A study of 29 European lakes has 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.
From: University of Cambridge
July 26, 2022 -- The
bacteria break down the carbon compounds in plastic to use as food for their
growth.
The scientists say that
enriching waters with particular species of bacteria could be a natural way to
remove plastic pollution from the environment.
The effect is
pronounced: the rate of bacterial growth more than doubled when plastic
pollution raised the overall carbon level in lake water by just 4%.
The results suggest
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.
Lake bacteria were
found to favour plastic-derived carbon compounds over natural ones. The
researchers think this is because the carbon compounds from plastics are easier
for the bacteria to break down and use as food.
The scientists caution
that this does not condone ongoing plastic pollution. Some of the compounds
within plastics can have toxic effects on the environment, particularly at high
concentrations.
The findings are published
today in the journal Nature Communications.
“It’s 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,” said Dr Andrew Tanentzap in the University of Cambridge’s
Department of Plant Sciences, senior author of the paper.
He added: “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.”
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.
A study published by
the authors last year found that European lakes are potential hotspots
of microplastic pollution.
When plastics break
down they release simple carbon compounds. The researchers found that these are
chemically distinct to the carbon compounds released as organic matter like
leaves and twigs break down.
The carbon compounds
from plastics were shown to be derived from additives unique to plastic
products, including adhesives and softeners.
The new 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
to prioritise lakes where pollution control is most urgent. If a lake has a lot
of plastic pollution, but low bacterial diversity and a lot 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 helps to identify microbes that could be harnessed to help break down
plastic waste and better manage environmental pollution," said Professor
David Aldridge in the University of Cambridge’s Department of Zoology, who was
involved in the 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.
The research was funded
by the European Research Council.
No comments:
Post a Comment