Microplastics could be impairing the oceans’ ability to absorb carbon dioxide, according to a new study.
Microplastics - plastic fragments smaller than five millimeters in size – are now found almost everywhere, with scientists keen to understand the impact of their spread through the environment.
The study published in the Journal of Hazardous Materials: Plastics said that the role of microplastics in climate change has received limited attention. But in marine ecosystems microplastics alter natural carbon sequestration by affecting phytoplankton and zooplankton - key agents of carbon cycling.
Microplastics are widely recognized as pollutants, but the study shows they also interfere with the ocean’s ability to absorb carbon dioxide, said Ihsanullah Obaidullah, associate professor of integrated water processing technologies at the University of Sharjah, UAE, and the study’s corresponding author.
“Microplastics disrupt marine life, weaken the 'biological carbon pump,’ and even release greenhouse gases as they degrade. Over time, these changes could lead to ocean warming, acidification, and biodiversity loss, threatening food security and coastal communities worldwide,” Obaidullah said.
Biological carbon pumping - the process that transfers carbon from the atmosphere into the deep sea layers - is the primary mechanism linking microplastics to global warming and climate change, according to the study. The microplastics interfere with this process by reducing phytoplankton photosynthesis and impairing zooplankton metabolism, the authors note.
Oceans are Earth’s largest carbon sink, Obaidullah said: “Microplastics are undermining this natural shield against climate change. Tackling plastic pollution is now part of the fight against global warming.”
The study noted: “The impact of [microplastics] on ocean health, particularly concerning potential ocean warming and acidification, remains an area of concern; however, existing literature has notable gaps in methodologies for calculating or predicting these impacts, highlighting important avenues for future research."
Over 10 million tonnes of plastic waste enter the oceans each year, with 99% primarily made up of fibres from textiles and clothing sinking into the deep ocean. Microplastics on their own can be toxic to deep-sea life, but they can also transfer other harmful pollutants such as PFAS and heavy metals, which makes them an environmental ‘multistressor’ which can affect the entire food chain,” according to seperate research published last year.
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