Assessment of Bioconcentration Factor of Chromium by Instrumental Neutron Activation Analysis in Argyrodiaptomus falcifer Daday, a Subtropical Freshwater Copepod Ana María Gagneten & Rita R. Plá & Luciana Regaldo & Juan César Paggi Received: 15 September 2008 / Accepted: 25 February 2009 / Published online: 20 March 2009 # Springer Science + Business Media B.V. 2009 Abstract The objectives of this study were to determine the capacity of the freshwater calanoid copepod Argyrodiaptomus falcifer (Daday, 1905) to accumulate Cr from water, to know the bioconcentra- tion factors in order to evaluate its potential as a biomonitor, and to compare this with data previously obtained with Daphnia magna Straus under identical conditions. By static bioassays using triplicates and a control, a pool of A. falcifer was exposed to three concentrations of Cr (VI): 150 μg/L (T1), 280 μg/L (T2), and 350 μg/L (T3) for 48 h to later determine by Instrumental Neutron Activation Analysis the amount of Cr accumulated. A. falcifer accumulated Cr in all the three concentrations tested. The comparison of T1, T2, and T3 and the control showed significant differences (p <0.05) but not between the treatments (p >0.05). On the other hand, A. falcifer accumulated more Cr than D. magna, but these differences were not significant (p >0.05). Almost no information is available about metal toxicity in freshwater copepods so the reported results are of high importance in order to detect good biomonitors of freshwater Cr-polluted environments. Keywords Argyrodiaptomus falcifer . Bioconcentration factor . Biomonitor . Chromium . Freshwater copepod . Instrumental neutron activation analysis . Static bioassay 1 Introduction Concentrations of chemicals in organisms are regarded as being indicators of the bioavailable fraction of those substances in the environment. Delineating metal uptake in freshwater invertebrates is important for understanding metal bioaccumulation and toxicity and for setting appropriate water quality criteria. Zooplanktonic organisms are suitable for this purpose because of their short life span, their presence in any season, and their great capacity to accumulate several pollutants. Among zooplanktonic organisms, most of previous work has been performed with cladocerans, although accumulation capacity of some Water Air Soil Pollut (2009) 204:133–138 DOI 10.1007/s11270-009-0032-x A. M. Gagneten (*) : L. Regaldo Departamento de Ciencias Naturales, Facultad de Humanidades y Ciencias, Universidad Nacional del Litoral, Ciudad Universitaria, (3000) Santa Fe, Argentina e-mail: amgagnet@fhuc.unl.edu.ar R. R. Plá Técnicas Analíticas Nucleares-CAE, Comisión Nacional de Energía Atómica, Av. del Libertador 8250, 1429 Buenos Aires, Argentina J. C. Paggi Instituto Nacional de Limnología, CONICET-UNL, Ciudad Universitaria, 3000 Santa Fe, Argentina