Effects of land use on streams: traditional and functional analyses of benthic diatoms

Agriculture and urbanisation, the two forms of land use, represent serious threats to the ecological status of aquatic ecosystems, especially in the case of small streams at low altitudes. In this study, 75 Hungarian streams were analysed to explore the effects of these land use types on the composition of benthic diatom communities and their richness. In the Carpathian region, species and trait composition, as well as species richness, varied primarily according to the local environmental variables followed by the shared effects of the environmental factors and land use types. At the same time, functional richness was chiefly explained by the pure effects of land use. However, the difference in trait composition between areas dominated by forest (low profile guild, small cell size) and agriculture (motile ecological guilds with middle size, linear-lanceolate shape) was obvious. Higher proportion of water and artificial surfaces might support the spread of diatom species with specific traits: low profile guild with a slightly elongated outline. Nevertheless, no effect of urbanisation on the set of traits, species composition and richness was detected at either local or catchment scale, which might be due to the relatively small portion of artificial surfaces in the watersheds as a whole.