The polycyclic musks tonalide (R) (acetyl hexamethyltetraline = 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone, AHTN), galaxolide (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta(g)-2-benzopyrane, HHCB) and the degradation product HHCB-lactone were determined in water samples and brown trouts (Salmo trutta fario) of the river Ammer, a small catchment in the state of Baden-Wurttemberg, south-west Germany. The Ammer receives the effluent discharge of two municipal wastewater treatment plants (WWTPs) with 90,000 population equivalents. The wastewater contributes 14% of the total discharge of the river (average 1.0 m(3)/s). Water samples were collected monthly at 12 sampling points from June 2010 to May 2011. Downstream the WWTPs the median concentrations of HHCB, AHTN and HHCB-lactone were 0.26 mu g/L, 0.06 mu g/L and 1.0 mu g/L, respectively. The effluent of the WWTPs was identified as main source of the synthetic musks in the surface water. The ratio of HHCB-lactone/HHCB showed significant seasonal variations indicating the influence of the water temperature on the degradation of HHCB in the surface water. A total of 251 trout was caught in two campaigns in October 2010 at 12 sampling points. The median concentrations of HHCB and AHTN in the trouts downstream the WWTPs significantly increased to 10.8 mu g/g lipid weight (LW) and 3.7 mu g/g LW, respectively. (C) 2014 Elsevier B.V. All rights reserved.