Response of aquatic communities from a vermont stream to environmentally realistic atrazine exposure in laboratory microcosms

Abstract

Abstract-The direct and indirect effects of the herbicide atrazine were assessed at the community level under exposure patterns likely to be experienced by stream organisms in Vermont. Both attached algae and benthic invertebrates were collected from a clean site using artificial substrates and established in recirculating 120-L laboratory microcosms. On day 1 of the 14-d experiment, three of six microcosms were treated with 5 g/L atrazine. Concentrations were gradually reduced by replacing a portion of the water in the systems over time so that by day 7, atrazine concentrations were only about 1 g/L. Direct effects of atrazine on algal biomass were assessed by measuring chlorophyll a concentrations in samples of attached algae. No differences in chlorophyll a were found between treatment and control microcosms. Potential indirect effects of reduced algal food availability on benthic invertebrate communities were assessed by comparing assemblages in treatment and control microcosms using both a functional (feeding) group classification and taxonomic composition. There were no significant differences in the functional or taxonomic composition of the benthic invertebrate communities; however, a greater number of insects emerged from the treatment microcosms early in the experiment compared to controls, suggesting some response to atrazine. Further community-level testing is needed to more clearly determine if atrazine is affecting stream organisms.

Influence of agricultural land-use and pesticides on benthic macroinvertebrate assemblages in an agricultural river basin in southeast Brazil

“…Concentration of pesticides in water is usually low, since most formulations are soluble in water and are affected by dilution (Wauchope, 1978). Also, chemical inputs in streams and rivers may occur in pulses following rainfall events and soon after pesticide applications (Gruessner and Watzin, 1996).…”

Atrazine induction of a family 4 cytochrome P450 gene in Chironomus tentans (Diptera: Chironomidae)

“…Atrazine is used for control of broadleaf weeds in several major US grain crops. It is one of the most extensively used herbicides in North America, and has been detected in both surface water and groundwater (Gruessner and Watzin, 1996). Studies of its occurrence and behavior in streams and rivers draining agricultural lands have shown that the highest atrazine concentrations usually occur in relatively brief pulses following rain events, especially those that occur soon after herbicide application (DeNoyelles et al, 1982).…”

Development of Methods for Evaluating Toxicity to Freshwater Ecosystems

“…Schmitz and Nagel (1995) working with indoor streams have shown diversity and evenness of the benthic community to be signi"cantly reduced at a DCA concentration of 0.2 mg/L. Gruessner and Watzin (1996) could "nd no signi"cant e!ects on the community of attached algae and invertebrates in streams treated with atrazine at concentrations in the range 0.001 to 0.005 mg/L. Winner et al (1975) found the diversity and abundance of benthic invertebrates in a natural stream treated with copper over a 2 -year period to be a!ected at a copper concentration of 0.023 mg/ L. Algal photosynthesis and primary production have been found to be reduced by copper concentrations in the order of 0.010 mg/L (Eichenberger et al, 1981;Hedtke, 1984).…”