How does microplastics in the oceans affect climate change?

The study, the results of which were published in the February issue of the Journal of Hazardous Materials: Plastics, addresses the issue of the impact of plastic pollution on climate processes, which has rarely been addressed to date. As the study suggests, the presence of microplastics in the oceans impairs their ability to regulate temperature and sequester carbon, going far beyond the classically understood degradation of ecosystems.

Weakening of the biological carbon pump

Each year, 4.8-12.7 million tons of mismanaged plastic waste enters the environment, about 40 percent of which is single-use plastics. The amount of plastic entering aquatic ecosystems in 2014 was estimated at 35,000 tons, and projections suggest it could be as much as 270 million tons by 2060. Due to their small size and resistance to decomposition, microplastics accumulate in the oceans and become a permanent fixture.

The most important mechanism linking microplastics to climate change is the so-called biological carbon pump. Phytoplankton, in the process of photosynthesis, absorb carbon dioxide from the atmosphere, and when they die, the trapped carbon is transferred to the deep layers of the ocean. The operation of this pump, however, is increasingly ineffective. Increasing concentrations of microplastic reduce the penetration of light in the water depths, which reduces the efficiency of photosynthesis. Studies cited by the paper’s authors show a decline in the photosynthetic efficiency of algae exposed to polystyrene microplastics. In the long term, this means a weakening of the oceans’ ability to absorb_CO2, thereby reducing their role as a natural climate buffer.

Microplastics, zooplankton and oxygen deficit

Microplastics in the oceans also upset the balance of the food chain. Fine plastic particles are commonly consumed by zooplankton. Thus, they take the place of natural food, causing zooplankton to consume less phytoplankton. As a result, the latter can multiply more vigorously, leading to intense algal blooms. After they die, there is an increased decomposition of organic matter, during which dissolved oxygen in the water is consumed.

The authors note that this process can accelerate deoxygenation of the oceans, and they compare the scale of its impact to that of global warming. Oxygen deficiency disrupts the functioning of entire ecosystems and indirectly affects the carbon cycle in the oceans.

Ocean acidification and greenhouse gas emissions

Microplastics are made of carbon-carbon and carbon-hydrogen bonds. As they degrade, they emit_CO2, methane and ethylene, while modifying the activity of microorganisms responsible for carbon and nitrogen cycling. The result is a decrease in the pH of the water and a reduction in the availability of calcium carbonate, which is essential for the life of skeletal and shell-building organisms.

An additional climate risk factor is the so-called plastisphere, or biofilms of microorganisms developing on the surface of microplastics. These additional communities intensify metabolic processes, leading to further_CO2 emissions and disrupting the biogeochemical balance of the oceans.

Microplastics in oceans limit climate adaptation potential

According to the authors, blue carbon ecosystems such as mangroves and seagrass meadows are particularly sensitive to plastic pollution. The publication cites a study showing that the presence of microplastics reduces the productivity of these habitats, limits photosynthesis and the ability to sequester carbon. In extreme cases, the accumulation of plastic in root systems leads to plant death, reducing the natural resilience of coasts to the effects of climate change.

The authors point out that while the current impact of microplastics on the climate may seem moderate, their increasing accumulation promises much more serious consequences in the future. Microplastics weaken the biological carbon pump, intensify ocean acidification and deoxygenation, and reduce the resilience of key ecosystems to climate change.

The study clearly demonstrates the need for an integrated approach in which the problem of plastic pollution and climate policy are not treated separately. Without coordinated global action, microplastics could become an important, though often overlooked, factor in accelerating climate change.

pic. main: MechaOwl/Pixabay

Source:

Asim Nawab, Muhammad Tariq Khan, I. Ihsanullah, Mohammad Nafees, Aamir Mehmood Shah, From pollution to ocean warming: The climate impacts of marine microplastics, Journal of Hazardous Materials: Plastics, Volume 2, 2026, 100032, ISSN 3051-0600, https://doi.org/10.1016/j.hazmp.2025.100032.