Distributions and dynamics of microplastics in Georgia estuarine waters

Marine micro-plastic (particles smaller than 5 mm in length) pollution is a recently recognized, and growing, threat to the environment. Estimates of microplastic particle numbers are in the tens of trillions worldwide, and are under-sampled in many ecosystems. Also, public interest in the issue is high and growing. A primary challenge in mapping microplastic concentrations is collecting and processing samples in a manner that minimizes contamination, and in collecting enough samples to obtain statistically-relevant data. The challenge is especially acute in coastal ecosystems, where the interplay between human activities, tides, currents and ecosystems makes for a very heterogeneous distribution of microplastics. Our initial efforts in mapping microplastics in Georgia's intercoastal estuaries indicate the presence of a trillion or more microplastic particles in the region, primarily of the micro fiber category. However, spatial heterogeneity was high, with counts ranging from zero to over 80 microplastic particles (primarily fibers) per 4 l sample. Additional temporal sampling indicates a high level of heterogeneity in this dimension as well. The data suggests rapid cycling (input/removal) from this ecosystem, which further suggests that the primary source for these contaminants is local. Limited riverine sampling from the Savannah, Ogeechee, Satilla and Altamaha Rivers supports this hypothesis as well. The large degree of microplastic spatial and temporal heterogeneity in this ecosystem suggests that spot sampling efforts will likely not provide accurate estimates of contamination levels in aquatic systems.