Ocean acidification: a serious problem for the planet

Ocean acidification process could wipe out all marine life

ocean acidification

Edited and resized image by Yannis Papanastasopoulos, is available on Unsplash

When we think about carbon dioxide (CO2) emissions, factors such as the greenhouse effect and global warming come to mind. But climate change is not the only problem caused by excess CO2 in the atmosphere. The ocean acidification process is extremely dangerous and could wipe out marine life by the end of the century.

Acidification started since the first industrial revolution, in the mid-18th century, when the emission of pollutants increased rapidly and significantly thanks to the installation of industries throughout Europe. As the pH scale is logarithmic, a slight decrease in this value can represent, in percentage, large variations in acidity. Thus, it is possible to say that since the first industrial revolution, the acidity of the oceans has increased by 30%.

But how does this process take place? Studies show that, throughout history, 30% of the CO2 emitted by human action ended up in the ocean. When water (H2O) and gas meet, carbonic acid (H2CO3) is formed, which dissociates in the sea, forming carbonate (CO32-) and hydrogen (H+) ions.

The acidity level is given by the amount of H+ ions present in a solution – in this case, sea water. The greater the emissions, the greater the amount of H+ ions that form and the more acidic the oceans become.

Damage from ocean acidification

Any kind of change, however small, can drastically change the environment. Changes in temperature, climate, rainfall or even the number of animals can cause a total environmental imbalance. The same can be said about the change in pH (an index that indicates the level of alkalinity, neutrality or acidity of an aqueous solution) of the oceans.

Preliminary studies indicate that ocean acidification directly affects calcifying organisms, such as some types of shellfish, algae, corals, plankton and molluscs, hindering their ability to form shells, leading to their disappearance. In normal amounts of CO2 absorption by the ocean, chemical reactions favor the use of carbon in the formation of calcium carbonate (CaCO3), used by several marine organisms in calcification. The intense increase in CO2 concentrations in the atmosphere, however, causes a decrease in the pH of ocean waters, which ends up changing the direction of these reactions, causing the carbonate in marine environments to bind with H+ ions, becoming less available for the formation of calcium carbonate, essential for the development of calcifying organisms.

The decrease in calcification rates affects, for example, the initial life stage of these organisms, as well as their physiology, reproduction, geographic distribution, morphology, growth, development and lifespan. Furthermore, it affects tolerance to changes in the temperature of ocean waters, making marine organisms more sensitive, interfering with the distribution of species that are already more sensitive. Environments that naturally have high concentrations of CO2, such as volcanic hydrothermal regions, are demonstrations of future marine ecosystems: they have low biodiversity and a high number of invasive species.

Another consequence arising from the loss of biodiversity in marine ecosystems is the erosion of continental shelves, which will no longer contain corals to help fix the sediments. It is estimated that by 2100 about 70% of cold water corals will be exposed to corrosive waters.

On the other hand, other research points in the opposite direction, stating that some microorganisms benefit from this process. This is due to the fact that ocean acidification also has a consequence that is, for some marine micro-organisms, positive. The decrease in pH changes the solubility of some metals, such as Iron III, which is an essential micronutrient for plankton, thus making it more available, favoring an increase in primary production, which generates a greater transfer of CO2 to the oceans. In addition, phytoplankton produces a component called dimethylsulfide. When released into the atmosphere, this element contributes to the formation of clouds, which reflect the sun's rays, controlling global warming. This effect, however, is only positive until the absorption of CO2 by the ocean is reduced (due to the saturation of this gas in the waters), a situation under which the phytoplankton, due to the lower offer of Iron III, will produce less dimethylsulfide.

More economic losses

In short, we can say that the increase in the concentration of carbon dioxide in the atmosphere ends up increasing the acidity and temperature of ocean waters. To some extent, as we have seen, this is positive, as it increases the solubility of Iron III, which is absorbed by phytoplankton to produce dimethylsulfide, helping to minimize global warming. After this point, the saturation of CO2 absorbed by the marine environment, added to the increase in water temperature, changes the direction of chemical reactions, causing smaller amounts of this gas to be absorbed, harming calcifying organisms and increasing the concentration of gas in the atmosphere. In turn, this increase would contribute to intensify the effects of global warming. This creates a vicious cycle between ocean acidification and global warming.

In addition to all the impacts already described, with the reduction of the oceanic pH, there will also be an economic impact, since communities that are based on eco-tourism (dives) or fishing activities will be harmed.

Ocean acidification can also affect the global market for carbon credits. The oceans function as a natural deposit of CO2, which forms as a result of the death of limestone organisms. As acidification affects the formation of shells, it also affects the marine deposit of CO2 formed by the death of these calcareous organisms. Thus, carbon is no longer stored for long periods of time in the oceans and becomes concentrated in greater amounts in the atmosphere. This makes countries have to bear the consequences financially.

Seabed

Mitigation technology for acidification

Geoengineering has developed some hypotheses to end this problem. One is to use iron to “fertilize” the oceans. In this way, the metal particles would stimulate the growth of plankton, which are capable of absorbing CO2. Upon death, the plankton would carry the carbon dioxide to the bottom of the sea, creating a deposit of CO2.

Another proposed alternative was the addition of alkaline substances to ocean waters to balance the pH, such as crushed limestone. However, according to Professor Jean-Pierre Gattuso of the French National Research Agency, this process could only be effective in bays with limited water exchange with the open sea, which would provide local relief but is not practical on a global scale , as it consumes a lot of energy, in addition to being an expensive alternative.

In reality, carbon emissions should be the focus of the discussion. The ocean acidification process does not just affect marine life. Villages, cities and even countries are totally dependent on fishing and maritime tourism. The problems go far beyond the seas.

Incisive attitudes are increasingly needed. On the part of the authorities, laws on emission levels and increasingly stricter inspections. For our part, to reduce our carbon footprint with small measures, such as using more public transport, especially in vehicles powered by renewable energy sources, or opting for organic food, which comes from low-carbon agriculture. But all these choices are only possible if the industry changes its ways of dealing with natural resources and also prioritizes the production of goods that use sustainable raw materials.

Watch a video about the acidification process:



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