August 12, 2016 Climate Change Written by Greentumble
what causes ocean acidification
Ocean acidification is a chemical process

caused by elevated carbon dioxide concentrations in the atmosphere. It is one of the more severe effects of global warming, and has the potential to devastate sensitive marine ecosystems over the coming years.

PH sensitive species such as corals and shellfish are especially at risk, as more acidic conditions reduce their ability to build shells or skeletons. This has led to widespread cases of coral bleaching and negative events throughout the planet’s oceans [1]. Unfortunately, the frequency of these events seems to be increasing.

The most common causes of ocean acidification

Around half of the carbon dioxide produced by modern industry and other polluting practices is dissolved in the ocean. Here it reacts with water to form carbonic acid, which lowers ocean pH and reduces the concentration of carbonate ions – an essential component for the formation of corals, shells, and other hard skeletal structures [2].

Obviously, the main cause of ocean acidification is the emission of greenhouse gases (namely carbon dioxide) through a number of human activities.

These include:

    • Fossil fuel emissions

Fossil fuels could be thought of as the ‘evil good’. They have played a huge role in developing society into what it is today. Without them, it is highly unlikely that we would have some of the advanced technology which people take for granted, and it is entirely possible that we would still be living in the age of the horse and cart.

However, burning fossil fuels releases carbon dioxide – a fact which most people would be aware of. Cars, airplanes, factories, and power plants all burn fossil fuels, and therefore all contribute to carbon dioxide emissions.

Therefore, we can conclude quite easily that fossil fuels are a leading cause of ocean acidification [3].

    • Deforestation

Deforestation is a complex issue. While the obvious effects include the reduction of habitat and loss of biodiversity, a less known effect is carbon dioxide emission.

The large scale burning which usually accompanies deforestation is similar to burning fossil fuels, and releases a lot of carbon itself.

However, since forests also act as large ‘carbon sinks’ – they absorb carbon dioxide from the atmosphere and store it – their removal also reduces the earth’s carbon dioxide storage capacity [3]!

    • Algal blooms

This is a less-known cause of localized ocean acidification. When nutrient concentrations in an area become too high (usually due to fertilizer runoff), algal blooms occur.

After these algal blooms are finished, there is generally a lot of organic matter remaining, which begins to decay. This decaying process releases large amounts of carbon dioxide and can lead to acidifications.

The chemistry

It is estimated that the ocean absorbs around 22 million tons of carbon dioxide per day. Yes, per day. Every molecule of this carbon dioxide contributes to ocean acidification, and therefore is harmful to the environment.

The process is as follows:

  1. When the carbon dioxide dissolves, it reacts with water to form carbonic acid (H2CO3).
    CO2 + H2O → H2CO3


  1. This carbonic acid then reacts with carbonate ions to form bicarbonate ions (HCO3)
    H2CO3 + CO3 → HCO3

The harmful part of the process is the second step, which involves the removal of carbonate ions, an essential building block for a number of marine organisms [5]. The effects of ocean acidification provide just one more reason for us to act.

We need to reduce our dependence on fossil fuels, reduce greenhouse gas emissions, and save the planet, one step at a time.