‘One more thing’ about plastics: they could be acidifying the ocean, study says

A coral reef in Sharm el Sheikh, Egypt. Lowered pH obstructs the ability of marine organisms, such as corals, planktons, oysters and urchins, to build skeletons and shells out of calcium carbonate and to generally survive. Image by Renata Romeo / Ocean Image Bank.

The trillions of pieces of plastic currently roving through the global ocean are known to be an assault on life. Turtles get tangled up in discarded plastic fishing nets. Whales open their mouths to eat and unwittingly fill their stomachs with shopping bags. Filter-feeding fish and other organisms gobble up tiny plastic particles, poisoning themselves with the plastic’s toxins and passing that toxicity along to any animal that consumes them.

And now, new research suggests that plastic pollution could be harming the ocean in an additional way: by contributing to its acidification.

Through a series of laboratory experiments, scientists from the Marine Sciences Institute in Barcelona, known as ICM-CSIC by its Spanish acronym, found that when plastic — especially aged, degraded plastic — interacts with sunlight, it releases a cocktail of chemicals, including organic acids, into the ocean. Organic acids are known to lower the pH of seawater, causing it to become more acidic. In addition, the sun’s degradation of plastic can lead to carbon dioxide (CO2) release, which can cause pH to plummet further.

In highly polluted parts of the ocean, such as coastal areas, plastic could contribute to a drop of up to 0.5 pH units, which is “comparable to the pH drop estimated in the worst anthropogenic emissions scenarios for the end of the 21st century,” says Cristina Romera-Castillo, a postdoctoral researcher at ICM-CSIC and lead author of the study documenting the findings.

Elizabeth Claire Alberts, Mongabay, 4 October 2022. Full article.

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