title: Direct and indirect responses of a freshwater food web to a potent synthetic oestrogen.
abstract: Endocrine-disrupting chemicals (EDCs) in municipal effluents directly affect the sexual development and reproductive success of fishes, but indirect effects on invertebrate prey or fish predators through reduced predation or prey availability, respectively, are unknown. At the Experimental Lakes Area in northwestern Ontario, Canada, a long-term, whole-lake experiment was conducted using a before-after-control-impact design to determine both direct and indirect effects of the synthetic oestrogen used in the birth control pill, 17α-ethynyloestradiol (EE2). Algal, microbial, zooplankton and benthic invertebrate communities showed no declines in abundance during three summers of EE2 additions (5-6 ng l(-1)), indicating no direct toxic effects. Recruitment of fathead minnow (Pimephales promelas) failed, leading to a near-extirpation of this species both 2 years during (young-of-year, YOY) and 2 years following (adults and YOY) EE2 additions. Body condition of male lake trout (Salvelinus namaycush) and male and female white sucker (Catostomus commersonii) declined before changes in prey abundance, suggesting direct effects of EE2 on this endpoint. Evidence of indirect effects of EE2 was also observed. Increases in zooplankton, Chaoborus, and emerging insects were observed after 2 or 3 years of EE2 additions, strongly suggesting indirect effects mediated through the reduced abundance of several small-bodied fishes. Biomass of top predator lake trout declined by 23-42% during and after EE2 additions, most probably an indirect effect from the loss of its prey species, the fathead minnow and slimy sculpin (Cottus cognatus). Our results demonstrate that small-scale studies focusing solely on direct effects are likely to underestimate the true environmental impacts of oestrogens in municipal wastewaters and provide further evidence of the value of whole-ecosystem experiments for understanding indirect effects of EDCs and other aquatic stressors.
authors.affiliation: Canadian Rivers Institute and Biology Department, University of New Brunswick, Saint John, New Brunswick, Canada E2L 4L5 kiddk@unb.ca.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Kidd
authors.affiliation: Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, Canada R3T 2N6 International Institute for Sustainable Development-Experimental Lakes Area, 161 Portage Avenue East, 6th Floor, Winnipeg, Manitoba, Canada R3B 0Y4.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Paterson
authors.affiliation: Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, Canada R3T 2N6 International Institute for Sustainable Development-Experimental Lakes Area, 161 Portage Avenue East, 6th Floor, Winnipeg, Manitoba, Canada R3B 0Y4.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Rennie
authors.affiliation: Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, Canada R3T 2N6.
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Podemski
authors.affiliation: Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, Canada R3T 2N6.
authors.forename: Dave L
authors.initials: DL
authors.lastname: Findlay
authors.affiliation: Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, Canada R3T 2N6.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Blanchfield
authors.affiliation: Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5B3.
authors.forename: Karsten
authors.initials: K
authors.lastname: Liber
mesh_terms: D000818:Animals; D003530:Cyprinidae / Q000502:physiology*; D004997:Ethinyl Estradiol / Q000737:chemistry / Q000633:toxicity*; D020387:Food Chain; D005618:Fresh Water; D006801:Humans; D007448:Invertebrates / Q000187:drug effects*; D008297:Male; D009864:Ontario; D012098:Reproduction / Q000187:drug effects; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D004997:Ethinyl Estradiol
keywords: aquatic toxicology; endocrine disrupters; ethynyloestradiol; indirect food-web effects; whole-ecosystem study