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Additive toxicity of herbicide mixtures and comparative sensitivity of tropical benthic microalgae |
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| Authors: | Marie Magnusson Kirsten Heimann Andrew P Negri |
| Institution: | a AIMS@JCU, Australian Institute of Marine Science, James Cook University, Townsville, QLD 4811, Australia b School of Marine and Tropical Biology, James Cook University, Townsville, QLD 4811, Australia c School of Pharmacy and Molecular Sciences, James Cook University, Townsville, QLD 4811, Australia d The University of Queensland, National Research Centre of Environmental Toxicology (EnTox), 39 Kessels Road, Coopers Plains 4108, Australia e Australian Institute of Marine Science, PMB 3, Townsville, MC, QLD 4810, Australia |
| Abstract: | Natural waters often contain complex mixtures of unknown contaminants potentially posing a threat to marine communities through chemical interactions. Here, acute effects of the photosystem II-inhibiting herbicides diuron, tebuthiuron, atrazine, simazine, and hexazinone, herbicide breakdown products (desethyl-atrazine (DEA) and 3,4-dichloroaniline (3,4-DCA)) and binary mixtures, were investigated using three tropical benthic microalgae; Navicula sp. and Cylindrotheca closterium (Ochrophyta) and Nephroselmis pyriformis (Chlorophyta), and one standard test species, Phaeodactylum tricornutum (Ochrophyta), in a high-throughput Maxi-Imaging-PAM bioassay (Maxi-IPAM). The order of toxicity was; diuron > hexazinone > tebuthiuron > atrazine > simazine > DEA > 3,4-DCA for all species. The tropical green alga N. pyriformis was up to 10-fold more sensitive than the diatoms tested here and reported for coral symbionts, and is recommended as a standard tropical test species for future research. All binary mixtures exhibited additive toxicity, and the use of herbicide equivalents (HEq) is therefore recommended in order to incorporate total-maximum-load measures for environmental regulatory purposes. |
| Keywords: | Herbicide Great Barrier Reef Photosynthesis Pollution Fluorometry |
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