title: Toxicity of atrazine to the estuarine phytoplankter Pavlova sp. (Prymnesiophyceae): increased sensitivity after long-term, low-level population exposure.
abstract: Phytoplankton are potentially more at risk to the adverse effects of herbicides than many other organisms in estuarine ecosystems. The focus of this study was to characterize the toxicity of a widely used herbicide, atrazine, to a single species of phytoplankton. The nanoplankter Pavlova sp. was grown under controlled laboratory conditions and was used to elucidate short-term, high-level population effects of atrazine. Secondly, a long-term, multigenerational population exposure was performed with a low level of atrazine followed by an additional short-term, high-level exposure on the same population with no recovery period. The 96-h growth rate of 50% effective concentration (EC50) for Pavlova sp. was 147 [microg/L (95% CI = 116.4-178.7 microg/L). Long-term exposure at 20 [microg/L for four (batch culture) growth cycles (approximately 20 generations) had no significant effect on the growth rate of Pavlova sp. except during the fourth growth cycle. However, a subsequent short-term, high-level 96-h exposure inoculated from the long-term, low-level exposed population showed increased sensitivity to atrazine (96-h growth rate EC50 = 96.0 microg/L, 95% CI = 90.2-103.7 microg/L). Multigenerational exposure to atrazine appeared to render phytoplankton significantly more sensitive (35%) to atrazine effects. Given the documented persistence of atrazine in surface waters, long-term exposure to low levels of atrazine without recovery may lead to shifts in species sensitivity and potential alterations in phytoplankton population dynamics.
authors.affiliation: Department of Biology, University of Charleston, South Carolina 29412, USA. paul.pennington@noaa.gov
authors.forename: P L
authors.initials: PL
authors.lastname: Pennington
authors.forename: G I
authors.initials: GI
authors.lastname: Scott
mesh_terms: D001280:Atrazine / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D006540:Herbicides / Q000633:toxicity*; D007928:Lethal Dose 50; D010839:Phytoplankton; D011157:Population Dynamics; D018570:Risk Assessment; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D001280:Atrazine