In a major development, a group of scientists have found that some naturally-occurring lake bacteria grow faster and more efficiently on the remains of plastic bags than on natural matter like leaves and twigs. This means that these natural bacteria help in curtailing plastic pollution.
The study of 29 European lakes found that the bacteria break down the carbon compounds in plastic to use as food for their growth. The researchers said that enriching waters with particular species of bacteria could be a natural way to remove plastic pollution from the environment.
PLASTIC; WHAT DOES THE RESULTS SAY?
The researchers said that their study suggested that 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. They believe that carbon compounds from plastics are easier for the bacteria to break down and use as food.
Senior author of the paper Andrew Tanentzap from the University of Cambridge’sDepartment of Plant Sciences, said that it was almost like the plastic pollution is getting the bacteria’s appetite going. “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 author said.
He also said, “this suggests that plastic pollution is stimulating the whole food web in lakes, because more bacteria means more food for the bigger organisms like ducks and fish.”
PLASTICS; THE METHOD OF STUDY
The study involved sampling 29 lakes across Scandinavia between August and September 2019. To assess a range of conditions, these lakes differed in latitude, depth, area, average surface temperature and diversity of dissolved carbon-based molecules.
The scientists cut up plastic bags from four major UK shopping chains, and shook these in water until their carbon compounds were released.
At each lake, glass bottles were filled with lake water. A small amount of the ‘plastic water’ was added to half of these, to represent the amount of carbon leached from plastics into the environment, and the same amount of distilled water was added to the others. After 72 hours in the dark, bacterial activity was measured in each of the bottles.
The study measured bacterial growth – by increase in mass, and the efficiency of bacterial growth – by the amount of carbon-dioxide released in the process of growing.
In the water with plastic-derived carbon compounds, the bacteria had doubled in mass very efficiently. Around 50% of this carbon was incorporated into the bacteria in 72 hours.
“Our study shows that when carrier bags enter lakes and rivers they can have dramatic and unexpected impacts on the entire ecosystem. Hopefully our results will encourage people to be even more careful about how they dispose of plastic waste,” said Eleanor Sheridan in the University of Cambridge’s Department of Plant Sciences, first author of the study who undertook the work as part of a final-year undergraduate project.
Nature Communications published the study.