title: Do titanium dioxide nanoparticles induce food depletion for filter feeding organisms? A case study with Daphnia magna.
abstract: Although nanoparticles are increasingly investigated, their impact on the availability of food (i.e., algae) at the bottom of food chains remains unclear. It is, however, assumed that algae, which form heteroagglomerates with nanoparticles, sediment quickly limiting the availability of food for primary consumers such as Daphnia magna. As a consequence, it may be hypothesized that this scenario - in case of fundamental importance for the nanoparticles impact on primary consumers - induces a similar pattern in the life history strategy of daphnids relative to situations of food depletion. To test this hypothesis, the present study compared the life-history strategy of D. magna experiencing different degrees of food limitation as a consequence of variable algal density with daphnids fed with heteroagglomerates composed of algae and titanium dioxide nanoparticles (nTiO2). In contrast to the hypothesis, daphnids' body length, weight, and reproduction increased when fed with these heteroagglomerates, while the opposite pattern was observed under food limitation scenarios. Moreover, juvenile body mass, and partly length, was affected negatively irrespective of the scenarios. This suggests that daphnids experienced - besides a limitation in the food availability - additional stress when fed with heteroagglomerates composed of algae and nTiO2. Potential explanations include modifications in the nutritious quality of algae but also an early exposure of juveniles to nTiO2.
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Germany; Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden. Electronic address: mirco.bundschuh@slu.se.
authors.forename: Mirco
authors.initials: M
authors.lastname: Bundschuh
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Germany; Research Institute for Limnology, University of Innsbruck, Mondsee, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Vogt
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Germany; nEcoTox Consult, Schifferstadt, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Seitz
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Germany; nEcoTox Consult, Schifferstadt, Germany.
authors.forename: Ricki R
authors.initials: RR
authors.lastname: Rosenfeldt
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Schulz
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D003621:Daphnia / Q000187:drug effects / Q000502:physiology*; D020387:Food Chain; D053768:Metal Nanoparticles / Q000633:toxicity*; D058086:Microalgae / Q000187:drug effects*; D014025:Titanium / Q000633:toxicity*; D015048:Zooplankton / Q000502:physiology*
chemical_list: C009495:titanium dioxide; D014025:Titanium
keywords: Energy budget; Food quality; Heteroagglomerates; Nanomaterials; Physiology; Trophic interaction