The world’s oceans absorb roughly a quarter of annual anthropogenic carbon dioxide emissions, according to long established climate assessments, making them a central stabilizing force in the global climate system.
New research now suggests that this buffering capacity may be weaker than assumed, not because of temperature or circulation changes alone, but due to the growing concentration of microplastics in marine environments.
A study published in Journal of Hazardous Materials: Plastics argues that microplastics are interfering with core oceanic carbon sequestration processes, particularly the biological carbon pump. This mechanism relies on phytoplankton absorbing CO2 through photosynthesis and transferring carbon to deeper ocean layers as organic matter sinks. The authors synthesize evidence showing that microplastics reduce phytoplankton photosynthetic efficiency and disrupt zooplankton metabolism, impairing the transfer of carbon from surface waters to the deep sea.
Microplastics, defined as plastic particles smaller than five millimeters, are now detected across virtually all environmental compartments, including deep oceans, polar ice, freshwater systems, soils, air, and human tissues. Their environmental risks have been extensively documented in toxicology and ecology literature, yet their interaction with climate processes has received comparatively limited scrutiny. The study positions this omission as increasingly problematic, given the scale of plastic pollution and the oceans’ central role in climate regulation.
The researchers highlight that microplastics influence carbon cycling through multiple pathways. Beyond direct impacts on plankton, they point to the plastisphere, microbial communities that colonize plastic surfaces. These biofilms host diverse microorganisms involved in nitrogen and carbon cycling, some of which contribute to greenhouse gas production. Laboratory and field studies cited in the review indicate that degrading plastics can emit gases such as methane and carbon dioxide, adding a small but measurable source of greenhouse gas emissions that is rarely incorporated into climate accounting.
This interaction complicates existing assumptions embedded in climate models, many of which treat ocean carbon uptake as a function of temperature, chemistry, and circulation, without accounting for widespread particulate pollution. If microplastics reduce the efficiency of biological carbon pumping, the ocean’s future capacity to absorb CO2 could be overstated, particularly under high plastic leakage scenarios.
The study adopts an integrative narrative approach rather than a formal systematic review, drawing on 89 peer reviewed studies published largely after 2015. While this methodology prioritizes conceptual linkage over statistical aggregation, it allows the authors to map connections across marine biology, biogeochemistry, pollution science, and climate research. The absence of rigid inclusion criteria limits quantitative conclusions, but the synthesis underscores the consistency of observed disruptions across multiple experimental and observational studies.
Plastic production trends reinforce the urgency of the issue. United Nations estimates indicate that global plastic production now exceeds 400 million metric tons annually, with less than 10 percent recycled and roughly half designed for single use. Cumulative plastic production has surpassed 8 billion metric tons, with the majority accumulating in landfills or the natural environment. Without policy intervention, production is projected to continue rising for decades, increasing the baseline level of microplastics entering marine systems.
From a climate perspective, this trajectory matters because microplastics persist for long periods and fragment further over time, expanding their surface area and interaction with biological and chemical processes. The study links this persistence to potential long term effects on ocean warming and acidification, as reduced carbon uptake could amplify atmospheric CO2 concentrations, reinforcing feedback loops already under strain.
The authors argue that policy frameworks continue to treat plastic pollution and climate change as largely separate challenges. Within the UN Sustainable Development Goals, plastics are represented by a narrow set of indicators that do not capture systemic risks to ocean carbon cycling. The study suggests that this separation obscures compounding effects, particularly for coastal communities and food systems dependent on stable marine ecosystems.
Proposed responses focus less on cleanup technologies and more on upstream interventions. Reducing single use plastics, improving waste management infrastructure, and accelerating the adoption of biodegradable materials are framed as climate relevant actions, not solely pollution controls. The authors also call for expanded research to quantify the net climate forcing associated with microplastics, noting that current estimates are fragmented and insufficient for integration into climate models.
