VITELLOGENIN CONCENTRATIONS IN FERAL DANISH BROWN TROUT HAVE DECREASED: AN EFFECT OF IMPROVED SEWAGE TREATMENT IN RURAL AREAS?

Abstract

Feminization of male and juvenile fish caused by exposure to estrogens or estrogenic chemicals in effluents from central wastewater treatment plants (WWTP) is a worldwide issue of concern. Intersex and induction of the female yolk protein, vitellogenin, in male and juvenile fish are robust biomarkers for estrogenic exposure, and feminized fish have been observed downstream WWTP outlets in many countries. Danish central WWTPs reduce effluent estrogenicity effectively by advanced sewage treatment, and feminizations have not been observed downstream central WWTP outlets. However, between 2000 and 2004 investigations of Danish streams not receiving sewage from central WWTPs revealed a high variation in vitellogenin concentrations of male juvenile brown trout (Salmo trutta); some individuals had high concentrations probably due to point sources, and the plasma concentration was >50 ng mL⁻¹ in 79 % of the juvenile males. The streams were re-investigated in 2010-2016, and the average male level had decreased to a hitherto unseen baseline level; in 2010 only 0.7% (one individual) of the males had a vitellogenin concentration >50 ng mL⁻¹, and could indicate that the estrogenicity of the streams decreased after 2004. We examined possible estrogenic sources in streams unaffected by central WWTP effluents, and found that the reduced vitellogenin levels are most likely explained by a national effort to improve on-site wastewater treatment in scattered houses not connected to central WWTPs. This article is protected by copyright. All rights reserved

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