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Environment: Microplastic pollution gets inside crabs via gills

Caption: This image depicts polystyrene microspheres inside the gills of a shore crab. Credit: Andrew Watts

This image depicts polystyrene microspheres inside the gills of a shore crab. Image by Andrew Watts, University of Exeter, UK.

Is there a risk higher up the food chain?

By Bob Berwyn

* Read more Summit Voice stories on ocean plastic pollution here.

FRISCO — By some estimates, humankind now produces about 288 million tons of plastic per year, and about 10 percent of that likely ends up in the world’s oceans as a finely ground, totally human-produced source of pollution. Floating about in the seven seas, the microplastics can form rafts that harbor non-native bacteria and scientists know that the plastic is being eaten  by marine critters.

Along with direct ingestion, a new study by scientists at the University of Exeter shows that the microplastics are not only orally ingested by marine creatures, but also enter their systems through their gills. When microplastics are drawn in through this method they take over six times longer to leave the body compared with standard digestion.

“Many studies on microplastics only consider ingestion as a route of uptake into animals. The results we have just published stress other routes such as ventilation,” said Dr. Andrew Watts of the University of Exeter. “We have shown this for crabs, but the same could apply for other crustaceans, molluscs and fish … simply any animal which draws water into a gill-like structure to carry out gas exchange.

“This is highly important from an ecological point of view, as if these plastics are retained longer within the animal there is more chance of them being passed up the food chain,” Watts said.

The researchers used fluorescently labelled polystyrene microspheres to show how ingested microplastics were retained within the body tissues of the common shore crab, Carcinus maenas. Multiphoton imaging suggested that most microspheres were retained in the foregut after sticking to hair-like ‘setae’ structures within the crabs.

Plastic is part of everyday life. About 40 percent of it is used for one-time packaging. At 2013 production levels, scientists say about 11 million tons end up in the environment every year. The plastic is then degraded by wave action, heat or UV damage and is created into microplastic (particles smaller than 5mm).

A recent study by Spanish scientists showed that ocean plastics pollution is pervasive around the world, even in the Arctic.

“This is a human issue. We have put this plastic there, mostly accidentally, but it is our problem to solve. The best way to do this is to reduce our dependency on plastic. It comes back to the old phrase: reduce, reuse and recycle,” Watts said.

Late last year, the U.S. Environmental Protection Agency announced a modest push to tackle plastic pollution by creating a framework for regulations that could address the problem at the local level.

The study, published in the journal Environmental Science and Technology, was funded by CleanSeas, a multidisciplinary and collaborative research project addressing marine litter from different perspectives. 

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