The world’s oceans have long acted as one of Earth’s most powerful natural defenses against climate change, absorbing nearly a quarter of the carbon dioxide released into the atmosphere each year. But new scientific research suggests this critical role is being quietly undermined by an unexpected pollutant: microplastics.
A recent study published in the Journal of Hazardous Materials: Plastics warns that microscopic plastic particles are interfering with the ocean’s natural carbon-absorbing systems, potentially reducing its capacity to regulate global temperatures. While plastic pollution has traditionally been viewed as a threat to marine life and ecosystems, researchers say its influence on the climate system has been largely overlooked.
Microplastics plastic fragments smaller than five millimetres are now found across virtually every part of the planet, from deep ocean trenches and Arctic ice to soil, air, and even the human body. Their persistence and chemical complexity allow them to interact with biological and chemical processes in ways scientists are only beginning to understand.
According to the study’s authors, microplastics disrupt the ocean’s “biological carbon pump” a natural mechanism through which marine organisms help transfer carbon from the atmosphere to deep ocean layers. Phytoplankton absorb carbon dioxide during photosynthesis, while zooplankton consume them and transport carbon deeper into the ocean through waste and sinking biomass. Microplastics, researchers argue, interfere with both groups.
“In marine ecosystems, microplastics affect phytoplankton photosynthesis and impair zooplankton metabolism, weakening the ocean’s natural carbon sequestration process,” the authors write.
The study also highlights the role of the “plastisphere” communities of microorganisms that colonise plastic surfaces in water. These microbial networks participate in nitrogen and carbon cycling and may produce greenhouse gases such as methane and carbon dioxide as plastics degrade. Over time, this could further contribute to warming, ocean acidification, and ecological instability.
Dr Ihsanullah Obaidullah, associate professor of integrated water processing technologies at the University of Sharjah and the study’s corresponding author, says the findings point to a hidden climate risk. “Microplastics are undermining one of the planet’s most important natural climate buffers,” he explains. “They disrupt marine life, weaken carbon storage mechanisms, and can even emit greenhouse gases during degradation.”
Rather than presenting new experimental data, the study synthesises existing research through an integrative narrative review of 89 scientific studies published between 2010 and 2025. The researchers aimed to identify patterns, knowledge gaps, and emerging links between microplastic pollution, ocean health, and climate change.
They argue that most previous research has focused on identifying microplastics and developing cleanup strategies, while their broader role in climate processes remains poorly quantified. “The extent to which microplastics affect climate change and ocean systems is still largely unknown,” the authors note, describing the issue as complex, novel, and multifaceted.
Plastic production continues to rise sharply worldwide. A United Nations estimate from 2025 suggests global plastic output exceeds 400 million tonnes annually, with nearly half designed for single use and less than 10 percent recycled. Without intervention, production could triple by 2060, further increasing the flow of plastics and microplastics into marine environments.
The researchers warn that even if current impacts appear modest, the long-term accumulation of microplastics could have serious consequences. They call for integrated policies that address plastic pollution and climate change together, rather than treating them as separate crises.
Among their recommendations are reducing single-use plastics, improving waste management systems, promoting biodegradable alternatives, and investing in advanced monitoring tools including AI-driven technologies to better track microplastic movement and impacts.
“Oceans are Earth’s largest carbon sink,” Dr Obaidullah says. “Protecting their ability to absorb carbon dioxide must now include tackling plastic pollution. This is not just an environmental issue it is a global sustainability challenge.”