Beaver-created microhabitats in a small water body and their impact on flora and fauna (the Khoper River floodplain, Russia)

Abstract

This study shows how beaver digging activity can affect water body morphology and local biota under modern environmental conditions in a small floodplain lake. The total area of microhabitats created by beavers was found to reach 7% of water body area and 30% of littoral-zone area. It was noted that the zoogenic microhabitats are different when depth is greater and plant cover is smaller, especially of emergent vegetation. Helophytes Sparganium erectum and Alopecurus aequalis were found to prefer the beaver-unaffected part of the littoral. Invertebrates Naucoris sp. and Hydrophilus sp. prefer beaver microhabitats, whereas Planorbis planorbis, Lymnaea palustris, and Hydrous sp. prefer thickets of emergent plants in beaver-unaffected littoral areas. Adult crucian carps Carassius carassius proved to be abundant in the beaver-unaffected part of the water body, while the adult weatherfish Misgurnus fossilis prefers beaver burrows, and its fry inhabit beaver-unaffected sites. A similar situation was observed for marsh frogs Pelophylax ridibundus: adults prefer beaver microhabitats in June, but frog tadpoles mainly inhabit a beaver-unaffected littoral. Tadpoles of Pelobates vespertinus proved to be slightly aggregated near beaver burrows in July. The beaver activity was found to slightly increase β-diversity within the water body according to Jaccard indices. The results confirm that the beaver-created heterogeneity is important for aquatic biota under conditions of shallowing of floodplain water bodies.