The lake’s natural bacteria can help eliminate plastic pollution

A study of 29 European lakes found that some natural lake bacteria grow faster and more efficiently on leftover plastic bags than on natural materials like leaves and twigs.

According to researchers from the University of Cambridge’s Department of Plant Science, bacteria first use plastic as food because it’s easy to break down.

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

The effect is pronounced, according to the researchers. The bacterial growth rate more than doubled when plastic pollution increased the overall carbon level in the lake water by just 4%.

The results suggest that plastic pollution in lakes “primes” bacteria for rapid growth – the bacteria not only break down plastic, but are then more able to break down other natural carbon compounds in the lake.

It has been found that bacteria in the lake favor plastic-derived carbon compounds over naturally occurring compounds. Researchers believe this is because the carbon compounds in plastics are easier to break down and use as food for bacteria.

Scientists warn that it does not condone ongoing plastic pollution. Some of the compounds in plastics can have toxic effects on the environment, especially at high concentrations.

The results were recently published in the journal Nature Communication.

“It’s almost as if plastic pollution is stimulating the appetite of bacteria,” said Dr Andrew Tanentzap of the University of Cambridge’s Department of Plant Science, lead author of the paper.

“The bacteria first use the plastic as food because it’s easy to break down, and then they’re better able to break down some of the more difficult foods – the lake’s natural organic matter,” he added.

“This suggests that plastic pollution stimulates the entire lake food web, as more bacteria means more food for larger organisms like ducks and fish.”

Plastic pollution and diversity of bacteria

The effect varied depending on the diversity of bacterial species present in the lake water. Lakes with more different species were better at breaking down plastic pollution.

European lakes are potential hotspots of microplastic pollution.

When plastics break down, they release simple carbon compounds. Researchers have found that these are chemically distinct from carbon compounds released as organic matter as decaying leaves and twigs.

Carbon compounds in plastics have been shown to come from additives unique to plastic products, including adhesives and softeners.

The study also found that bacteria removed more plastic pollution in lakes that had fewer unique natural carbon compounds. This is because the bacteria in the lake water had fewer other food sources.

The results will help prioritize lakes where pollution control is most urgent. If a lake has lots of plastic pollution, but low bacterial diversity and lots of different natural organic compounds, then its ecosystem will be more vulnerable to damage.

“Unfortunately, plastics will pollute our environment for decades. On the positive side, our study is helping to identify microbes that could be harnessed to help break down plastic waste and better manage environmental pollution,” said Professor David Aldridge from the University of Cambridge’s Department of Zoology, who has participated in the study.

Sto 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, mean surface temperature and diversity of dissolved carbon-based molecules.

Scientists cut plastic bags from four large UK chain stores and shook them in water until their carbon compounds were released.

At each lake, glass bottles were filled with water from the lake. A small amount of “plastic water” was added to half of them, 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 the increase in mass and bacterial growth efficiency – by the amount of carbon dioxide released during the growth process.

In the water containing plastic-derived carbon compounds, the bacteria had doubled in mass very effectively. About 50% of this carbon was incorporated into the bacteria in 72 hours.

The research was funded by the European Research Council.

Bryce K. Locke