The River Volga headwaters: Inventory, biodiversity and conservation

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River headwaters in the East European lowlands, such as the Upper Volga River, still contain large reaches exhibiting natural conditions and unaltered type-specific fauna. This article focuses on macroinvertebrate assemblages of this intact lowland river system. The presented inventory on aquatic biodiversity and habitat-specific invertebrate assemblages provides a basis to test general ecological theories in large European rivers and to define future management. A total of 204 taxa in seven phyla were identified in the headwaters of the Volga River, i.e. along 446 river kilometres, and its main tributaries. Arthropods were the most diverse group, followed by Annelida and Mollusca. Many species (up to 41 %) of the lake littoral were also common in the slow flowing (lentic) section of the river. Diversity, abundance and biomass increased along the river course. The number of reference taxa, defined in a previous paper, also increased downstream from 15 to 21. From the 30 tributaries 120 taxa were identified; 19 of which were from 24 reference taxa. Analysis of beta-diversity showed that 50 % of species were common to the main river and its tributaries. The Upper Volga lakes can be characterised as Chironomus plumosus lakes. The natural free flowing section and its tributaries comprise a diverse epipotamal fauna. Downstream from the Upper Volga Lakes, the functional feeding groups followed the predictions of the River Continuum Concept: in the upper reaches the community is composed of filter feeders, followed by grazers, predators, detritivores and shredders while further downstream detritivores became slightly dominant.