title: Determining in situ periphyton community responses to nutrient and atrazine gradients via pigment analysis.
abstract: Agrochemicals, including fertilizers and herbicides, are significant contributors of non-point source pollution to surface waters and have the potential to negatively affect periphyton. We characterized periphyton communities using pigment markers to assess the effects of nutrient enrichment and the herbicide atrazine with in situ experimental manipulations and by examining changes in community structure along existing agrochemical gradients. In 2008, the addition of nutrients (20 mg/L nitrate and 1.25 mg/L reactive phosphate), atrazine (20 μg/L) and a combination of both nutrients and atrazine had no significant effect on periphyton biomass or community structure in a stream periphytometer experiment. In 2009, similar experiments with higher concentrations of atrazine (200 μg/L) at two stream sites led to some minor effects. In contrast, at the watershed scale (2010) periphyton biomass (mg/m(2) chlorophyll a) increased significantly along correlated gradients of nitrate and atrazine but no direct effects of reactive phosphate were observed. Across the watershed, the average periphyton community was composed of Bacillariophyceae (60.9%), Chlorophyceae (28.1%), Cryptophyceae (6.9%) and Euglenophyceae (4.1%), with the Bacillariophyceae associated with high turbidity and the Chlorophyceae with nitrate enrichment. Overall, effects of nitrate on periphyton biomass and community structure superseded effects of reactive phosphate and atrazine.
authors.affiliation: Ottawa-Carleton Institute of Biology, 30 Marie Curie, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada. Electronic address: rdalt018@uottawa.ca.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Dalton
authors.affiliation: Ottawa-Carleton Institute of Biology, 30 Marie Curie, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada; Science and Technology Branch, Environment Canada, 1125 Colonel By Drive, Raven Road, Carleton University, Ottawa, Ontario K1A 0H3, Canada. Electronic address: Celine.Boutin@ec.gc.ca.
authors.forename: Céline
authors.initials: C
authors.lastname: Boutin
authors.affiliation: Ottawa-Carleton Institute of Biology, 30 Marie Curie, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada. Electronic address: Frances.Pick@uottawa.ca.
authors.forename: Frances R
authors.initials: FR
authors.lastname: Pick
mesh_terms: D001280:Atrazine / Q000633:toxicity*; D017377:Diatoms; D006540:Herbicides / Q000633:toxicity*; D009566:Nitrates / Q000633:toxicity*; D010710:Phosphates / Q000633:toxicity*; D010839:Phytoplankton / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006540:Herbicides; D009566:Nitrates; D010710:Phosphates; D014874:Water Pollutants, Chemical; D001280:Atrazine
keywords: Atrazine; CHEMTAX; Flowing waters; Nutrients; Periphytometer; Periphyton