“…Assemblages of benthic diatoms in rivers are influenced both by environmental descriptors that are not affected by human activities, such as the dominant geology of the river basin (Cantonati, 1998;Tison et al, 2004;Rimet et al, 2007), the altitude of the sampling site (Ndiritu et al, 2006;Rimet et al, 2007), the distance from the source (Potapova & Charles, 2002), and by others that can be affected by human activities, such as the organic load and nutrient concentration of the water (e.g., Van Dam et al, 1994;Kelly & Whitton, 1998;Kovács et al;. Within this framework, benthic diatoms have been recommended in the last several decades as an appropriate tool for pollution assessment in rivers (e.g., Round, 1991;Coste et al, 1991;Whitton, 1991;Whitton & Kelly, 1995), and have been routinely used throughout France since the late 1990s to indicate pollution levels of watercourses.…”