In a new report published in the Canadian Journal of Fisheries and Aquatic Sciences, researchers write that microbeads were discovered in almost every sediment sample taken from 10 different locations on the St. Lawrence River between Lake St. Francis and Québec City.
“We found them in nearly every grab sample taken,” said Rowshyra Castañeda, the lead author of the study. “The perfect multi-coloured spheres stood out from natural sediment, even though they were the size of sand grains.”
Microplastics have previously been found in the Arctic, in Lake Michigan and in 88 percent of ocean surface water, but this is the first time microplastic contamination has been documented in a North American river. And it has been documented in no small amount. Some sediments from the St. Lawrence were found to contain over 1,000 microbeads per liter, a concentration equal to the ocean’s most contaminated samplings.
“We were surprised to find such concentrations at the bottom of a river,” says McGill University professor Anthony Ricciardi, who supervised the study. “It was previously assumed that floating microplastics are flushed through rivers to the sea. Now we have evidence that rivers can act as a sink for this pollution.”
The direct environmental effects of microplastic are not fully understood, but it poses a health hazard to marine creatures, which often mistake the small, translucent pieces for bits of plankton. In addition to tearing at creatures’ insides, the plastic particles can attract chemical toxins, such as mercury, DDT and PCBs.