Increasing levels of persistent organic pollutants in rainbow trout (Oncorhynchus mykiss) following a mega-flooding episode in the Negro River basin, Argentinean Patagonia.

In 2006, a severe flooding episode in the Negro River basin, Argentinean Patagonia, occurred and mainly affected the middle valley where lands are devoted to agriculture and soils known to be polluted with persistent organic pollutants. The aim of this study was to estimate the effects of this event on polybrominated diphenyl ethers (PBDEs), endosulfans (α-, β-, sulfate), DDTs (p,p'-DDD, p,p'-DDE, p,p'-DDT) and polychlorinated biphenyls (PCBs) levels in rainbow trout (Oncorhynchus mykiss) tissues. Post-event fish showed higher contaminants levels than pre-event at expenses of all groups. DDTs presented the highest concentrations in all tissues followed by PCBs, endosulfans and PBDEs. The metabolite p,p'-DDE represented about 80% of total DDTs, while PCBs were dominated by penta- and hexa-chlorobiphenyls congeners. BDE-47 was the predominant congener among PBDEs. Endosulfan showed the maximum differences between post- and pre-flood fish (up to 43-fold) with a α-/β- ratio >1, suggesting exposure to fresh technical mixture. Contaminant profiles observed in rainbow trout tissues from both periods (pre- and post-event) were consistent with previous results from water, suspended particle matter and soils, showing that this species is a good biomonitor of aquatic pollution of Negro River basin. The presence of the pesticides in the Negro River system resulted from past and current agricultural practices and it was modified and enhanced by the flooding. Additionally, PCBs and PBDEs occurrence in the aquatic environment deserve more attention, and monitoring programs are recommended in order to diminish their incorporation to aquatic ecosystem.