Assessment of the Impact of Microplastics on Oceanic CO? Sequestration

Abstract

The biological carbon pump is a crucial oceanic process in mitigating climate change, fa-cilitating the natural sequestration of atmospheric carbon dioxide (CO?) through phytoplanktonphotosynthesis and the downward flux of organic matter into the deep ocean. However, the increas-ing presence of microplastics in marine environments poses an emerging threat to this ecologicalfunction. This article presents a critical review of recent scientific literature, analyzing experimental,observational, and modeling evidence regarding the effects of microplastics on key components ofthe biological pump. Multiple interference mechanisms are identified, including the inhibition ofphytoplankton photosynthesis, disruption of marine snow formation and density, and reductionsin the quality and sinking velocity of zooplankton fecal pellets. Indirect impacts on the marinetrophic web are also documented, alongside an examination of bioplastics as a new source of plasticmicrofragments functionally equivalent to conventional microplastics. Quantitative estimates sug-gest that global oceanic CO? sequestration efficiency may have decreased by tens to hundreds ofmillions of tons per year due to this contamination. These findings indicate that microplastics posenot only a physical and toxic threat to marine life but also a critical factor destabilizing a planetaryclimate regulator. It is concluded that plastic pollution should be integrated into global carbon mod-els and international climate mitigation policies.