Threat of ocean acidification

Dangerous levels of CO2 trigger a cascade of reactions in the oceans causing trouble to the marine ecosystem and our economy.

Bait fish refer to those fish that are used as bait to attract large fish. They are overly abundant in the oceans and seas as they breed rapidly. They serve as food for many predatory fish and marine animals. A recent study has found that ocean acidification has become so big a problem that these fish are not getting sufficient oxygen to breathe.

The level of atmospheric carbon dioxide has been increasing ever since the industrial revolution. The oceans absorb about a third of human-created CO2 emissions. The potent greenhouse gas is not only a threat to humans and land animals but also to the marine ecosystem. When carbon dioxide mixes with ocean water it lowers the pH — and causes acidification.

When carbon dioxide (CO2) reacts with water (H2O), it forms carbonic acid. It further reacts with water to release bicarbonate ions and hydronium ions. This increases acidity and creates a situation where there would be less of dissolved oxygen.

These changes will have an unprecedented impact on marine life. While some species like the sea star and shelled plankton flourish, calcifying organisms such as coral reefs will perish. Humans who are dependent on oceans for food and tourism will also be affected.

Organisms like corals, which produce calcium carbonate shells or skeletons will suffer because of increasing CO2 and decreasing pH.

Ocean acidification will affect the reef-building ability of corals. This will, in turn, affect one million species that have made corals their homes.

Coral reefs will erode faster than they can rebuild. When shelled organisms are at risk, the entire food web may also be at risk.

Increasing acidity could have direct consequences in reducing the metabolism of jumbo squids, immune responses of blue mussels and affect the sensory functions of clownfish.


1. Acidity can be mitigated primarily by controlling the fossil fuel emission.

According to one study, global warming should be brought down by atleast 2 degree Celsius for the surface ocean pH to be brought to 0.16 the pre-industrial levels.

2. Another approach is to add chemicals to counter the effects of acidification.

This could be expensive and only partly effective. The chemicals’ impact on aquatic life is not known.

3. By triggering photosynthesis in phytoplankton with the addition of iron in the water. This may increase the level of oxygen on the surface, but the acidification deep under the ocean may remain the same.

A global problem

A pH less than 7 is acidic. A pH greater than 7 is basic.

Calcifying species include oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton

30 to 40 per cent of the carbon dioxide from human activity released into the atmosphere dissolves in oceans, rivers and lakes.

By the end of this century, the surface waters of the ocean could be nearly 150 per cent more acidic.

R. Keerthana, The Hindu, 22 May 2016. Article.

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