RUI: Physiological heterogeneity of plastic-associated microbial communities in freshwater Lake Lacawac

Microplastics, which are plastic particles less than 5 millimeters in size, are a common pollutant that have seen widespread accumulation in the environment since World War II. Because microplastics are solid, they represent a distinct surface that microorganisms can colonize. In marine environments, studies have shown that these plastic-associated microbial communities are distinct from those that inhabit the water column. However, plastic-associated microbial communities in freshwater environments are ubiquitous but have received considerably less attention even though microorganisms are essential players in nutrient cycles in all ecosystems. This study will be the first of its kind to investigate what role microplastic accumulation may play in altering microbial communities and, by extension, essential metabolic processes, in freshwater environments. This project will support summer field research experiences for three undergraduate students per summer for two summers. These field experiences will take place at the Lacawac Sanctuary Biological Field Station and Environmental Education Center in Pennsylvania — a globally recognized location for freshwater research. In addition, students will gain experience with state-of-the-art software programs for analyzing microbial communities as well as learn critical programming languages used for statistical analyses. Quantities of two microplastics (polystyrene and polyethylene terephthalate) along with natural leaf litter will be placed within bioreactors fed with surface water from Lake Lacawac, Pennsylvania. Undergraduate researchers will monitor dissolved oxygen, pH, temperature, and conductivity in the bioreactors on a weekly basis for 24 weeks. To investigate how the composition of plastic-associated microbial communities differs from those found on natural debris, students will collect samples of microplastics, leaf litter, and water from each bioreactor every three weeks for 24 weeks. DNA will be extracted from each of these samples and the investigators will amplify the 16S rRNA gene sequences using universal (bacterial/archaeal) primers. These amplicons will be sequenced and the phylogenetic composition of each community will be determined using advanced statistical software. Students will produce reports from their data and make research presentations at regional and national conferences, which will inspire them to consider graduate studies in the future. 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.