Uptake, Elimination, and Biotransformation of 17α-Ethinylestradiol by the Freshwater Alga Desmodesmus subspicatus Hanna Maja Maes,* ,† Sibylle Xenia Maletz, † Hans Toni Ratte, † Juliane Hollender, ‡ and Andreas Schaeffer † † Institute for Environmental Research (Biology V), RWTH Aachen University, Worringerweg 1, Aachen 52074, Germany ‡ Environmental Chemistry, Eawag, U ̈ berlandstrasse 133, P.O. Box 611, Dü bendorf 8600, Switzerland * S Supporting Information ABSTRACT: Bioconcentration and transformation of the potent and persistent xeno-estrogen 17α-ethinylestradiol (EE2) by organisms at the basis of the food web have received only little research attention. In this study, uptake, elimination, and biotransformation of radiolabeled EE2 ( 14 C-EE2) by the freshwater green alga Desmodesmus subspicatus were investigated. The alga highly incorporated radioactivity following 14 C-EE2 exposure. Up to 68% of the test compound was removed from the medium by D. subspicatus within a rather short time period (72 h C algae /C water : 2200 L/kg wet weight). When the algae were transported to clear medium, a two-stage release pattern was observed with an initially quick elimination phase following slower clearance afterward. Interestingly, D. subspicatus brominated EE2 when bromide was available in the medium, a transformation process demonstrated to occur abiotically but not by algae. The consequence of the presence of more hydrophobic mono- and dibrominated EE2 in the environment remains to be further investigated, as these products were shown to have a lower estrogenic potency but are expected to have a higher bioaccumulation potential and to be more toxic than the mother compound. ■ INTRODUCTION The widespread use of 17α-ethinylestradiol (EE2) as the active agent of many contraceptive pills results in continuous release and distribution of this substance in the aquatic environment. Since the late 90s, EE2 has been detected in surface water all over the world, mostly in the nanogram per liter range. 1-5 Concentrations above reported predicted no effect concen- trations have been measured, which involves that this highly potent xeno-estrogen presents an unacceptable risk for wildlife of such sites. 6-8 In monitoring studies, chemical analysis is generally performed after pretreatment of water samples, in which phytoplankton is filtered out. 9 However, the fraction of hydrophobic compounds associated with these organisms might be large, since algae are lipid-rich and often highly abundant in aquatic ecosystems. 10,11 They may therefore act as important sinks for environmental chemicals. Furthermore, they represent a link to higher organisms, such as grazing zooplankton and herbivore fish, by transfer of substances along the food chain. In fact, it has been suggested that accumulation of persistent hydrophobic organic compounds in algae presents the first step of biomagnification. 10,11 Although EE2 is a moderately lipophilic compound (log K ow = 4.15), 12 only a few studies are available, in which bioconcentration of EE2 at this level of the trophic web was investigated. 13-18 As algal uptake of substances with similar hydrophobicity has been frequently reported, 19-21 it is obvious that more research is required to profoundly examine EE2 accumulation in algae and to assess the possibility of secondary poisoning of their consumers. Because of its physical chemical properties, EE2 is resistant to biodegradation processes. The majority of research on biodegradation of EE2 has focused on bacterial degradation during sewage treatment. 22 Very few studies have concentrated on EE2 transformation by organisms in environmental media, and only a low amount of publications is available demonstrating biotransformation of EE2 by algae. From 11 microalgae strains, 4 were able to transform the substrate by regio- and stereoselective hydroxylation and/or glucosylation. 23 In an experiment by Lai et al., EE2 was persistent in cultures of Chlorella vulgaris, whereas estradiol valerate was hydrolyzed to 17β-estradiol (E2) and further to estrone (E1). 14 The fate of substances is highly influenced by such degradation processes, and more knowledge on the possible biotransformation of EE2 by algae is required. Received: July 24, 2014 Revised: September 18, 2014 Accepted: September 19, 2014 Published: September 19, 2014 Article pubs.acs.org/est © 2014 American Chemical Society 12354 dx.doi.org/10.1021/es503574z | Environ. Sci. Technol. 2014, 48, 12354-12361