Diversity and Community Structure of Zooplankton in Reservoirs in South China

Abstract

Zooplankton diversity and its response to eutrophication were investigated in 15 reservoirs of South China from 2000 to 2003. So far, 105 species of Rotifera, 30 species of Cladocera and 24 species of Copepoda have been identified. The majority of rotifer species are monogononts, with bdelloids represented by Rotaria sp. only. Lecane (with 19 taxa), Trichocerca (15) and Brachionus (11) are the most speciose genera, with many species cosmopolitan. The most frequently observed genera were Keratella, Brachionus, Polyarthra, Trichocerca, Asplanchna, Conochilus, Ploesoma, Ascomorpha and Pompholyx. Daphniidae (10 species) and Chydoridae (11) were the two rich cladoceran families. Bosmina tripurae, Bosminopsis deitersi, Diaphanosoma orghidani, D. dubium, Moina micrura, Ceriodaphnia cornuta and C. quadrangula were most frequent in the pelagic zone. In addition, 10 calanoid and 14 cyclopoid species of copepods occurred. Most of the Calanoida are endemic to the tropics and subtropics in China. Phyllodiaptomus tunguidus, Neodiaptomus schmackeri, Mesocyclops thermocyclopoides and Thermocyclops taihokuensis were most frequently recorded. In the year 2000, total abundance of zooplankton varied from 11 to 290 ind./L during the period of June to July. Zooplankton was much more abundant in mesotrophic than in oligotrophic and eutrophic reservoirs. Rotifera numerically predominated in nine reservoirs and Copepoda in six reservoirs. The relative abundance of Brachionus, Trichocerca and Asplanchna increased and the ratio of Calanoida to Cyclopoida decreased with trophic level. Reservoir trophic state and predation were the most direct factors regulating zooplankton abundance and the dynamics of community structure. However, it was also found that hydraulic retention time affected the response of the zooplankton community structure to eutrophication. In reservoirs with long or short retention times, zooplankton showed no apparent variation across seasons. In reservoirs with intermediate retention time, in contrast, the zooplankton community changed significantly with trophy.