Ocean Acidification: Causes & its Effects | UPSC Notes

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This article is about ocean acidification: what causes it and what effects it has. It is for the UPSC IAS.

Ocean Acidification: Causes & its Effects – UPSC

Gases that cause acid rain

Acidic gasesSource
SOx (Sulphur oxides)Fossil fuel burning, power plants, smelting of metal sulphide ores, industrial sources, industrial production of sulfuric acid in metallurgical, chemical and fertiliser industries volcanoes, seas and oceans, decomposition of organic matter.
NO(Nitrogen oxides – NO, NO2 and N2O)Fossil fuel burning, lightning, biomass burning, forest fires, oceans, power plants.(NO and N2O are mentioned in NIOS Environment)

Ocean Acidification

  • People have called ocean acidification “global warming’s evil twin” and “the other CO2 problem.”
  • Ocean acidification is when the pH of the Earth’s seas keeps going down. This is caused by the oceans taking in carbon dioxide (CO2) from the air.
  • About 30–40% of the carbon dioxide that people put into the air by doing things dissolves in oceans, rivers, and lakes.
  • Some of it combines with the water to make carbonic acid (H2CO3) so that the chemicals can be in balance.
  • Some of these extra molecules of carbonic acid combine with a molecule of water to make a bicarbonate ion and a hydronium ion. This raises the amount of H+ ions in the ocean, which makes it more acidic.
  • When CO2 combines with water molecules (H2O), it makes carbonic acid, which is a weak acid. Most of this acid breaks down into bicarbonate ions (HCO3-) and hydrogen ions (H+). When the number of H+ ions goes up, the pH (a measure of acidity) goes down. This makes the seas more acidic, or less alkaline. This is called the ocean becoming more acidic.
  • The only way to stop ocean acidification is to stop CO and CO2 production and control pollution.

Large blooms of plankton are caused by eutrophication. When these blooms die off and sink to the sea floor, the algae are broken down by bacteria, which releases oxygen and increases CO2. This lowers the pH of the water.

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What changes in the pH of ocean has occurred?

On the pH scale, which goes from 0 to 14, liquids with low numbers are acidic and those with high numbers are basic. Seven is neutral. Since the industrial revolution, the pH of the ocean has dropped from 8.2 to 8.1, and it is expected to drop another 0.3 to 0.4 pH units by the end of the century.

But this change in pH isn’t very big. Is it really that scary?
A pH drop of 0.1 might not seem like much, but the pH scale is logarithmic, just like the Richter scale used to measure aftershocks. For example, pH 4 is 10 times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6. Small changes in pH can affect a lot of chemical processes, even ones that are necessary for life. Normal blood pH in people, for example, is between 7.35 and 7.45. A 0.2-0.3 pH drop in the blood can lead to seizures, comas, and even death. In the same way, even a small change in the pH of groundwater can hurt marine life by changing the way chemicals communicate, reproduce, and grow.

Okay, but when the ocean takes in CO2, it helps the atmosphere because it slows down global warming. So, why should you be worried?

At first, many experts focused on the benefits of this greenhouse gas being taken out of the air by the ocean. At first, scientists thought this might be a good thing because it leaves less carbon dioxide in the air to warm the world. But in the last 10 years, they’ve learned that this slowing of warming has changed the chemistry of the ocean.
Also worrying is the fact that as the seas keep taking in more CO2, their ability to store carbon could decrease. That means more of the carbon dioxide we put into the air will stay there, making climate change even worse. Ocean acidification will make it harder for the ocean to take CO2 made by humans, which will make climate change worse.

Consequences of Ocean Acidification

  • Oceans are becoming more dangerous for marine life because of plastic pollution, overfishing, global warming, and higher acidification from burning fossil fuels.
  • Corals will be hurt by ocean acidity. One million species that live in reefs will be affected by this.
  • Coral reefs will be destroyed more quickly than they can be rebuilt. When shelled creatures are in danger, the whole food chain may be in danger.
  • Higher CO2 levels may help some plants and seagrass because they may speed up their growth and photosynthesis.
  • Most sea species seem to be at greater risk when they are young.
  • Climate change, pollution, coastal growth, overfishing, and agricultural fertilisers will all make the changes caused by acidification worse.
  • All of the things that the ocean does for us will be affected by these changes.
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What happens to corals when the ocean gets too acidic?

