EAGER: Collaborative Research: NSF2026: Is Plastic Degradation Occurring in the Deep Ocean Water Column?

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With support from the NSF 2026 program in the NSF Office of Integrated Activities, a team of researchers from four institutions will investigate the processes that affect plastic debris and its ultimate fate once it enters the ocean interior. Since 1950, global production of plastic has grown exponentially. An estimated 5 to 13 million metric tons of plastic flows from the land and enters the ocean each year. However, model assessment indicates that 99% or more of the plastic entering the ocean is currently unaccounted for. The goal of the project is to understand the physical modification and biochemical transformation of plastic debris by microbial communities in the mid- and deep-waters of the open ocean near Bermuda. The project directly addresses two of the top thirty-three Idea Machine entries: “Imagine a Life With Clean Oceans” and “Global Microbiome in a Changing Planet.” The investigators will deploy incubators to evaluate plastic degradation at 600 meters and 3600 meters water depth at the NSF-funded Oceanic Flux Program (OFP) mooring site. Results from this project will further understanding of the mechanistic processes that govern decomposition of plastic particles in the mid-depth (600 meters) and deeper (3600 meters) ocean, as well as the microbial communities involved with biodegradation of plastics at those depths. The results will have broad implications to the fields of ocean biogeochemistry, environmental sciences, and microbial ecology. With the deep-sea incubator deployed inline on the OFP mooring being a new method to study plastic polymer degradation processes in situ, this research contributes significantly to technology development for oceanographic research. Results from this project will also provide insights into the global budget of plastics, potentially filling the knowledge gap on the fate of plastic and thus affecting plastic management policies. Knowledge of the role of deep ocean microbial communities in the degradation of synthetic plastic polymers will be very valuable information for industry and policymakers. The collaboration of the American Chemistry Council, which is providing polymers for the project, will strengthen the cooperation between academia and industry. Education is an essential part of this project, which includes one postdoctoral researcher and multiple undergraduate students. Project results will be incorporated into undergraduate courses and communicated through outreach activities for the broader public. The investigators propose to test three sets of hypotheses: (1) Different polymers promote the assembly of distinct microbiomes, and these microbiomes differ between the mesopelagic and bathypelagic ocean regimes; (2) Plastics are degraded within the ocean interior, different plastic polymer types are degraded at different rates, and these rates differ between the mesopelagic and bathypelagic ocean regimes; and (3) Deep ocean microbiomes actively degrade plastics and utilize plastic polymers as a carbon source. These hypotheses will be tested deploying custom-built deep-sea incubators at 600 m and 3600 m containing well-defined plastic polymer films and fibers on the OFP mooring, located in the northern Sargasso Sea about 75 km south-east of Bermuda. The polymers deployed will represent the diversity of plastics found in the marine environment and have different stabilities against microbial degradation (e.g., polyethylene, polyethylene terephthalate, and others). This project will combine state-of-the-art polymer chemistry analyses (pyrolysis-GCMS and Raman, and micro-FTIR) with microscopy, and lipid (GCMS and GCirMS) and nucleic acid sequencing analyses, to determine if microbial communities can degrade polymers in the deep mesopelagic and bathypelagic ocean. The results will determine if microbial communities living within the aphotic ocean interior actively degrade and utilize the synthetic carbon polymers that make up plastics, and thus play an important role in the removal of global plastics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.