Ocean acidification and its impacts

Imagine you could see the impact of ocean acidification on marine life. There's a simple experiment you can try at home: grab a seashell from your last beach trip, buy a fizzy drink, and put the seashell in it. After a few days, you'll notice the seashell dissolving — a rough illustration of what's happening, far more slowly, in the ocean itself.

The Arctic as a bellwether

Colder water absorbs CO2 more readily, which makes the Arctic Ocean an early-warning system for acidification happening elsewhere. Prof Helen Findlay, a biological oceanographer at Plymouth Marine Laboratory, studies how Arctic copepods respond to the pH levels projected for the rest of the ocean in coming decades.

Impact on marine life

Organisms that build shells or skeletons from calcium carbonate are most directly affected. As carbonate ions become less available, these organisms must expend extra energy maintaining their structures, leaving less for growth and reproduction — with knock-on effects for the fish and mammals further up the food web that depend on them. In severe cases, shells and skeletons can begin to dissolve outright.

Dr Ceri Lewis, from the University of Exeter, has warned that within a few decades, increased ocean acidity could become corrosive to some of the smaller marine creatures that underpin ocean ecosystems.

Just as the seashell dissolved in the fizzy drink, ocean acidification is already affecting the survival of a range of species, and the organisms most exposed are often the ones the rest of the food web depends on.