Abstract: An in situ experiment was conducted to study the population growth performance and productivity of protozoa community under two different industrialized grouper larval rearing systems. In the bacteria-added group, 13 new species of protozoa were recorded, and the total population density and the total biomass of protozoa community were 87.3×10³ ind·L^-1 and 502.9 mg·m^-3; in the microalgae-added group, there were 9 new species derived, and the total population density and the total biomass of protozoa community were 60.8×10³ ind·L^-1 and 70.3 mg·m^-3, respectively. For these two groups, Phyllomitus sp., Strobilidium gyrans, and Oxytricha sp. were the dominant species. The species with relatively high population growth rate in the bacteria-added group were Strombidinopsis sp. (0.0578),Halteria sp. (0.0493), Cyclidium litomesum (0.0405), Actinophrys sp. (0.0383), and Mesodimium sp. (0.0373), and those in the microalgae-added group were Lacrymaria sp. (0.0153), Strobilidium gyrans (0.0144), Strombidium sp. (0.0117) and Phyllomitus sp. (0.0100). The total protozoa community productivity varied with rearing-system, being 10.232 mg·m^-3·h^-1 in bacteria-added group and 1.22 mg·m^-3·h^-1 in microalgae-added group. In bacteria-added group, Euplotes eurystoma, Strobilidium gyrans, Amoeba sp., and Oxytricha sp. had higher productivity than other species; and in microalgae-added group, the species with relatively higher productivity were Actinophrys sp., Strobilidium gyrans, Phyllomitus sp., and Mesodimium sp. Overall, the ponds with bacteria added had more abundant diversity, higher biomass, and population growth rate of protozoa community than the ponds with microalgae added, and hence, the water culturing regime with bacteria added could attain more live preys during the mouth-opening period of grouper fry. In the cultured water, some species had high population growth rate, but their biomass was not large. The density of these species in breeding ponds was controlled by large zooplanktons, indicating that these plankton species probably played an important role in the balance of artificial ecosystem in the cultured water.

Key words: Apis cerana cerana, Habitat, Interspecific competition, Colony distribution