What Is the Impact of Ocean Acidification?

Ocean acidification could have a massively damaging impact on millions of people all over the world in the coming years and decades, according to a new study from the University of Plymouth. By concentrating on heavily acidified hotspots in Japan and the Mediterranean, the study’s authors claim they can predict what may happen on a global scale if carbon continues to seep into the sea.

The study is just latest in a growing body of work from its two authors, who have demonstrated that acidification can have a potentially devastating effect on marine ecosystems, with reefs under particular threat. This not only endangers the coral and oysters which comprise the reefs themselves, but also the myriad fish, crustaceans and other marine organisms which call them home.

What is ocean acidification?

Ocean acidification can be defined by a fall in pH levels in the water, caused primarily by carbon seeping into their vicinity. This can be caused naturally by volcanic fissures, such as at the two sites monitored by the study’s authors, but is becoming more and more commonplace through anthropomorphic activity, given that we release around a million tonnes of CO2 into the atmosphere every hour.

Roughly one quarter of that amount finds its way into the ocean and dissolves; once that happens, it reacts with the salty seawater to create a weak acidic substance. This causes surface ocean water to experience a fall in pH levels of approximately 0.002 units per year. That might not sound like much, but cumulatively it could have a sizable impact on the harmony of the water upon which so many marine creatures depend to survive and thrive.

Reefs at risk

The warming temperatures of the world’s oceans have already done significant damage to marine reefs; one only need to look at what's happened to the Great Barrier reef for confirmation. As if that wasn’t bad enough, the acidification studied by Professor Jason Hall-Spencer and Dr Ben Harvey has been found to further jeopardise their longevity, especially for those composed of oysters or corals, which are particularly sensitive to the acidic effect.

The degradation of reefs not only spells trouble for the corals themselves, but also for the more than 25% of all marine animals which use them as a habitat. As well as being a hammer blow for biodiversity, this could also deplete stocks of many varieties of fish and shellfish which are popular for human consumption. Finally, reefs also provide an important breakwater for coastal communities; losing them would mean reduced protection against extreme weather events at sea.

What can be done?

In a world in which our seas and oceans are already suffering from myriad different problems, such as plastic pollution, dangerous blue green algae, habitat disruption from shipping, oil spills and many more, the last thing that the Earth’s waterways need right now is another threat in the form of increased oceanic temperatures and acidification. As a result, the lead author of the study Professor Hall-Spencer has called for immediate action.

“The Paris Agreement on climate change was welcome, but it does not mention ocean acidification, nor the fact that this rapid change in surface ocean chemistry undermines the social, economic and environmental pillars of sustainable development,” he remarked. “The time is ripe for a 'Paris Agreement for the oceans', with the specific target to minimise and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels.”