Ocean microplastics a growing concern

Trillions of microscopic pieces of plastic are filling the oceans.

Laurel Kornfeld | May 23, 2020

A new study led by researchers at the Plymouth Marine Laboratory in England indicates Earth's oceans have much higher levels of microplastics than previously thought.

Microplastics are tiny pieces of plastic with diameters of less than five millimeters, produced by the disposal and breakdown of plastic products and industrial waste. Because they are so small, they often elude detection and become trapped in ocean sediment.

Scientists have had a difficult time measuring the amount of microplastics in oceans because the nets used to capture samples range from 333 to 500 micrometers, or 0.333 to 0.5 millimeters. Tiny particles can pass through nets of this size.

Together with scientists from the University of Exeter, the Plymouth Marine Laboratory researchers collected samples from two locations on opposite sides of the Atlantic Ocean using a 100-micrometer or 0.1-millimeter net.

Both sites chosen, one off the coast of Maine and the other in the English Channel, are coastal locations, where microplastics are most likely to be heavily concentrated and harm ocean life.

The researchers collected 2.5 times as many microplastics using the 100-micrometer net as they did with the 333-micrometer net and ten times more than they did with the 500-micrometer net.

From this data, they calculated that one cubic meter holds approximately 3,700 pieces of microplastic, suggesting the world's oceans contain between 12.5 and 125 trillion particles rather than the previously estimated five to 50 trillion particles.

"There is often a mismatch between the number and type of microplastics used in experimental studies and those found in the natural environment. This study confirms that microplastic concentration increases with decreasing size and also provides a framework for determining microplastic concentrations in exposure studies, particularly with animals such as zooplankton, that eat micron-sized food," explained Rachel Coppock, a marine ecologist at Plymouth Marine Laboratory.

Pennie Lindeque, also of the Plymouth Marine Laboratory, said she was surprised by the consistency of the study's microplastic level findings on opposite sides of the Atlantic Ocean.

A paper on the study has been published in the journal Environmental Pollution.