Marine plastic is impairing oxygen-producing bacteria

A study published in Communications Biology has revealed that the marine bacteria producing 10% of our oxygen supply are under threat from plastic pollution.

The laboratory-based study conducted by researchers at Macquarie University examined the effects of chemicals leached from plastic pollution on photosynthetic marine bacteria. These microbes play an important role in carbohydrate and oxygen production in the ocean via photosynthesis.

In the lab, the team exposed two strains of Prochlorococcus, found at different depths in the ocean, to chemicals leached from two common plastic products — grey plastic shopping bags (made from high-density polyethylene) and PVC matting.

“We looked at a group of tiny, green bacteria called Prochlorococcus, which is the most abundant photosynthetic organism on Earth, with a global population of around three octillion (~10²⁷) individuals,” said Dr Sasha Tetu, lead author and Macquarie University researcher.

“One in every 10 breaths of oxygen you breathe in is thanks to these little guys, yet almost nothing is known about how marine bacteria such as Prochlorococcus respond to human pollutants.

“We found that exposure to chemicals leaching from plastic pollution interfered with the growth, photosynthesis and oxygen production of Prochlorococcus, the ocean’s most abundant photosynthetic bacteria,” said Dr Tetu.

“Our data shows that plastic pollution may have widespread ecosystem impacts beyond the known effects on macroorganisms, such as seabirds and turtles.”

Plastic pollution has been estimated to cause more than US$13 billion in economic damage to marine ecosystems each year, and the problem is getting worse. Marine plastic pollution is estimated to outweigh fish by 2050.

Co-author Dr Lisa Moore said, “This pollution can leach a variety of chemical additives into marine environments, but unlike the threats posed by animals ingesting or getting entangled in plastic debris the threat these leachates pose to marine life has received relatively little attention.

“These tiny microorganisms are critical to the marine food web, contribute to carbon cycling and are thought to be responsible for up to 10% of the total global oxygen production,” she explained.

Dr Tetu said, “If we truly want to understand the full impact of plastic pollution in the marine environment and find ways to mitigate it, we need to consider its impact on key microbial groups, including photosynthetic microbes.”

The researchers’ next step is to investigate whether chemicals leached from plastic pollution are having the same impact on the microbes in an ocean setting.

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