Spatial and Temporal Distribution and Abundance Microplastics in Lake Champlain Long-Term Monitoring Samples

Abstract

Microplastics are particles less than 5mm in size, characterized as fibers, fragments, beads, foams, and pellets. Microplastics (MP) arise from four main processes: environmental degradation (UV exposure, mechanical and/or biological), direct release by means of wastewater treatment processing, unintentional loss of raw materials, and discharge of macerated wastes. Microplastics are potentially toxic to aquatic biota and the presence of microplastics in freshwater ecosystems is largely under-researched. The goal of our research was to examine the spatial and temporal distribution of microplastics and pre-production particulate (nurdles) from long-term monitoring (LTM) zooplankton samples within Lake Champlain collected between 1992-2016. Nurdles were counted in full from samples, whereas microplastics (e.g., fragments, fibers) were subsampled due to size. Fourier Transform Infrared Spectroscopy (FTIR) characterized nurdles as polyisoprene rubber ribbon. Within the LTM samples (n = 2265), nurdles (n = 3455) and microplastics (n = 249), predominantly fibers, were identified. The greatest microplastic abundance was noted in 2015 (n = 73 microplastics, n = 494 samples). Nurdles were found only in samples that had been collected 2012-2016, with the greatest nurdle abundance noted in 2012 (n = 1,169 nurdles, n = 412 samples) and at varying depths. Nurdle abundance declined since the 2012 peak and in 2015 was greatly reduced (n = 531 nurdles, n = 494 samples). Spatial distribution maps suggest the complexity of the story with high abundances at deep central locations, as well as shallow isolated bays. The high influx of nurdles in 2012 may be related to the 2011 Lake Champlain flood; however more research will need to be conducted to tease apart timing and potential nurdle point-sources (e.g., train tracks, industrial/urban centers).