Biodiversity of diatoms and macroinvertebrates in an east European lowland river, the Tudovka River (Tver Region, Russia)

Knowledge about river ecosystems in the east European lowlands is scattered, however it is strongly needed for water management and conservation issues. The aim of the present study was to provide information on biotic key elements and their responses to major environmental gradients in a European lowland river. During the summers of 2006 and 2007, 124 diatom and 128 macroinvertebrate species were recorded in a pristine brown-water river, the Tudovka, a tributary of the Volga River. The canonical correspondence analysis showed that conductivity, pH and colour were significant environmental variables in explaining diatom data, while macroinvertebrate distribution was most related to distance from source (rkm). The eigenvalues of the first two CCA axes were significant (p < 0.05) for diatoms and invertebrates. However, the diatom analysis explained more of the taxonomic variation (41.7% vs. 34.6%). Overall, invertebrates responded more to physical factors, while diatoms depended on water chemistry, thus both components are needed for assessing river health. We suggest the use of a combination of diatom (Austrian saprobic and trophic indices, TDI and IBD) and macroinvertebrate (Austrian saprobic index, the SPEAR pesticides index and ITC) indices for further monitoring programmes in the Tver Region. With this study we provide important information on the riverine biocenosis in this ecosystem, as this river type is elsewhere affected by human activities.