title: Cadmium accumulation and toxicity in the unicellular alga Pseudokirchneriella subcapitata: Influence of metal-binding exudates and exposure time.
abstract: Predicting metal availability and toxicity for chronic (several hours or days) metal exposure scenarios, even for unicellular algae, is a major challenge to existing toxicity models. This is because several factors affecting metal uptake and toxicity, such as the release of metal-binding exudates, changes in the kinetics of metal uptake and toxicity over time, and algal physiological acclimation to internalized metals, are still poorly understood. The present study assessed the influence of these factors on Cd uptake and toxicity in laboratory batch cultures of the freshwater alga Pseudokirchneriella subcapitata. To do so, changes in the free Cd(2+) concentrations caused by the release of metal-binding algal exudates were monitored, (109)Cd accumulation in algal cells was measured, and Cd-induced inhibition of algal growth as a function of exposure time (from 12 h to 96 h) was followed. Results indicate that metal-binding exudates may decrease the proportion of the free Cd(2+) ion in solution up to 2-fold, a decrease that affects Cd uptake and toxicity. Pseudokirchneriella subcapitata has the capacity to decrease net Cd uptake rate on short time scales (<24 h), but this reduction in the Cd uptake rate disappeared after 24 h, and Cd toxicity occurred at relatively high Cd concentrations in solution. These data illustrate some of the pitfalls of standard algal toxicity assays, which were designed for acute exposures, and suggest how robust chronic bioassays might be developed.
authors: Institut national de la recherche scientifique, Centre Eau Terre Environnement (INRS-ETE), Québec, Québec, Canada.|Centre d'expertise en analyse environnementale du Québec, Ministère du développement durable, de l'Environnement et de la Lutte contre les changements climatiques, Québec, Québec, Canada.
authors: Nathalie
authors: N
authors: Paquet
authors: Institut national de la recherche scientifique, Centre Eau Terre Environnement (INRS-ETE), Québec, Québec, Canada.|Québec-Océan and Takuvik Joint Université Laval/CNRS Research Units, Département de Biologie, Université Laval, Québec, Québec, Canada.
authors: Michel
authors: M
authors: Lavoie
authors: Institut national de la recherche scientifique, Centre Eau Terre Environnement (INRS-ETE), Québec, Québec, Canada.|Administration portuaire de Québec, Québec, Québec, Canada.
authors: Frédéric
authors: F
authors: Maloney
authors: Laboratoire interdisciplinaire des Environnements Continentaux (LIEC, UMR7360), CNRS-Université de Lorraine, Vandoeuvre-lès-Nancy, F-54501, France.
authors: Jérôme F L
authors: JF
authors: Duval
authors: Institut national de la recherche scientifique, Centre Eau Terre Environnement (INRS-ETE), Québec, Québec, Canada.
authors: Peter G C
authors: PG
authors: Campbell
authors: Institut national de la recherche scientifique, Centre Eau Terre Environnement (INRS-ETE), Québec, Québec, Canada.
authors: Claude
authors: C
authors: Fortin
mesh_terms: D002104:Cadmium / Q000378:metabolism / Q000633:toxicity*; D000460:Chlorophyta / Q000187:drug effects* / Q000254:growth & development; D004781:Environmental Exposure; D005618:Fresh Water / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D008670:Metals / Q000378:metabolism / Q000633:toxicity; D008962:Models, Theoretical; D013997:Time Factors
chemical_list: D007477:Ions; D008670:Metals; D002104:Cadmium
keywords: Ecological risk assessment; Green alga; Metal uptake; Phytoplankton; Toxicity testing