title: Acute and additive toxicity of ten photosystem-II herbicides to seagrass.
abstract: Photosystem II herbicides are transported to inshore marine waters, including those of the Great Barrier Reef, and are usually detected in complex mixtures. These herbicides inhibit photosynthesis, which can deplete energy reserves and reduce growth in seagrass, but the toxicity of some of these herbicides to seagrass is unknown and combined effects of multiple herbicides on seagrass has not been tested. Here we assessed the acute phytotoxicity of 10 PSII herbicides to the seagrass Halophila ovalis over 24 and/or 48 h. Individual herbicides exhibited a broad range of toxicities with inhibition of photosynthetic activity (∆F/F(m)') by 50% at concentrations ranging from 3.5 μg l(-1) (ametryn) to 132 μg l(-1) (fluometuron). We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides. The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses. This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/F(m)'.
authors.affiliation: College of Marine and Environmental Sciences, James Cook University, Townsville, Queensland, 4811, Australia.|Australian Institute of Marine Science, Townsville, Queensland, 4810, Australia.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Wilkinson
authors.affiliation: College of Marine and Environmental Sciences, James Cook University, Townsville, Queensland, 4811, Australia.|Centre for Tropical Water &Aquatic Ecosystem Research (TropWATER), James Cook University, Cairns, Queensland, 4870, Australia.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Collier
authors.affiliation: Australian Institute of Marine Science, Townsville, Queensland, 4810, Australia.
authors.forename: Florita
authors.initials: F
authors.lastname: Flores
authors.affiliation: Australian Institute of Marine Science, Townsville, Queensland, 4810, Australia.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Negri
mesh_terms: D004305:Dose-Response Relationship, Drug; D006540:Herbicides / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D013997:Time Factors; D064028:Tracheophyta / Q000187:drug effects* / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006540:Herbicides; D045332:Photosystem II Protein Complex; D014874:Water Pollutants, Chemical