How does ocean acidification affect marine life?

What is ocean acidification and why is it important? How does it affect marine life? Oceans are absorbing increasing levels of carbon dioxide from the atmosphere and that makes the oceans more acidic. This is affecting marine life like corals and shellfish.

What is ocean acidification?

Ocean water is normally ph neutral or slightly alkaline at 8.2 (Natural History Museum). It has been this way for millions of years. 

We know that the levels of carbon dioxide (CO2) are increasing. This is mainly due to industrial processes like the burning of fossil fuels. It is also due to the reduction in forests, which absorb carbon dioxide from the air. 

Carbon dioxide is dissolving in the ocean, making it more acidic. It is now 8.1%, a 0.1 unit change. In reality, the scale is exponential and that unit change is effectively a 25%-28% increase in acidity. By 2100, it could be as low as 7.8 (National Geographic). This ‘small’ change is having a big impact on marine life. 

How does ocean acidification affect marine life?

Ocean acidification affects corals, oysters and other shellfish with carbonate shells or skeletons. An Italian study of snails found near volcanic vents beneath the ocean, where the ocean is naturally more acidic, found that they had dissolving shells. The snails spend all their energy repairing their shells and have no energy to eat or reproduce. 

Ocean acidification also softens the shells of scallops and oysters. It affects the moulting of crabs and lobsters. It also affects the sense of smell in fish. The response to ocean acidification is different for different species. Some of these animals will die. Others will adapt. 

How does ocean acidification affect coral?

“Coral is an animal made out of calcium carbonate. It looks like a tree or a rock. If you just drop a little bit of acid on any of those, you watch them bubble away and dissolve. It’s not that dramatic in the ocean, but it’s just slowly becoming more difficult for these creatures to secrete their shells.”

Joanie Kleypas, Coral Reef and Ocean Acidification Expert

Coral bleaching occurs when a coral is stressed, mainly due to rising ocean temperatures, and it rejects the algae that live in its branches. The coral gets energy from the sun through the algae and they give it colour. The coral turns white and it weakens or it dies. This has an impact on at least a third of fish species who live in and around coral reefs. Fish species that we eat. 

What can be done about ocean acidification?

“Realistically, there isn’t actually anything that can be done beyond what is already happening, which is cutting down emissions”

Professor Richard Twitchett

Coral reef restoration projects can help to re-establish colonies of coral. The biggest change we can make that will have an impact on ocean acidification is to reduce our carbon dioxide emissions. However, ‘halting ocean acidification is practically impossible’ (Natural History Museum). 

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Annette Clubley

Annette is a keen wildlife conservationist, mindful of sustainability and our impact on the environment. Outside of work, family is her focus and she loves teaching the next generation to enjoy the outdoors.