Microplastics in the ocean reduce algae's photosynthetic efficiency, potentially disrupting one of Earth's most important carbon sinks. A team of researchers quantified how this interference affects the planet's ability to absorb atmospheric carbon dioxide through marine ecosystems.
Algae form the base of ocean food webs and play a critical role in the biological carbon pump, the process by which surface waters absorb CO2 and transport it to the deep ocean. When microplastics accumulate in seawater, they interfere with light penetration and can coat algal cells, reducing photosynthetic rates. The researchers modeled how widespread microplastic contamination impairs this process on a global scale.
The study reveals that microplastic-induced reductions in algal productivity translate directly into diminished carbon sequestration. Less photosynthesis means less organic matter sinking to the deep ocean, where carbon remains locked away for centuries. This creates a feedback loop amplifying climate warming, since CO2 that would have been removed from the atmosphere stays in circulation longer.
The research builds on emerging evidence that ocean pollution carries climate consequences beyond immediate ecosystem damage. Previous work established that microplastics physically harm marine organisms. This analysis extends those findings to atmospheric carbon cycling, a planetary-scale process affecting all life.
The magnitude of the effect depends on microplastic concentration levels and regional variation in ocean conditions. Areas with heavy plastic pollution and high algal productivity face the largest impacts. The researchers note that without intervention, accumulating microplastics will continue degrading the ocean's natural carbon removal capacity just when the planet needs it most.
The findings underscore a largely overlooked dimension of plastic pollution. Most climate discussions focus on emissions reduction, yet the oceans' diminished ability to absorb existing atmospheric CO2 represents a parallel threat. This work demonstrates that addressing ocean plastic requires framing it not