Immediate and long-term impacts of UV-C irradiation on photosynthetic capacity, survival and microcystin-LR release risk of Microcystis aeruginosa.
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 4.0×10(6) cells mL(-1) and 8 μg L(-1) to 5.1×10(6) cells mL(-1) and 20 μg L(-1), respectively. Significant M. aeruginosa cytoclasis (cell density from 4.0×10(6) to 1.0×10(6) 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.
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.
Huase
H
Ou
Naiyun
N
Gao
Yang
Y
Deng
Junlian
J
Qiao
Hao
H
Wang
D015169:Colony Count, Microbial; D005434:Flow Cytometry; D042541:Intracellular Space / Q000528:radiation effects; D008387:Marine Toxins; D050296:Microbial Viability / Q000528:radiation effects*; D052998:Microcystins / Q000378:metabolism*; D046931:Microcystis / Q000166:cytology / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D010788:Photosynthesis / Q000528:radiation effects*; D010860:Pigments, Biological / Q000378:metabolism; D012307:Risk Factors; D013997:Time Factors; D014466:Ultraviolet Rays
D008387:Marine Toxins; D052998:Microcystins; D010860:Pigments, Biological; C057862:cyanoginosin LR