Ocean acidification

The main assumption made in this study is that the results of reviewed studies, which were done on small case studies, could be applied to the real situation happening on our oceans.

Ocean acidification refers to an ongoing reduction of pH measured on the surface of the ocean.  This is caused by anthropogenic intake of carbon dioxide which is derived from the atmosphere. It is has been recorded that over the years, the amount of carbon dioxide has decreased from 8.179 to 8.104 between 11751 and 1994. Research shows that increased emission of carbon dioxide into the atmosphere has led to increased rate of ocean acidification. It has been shown that ocean acidification is a growing major problem which will have negative effects on the balance of the carbon cycles.  Ocean acidification is also a challenge facing the marine world. Recent research release in Copenhagen shows that the seas are absorbing carbon dioxide at unprecedented rate posing major challenge to marine life. Since the start of industrial revolution, scientists estimate that there has been an increase of about 30 in ocean acidification.  Therefore ocean acidification is a major problem facing the world that need to be tackled by decreasing emission of carbon dioxide.

How is carbon maintained in the atmosphere
In order to understand ocean acidification, it is important to understand how carbon dioxide is maintained in the atmosphere. Like other major gases, carbon dioxide is maintained in the atmosphere through the carbon cycle.  This cycle describes how carbon dioxide is generated and used in atmosphere.  Carbon cycle ensures that there is a flux of carbon dioxide between biosphere, lithosphere and the atmosphere. However, increase human activities which emit carbon dioxide like use of fossil fuel have led to new flux of carbon dioxide. While some of the carbon dioxide has been taken up by terrestrial plants and oceans, there is a substantial amount that remains in the atmosphere

There is organic and inorganic carbon cycle.  Comparing the two, the organic cycle is relevant in ocean acidification since it takes into consideration the different forms of carbon dioxide that is existent in the atmosphere today.

Ocean acidification
Ocean acidification can be described as the process through which carbon dioxide get dissolved into the ocean.  Carbon is a soluble gas and when it comes into contact with water, it is dissolved. When carbon dioxide is dissolved in water, it reacts forming a balance of ionic and non-ionic compounds which include.

Dissolved free carbon dioxide
Carbonic acid
The ratio of these by-products varies greatly depending on a number of factors like water temperature and alkalinity. Once dissolved in water, carbon dioxide increased the amount of hydrogen ion concentration (H). The increase of pCO2 in the surface of the ocean comes with different effects on the seawater carbon system (Sabine, 2004).  It leads to reduction in the pH, decreased availability of carbonate (CO32-) ions and in addition, it lowers the saturation of major shell forming mineral which means it will have an impact on the life of most marine animals that live in shells, as can be illustrated in the following chemical reaction (Kolbert, 2006)
CO2  CO32-  H2O  2HCO3-

Therefore, the term ocean acidification can be understood in terms of pH changes. It refers to the reduction in pH and it does not simply imply that the ocean surface pH water comes below the neutral (7.0) level.

The additional carbon dioxide which is not absorbed by the sea or through the terrestrial plants is already having an impact on the world.  It has been shown to affect the carbonate chemistry by reducing ions, aragonite, and calcite, which are used by most marine organism to make their external skeletons and shells. This implies that if the current trend in emission is maintained or increased, our oceans will become more acidic by the end of the century and this could decrease the pH of  seawater by more than 0.34 units compared to the pre-industrial levels. This change in ocean chemistry has been scientifically proved and its effects are well known.

Is there scientific evidence to prove ocean acidification
There is well documented scientific evidence that shows that ocean acidification is taking effects on  our oceans. Historical science evidence shows that a study of carbon dioxide that has been preserved in ice shows that before the industrial revolution, the oceans had a pH of 8.2. However, since the industrial revolution, the level of oceanic pH has dropped by more than 0.1 units. Although this may be perceived to be insignificant, scientific evidence shows that the level of acidity has increase by a value of 30. This trend is like to grow considered the current standards where the ocean is absorbing about 2.2 million tons of carbon dioxide every day,  implying that unless stern measures are taken, our oceans will become more acidic and marine life will be endangered.

It is estimated that if nothing is done to mitigate the current situation, there will be further ocean acidification and the pH will drop by further 0.3 to 0.5 units by the time the world ushers 2100.  Since the ocean will continue to absorb more anthropogenic carbon dioxide, there is a possible that the marine life will have changed drastically and marine ecosystem will be severely affected. The future ocean pH will depend on the mitigation strategy that will be taken by the society to curb emission of carbon dioxide into the atmosphere or the rate at which the world will increase the number of terrestrial plants to capture carbon dioxide in the atmosphere.

Impacts of ocean acidification
It is postulated that the current rate of ocean acidification will have an impact on the oceans in different ways. One way in which it affects marine life is through calcification. This implies that change in ocean chemistry has a direct and indirect impact on the marine habitats through calcification process. Calcification is an important process for marine animals as it enables them to make their out skeleton and shells through calcium bicarbonate.  This process is important for biological survival of most marine organisms and if affected, their life will also be directly affected. Calcification process mainly involves precipitation of dissolved calcium ions to form a solid calcium-carbonate structure like coccoliths.  Once they are formed, these structures are chemically soluble and can be dissolved unless the surrounding sea water is saturated with carbonate ions.  Calcium carbonate occurs as aragonite and calcite. Comparing the two, aragonite is more soluble. This implies that marine organism which product aragonite as their skeleton and cells are more vulnerable to dissolution if there is an increase in ocean acidity compared to those that produce calcite.  Increase in carbon dioxide result to lower pH and this decrease the saturation of calcium carbonate compounds. This raises the saturation horizons to the sea surface.

It is believed that through interfering with calcification process, ocean acidification will have an impact on the marine ecosystem. It will lead to destruction of important food chain which involves both autrophs and heterotrophs in organism like coccoilthophooers, corals, foraminifera, molluscs, crustaceans, and many others.  Research has already found out that the above mentioned marine organism experienced reduced calcification and dissolution when they are exposed to higher levels of carbon dioxide.

Apart from problems associated with calcification, it is also estimated that animal will also suffer from other reproductive and physiological effects. For example, they are likely to suffer from carbon dioxide induced acidification in their body fluids or hypercapnia. They are also likely to suffer indirectly through food inadequacies due to destabilization of the food chain. In addition, this may also force come of the marine organism to relocated to  other areas  due to decrease in food resources and deterioration of conditions in the environment and this will have  a direct impact on survival of  other animals.

Ocean acidification may also have other impacts which are not related to marine life. It will decrease burial of carbonate sediments for a number of centuries and in some cases it will lead to dissolution of existing carbonate sediments.  This will have an effect in that more carbon dioxide may leave the atmosphere and enter into the ocean.


Ocean acidification is a process that leads to increased deposition of carbon dioxide into the seawater. Carbon dioxide is maintained by the atmosphere by the carbon cycle where excess carbon is absorbed by the terrestrial plants and the sea. Human activities have increased carbon dioxide in the atmosphere and this has led to increased deposition carbon dioxide into the ocean reducing the pH and increased acidity. This has affected the calcification process which is important for marine animals. Therefore ocean acidification is a major problem facing the world that need to be tackled by decreasing emission   of carbon dioxide.


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