Affiliations: Donghu Experimental Station of Lake Ecosystems, State
Key Laboratory for Freshwater Ecology and Biotechnology of China, Institute of
Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China | Nanjing Institute of Geography and Limnology, Chinese
Academy of Sciences, Nanjing 210008, China
Abstract: Effects of Microcystis blooms on the crustacean plankton were
studied using enclosure experiments during July–September, 2000. Eight
enclosures were set in the hypereutrophic Donghu Lake. Different nutrient
concentrations through additional nutrient and sediment in enclosures were
expected to result in different abundance of Microcystis. From July to early
August, the phytoplankton community was dominated by Chlorophyta, Cryptophyta,
Bacillariophyta and Cyanophyta other than Microcystis aeruginosa. M. aeruginosa
showed a rapid increase during early August in all enclosures and predominated.
Crustacean plankton was dominated by the herbivorous Moina micrura,
Diaphanosoma brachyurum and Ceriodaphnia cornuta, and the predaceous
Mesocyclops sp. and Thermocyclops taihokuensis. During the pre-bloom period,
the dynamics of M. micrura population appeared to be mainly affected by the
predaceous cyclopoids. With the development of Microcystis blooms, such
interaction between M. micrura and cyclopoids seemed weakened, especially when
the Microcystis biomass was high. But there was no apparent influence on the
interaction between Leptodora kindti and its zooplanktonic prey. The density of
two cyclopoids decreased with the enhancement of Microcystis. The density
decline of M. micrura was caused by both predation and inhibition by
Microcystis. The low food availability of other edible phytoplankton during the
blooms led to low densities of both C. comuta and D. brachyurum by late August.
lt appears that dense Microcystis blooms exert strong negative effects on the
herbivorous cladocerans and the predaceous cyclopoids.
