Ocean Acidification

Ocean acidification, a stealthy side effect of rising anthropogenic carbon dioxide emissions, is a recently discovered, little recognized global climate-change threat that should be more widely known.

Unlike the warming effect on air temperatures that rising atmospheric carbon dioxide levels cause, – which scientists understood theoretically since the late 1800s and began describing forcefully in the late 1970s, – the alarm bell for “ocean acidification” was rung only in 2003, in a brief scientific paper. It introduced the term “ocean acidification” to describe how some of the rising carbon dioxide levels are absorbed into the ocean’s surface waters. This has the benefit of slowing the pace of air-temperature warming, – thus far, oceans have absorbed at least a quarter of anthropogenic carbon dioxide emissions, – but the detriment of lowering the pH of the world’s oceans.

The increasing abundance of bicarbonate ions leads to decreased availability of calcite and aragonite minerals in ocean water, depriving marine mollusks, crustaceans, and corals of primary ingredients from which they build their protective shells and skeletons. Of the familiar organisms, oysters and mussels are especially vulnerable, but the detrimental effects of ocean acidification go far beyond shelled seafood. How these multiple cascading effects will play out for the planet’s marine ecosystem is unknown.

Scientists are now investigating new ways to mitigate the ocean-acidification problem. Certain species of sea grass, for example, may locally buffer pH. Planting or reintroducing sea grasses could provide some relief in protected estuaries and coves. Selective breeding experiments are underway to develop strains of aquatic plants and animals more tolerant of low pH waters. At the extreme end of scientific tinkering, new genetically engineered marine organisms may be on the horizon.

While some of these ideas hold promise for particular locations and species, none can stabilize pH on a global scale. Genetic engineering raises a whole other set of ethical and environmental issues. Furthermore. some of the more hopeful geo-engineering solutions proposed to combat air-temperature warming work by increasing the earth’s reflectivity. These strategies have problems of their own, like unknown effect on global rainfall patterns, but they might mitigate CO2 induced air-temperature warming. However, because they do nothing to reduce atmospheric C)2 levels, they will have zero effect on ocean acidification.

Today the only viable way to slow ocean acidification on a global scale is to reduce human-induced carbon dioxide emissions.

Ocean Acidification
Lawrence C. Smith
Professor of Earth, Planetary, and Space Sciences, UCLA
Author, The World in 2050