Microplastic occurrence in central Iowa's reservoirs: Saylorville and Red Rock

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Eads, Danielle Lynnae
Major Professor
Jovanović, Boris
Crumpton, William G.
Isenhart, Thomas
Committee Member
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Ecology, Evolution, and Organismal Biology
Consumption of plastics has been increasing steadily since they were first produced, with most ending up in landfills or as litter and being transported into terrestrial and aquatic ecosystems where they do not decompose and accumulate. Microplastics can build up in aquatic ecosystems over time, potentially impacting human and aquatic species' health. However, despite the increasing prevalence of microplastics in aquatic environments, this contaminant has yet to be extensively surveyed in freshwater reservoirs. This study aimed to look at microplastic occurrence in the two primary flood control and recreational impoundments connected by the Des Moines River in central Iowa, Saylorville and Red Rock Reservoirs. These reservoirs were chosen because of their connectivity by the Des Moines River and proximity to the city of Des Moines, highlighting the possible reflection of the influence of the urban environment on microplastic loads. Samples were collected every two weeks at each reservoir using a 53 μm Wisconsin zooplankton net for a vertical water column sample and a 64 μm manta net for a horizontal surface water sample. Samples were digested in KOH, filtered onto a 0.2 μm aluminum oxide filter, and analyzed on a Bruker LUMOS-II microscope using FTIR spectroscopy in transmission mode with OPUS software. Samples were analyzed for the presence of plastic polymers, and particle sizes were recorded for each positively identified microplastic particle. This survey found 2,157 particles belonging to 11 unique plastic polymers, with the dominant types of PVC, PE, PEST, and PS accounting for 82.5% of all particles. Particle lengths ranged from 56 to 4,198 μm, with smaller particles significantly more abundant than larger particles. No significant differences were found in microplastic concentrations between the two reservoirs or between the zooplankton and manta net, giving low concentrations at Saylorville (1.39 ± 1.31 and 1.65 ± 1.72 MP/L) and Red Rock (1.16 ± 1.09 and 1.16 ± 0.85 MP/L) in the zooplankton and manta nets, respectively.
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