title: Effects of monensin on zooplankton communities in aquatic microcosms.
abstract: The effects of monensin, an antibiotic widely used in the poultry and beef industry, were evaluated on zooplankton community structure and population dynamics. Monensin was added to 12 000 L aquatic microcosms as a single treatment at concentrations ranging from 0.5 to 500 microg/L, and they were evaluated over a 50 day period. Changes in the zooplankton assemblage were evaluated by principal response curves (PRC), while changes in abundance and species richness were evaluated by analysis of variance (ANOVA). Monensin did not significantly affect community structure. However, significant changes within specific taxonomic groups were observed with decreases in the abundance of Rotifera and Copepoda nauplii and in the richness of Rotifera and Cladocera. Concentration-dependent increases in Ostracoda abundance were also observed. Changes in chlorophyll-a concentrations within the microcosms over the course of the study indicated that the changes in zooplankton populations were the indirect result of the effects of monensin on the algal community. Monensin concentrations measured in surface waters were 40 times lower than the determined no-observable effect concentration (NOEC) of 50 microg/L and do not likely present a risk to zooplankton.
authors.affiliation: Department of Environmental Biology, Ontario Agricultural College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada. dhillis@uoguelph.ca
authors.forename: Derek G
authors.initials: DG
authors.lastname: Hillis
authors.forename: Linda
authors.initials: L
authors.lastname: Lissemore
authors.forename: Paul K
authors.initials: PK
authors.lastname: Sibley
authors.forename: Keith R
authors.initials: KR
authors.lastname: Solomon
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D017753:Ecosystem; D008985:Monensin / Q000494:pharmacology*; D019055:No-Observed-Adverse-Effect Level; D013997:Time Factors; D015048:Zooplankton / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000981:Antiprotozoal Agents; D008985:Monensin