Microplastics may seem innocuous enough. They are barely visible plastic beads that are the size of sand grains. What harm could they do?
Plenty. Microplastics have spread far and wide in the world’s oceans, entering food chains. Even table salt has been contaminated by these tiny pollutants. A myriad of marine animals large and small have been affected by microbeads, which they may end up swallowing in large quantities by accident.
Among the worst affected creatures are some of the planet’s largest animals. According to a new study published by an international team of researchers in the journal Trends in Evolution & Ecology, filter feeders like baleen whales and basking sharks are at especial risk of ingesting large quantities of microplastics because of their feeding habits that involve filtering vast amounts of seawater for plankton. By accidentally swallowing these tiny plastic beads while they are gulping down plankton, filter-feeding whales, sharks and rays may suffer from harmful side-effects that could prove lethal.
“[M]icroplastic contamination has the potential to further reduce the population numbers of these species, many of which are long-lived and have few offspring throughout their lives,” says Elitza Germanov, an Australian marine scientist who is a co-author of the study. As a result, key species of marine megafauna could be pushed closer to extinction.
“Exposure to these plastic-associated toxins pose a major threat to the health of these animals since it can alter the hormones, which regulate the body’s growth and development, metabolism, and reproductive functions, among other things,” adds Maria Fossi, a researcher at the University of Siena in Italy, who worked on the study.
The researchers cite the example of a whale found dead on a beach in France with 800kg of plastic inside its body. Another whale found dead in Australia was found to have six square meters of plastic sheeting and 30 shopping bags inside its stomach and intestines. Such cases indicate that countless other large sea animals could die after ingesting large quantities of plastic.
More and more countries are banning the use of microbeads in household products like cosmetics yet microplastics continue to be used on a large scale. To make matters worse, they are regularly so small that they are left unfiltered by water treatment plants and so can escape into rivers, lakes and seas.