Metazoan zooplankton communities in a tropical eutrophic reservoir: Henggang Reservoir, Guangdong

Metazoan zooplankton was sampled in the Henggang Reservoir, a hypertrophic reservoir in Guangdong Providence in May and November of 2005. The results showed that the zooplankton was characterized by a few species with low abundance. 4 species of cladocera, 4 species of adult copepod and 17 species of rotifer were observed. The total species number in May and November was 15 and 20, respectively. Rotifer was the most common group. The mean relative abundances of rotifer in May and November were 82.8% and 78.8% respectively. The dominant species were Asplanchna priodonta, Brachionus calyciflorus and Brachionus diversicornis. Copepod was a less common group; its mean relative abundances in May and November were 16.6% and 19.9%, respectively. Copepod was composed mainly by nauplii and copepodid. Phyllodiaptomus tunguidus was the common species in adult copepod. Cladocera was the least common group; its mean relative abundances in May and November were only 0.6% and 1.3% respectively. Moina marocopa was the common species in this group. The composition, abundance and biomass of zooplankton had tempo-spatial heterogeneity in the reservoir. The mean abundance was 242.6 ind. ·L-1 in May and 138.5 ind. ·L-1 in November. The mean biomass was 0.912mg·L-1 in May and 0.317 mg·L-1 in November. The abundance and biomass of zooplankton tend to decrease from riverine to lacustrine, corresponding to the morphology and hydrodynamics of Henggang Reservoir. Compared with other waters, the high abundance of Asplanchna priodonta in Henggang Reservoir lead to higher biomass of zooplankton than other tropical eutrophic lakes, such as Xinghu Lake, which had similar zooplankton abundance. However, both abundance and biomass of zooplankton in Henggang Reservoir were far lower than those temperate eutrophic reservoirs.