QJScience: Ocean acidification

In an alarming statement, scientists say that at its current rate, acidification of the oceans will increase by 170 per cent by the year 2100.

Since the Industrial Revolution, ocean acidification has increased by 26 per cent, and this drastic rate of change hasn’t been seen in the past, according to the fossil record.

What’s to blame for this acidification? If you guessed carbon dioxide emission from humans, you’re correct. Carbon dioxide dissolves in salt water, producing hydrogen ions and bicarbonate. The hydrogen ions make the water more acidic by lowering the overall pH of the water. Arctic and Antarctic oceans appear to be experiencing the worst acidification of all the world’s oceans because they have the coldest waters, and cold water is excellent at retaining carbon dioxide.

This change in acidification can have huge impacts on various forms of marine life. Deep sea vents are carbon dioxide rich and recent studies have shown that they have lost nearly 30 per cent of their biodiversity. Here are some examples of marine life that are known to be negatively impacted from increased acidification.

1) Creatures that build their shells out of calcium carbonate

Studies suggest that by 2020, these creatures will be unable to survive in approximately ten per cent of the Arctic. Furthermore, a study has shown that the phylum mollusca, which includes creatures such as snails and clams, will be unable to exist in the pH level expected for the year 2100.

2) Corals

They rely on calcium to build their carbonate skeleton, and acidification will result in less calcium availability for them. Increased carbon dioxide emissions are also linked to global warming, which is detrimental to corals because they are temperature-sensitive. An increase of even one or two degrees can lead to coral bleaching, which is caused by the loss of algae that reside on the corals. These algae are critical to the corals’ survival, mainly because they provide them with protection against pathogens.

3) Cephalopods, such as squid

They require high oxygen levels because of their energetically expensive mode of swimming. This oxygen level will be impaired by increases in carbon dioxide and the associated acidification.

Essentially, the entire food web will be affected by this acidification, either directly or indirectly. If organisms such as corals are lost, then all life forms that depend on them will eventually be lost as well, leading to a cascade of decreased biodiversity.

Economic losses associated with decreasing biodiversity are also huge. For example, the global cost of the anticipated decline in mollusks could be around $130 billion by the year 2100. Attempts at mitigating the issue include adding chemicals such as crushed limestone into oceans that have a basic pH. However, scientists say this is only a band-aid solution, and that while it might provide relief on a local scale, it certainly won’t be able to improve the global issue. They say the only way to truly solve the issue is to drastically cut down on carbon dioxide emissions.

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