As the acidity of the ocean increases this causes various impacts upon the physiology of the animals, this includes respiration of CO2, internal pH regulations and growth. In a study that was published by Nature climate change they researched the effects of ocean acidification on Diatoms such as Phytoplankton. The study that was undertaken allowed for the researchers to see what species of Phytoplankton would survive and grow, it was discovered than in some cases some species of Phytoplankton where able to grow in these conditions but that there where also some species that where unable to survive. (Office, 2018)

In relation to this if some species of Diatom died off this can have huge changes to other marine animals as the organisms that would usually eat a species which could die off will have huge changes to the food change on a larger scale. As shown in figure 2 the Diatoms are at the bottom of the food chain which are preyed upon by Copepods. If the Copepods where then no longer able to prey upon certain species this can then eventually lead to affecting other large marine animals.

Additionally, as the food chain is impacted this will eventually cause problems with not just the marine populations but also the human populations as well, as one of the main sources of food will be depleting due numbers of fish decreasing.

Figure 2– An example of the marine food chain and food web.

2.1- calcification

For various marine organisms such as molluscs and crustacean’s calcification is vital, as the calcium carbonate is used for many functions. The carbonate is the most needed material as it is needed “in the formation of skeletons, shells and protective structures.” (Committee on the Development of an Integrated Science Strategy for Ocean Acidification Monitoring., 2010).In relation to this an example of how this effects marine organisms can be seen in Pteropods such as the sea butterfly (Limacina helicina).The sea butterfly is towards the bottom of the food chain and as the effects of ocean acidification is making their shells weaker , this means they are not able to efficiently protect themselves against predators . (National geographic, 2014) Additionally the results of ocean acidification are causing their shells to become thin and misshapen which can be seen in figure 3. This can cause major impacts upon the health of the organism as they will not be able to protect themselves against infections efficiently which may lead to their numbers dropping. (National geographic, 2014).

Figure 3-the effects of pH change on the shell of a sea butterfly (Limacina helicina) over the course of 45 days. (Liittschwager, 2014)

Most importantly “organisms that have currently been studied have shown decreases in their shell weight and decreases in calcification when the pH of the water is reduced, and the CO2 levels increased “which mimics the effects of the acidification of the seawater. Similar effects have also been seen in other organisms like mussels, urchins and oysters. (Fabry et al,2008)


The olfactory system has 3 types of sensory neurons that overlap each other in the folds of the olfactory epithelium. The axons of these 3 sensory neurons meet in the olfactory bulb (which can be seen in figure 4) and connects to relay neurons that will then arrive to the telencephalon in 3 bundles. Each bundle contains sets of information such as social cues, sex pheromones and food odours. (Hamdani and Doving, 2007) However as the pH of the ocean is changing this is affecting many fishes ability to be able to detect predators. This has been shown in in a study where “settlement stage Amphiprion percula larvae where unable to tell the difference between non-predatory and predatory species” when they were placed in an environment that simulates the conditions caused by ocean acidifications. (Dixson, Munday and Jones, 2010) This can pose a huge risk to fish species as it can increase the death rate especially if they are unable to distinguish key differences between other marine animals.

Figure 4– a diagram showing the olfactory system. (Munro, n.d.)



Ocean acidification is already causing problems in the marine ecosystem through the bleaching of coral reefs. Coral reefs are made up of calcium carbonate and acidification is having huge impacts as the number of calcium carbonate molecules is decreasing, this is meaning that the coral is struggling to grow efficiently and be healthy. When corals do not have enough nutrients, this causes them to turn white. Corals have a “symbiotic relationship with zooxanthellae which is a species of microscopic algae, the algae are the main source of food for the coral and provides them with the nutrients to give them colour”. (, n.d.) However, as the “conditions of the ocean is changing such as pH and temperature this is causing stress upon both organisms and can result in the algae leaving the corals tissue”. (, n.d.) Furthermore, due to this the corals are left with very little food which causes bleaching and leaves them vulnerable, as seen in figure 5.


Figure 5- The effects of coral bleaching over the course of 9 months. (XL Catlin Seaview Survey, 2016)

4         Conclusion

Overall ocean acidification is having huge implications in the ocean and altering its chemistry which is affecting the entire marine ecosystem. More importantly the amount of carbon dioxide that will be dissolved in the ocean is only set to rise (see figure 6) which will likely cause more stress upon the marine ecosystem. Additionally, it may also cause more noticeable impacts upon the human population as the marine ecosystem provides various economic benefits such as recreational activities and marine fisheries that provide seafood (Committee on the Development of an Integrated Science Strategy for Ocean Acidification Monitoring. (2010).In relation to this if the pH in the ocean continues to decline and CO2 levels continue to rise this will result in a loss of marine life and with this comes problems such as briefly discussed before such as marine fisheries. The human population will lose a main food source which may have detrimental impacts.

Figure 6-Graph showing current and estimated pH and CO2 levels. (Pearson Prentice Hall, n.d.)


5          References

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