Fish are not the only beings that are harmed by the plastic that pollutes the seas. According to a recent study, published in Communications Biology , the bacteria responsible for producing one-tenth of the oxygen we breathe are also damaged.
“We found that exposure to chemicals leaked by plastic pollution interferes with the growth, photosynthesis, and oxygen production of Prochlorococcus , the most abundant photosynthetic bacteria in the ocean,” says Dr. Sasha Tetu, lead author of the study and researcher at Macquarie University (Australia).
Plastic pollution causes damage to marine ecosystems valued at more than $ 13 billion each year, and it is estimated that by 2050 there will be more plastic in the oceans than fish. “This pollution can leach various chemical additives in marine environments,” says Dr. Lisa Moore, another of the study’s authors, “but unlike the threats it poses to animals, which ingest or become entangled in plastics, the threat that leaked chemicals represent marine life has received relatively little attention. “
Small but essential
This is the first study of its kind to be carried out, and in it they analyzed the effects that the chemicals mentioned by Moore have on the tiniest form of life in our oceans: photosynthetic marine bacteria.
“We observed a group of tiny green bacteria called Prochlorococcus , which is the most abundant photosynthetic organism on Earth,” explains Dr. Tetu. These microbes are champions when it comes to producing carbohydrates and oxygen in the ocean through photosynthesis.
“These small microorganisms are critical to the marine food web, contribute to the carbon cycle and are believed to be responsible for up to 10% of the world’s total oxygen production,” explains Moore, who emphasizes the fundamental importance of these microbes. for ocean health: “One in ten puffs of oxygen you breathe is owed to those little guys, but almost nothing is known about how marine bacteria respond to human pollutants.”
The team of researchers exposed two strains of Prochlorococcus – found at different depths in the ocean – in the laboratory to chemicals leaked from two common plastic products: plastic bags made of high-density polyethylene and PVC mats. They found that exposure to these chemicals impaired the growth and function of these microbes, including the amount of oxygen they generate, and altered the expression of a large number of their genes.
“Our data show that plastic pollution can have widespread impacts on the ecosystem beyond the known effects on macro-organisms, such as seabirds and turtles,” says Tetu. “If we really want to understand the full impact of plastic pollution on the marine environment and find ways to mitigate it, we must consider its impact on key microbial groups, including photosynthetic microbes,” he concludes.