  • The oceans are an important place for CO2 to be stored because they absorb a lot of it (one-third) that comes from human actions. This helps to slow down climate change.
  • Atmospheric carbon dioxide is being taken up at a rate that is faster than the seas’ natural ability to act as a buffer.
  • Some organisms’ metabolic rates and immune reactions slow down when acidity goes up.
  • When CO2 is taken up by seawater, carbonic acid, bicarbonate, and carbonate ions are made.
  • But when the amount of CO2 in the air goes up, the pH level goes down, the concentration of carbonic acid and bicarbonate ions goes up, and the concentration of carbonate ions goes down.
  • Because there are less carbonate ions in the water, it is harder for marine organisms like coral and some plankton to make biogenic calcium carbonate. • Acidification is a threat to commercial fisheries because it hurts calcifying organisms that are the foundation of Arctic food webs.
  • Increasing acidity makes coral bleaching worse because corals are very sensitive to changes in the water.

What Happens to Clouds When the Ocean Gets Too Acidic?

Most of the sulphur in the air comes from the ocean, usually in the form of dimethylsulfide (DMS), which is made by phytoplankton. Some of the DMS made by phytoplankton gets into the air and reacts to make sulphuric acid, which clumps into tiny airborne particles called aerosols.Aerosols help clouds grow, and clouds help cool the Earth by reflecting the sun.But when ocean water becomes more acidic, algae makes less DMS. This may cause fewer clouds to form, which raises temperatures around the world.

Artificial Cloud Seeding:

• Cloud seeding is the process of putting dry ice or, more often, silver iodide aerosols in the top part of clouds to try to make it rain.

  • Since most rain starts when supercooled cloud droplets in the upper parts of clouds turn into ice crystals, the silver iodide particles are supposed to make more ice crystals.
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Socio-economic Impacts

Food: • Ocean warming could make it harder to get enough food.By 2100, the loss of mollusks due to ocean acidity could cost the world more than $100 per year.

Coastal protection

  • Marine habitats like coral reefs, which protect shorelines from the damage of storm surges and cyclones, will be affected.The coastal estuaries and rivers are being affected by the acidification of the ocean.

Tourism: • The effects of ocean acidification on marine ecosystems could have a big impact on this industry. • Ocean acidification could hurt the Arctic’s tourist industry and change the way native people live.

Carbon storage and climate regulation

  • As ocean acidification gets worse, the ocean’s ability to absorb CO2 gets worse. • Oceans that are more acidic are less successful at stopping climate change.

Ocean Acidification in Indian Ocean

  • The Arabian Sea’s top waters are getting more acidic because there is too much carbon dioxide in the air.
  • Most of the acidification in the northern Bay of Bengal is caused by pollution from the Indo-Gangetic plains mixing with the seawater. • During the winter, air blowing from land to sea takes all the pollution with it and dumps it in the ocean as it moves.A study shows that the amount of marine algae in the western Indian Ocean is going down quickly.
  • A study says that the levels of ocean warming could turn the Indian Ocean into an ecological desert. • Ocean acidification in the Arabian Sea and Bay of Bengal will destroy the Indian Ocean, which is one of the cleanest and most fertile places on Earth.

Way Forward

  • Reducing world greenhouse gas emissions is the best way to stop ocean acidification. This is called mitigation.
  • Improving the quality of the water by keeping an eye on and controlling localised sources of acidification, such as waste and pollution from things like fertilisers.
  • Creating ways to handle fisheries that are good for the environment: Controlling catches to stop too much fishing
  • Managing habitats in a way that is good for the environment: protecting the coasts more, lowering the amount of sediment in the water, and using marine spatial planning.
  • A lot of study on climate engineering to find out if it is possible and what effects it has.
  • Teach or make people aware of the risks that climate change and ocean acidification bring.
  • Using less energy that releases carbon into the air.