Marine microplastic pollution is worse than we thought

There are plenty of microplastics in the oceans, yet just how much of the stuff is out there may come as a shock. Brace yourself: the amount is many times more than previously thought.

So says a team of scientists in the United Kingdom who used nets with a mesh size of 100 micrometers (0.1mm), the width of a human hair, to see how many tiny plastic particles ended up in those nets. The researchers sampled water taken at two locations on both sides of the Atlantic: the English Channel in Europe and off the coast of Maine in North America.

For many previous measurements, nets with a mesh size of 333 micrometers were used, but those failed to nab finer particles of plastic debris floating in the seas, explain the researchers who published their findings in a study. Using the finer 100μm mesh nets, however, the scientists found that the concentration of microplastics were between  2.5 and 10 times greater than when nets with 333μm and 500μm meshes were employed.

In other words, previous measurements missed large quantities of extra-fine particles, most of which are fibers from textiles like ropes, nets and clothing.

“Microplastic pollution is a widespread pollutant, found all throughout the oceans, but working out how much is there has been a major challenge for scientists,” notes Matthew Cole, a lead author of the study who is a marine ecologist and ecotoxicologist at Plymouth Marine Laboratory.

“Typically, scientists use specialized nets to sieve out microplastics from the sea surface,” Cole explains. “Normally these nets are quite coarse so they don’t get clogged up with microscopic plants and animals that live in the sea, but it also means they’re unable to sieve out the very smallest plastics that are present.”

Owing to data gathered with a much finer mesh size, microplastic concentrations could exceed 3,700 microplastics per cubic meter. That is far more than the concentrations of tiny zooplanktons (which are among the most abundant animals on Earth) in the same amount of water in parts of the oceans, the researchers note in a statement on their findings.

“Global estimates of floating microplastic debris modelled on data primarily gathered from 333μm net samples are in the order of 5-50 trillion particles,” they say. In total, plastic particles could amount to 125 trillion in the oceans, including much finer particles. The effects of so much plastic in the environment could be devastating for marine creatures large and small.

“Our results, based on sampling in the UK and US, suggests we are underestimating the really small pieces of plastic in the marine environment,” explains Pennie Lindeque, the study’s lead author who is head of marine ecology and biodiversity at Plymouth Marine Laboratory.

Studies have shown that marine organisms from plankton to fish to birds are suffering a variety of harmful side-effects, including reduced fertility, stunted growth and premature death. Plastic pollution has also been linked to changes in the behaviors and ecological functions of numerous species.

“Microplastics aren’t a uniform type of pollutant; rather they come in all different shapes, sizes and polymer types. Determining how many of which types are in the natural environment is rather like looking for needles in a haystack,” Lindeque says.

“A better understanding of how many microplastics are in our seas and a more detailed description of what type of microplastics they are, helps to determine what risk they pose to marine animals and ecosystems, which in turn can help influence societal behavior and drive future policy intervention,” the scientist adds.