The occurrence of the new zooplankton species in the Lena river delta

Abstract

The Lena River impact on the water bodies of its catchment area increases in connection of climate warming. During spring floods the river water enters the numerous floodplain water basins, further promotes the passive dispersal of their fauna in the northern direction. The occurrences of new (for the local fauna) zooplankton species repeatedly documented in the lakes on Samoylov Island in the south part of the Lena Delta over the last 15 years. Seven “invasive species” belong to Cladocera, four to Copepoda and one species of Rotifera. Some cladocerans –Sida crystallina (O.F. Muller, 1776), Limnosida frontosa (Sars, 1862), Diaphanasoma brachyurum (Lievin, 1848) and Polyphemus pediculus (Linnaeus, 1761) – several times appeared and disappeared in the floodplain aquatic habitats on Samoilovsky Island during the observation period. Simocephalus vetulus (O.F. Muller, 1776) found conditions here to be favorable and formed the local population in the floodplain pools. Acroperus harpae (Baird, 1834) and Holopedium gibberum Zaddach, 1855 started to settle from low floodplain in neighboring water ecosystems of the first delta terrace with a height of 10–16 m. The spread of resting stages of zooplankton are likely to occur with the participation of waterfowl. In years with extremely high spring tide, the expansion of species, not typical for the area, was of a catastrophic nature. A massive invasion of certain species, for example Holopedium gibberum Zaddach, 1855, can cause a rapid restructuring of the lake biocoenosis and disturb the ecological balance in it, resulting in parasitic epizootic.