Effects of waste water on fish health: An integrated approach to biomarker responses in brown trout (Salmo trutta L.)

The impact of wastewater effluent from a sewage treatment works (STW) on the health of brown trout held in cages and wild brown trout in a river was investigated. Biochemical, histological, and organismal responses as well as parasite abundances were monitored and then analyzed using multivariate analyses. Stress responses in trout induced by the water quality of the river upstream of the STW were enhanced by the discharge of the STW. For caged fish, the serum chemistry values alkaline phosphatase, blood urea nitrogen, and creatinine, as well as histological indices of gills and liver, were most effective at distinguishing among fish held in river water, a mixture of river water and wastewater, and tap water. For wild fish, total protein, histological liver alterations and abundance of two parasites (sessile peritrichia, Sphaerospora sp.) were the most indicative parameters for discriminating the health of fish between sites upstream and downstream of the STW. Considering the relationships between the measured parameters concurrently, the multivariate discriminant analysis is an effective method to evaluate which combination of parameters provide the best discrimination between the treatment groups. In contrast to the calculation of group differences based on individual responses, the integrated responses of parameters representing different biological levels lead to a more comprehensive assessment of organismal health and a more accurate distinction in differences between treatment groups.