Effect of Water Treatment Residuals and Microcystin on Soil Chemical Properties, Soil Arylsulfatase Activity and Microbial Community Composition
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Date
2021-12
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The Ohio State University
Abstract
Microcystins (MCs) are monocyclic heptapeptides that are produced by the cyanobacteria, Microcystis, and have high structural variability. They are hepatotoxins and therefore, pose health risks to humans and animals who consume them. Application of MC contaminated water treatment residuals (WTR) to agricultural fields can potentially pose a threat to the soil ecosystem in terms of soil health and food production. Therefore, developing a method to quantify the total concentration of MC in WTR is needed in order to determine the fate and toxicity of MC in the environment. In this study, a MC extraction method was successfully tested, and two out of eight WTR samples analyzed (WTR 2 and 6) had the highest concentrations of MC while WTR 3 had no detectable MC. To determine the effect of MC on soil microbial properties, a 4-week incubation study, using a clay loam and sandy loam soil from northwestern Ohio, was conducted. The treatments were: WTR (no MC), WTR+MC, and MC. The treatments were analyzed for soil chemical properties, arylsulfatase activity, and microbial community composition by microbial phospholipid fatty acids (PLFAs). In both soils, the pH and EC significantly increased in all treated soils, whereas available P content significantly decreased in all treatments. Following the addition of MC in the sandy loam soil, arylsulfatase activity significantly increased. Application of MC and WTR+MC to both soils significantly increased total PLFA, gram-negative bacteria, and total fungal concentrations. The WTR treatment had a significant effect on gram-negative bacteria in the sandy loam. The gram-negative to gram-positive bacteria biomass ratio significantly increased in all the treatments in the clay loam and sandy loam. In addition, each treatment significantly decreased the microbial PLFA stress ratio (17:0cyc and c19:0cyc divided by 16:1w7c and 18:1w7c) in the clay loam and sandy loam. The results indicate that the application of MC, with or without WTR, stimulates the soil microbial community.
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Keywords
Microcystin, Arylsulfatase, Harmful Algal Blooms, Water Treatment Residual, Agriculture, Microbial Community Composition, Phospholipid Fatty Acids (PLFA)