Microplastics in the Ocean: Their Effects on the Biological Carbon Pump
Microplastics, characterized by NOAA as plastic fragments smaller than five millimeters, have surfaced as a major contaminant in marine ecosystems. These minute particles, differing in shape, density, and behavior, have permeated environments ranging from Arctic ice to the most profound oceanic trenches. Research such as that conducted by Ilka Peeken in 2018 and Alan Jamieson in 2019 has recorded the presence of microplastics in these isolated areas, showcasing their widespread nature and potential consequences for marine organisms.
A focal point of concern is the biological carbon pump, an essential mechanism where phytoplankton in sunlit ocean zones transform atmospheric CO₂ into organic matter through photosynthesis. This organic carbon is subsequently transferred to deeper oceanic layers, often through marine snow and fecal pellets produced by organisms like copepods. The long-term storage of carbon in the deep sea is crucial for maintaining atmospheric CO₂ levels.
Nevertheless, laboratory findings have revealed that microplastics can disrupt these mechanisms. In investigations led by Matthew Cole and associates, copepods subjected to microplastics exhibited diminished algal ingestion and changes in the density and sinking rates of fecal pellets. Likewise, Cordelia Roberts’ studies showed that microplastics within marine snow can reduce sinking velocities, potentially hindering carbon export.
Such disturbances have been modeled, as seen in Karin Kvale’s 2023 research, which indicated a conditional decrease in oceanic carbon absorption due to the slowed sinking of fecal pellets. However, these conclusions are still based on scenarios rather than direct measurements of global changes.
To genuinely comprehend the effects of microplastics on the carbon pump, a holistic approach is necessary—one that simultaneously measures exposure and carbon transport. Standardized techniques for particle collection and thorough field studies of plankton and sinking carbon are vital for determining where microplastics significantly influence carbon transport and where their impact may be minimal.