Experimental assessment of the bioconcentration of 15N-tamoxifen in Pseudokirchneriella subcapitata

Nowadays, pharmaceutical compounds (PC) are ubiquitous in aquatic ecosystems. In addition to direct ecotoxicity, the bioconcentration of PC in organisms is a phenomenon which could have an impact on the whole ecosystem. In order to study this phenomenon, we exposed unicellular algae (Pseudokirchneriella subcapitata) to N-15-tamoxifen, an anticancer drug labelled with a stable nitrogen isotope used as a tracer. By measuring N-15 enrichment over time, we were able to measure the increase of tamoxifen content in algae. This enrichment was measured by an elemental analyser coupled with an isotopic ratio mass spectrometer (EA-IRMS). Algal cells were exposed for 7 d to 3 concentrations of tamoxifen: 1, 10 and 100 mu g L-1. Our result shows a high bioconcentration in algae from the first minutes of contact. The highest bioconcentration factor measured is around 26500. We also observe that bioconcentration is not linked to the exposure concentration. This study is the first to use stable isotopes in order to monitor PCs in aquatic organisms such as algae. The use of stable isotopes in ecotoxicology offers interesting perspectives in the field of contaminant transfer in organisms and along the trophic web. (C) 2014 Elsevier Ltd. All rights reserved.