The combined use of chemical and biochemical markers in Rutilus rutilus to assess the effect of dredging in the lower course of the Ebro River

The lower course of the Ebro River is polluted with high concentrations of organochlorine compounds dumped by a chloro-alkali plant during the last century. A remediation plan, including building of a protective wall, removal and disposal of polluted sediments started in 2012. With the aim of assessing the effects of dredging of contaminated sediments and potential alterations of water quality, areas located upstream (RR) and downstream (BE, A) the chemical plant (FL) were monitored prior (October 2012) and during dredging (June 2013) using roach (Rutilus rutilus) as sentinel organisms. Concentrations of organochlorine compounds (OCs) in fish muscle and biliary levels of polycyclic aromatic hydrocarbons (PAHs), galaxolide (HHCB) and alkyphenols (APEs) were determined together with selected enzymatic activities (7-ethoxyresorufin-O-deethylase (EROD), 7-benzyloxy-4-trifluoromethyl-coumarin O-debenzyloxylase (BFCOD) and UDP-glucuronyltransferase (UGT)) in the liver. The obtained results proved the effectiveness of the wall retaining suspended particles and avoiding further contamination of downstream sites as fish sampled at downstream sites showed up to 9-fold higher concentrations of OCs in muscle during wall construction than during dredging. EROD and UGT activities were induced in fish from downstream sites; however, no clear response to the observed pollution gradient was detected.