[en] Emerging contaminants, including pharmaceuticals and personal care products, represent a threat to aquatic ecosystems and, in particular, to the microalgal community, on which most of the primary production of these environments depends. The non-steroidal antiinflammatory diclofenac is one of the most consumed and most prevalent drug in world's waters; however, not much is known about its ecotoxicity potential. In this work the potential cytotoxic effect of diclofenac on the freshwater microalgae Chlamydomonas reinhardtii and the marine diatom Phaeodactylum tricornutum was studied. Microalgal cultures were exposed to concentrations of 50, 100, 125 and 150 mg L-1 of diclofenac for 24 and 96 h. Multiple biomarkers of cytotoxicity were analyzed: growth, photosynthetic pigment content, photosynthetic efficiency, inherent properties, cell viability, metabolic activity, intracellular pH, cytoplasmic membrane potential and oxidative stress. Results showed that diclofenac is toxic to both species assayed. The most sensitive species was P. tricornutum, whose growth was completely inhibited at the highest concentrations. Photosynthetic efficiency, cellular complexity, autofluorescence, intracellular pH and cytoplasmic membrane potential were also significantly affected; however, for C. reinhardtii, only metabolic activity and photosynthetic efficiency were found to be sensitive. The only parameter significantly affected in both species was photosynthetic efficiency. Cell viability, photosynthetic pigment content and oxidative stress were not significantly affected in either species.

[gl] Os contaminantes emerxentes, entre os que se atopan os fármacos e produtos de hixiene persoal, representan unha ameaza para os ecosistemas acuáticos e, en particular, para a comunidade microalgal, de quen depende a maior parte da produción primaria destes ambientes. O anti-inflamatorio non esteroideo diclofenaco é un dos medicamentos máis consumidos e con maior presencia nas augas de todo o mundo; porén, non se coñece moito acerca da súa potencial ecotoxicidade. Neste traballo, estudouse o potencial efecto citotóxico do diclofenaco sobre a microalga dulceacuícola Chlamydomonas reinhardtii e a diatomea mariña Phaeodactylum tricornutum. Os cultivos de microalgas expuxéronse a concentracións de 50, 100, 125 e 150 mg L-1 de diclofenaco durante 24 e 96 h. Múltiples biomarcadores de citotoxicidade foron analizados: crecemento, contido de pigmentos fotosintéticos, eficiencia fotosintética, propiedades inherentes, viabilidade celular, actividade metabólica, pH intracelular, potencial membrana citoplasmática e estrés oxidativo. Os resultados mostraron que o diclofenaco é tóxico para as dúas especies ensaiadas. A máis sensible foi P. tricornutum cuxo crecemento se viu completamente inhibido ás concentracións máis altas. A eficiencia fotosintética, a complexidade celular, a autofluorescencia, o pH intracelular e o potencial de membrana citoplasmática tamén se viron significativamente afectados; porén, para C. reinhardtii, só a actividade metabólica e a eficiencia fotosintética resultaron ser sensibles. O único parámetro que se viu afectado significativamente en ambas especies foi a eficiencia fotosintética. A viabilidade celular, o contido de pigmentos fotosintéticos e o estrés oxidativo non se viron significativamente afectados en ningunha das dúas especies.