Our oceans are getting more acidic. Why?

Cliff Mitchell - 17/01/2020

We are killing coral!

If we continue emitting CO2 at the current rate by 2100 ocean acidity will increase by about 150%, a rate that has not been experienced for at least 400,000 years.

For more than 200 years the concentration of carbon dioxide (CO2) in the atmosphere has increased due to the burning of fossil fuels and land use change.

Since the start of the Industrial Revolution humans have added some 400 billion tons of carbon to the atmosphere.

The ocean absorbs about 30 percent of the CO2 that is released in the atmosphere, and as levels of atmospheric CO2 increase, so do the levels in the ocean.

When CO2 is absorbed by seawater, a series of chemical reactions occur resulting in Carbonic Acid and the increased concentration of hydrogen ions. This increase causes the seawater to become more acidic and causes carbonate ions to be relatively less abundant.

Carbonate ions are an important building block of structures such as sea shells and coral skeletons. Decreases in carbonate ions can make building and maintaining shells and other calcium carbonate structures difficult for calcifying organisms such as oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton, which are weakened by even very slight changes in the ocean’s acid balance—similar to the way acid rain corrodes stone gargoyles and limestone buildings.

These changes in ocean chemistry can affect the behavior of non-calcifying organisms as well. Certain fish's ability to detect predators is decreased in more acidic waters. When these organisms are at risk, the entire food web may also be at risk.

Check out this short (2 minutes 37 seconds), easy to understand, video that summarises the problem.

Ocean acidification is affecting the entire world’s oceans, including coastal estuaries and waterways. Many economies are dependent on fish and shellfish and people worldwide rely on food from the ocean as their primary source of protein.

Increasing acidity is thought to have a range of potentially harmful consequences for marine organisms such as depressing metabolic rates and immune responses in some organisms and causing coral bleaching

According to a statement by Jane Lubchenco, head of the U.S. National Oceanic and Atmospheric Administration

"surface waters are changing much more rapidly than initial calculations have suggested. It's yet another reason to be very seriously concerned about the amount of carbon dioxide that is in the atmosphere now and the additional amount we continue to put out."