title: Reproductive and developmental effects of atrazine on the estuarine meiobenthic copepod Amphiascus tenuiremis.
abstract: Atrazine is one of the most widely used herbicides in the United States. Atrazine concentrations in coastal environments chronically range from 90 ng/L to 46 microg/L, with rare but measured concentrations near 60 microg/L at edge-of-field conditions. Chronic atrazine effects on estuarine benthos exposed to environmentally relevant concentrations are unknown. The purpose of this research was to assess atrazine reproductive and developmental effects over multiple-generation exposures of the copepod Amphiascus tenuiremis. Copepods were chronically exposed to two environmentally relevant nominal atrazine concentrations (2.5 and 25 microg/L, and to an environmentally unrealistic concentration (250 microg/L). Chronic exposures were performed using a 96-well microplate life cycle bioassay. Individual stage I copepodites (C1, n = 60/treatment) were reared through two generations (F0 and F1) to sexual maturity and individually mated in microwells containing 200 microl of atrazine solution. Copepod survival across all treatments and generations was >95%. Atrazine did not affect development to reproductive maturity, time to egg extrusion, or time to egg hatch (p > 0.05). However, reproductive failures increased across generations with increasing atrazine concentrations. Reproductive failures in the 0-, 2.5-, 25-, and 250-microg/L atrazine treatments were 11, 11, 20, and 24% for the F0 and 4, 9, 26, and 38% for the F1, respectively. Compared to controls, total nauplii production per female was reduced by approximately 22% in F0 females exposed to 250 microg/L atrazine (p < 0.05), and by approximately 23%, approximately 27%, and approximately 32% in F1 females exposed to 2.5-, 25-, and 250-microg/L atrazine treatments, respectively (p < 0.05). The combined effect of reproductive failure and reduced offspring production significantly reduced total population growth in the F1 generation (p < 0.05) even at atrazine concentrations lower than that considered safe for seawater chronic exposure (26 microg/L).
authors.affiliation: Department of Environmental Health Sciences, Norman J. Arnold School of Public Health, University of South Carolina, Columbia, South Carolina 29208, USA. acbejara@mailbox.sc.edu
authors.forename: Adriana C
authors.initials: AC
authors.lastname: Bejarano
authors.forename: G Thomas
authors.initials: GT
authors.lastname: Chandler
mesh_terms: D000818:Animals; D001280:Atrazine / Q000633:toxicity*; D001681:Biological Assay; D033342:Copepoda / Q000254:growth & development / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005298:Fertility / Q000187:drug effects*; D006540:Herbicides / Q000633:toxicity*; D007814:Larva / Q000254:growth & development; D011157:Population Dynamics; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D001280:Atrazine