title: Assessing interactions of multiple agrichemicals by using bacterial assemblages in a wetland mesocosm system.
abstract: Agrichemicals may enter wetlands located adjacent to or downstream from agricultural fields. We investigated the individual and interactive effects of three agrichemicals [atrazine, chlorpyrifos, and monosodium acid methanearsonate (MSMA)] and methyl mercury on abundance and heterotrophic potential of wetland heterotrophic bacteria assemblages. We used a factorial experimental design, in which chemicals were introduced in all possible combinations to 66 500-liter mesocosms at the Biological Field Station of the University of Mississippi. Methyl mercury was added to bring the total mercury (HG) concentration to 0.4 mg/Kg wet weight at the sediment surface. Atrazine, chlorpyrifos, and MSMA were added at concentrations of 192, 51, and 219 microg/L, respectively. Over 32 days of exposure, microbial heterotrophic activity was sensitive to only the interactive effect of HG*ATR*CPF in the sediments and only CPF in the water. Total bacterial numbers did not exhibit any significant treatment effects. Therefore, the effects of agrichemicals were reflected on cell-specific bacterial heterotrophic activity rather than bacterial population size.
authors.affiliation: Department of Biology, Jackson State University, Jackson, MS 39217, USA. hwang@ccaix.jsums.edu
authors.forename: Huey-Min
authors.initials: HM
authors.lastname: Hwang
authors.forename: Neisee
authors.initials: N
authors.lastname: McArthur
authors.forename: Clifford
authors.initials: C
authors.lastname: Ochs
authors.forename: Bruce
authors.initials: B
authors.lastname: Libman
mesh_terms: D016573:Agrochemicals / Q000633:toxicity; D001152:Arsenicals / Q000009:adverse effects*; D001280:Atrazine / Q000633:toxicity*; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D004390:Chlorpyrifos / Q000633:toxicity*; D015169:Colony Count, Microbial; D004347:Drug Interactions; D019015:Geologic Sediments / Q000382:microbiology; D005947:Glucose / Q000378:metabolism; D006540:Herbicides / Q000633:toxicity; D007306:Insecticides / Q000633:toxicity; D008767:Methylmercury Compounds / Q000633:toxicity*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D016573:Agrochemicals; D001152:Arsenicals; D006540:Herbicides; D007306:Insecticides; D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D005947:Glucose; C020300:monomethylarsonic acid; D004390:Chlorpyrifos; D001280:Atrazine