title: Species interactions and chemical stress: combined effects of intraspecific and interspecific interactions and pyrene on Daphnia magna population dynamics.
abstract: Species interactions are often suggested as an important factor when assessing the effects of chemicals on higher levels of biological organization. Nevertheless, the contribution of intraspecific and interspecific interactions to chemical effects on populations is often overlooked. In the present study, Daphnia magna populations were initiated with different levels of intraspecific competition, interspecific competition, and predation and exposed to pyrene pulses. Generalized linear models were used to test which of these factors significantly explained population size and structure at different time points. Pyrene had a negative effect on total population densities, with effects being more pronounced on smaller D. magna individuals. Among all species interactions tested, predation had the largest negative effect on population densities. Predation and high initial intraspecific competition were shown to interact antagonistically with pyrene exposure. This was attributed to differences in population structure before pyrene exposure and pyrene-induced reductions in predation pressure by Chaoborus sp. larvae. The present study provides empirical evidence that species interactions within and between populations can alter the response of aquatic populations to chemical exposure. Therefore, such interactions are important factors to be considered in ecological risk assessments.
authors.affiliation: Laboratory of Environmental Toxicology and Aquatic Ecology, Environmental Toxicology Unit (GhEnToxLab), Ghent University, Ghent, Belgium.
authors.forename: Karel P J
authors.initials: KP
authors.lastname: Viaene
authors.affiliation: Research Unit in Environmental and Evolutionary Ecology, Namur University, Namur, Belgium.
authors.forename: Frederik
authors.initials: F
authors.lastname: De Laender
authors.affiliation: Alterra, Wageningen University and Research Centre, Wageningen, The Netherlands.
authors.forename: Andreu
authors.initials: A
authors.lastname: Rico
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, Wageningen, The Netherlands.|Alterra, Wageningen University and Research Centre, Wageningen, The Netherlands.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Van den Brink
authors.affiliation: Department of Science and High Technology, University of Insubria, Como, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Guardo
authors.affiliation: Department of Science and High Technology, University of Insubria, Como, Italy.
authors.forename: Melissa
authors.initials: M
authors.lastname: Morselli
authors.affiliation: Laboratory of Environmental Toxicology and Aquatic Ecology, Environmental Toxicology Unit (GhEnToxLab), Ghent University, Ghent, Belgium.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Janssen
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects* / Q000254:growth & development; D004175:Diptera / Q000187:drug effects / Q000254:growth & development; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D011156:Population Density; D011157:Population Dynamics; D011235:Predatory Behavior / Q000187:drug effects; D011721:Pyrenes / Q000737:chemistry / Q000633:toxicity*; D018570:Risk Assessment; D018675:Toxicity Tests
chemical_list: D011721:Pyrenes; C030984:pyrene
keywords: Competition; Daphnia magna; Predation; Pyrene; Species interactions