In a study of bacterial populations from 29 Scandinavian lakes, scientists found that some bacteria grow quickly and efficiently on the remains of plastic bags. Their findings may help inform plastic pollution remediation efforts.


The study was led by Andrew Tanentzap, PhD, a professor of global change ecology at the University of Cambridge. His team’s findings were published in the journal Nature Communications (“Plastic pollution fosters more microbial growth in lakes than natural organic matter”).


Plastic waste leaches dissolved organic matter (DOM) into rivers, lakes, and oceans. This DOM, in turn, likely affects the feeding habits and growth of bacteria that inhabit those waters.


“Few data exist on the molecular composition and fate of plastic leachate in freshwaters, especially compared with natural DOM,” the researchers wrote. “Here, our aim was to determine the effects of plastic leachate on bacteria in the northern lakes that dominate the world’s freshwater area.”


The scientists took water samples from the lakes, which differed in latitude, depth, area, average surface temperature, and other characteristics. To a set of the samples, they added a small amount of “plastic water”—representing plastic leachate—which they generated by shaking plastic shopping bags in water until carbon compounds were released.


“[Plastic] leachate increased bacterial biomass acquisition by 2.29-times when added at an environmentally-relevant concentration to lake surface waters,” the researchers wrote.


Furthermore, the researchers found that the carbon compounds released when plastics break down are chemically distinct to the carbon compounds released from organic matter like leaves and twigs. And the lake bacteria grew efficiently on the plastic-derived carbon compounds.


“Bacterial growth was 1.72-times more efficient with plastic leachate because the added carbon was more accessible than natural organic matter,” the researchers wrote. In other words, the carbon compounds from plastics are easier for the bacteria to break down and use as food.


In sum, the results suggested that the plastic pollution in lakes is “priming” the bacteria for rapid growth—the bacteria are not only breaking down the plastic but are then more able to break down other natural carbon compounds in the lake.


“It’s almost like the plastic pollution is getting the bacteria’s appetite going,” Tanentzap said. “The bacteria use the plastic as food first, because it’s easy to break down, and then they’re more able to break down some of the more difficult food—the natural organic matter in the lake.”


The scientists say that enriching waters with particular species of bacteria could be a natural way to remove plastic pollution from the environment.


“Unfortunately, plastics will pollute our environment for decades,” said David Aldridge, PhD, an applied freshwater ecologist at the University of Cambridge and co-author on the study. “On the positive side, our study helps to identify microbes that could be harnessed to help break down plastic waste and better manage environmental pollution.”


But they caution that this does not condone the ongoing plastic pollution. Some of the compounds within plastics can have toxic effects on the environment, particularly at high concentrations.

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