Fate and Effects of the Herbicide Atrazine in Flow-Through Wetland Mesocosms

Abstract

Abstract-Wetland mesocosms were exposed to increasing concentrations of atrazine over time at levels typical of midwestern surface waters following spring runoff (15 to 75 g/L). Atrazine had a half-life of 8 to 14 d in the 230-m-long wetlands. End points measured included nutrient levels; periphyton biomass; periphyton productivity and respiration; growth of selected macrophytes; and survival and growth of Daphnia magna (15, 25 g/L atrazine), Rana pipiens (15, 25 g/L), and Pimephales promelas larvae (25 to 75 g/L) and adults (50, 75 g/L). Interaction between nutrient status or grazing intensity and atrazine effects were measured using periphyton enrichment and grazing exclosure experiments. Only periphyton, Ceratophyllum demersum, Zizania aquatica, and Daphnia were significantly affected by atrazine at any of the concentrations tested. Periphyton net productivity was significantly depressed by incubation in treated water as compared to control water at Ն25 g/L atrazine (9 to 27-d exposures). In response, dissolved nutrient concentrations increased in treated mesocosms after 14 d. Ceratophyllum length/weight ratios increased after 6-d exposures to 50 g/ L atrazine, while Zizania senesced prematurely during treatments of 50 or 75 g/L atrazine (97 d of cumulative exposure). Periphyton developed resistance to atrazine only at concentrations Ն50 g/L. Atrazine effects on periphyton composition varied with the N:P supply ratio. Daphnia survival was significantly depressed at 15 g/L atrazine (48-h exposures).

Cleanup of atrazine-contaminated soils: ecotoxicological study on the efficacy of a bioremediation tool with Pseudomonas sp. ADP

“…They also support the notion that the indirect effects of atrazine agricultural applications via surface runoff to adjacent streams and leaching to groundwater reservoirs constitute a serious risk for aquatic systems (Detenbeck et al 1996;Graymore et al 2001).…”

Determining in situ periphyton community responses to nutrient and atrazine gradients via pigment analysis

“…In contrast, an increase in chlorophyll c relative to chlorophyll a at 12 μg/L atrazine was observed in an earlier periphytometer experiment, suggesting that chlorophyll c containing Bacillariophyceae were more atrazine tolerant compared to the Chlorophyceae (Kish, 2006). Detenbeck et al (1996) observed reductions in gross primary productivity at 15 μg/L atrazine but a similar reduction was not observed at higher concentrations. However, they also provided evidence of a shift in species dominance or selection for tolerant species at ≥50 μg/L atrazine.…”

Application of in-situ bioassays with macrophytes in aquatic mesocosm studies

“…However, an explanation for this effect is hard to find. Overcompensation of slight impairment in photosynthetic activity would be analogous to the response under light limitation (Kemp et al 1985;Detenbeck et al 1996). Decreased competition for nutrients due to direct and more severe effects on phytoplankton could be another possibility.…”

“…Interestingly, the second application led to higher TBA concentrations but not to a more pronounced effect on functional parameters or phytoplankton abundance. Other studies have demonstrated that tolerant species may replace herbicide-affected species in the phytoplankton or periphyton (Detenbeck et al 1996;Cuppen et al 1997;Hartgers et al 1998). Explaining the lack of effect on algal abundance after the second TBA application with development of TBA resistant chryptophyceen strains or other algae within only 4 weeks would be highly hypothetical and needs confirmation.…”