Led by a global network of scientists and covering data from over 1,800 sampling locations collected between 2014 and 2024, the study reveals that microplastics have infiltrated not only surface waters but also the mesopelagic and bathypelagic zones. At depths reaching 2,000 meters, researchers found microplastic concentrations with potential to alter marine chemistry and misrepresent carbon sink metrics.
Central to the study’s success was the use of the Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS), a sophisticated sampling system that allows scientists to collect water and microplastic particles at discrete ocean depths. Equipped with multiple nets of varying mesh sizes—from 64 microns to 3 millimeters—MOCNESS captured a broad spectrum of plastic particle sizes, including those typically missed in traditional surface trawls.
Paired with Niskin bottle sampling for targeted depth analysis, the technology allowed for a vertical profile of microplastic distribution previously unattainable at this scale.
In the lab, Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy enabled researchers to classify microplastics by polymer type—identifying more than 56 varieties. These spectroscopic tools are key in distinguishing synthetic polymers from organic matter, ensuring data accuracy critical to modeling pollution sources and ecological risks.
Density separation using zinc chloride (ZnCl₂) solutions further improved precision by isolating plastics based on buoyancy, while size-based filtration systems separated particles into meaningful categories.
The study’s authors emphasize that technology is not just revealing the problem—it is reshaping how we define and address it. A critical takeaway is the urgent need for standardized global protocols in microplastic sampling and analysis. The lack of consistency across studies has resulted in reported concentration values that vary by up to eight orders of magnitude.
As sensors become more compact and autonomous platforms (such as AUVs and ocean gliders) more accessible, the researchers advocate for the deployment of real-time, in situ detection tools. These would allow continuous global monitoring of microplastic levels and polymer types, delivering high-resolution data to marine modelers and policymakers.
Beyond its technological insights, the study makes a startling observation: microplastics now make up as much as 5% of the particulate organic carbon (POC) at 2,000 meters. This has serious implications for oceanic carbon accounting, including radiocarbon dating—which could be skewed by the presence of "fossil carbon" in plastics, leading to samples that appear hundreds of years older than they are.
This research marks a pivotal shift in marine science—from a surface-level view of plastic pollution to a vertically integrated, data-driven understanding. Technology has not only enabled this leap but will continue to drive innovations in environmental sensing, ocean modeling, and ultimately regulation.
