Plasma biomarkers in fish provide evidence for endocrine modulation in the Elbe River, Germany

Blood plasma samples were collected from wild bream (Abramis brama L.) in the Elbe River, Germany, and analyzed for the yolk protein precursor vitellogenin (VTG), a biomarker for estrogen exposure, and the sex steroids 11-ketotestosterone (11KT), testosterone (T), and 17beta-estradiol (E2) to investigate for evidence of endocrine modulation. In addition, the gonadal status and the prominence of spawning tubercles were investigated. Nine riverine sites were investigated on the Elbe that were influenced by different sources of endocrine-active substances. Bream were collected from a lake that received no domestic or industrial discharges as a control. Plasma VTG concentrations were significantly higher in male bream from the Czech border to the middle Elbe, with the highest concentrations in fish sampled at the locations near Magdeburg and downstream of Dresden (between 20 and 100 times higher than in the controls), regions that are characterized by high levels of effluent discharges into the river. Following the Elbe from this site to the sea, the concentrations of plasma VTG in males were lower than at Meissen but were still elevated above the controls. 11KT and E2 titers showed suppressions in their normal concentrations at some locations (those receiving the greatest industrial discharges). There were reciprocal relationships between inhibitory effects on gonadal growth, maturation, and plasma sex steroids and exposure to pollutants, such as organotins, pesticides, or metals. However, there was no single chemical that alone could explain the observed inhibitory effects on sexual development. The results indicate that the endocrine system in wild bream is disrupted in stretches of the Elbe River.