Magnifying Microplastics Monitoring With a Community Science Sampling and Analysis Program

Microplastics, plastic particles less than 5 mm in length, are ubiquitous environmental pollutants that affect environmental quality globally. This study aims to address critical knowledge gaps in the distribution and abundance of microplastics in the Charleston Harbor Watershed in South Carolina, USA, through community science, or the involvement of the public in research. Community scientists collected, processed, and analyzed water samples from 12 sites spanning the Charleston Harbor Watershed monthly from July to December of 2023 for microplastic counts, colors, sizes, and types, which were cross-checked against a second researcher’s analysis using a hot needle test and micro-Raman spectroscopy for quality assessment. Surveys were administered before, during, and after the pilot study to understand volunteer motivations and inform program improvements. Suspected microplastics, dominated by fibers, were identified by volunteers in 100% of samples collected, and site average blank-corrected total concentrations ranged 0.9-4.5 particles/L. Total counts (anthropogenic + MPs) by volunteers and cross analysis were closer on average for particles >300 µm than particles 63-300 µm, suggesting a higher confidence level by volunteers to identify larger particles. With the aid of secondary verification tools, cross analysis found significantly lower site average blank-corrected microplastic concentrations than volunteers, ranging 0.6-2.3 particles/L. A spike recovery test identified steps for method improvement. While volunteers expressed concern over time commitment and microscopy skills in survey responses, they also reported skill development and satisfaction with the program. Community science offers a promising study design to increase understanding of microplastic pollution at a watershed scale. • Community science advanced as a novel microplastics monitoring program study design • Suspected microplastics were found in 100% of samples by volunteer analysts • QA/QC included blanks, spike recovery, hot needle testing, and Raman spectroscopy • Surveys effectively informed areas of volunteer concern and program improvements • Leveraging academic-nonprofit partnership can foster program sustainability