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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7103

Hanazato Takayuki, Arakawa Takashi, Sakuma Masataka, Chang Kwang-Hyeon, and Okino Tokio; [Zooplankton community in Lake Suwa: Community structure and its role in the ecosystem]. Jap.J.Limnol. 62:151-167, 2001

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Studies on the zooplankton community in Lake Suwa since the 1960s are reviewed, and the role of zooplankton in the lake ecosystem is discussed. The community is dominated by rotifers in spring and by small cladocerans in summer and fall. It seems that the zooplankton community structure has not been changed markedly since the 1960s. Two Bosmina species, B. longirostris and B. fatalis, show seasonal and reciprocal succession: the dominance of B. longirostris occurs in spring and fall and that of B. fatalis in summer. The summer dominance of B. fatalis has positive correlations with the mean summer water temperature and the mean summer chlorphyll a concentration, suggesting that it is induced by the occurrence of the cyanobacterium Microcystis bloom. Voluminous enclosures were set up in the lake, and experiments were conduced with them to understand the mechanisms maintaining the lake ecosystem. Results of the experiments have shown some important biological interactions related to zooplankton, such as predator-prey relationships and competition. In Lake Suwa, not only the pelagic community but also the community in vegetation areas has been studied. These studies have demonstrated that environment is highly diverse in the vegetation area, and that the zooplankton community achieves a higher species richness in the vegetation area than in the pelagic one. It is suggested that the zooplankton community in Lake Suwa is exposed to heavy predation pressure by planktivorous fish, and that the major food chain from primary producer to zooplankon in summer is a detritus food chain.