Mentor: Arijit Bose, University of Rhode Island
Co-Mentor: Tania Silva de Oliveira, University of Rhode Island

Project Location

University of Rhode Island-Kingston

Project Description

Plastics are ubiquitous, the worldwide annual consumption is approximately 300 million tons. Most of these plastics are not recycled, and they eventually make their way into the ocean. About 150 million tons of plastic are in the world’s oceans currently, and 8 million additional tons of plastics are dumped into the ocean each year. Sources include packaging, straws, bags, soaps, cosmetics, utensils, and cups. By 2050, the weight of plastics in the ocean will exceed the weight of all marine organisms. The Narragansett Bay is a microcosm of what is happening to ocean waters all over the world. Through ocean action, light and wind exposure these plastics eventually break up into millimeter- and lower-sized objects, known as microplastics. The role of this anthropogenic stressor on marine life must be understood for remediation strategies as well as for policy decisions. While images of plastic material floating in large patches in the ocean and in fresh water have received wide publicity, what is visible is only the tip of the “plastic-berg”.

The densities of many commercial plastics are larger than that of water. These materials sink deeper into the water column. About 14 million tons of microplastics are estimated to be on the ocean floor. These plastics not only encounter fish, but also marine cyanobacteria (CB) that reside near the ocean surface as well as deeper ocean bacteria such as Nitrobacter. Both are ubiquitous and are a critical part of the aqueous ecosystem because they help maintain the nitrogen balance. Very little is currently known about the fate of plastics or these bacteria after exposure. Recent collaborative results from our laboratories using spherical polystyrene and polyethylene nano and microparticles (Langmuir, 36, 3692-3699 (2020); PLoS ONE, 15, e0232745 (2020)) revealed that cyanobacteria attach to the plastics efficiently, and they overexpress genes responsible for making plastic-specific degrading enzymes. Thus, the bacteria may be partially mitigating the deleterious effect of plastics in the ocean

Planned experiments

We will expose plastic of different shapes, sizes and chemistries to marine cyanobacteria and nitrogen fixing bacteria such as nitrobacter. We will include weathered and non-weathered plastics, as well as those from non-renewable and renewable sources.

We will monitor (a) the degree of colonization of bacteria, bacteria growth over time, and biofilm formation using time-resolved cryogenic scanning electron microscopy and fluorescence microscopy, (b) changes to the bacterium DNA and RNA over time after exposure to the plastic (c) the chemical nature of the enzymes and any degradation products being produced by the bacterium using liquid chromatography-mass spectroscopy, and (d) changes to the size and morphology of the particles as evidence of degradation. This comprehensive study will provide qualitative and quantitative data on the damage being caused to the marine ecosystem after exposure to plastics, as well as on nature’s remediation strategies. SURF students will be responsible for one or more of these experiments.