Immediate and long-term impacts of UV-C irradiation on photosynthetic capacity, survival and microcystin-LR release risk of Microcystis aeruginosa |
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Authors: | Ou Huase Gao Naiyun Deng Yang Qiao Junlian Wang Hao |
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Affiliation: | a State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Mingjing building, 1239# Siping Road, Shanghai 200092, PR China b Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ 07043, United States |
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Abstract: | In this study, the immediate and long-term impacts of shortwave ultraviolet (UV-C) irradiation on photosynthetic capacity, survival, and recovery of Microcystis aeruginosa were investigated. The risk of microcystin-LR (MC-LR) release during irradiation was also estimated. The cell density was determined by a flow cytometry, and typical chlorophyll fluorescence parameters, including the effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse amplitude modulated (PAM) fluorometer. Under various UV-C dosages (140-4200 mJ cm−2), photosynthetic capacities were reduced, to different degrees, accompanied by slight cytoclasis and complete degradation of extracellular MC-LR immediately after irradiation. In a 6-d cultivation following UV-C irradiation, cell density and extracellular MC-LR in the samples treated by 140 mJ cm−2 UV-C irradiation increased from 4.0 × 106 cells mL−1 and 8 μg L−1 to 5.1 × 106 cells mL−1 and 20 μg L−1, respectively. Significant M. aeruginosa cytoclasis (cell density from 4.0 × 106 to 1.0 × 106 cells mL−1) and MC-LR release (2-25 μg L−1) occurred when the UV-C dosage reached 350 mJ cm−2. Cell cytoclasis and MC-LR release were enhanced in the cultivated samples under higher UV-C dosages. Results revealed that photosynthetic parameters were useful tools to predict the recovery profiles of M. aeruginosa cells, and the MC-LR release risk should be considered after UV-C inactivation. |
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Keywords: | Ultraviolet irradiation Cyanobacteria Photosynthesis UV-C Microcystis aeruginosa Microcystin-LR |
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