IT’S COMPLICATED: SPATIAL AND TEMPORAL VARIATION IN MICROPLASTIC POLLUTION IN SENECA LAKE, FINGER LAKES, NEW YORK, USA

Microplastics—particles and fibers of synthetic polymers smaller than 5 mm in diameter—are ubiquitous in the environment and may constitute a danger to human and ecosystem health. Understanding microplastic contamination in human drinking water sources like Seneca Lake is particularly urgent. In 2021, we examined a handful of samples from Seneca Lake, which provides drinking water to 100,000 residents of the Finger Lakes region. From this small number of samples, clear patterns emerged: Fibers dominated all samples; contamination in surface water was higher than bottom water; and microplastic concentrations were higher at the north end of the lake. In 2022, we sought to document spatial and temporal variability in more detail. We sampled surface and bottom water at 11 sites along a 24 km transect in the northern half of the lake and extracted microplastics from water using a vacuum filter system and 0.45 µm Millipore filters. We correlated these measurements with meteorological variables. Over seven cruises between 17 May and 29 June 2022 we found tremendous variability in microplastic contamination. More data complicated the preliminary relationship between surface and deep water. Surface water closer to the north end of the lake generally contained more microplastic particles, still dominantly fibers, but only after several days of sustained wind from the south. There was no consistent relationship between contamination and the time since last rainfall suggesting that precipitation, stream, and storm runoff aren’t systematically increasing contamination. Our data show that 1) microplastic contamination is dynamic with patterns changing daily with limnological and meteorological conditions. This means that modeling and monitoring based on a few grab samples will be inaccurate. 2) We have identified microplastic inputs into the lake from precipitation, wastewater, and streams. Therefore, mitigation focused only on wastewater treatment will not significantly reduce microplastic contamination. We also report on significant factory contamination in the Millipore filters and describe our correction for this issue.