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Effects of diquat on freshwater microbial communities


, : Effects of diquat on freshwater microbial communities. Archives Of Environmental Contamination & Toxicology. 25(1): 95-101

A static microcosm system was used to evaluate effects of the herbicide diquat (0.3-30 mg/L) on the structure and function of naturally derived microbial communities on polyurethane foam substrates. Microbial communities were exposed to a single application of diquat and were monitored for 21 days. Effects on community structure included changes in algal cell density at diquat concentrations gtoreq 0.3 mg/L (after an initial decrease in net productivity), bacterial cell density (1 mg/L diquat), and increased biomass accumulation (10 and 30 mg/L diquat). The species richness of protozoa was reduced at diquat concentrations gt 0.3 mg/L; protozoan species composition was progressively more dissimilar with diquat treatment. Effects on community function included inhibition of net productivity and community respiration (10 and 30 mg/L diquat), and decreased enzyme activities (alkaline phosphatase (1, 10, and 30 mg/L diquat), electron transport system ( gtoreq 0.3 mg/L diquat), and beta-glucosidase ( gtoreq 0.3 mg/L diquat)). Both photosynthetic and nonphotosynthetic organisms were affected by diquat. Most structural and functional responses were sensitive indicators of stress. Estimated chronic toxicity values ranged from 0.3 mg/L (day 3) to 5.5 mg/L (day 21). Most microbial responses indicated that microbial community structure and function did not recover within the 21-day exposure period.

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Accession: 008565079

DOI: 10.1007/bf00230718

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