Effect of pollution on early diatom colonisation on artificial substrata in urban lowland streams

Abstract

The colonisation patterns of diatom assemblages were studied on artificial substrates in lowland streams with different urban pollution levels. Density, diversity, colonisation rates, ecological guilds and cell size classes of the assemblage at each of two sites were followed for 1 week. In addition, assemblages growing on glass, in natural epipelic biofilm and in water were compared at each site. At both sites, diatom colonisation on glass substrates had already started after 30-min exposure. At the less polluted site, total diatom density was higher, along with the proportion of low-profile and motile species, and there was a higher amount of diatoms in size class 5 (>1500 μm3). At the more polluted site, species from the high-profile guild and size class 3 (300-599 μm3) dominated. Ecological traits (ecological guilds and size class) were not sensitive enough descriptors of early colonisation in nutrient-rich lowland, but the largest cells constituted the first settlers. The results show that the assemblage developed on artificial substrata was a good proxy of the composition in the sediment.