title: Descriptive and mechanistic toxicity of conazole fungicides using the model test alga Dunaliella tertiolecta (Chlorophyceae).
abstract: Conazole fungicides are commonly used to prevent fungal growth on turf grass and agricultural crops. As many of these sites are adjacent to coastal waterways and estuaries, there exists the potential for nontarget effects of runoff on marine organisms. This study reports 96 h EC(50) values for four selected conazole fungicides (triadimefon = 5.98 mg/L; triadimenol = 5.51 mg/L; propiconazole = 2.33 mg/L; hexaconazole = 0.91 mg/L) to the model test alga Dunaliella tertiolecta. We further investigated possible mechanisms of toxicity by examining sublethal effects of exposure on cell morphology, osmoregulatory function, and lipid composition. These mechanistic studies revealed that conazole exposure does not inhibit synthesis of the cell's glycerol osmolyte, but does result in an overall increase in cellular volume and total lipid content. Both fungi and chlorophytes rely on ergosterol to maintain membrane structure and fluidity, and we provide evidence that the sterol-inhibiting conazoles may interfere with ergosterol biosynthesis in the cell membrane of Dunaliella. These findings suggest that green algae may be especially susceptible to nontarget effects of sterol-inhibiting fungicides in marine systems.
authors.affiliation: Grice Marine Biological Laboratory, College of Charleston, 205 Fort Johnson Rd., Charleston, SC 29412, USA.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Baird
authors.forename: Marie E
authors.initials: ME
authors.lastname: DeLorenzo
mesh_terms: D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D004875:Ergosterol / Q000096:biosynthesis; D005659:Fungicides, Industrial / Q000737:chemistry / Q000633:toxicity*; D005990:Glycerol / Q000378:metabolism; D007928:Lethal Dose 50; D008560:Membrane Fluidity / Q000187:drug effects; D015394:Molecular Structure; D019055:No-Observed-Adverse-Effect Level; D009997:Osmotic Pressure / Q000187:drug effects; D018675:Toxicity Tests / Q000379:methods*; D014230:Triazoles / Q000737:chemistry / Q000633:toxicity*; D016823:Volvocida / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism
chemical_list: D005659:Fungicides, Industrial; D014230:Triazoles; D005990:Glycerol; D004875:Ergosterol