This paper describes recent levels of surfactants measured in a coastal lagoon ecosystem highly stressed by human ac- tivites: the Orbetello lagoon (Southern Tuscany, Italy, Ramsar Site IT008). Significance of difference among concentra- tions measured before and after summertime are explored in order to evaluate effects related to tourism exploitation. Among surfactants, methylene blue active anionic substances (MBAS) are selected as tracers for untreated discharges originated by domestic and urban activities. Water samplings were performed in 2011 following a randomly repli- cated nested logic model (n = 144). MBAS mean level of 0.070 mg·L–1 (<0.001 - 0.259 mg·L–1) and 0.530 mg·L–1 (
