Pineapple sea cucumber underwater Photo: © ead72 – stock.adobe.com

Climate change impacts every corner of the planet, and the ocean is no exception. As climate change raises temperatures and leads to more unpredictable weather patterns, the delicate balance of marine ecosystems is increasingly at risk.

The ocean is the world’s largest carbon sink, absorbing approximately 90% of the excess heat caused by greenhouse gases and taking in 30% of carbon emissions. The carbon stored by the ocean is known as blue carbon. Its health and stability are critical in mitigating the effects of climate change. So, if we don’t prioritise the health of our oceans, we’ll be losing one of our greatest assets in the fight against climate change.

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Ocean acidification

Ocean acidification is a lesser-known but equally significant consequence of climate change that poses a grave threat to marine ecosystems worldwide. The ocean is a huge carbon sink, absorbing carbon dioxide from the atmosphere. However, it can only absorb so much before it affects the oceans’ ecosystems.

When CO2 dissolves in seawater, it reacts with water molecules to form carbonic acid, leading to a decrease in pH and an increase in the water’s acidity. This process, known as ocean acidification, has caused a decline in the average pH of seawater from a slightly more alkaline level of 8.2 to a more acidic level of 8.1. Though this may not appear to be a significant drop in pH levels, it actually represents a 25% increase in acidity over the last two centuries. 

Why it’s a problem

Ocean acidification poses a significant threat to marine organisms, particularly those with calcium carbonate shells or skeletons, such as corals, shellfish, and certain types of plankton. As seawater becomes more acidic, these creatures’ calcium carbonate shells dissolve. The more acidic the water is, the faster these shells will dissolve. Their weakened structural integrity can make them more susceptible to damage from physical disturbances, disease, and predation. The creatures then need to expend more energy thickening or repairing their damaged shells, which can inhibit their growth. This can affect the food web, with less food available to their predators.

Moreover, these creatures act as carbon stores, which helps mitigate climate change. But as their shells dissolve, this natural way of removing carbon from the atmosphere is threatened.

IFAW, 28 May 2024. Article.

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