Leaked chemicals from plastic pollution kill key marine microbes: study

Research has found that the chemicals leaking from plastics can change the mix of microbial life in seawater and harm the tiny life forms that are critical to oxygen production in our oceans.

A new study has found that the chemicals leaking into seawater from plastic waste can disrupt microbes, which form an essential part of the marine food web. It is estimated that about 50 percent of the Earth’s oxygen is produced by photosynthetic microbes in our oceans.

About 9.5 million tons of plastic waste enter the oceans every year. Larger plastic items cause immense damage to sea creatures that become entangled or accidentally eat the plastic. The degraded microplastics then end up in the marine food web.

“This study shows that the chemicals leached from plastic can also disrupt the health of microbial ocean communities by harming the tiny life forms that we cannot see but that play a critical role in the health of our oceans,” says Microbes from Macquarie University ecologist Dr. Sasha Tetu.

The latest study builds on earlier laboratory research by Dr. Tetu at Macquarie University, who showed that chemicals leached from plastic are harmful to a single-organism community of Prochlorococcus, the most abundant plankton in the ocean.

Now researchers have tested the effects of chemicals leached from common plastics on a living microbiological community in the ocean – and the news is worrying.

“We found that our plastic leachate mix harmed a number of different microorganisms, including both bacteria and eukaryotes,” says Tetu.

She said the research aims to show which microbial groups could be “winners” and which are likely to be “losers” when exposed to plastic leaching.

We need to understand the impact of plastic waste on these organisms, which form the basis of our food web and play an important role in the carbon cycle and producing oxygen for our planet.

While certain microbes in the leachate mix were unaffected and even thrived, it came at the expense of other groups, which declined significantly, she says.

“Photosynthetic microorganisms were severely affected – they showed a significant decline in numbers, but also in their photosynthetic efficiency and diversity.” These marine photosynthetic microbes play a crucial role in the ecosystem, contributing to carbon cycling and oxygen production and supporting the marine food web, says Tetu.

“When researching the effects of human pollutants on microorganisms, it is not always possible to distinguish which ones thrive and which do not. For example, heterotrophic bacteria can tolerate certain chemicals that photosynthetic microbes cannot.”

Message in a bottle: Plastic kills plankton

message in a bottle: The research addresses the environmental burdens of human pollutants on important marine microbes.

That’s a problem, says Tetu, because risks to marine microbes and the marine ecosystem at large can be downplayed if we don’t understand the impact of pollution on all members of the community, especially photosynthetic microbes.

Testing microbial communities in seawater

Researchers used surface seawater samples from a monthly standard collection collected in 2019 at a marine reference station off the coast of Sydney. “It’s a good reference point because microbial data has been collected regularly from here over a long period of time,” explains Tetu.

There are more than 10,000 chemical compounds known to leach from plastic, with at least 2,400 of these chemicals recognized by the EU as substances of concern.

“We made a seep fluid that was a kind of plastic tea, containing a mixture of chemicals leached from a common type of plastic, polyvinyl chloride (PVC), as well as studying the effects of a specific plastic additive, zinc,” he told Tetu .

The microbial communities were exposed to the leachate and monitored for six days. Within 48 hours, the researchers were able to identify negative effects on photosynthetic microbes.

Tetu points out that the ocean is a big place and both the composition of microbial communities and the concentration and composition of plastic leachate vary widely from place to place.

“Rather than trying to mimic specific concentrations of plastic in the ocean, we looked at previous studies that performed similar tests and used similar concentrations. In the future we would like to expand this work by looking at more concentrations and more types of plastics. “

Future Impact

Tetu says another interesting aspect of this study is that most of the time, the harmful substances are the additives that are put into plastic polymers to give them color or flexibility, for example.

“This is important to know because a lot of effort goes into making plant-based plastics and it will be crucial to consider the additives used in them,” she says. “They might be biodegradable, but still release chemicals that can harm microbial life in the ocean.”

Despite ongoing efforts in many countries to reduce the production of single-use plastic and prevent plastic from entering the oceans, the OECD forecast that global plastic waste will almost triple by 2060.

dr  Sasha Tetu

Test times: Dr. Sasha Tetu, pictured, says there are more than 10,000 chemical compounds known to leach out of plastic.

“We need to understand the impact of plastic waste on these organisms, which are at the base of our food web and play an important role in the carbon cycle and producing oxygen for our planet,” says Tetu.

“If plastic waste leads to the decline of these critical organisms, we can expect that there will be an impact and it is critical that we get a handle on it.”

dr Sasha Tetu is Senior Lecturer in the Department of Molecular Sciences, School of Natural Sciences, Macquarie University. Sasha is also a Principal Investigator at the ARC Industrial Transformation Training Center for Facilitated Advancement of Australia’s Bioactives and an Associate Investigator at the ARC Center of Excellence in Synthetic Biology.

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