title: Comparative effects of herbicides on photosynthesis and growth of tropical estuarine microalgae.
abstract: Pulse amplitude modulation (PAM) fluorometry is ideally suited to measure the sub-lethal impacts of photosystem II (PSII)-inhibiting herbicides on microalgae, but key relationships between effective quantum yield [Y(II)] and the traditional endpoints growth rate (micro) and biomass increase are unknown. The effects of three PSII-inhibiting herbicides; diuron, hexazinone and atrazine, were examined on two tropical benthic microalgae; Navicula sp. (Heterokontophyta) and Nephroselmis pyriformis (Chlorophyta). The relationships between Y(II), micro and biomass increase were consistent (r2 > or =0.90) and linear (1:1), validating the utility of PAM fluorometry as a rapid and reliable technique to measure sub-lethal toxicity thresholds of PSII-inhibiting herbicides in these microalgae. The order of toxicity (EC50 range) was: diuron (16-33 nM) > hexazinone (25-110 nM) > atrazine (130-620 nm) for both algal species. Growth rate and photosynthesis were affected at diuron concentrations that have been detected in coastal areas of the Great Barrier Reef.
authors.affiliation: AIMS@JCU, Australian Institute of Marine Science, School of Marine and Tropical Biology, James Cook University, Townsville, QLD, Australia.
authors.forename: Marie
authors.initials: M
authors.lastname: Magnusson
authors.forename: Kirsten
authors.initials: K
authors.lastname: Heimann
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Negri
mesh_terms: D000704:Analysis of Variance; D001280:Atrazine / Q000633:toxicity; D018533:Biomass; D004237:Diuron / Q000633:toxicity; D056890:Eukaryota / Q000187:drug effects* / Q000254:growth & development*; D005470:Fluorometry; D006540:Herbicides / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects*; D014227:Triazines / Q000633:toxicity
chemical_list: D006540:Herbicides; D014227:Triazines; D004237:Diuron; D001280:Atrazine; C025641:hexazinone