title: How benthic diatoms within natural communities respond to eight common herbicides with different modes of action.
abstract: Herbicides are common pollutants of rivers in agricultural regions. These contaminants include various types of chemicals with different modes of toxic action. Herbicides can have toxic effects on freshwater benthic diatoms, the base of the aquatic food web. We examined the effects of (non-mixture) herbicide exposure to the health of diatoms for eight common herbicides with three different modes of action; the photosystem II (PSII) inhibitors: atrazine, simazine, hexazinone, tebuthiuron and diuron; two auxinic herbicides: MCPA and 2,4-D; and the EPSP synthase inhibitor: glyphosate. Benthic diatoms within riverine communities were exposed to each herbicide in rapid toxicity tests at concentrations of 50, 200 and 500μgL(-1). The most sensitive taxa were Gomphonema spp. and Encyonema gracilis. Navicula cryptotenella was the most tolerant to herbicide exposure. There was no significant effect of the different herbicide modes of action at the community level. Herbicide mode of action did not alter which taxa were most sensitive within the community and sensitivity rankings of the dominant diatom taxa were similar for each of the eight herbicides. The consistency of the results between herbicides suggests that freshwater benthic diatoms may be suitable in situ indicators for detecting the toxicity of herbicides with differing modes of action.
authors.affiliation: School of Life Sciences, Applied Ecology Team, University of Technology Sydney, PO Box 123, NSW 2007, Australia. Electronic address: Wood.Rebecca.Jane@gmail.com.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Wood
authors.affiliation: School of Life Sciences, Applied Ecology Team, University of Technology Sydney, PO Box 123, NSW 2007, Australia.
authors.forename: Simon M
authors.initials: SM
authors.lastname: Mitrovic
authors.affiliation: School of Life Sciences, Applied Ecology Team, University of Technology Sydney, PO Box 123, NSW 2007, Australia.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Lim
authors.affiliation: Institute for Applied Ecology, University of Canberra, ACT 2601, Australia.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Kefford
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000633:toxicity; D001280:Atrazine / Q000633:toxicity; D017377:Diatoms / Q000502:physiology*; D006540:Herbicides / Q000633:toxicity*; D008782:Methylurea Compounds / Q000633:toxicity; D012839:Simazine / Q000633:toxicity; D018675:Toxicity Tests; D014227:Triazines / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006540:Herbicides; D008782:Methylurea Compounds; D014227:Triazines; D014874:Water Pollutants, Chemical; D015084:2,4-Dichlorophenoxyacetic Acid; C010346:tebuthiuron; D001280:Atrazine; D012839:Simazine; C025641:hexazinone
keywords: Algae; Benthic diatoms; Herbicide; Rivers; Sensitivity; Toxicity