Relationship Between Fecal Indicators in Sediment and Recreational Waters in a Danish Estuary Peter Roslev & Søren Bastholm & Niels Iversen Received: 27 November 2007 / Accepted: 15 April 2008 / Published online: 30 May 2008 # Springer Science + Business Media B.V. 2008 Abstract The European Union has introduced a new bathing water directive where future classification of recreational waters will be based on the microbial parameters Escherichia coli, and intestinal enterococci. Introduction of enterococci as a new quality param- eter may pose a challenge in some areas because relatively less is known about these organisms compared to E. coli. In the present study, the relative abundance of intestinal enterococci, E. coli, and ten fecal sterol and stanol biomarkers were investigated in water and sediment at two estuarine beach sites affected by fecal pollution. In the bathing water, enterococci were relatively more abundant at low E. coli concentrations. In the sediment, enterococci were generally more abundant than E. coli with surface concentrations between 1.0×10 2 and 4.5×10 3 CFU cm -3 . Enterococci populations were relatively similar in water and sediment, and were phenotypically different from that of nearby pollution sources. The putative human specific genetic marker esp in Entero- coccus faecium was not detected in water or sediment samples despite occasional inputs of human waste from storm water overflows. Sterol and stanol profiles suggested a direct link between water and sediment pollution profiles on days with wind conditions that facilitated resuspension. Sediment resuspension may occur at wind speeds exceeding 6–8ms -1 , and could contribute significantly to enterococci concentrations in the overlying water. The study emphasized that recontamination of the water column due to wind induced resuspension should be considered when evaluating indicator levels and microbial hazards in estuarine recreational waters. Keywords Surface water quality . Sediment resuspension . Fecal indicators . E. coli . Enterococci . Microbial source tracking 1 Introduction The European Union has recently introduced a new Bathing water Directive that is going to be imple- mented in all member states from 2008–2013 (EU 2006). According to this directive, future classifica- tion of bathing water into “excellent”, “good”, and “sufficient” quality will be based on the microbial parameters E. coli and intestinal enterococci. Introduc- tion of enterococci concentrations as a quality param- eter will be new in some member states, and may constitute a challenge for regulatory agencies because relatively less is known about these organisms in recreational waters compared to E. coli. However, it is now accepted that enterococci are often better indica- Water Air Soil Pollut (2008) 194:13–21 DOI 10.1007/s11270-008-9715-y P. Roslev (*) : S. Bastholm : N. Iversen Section of Environmental Engineering, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000, Aalborg, Denmark e-mail: pr@bio.aau.dk