Species diversity and community structure of rotifers in pelagic zones of seven reservoirs,Hainan Province

Hainan Province is at a tropical zone in South China.Zooplankton diversity there has rarely been investigated.In order to collect basic data and understand the community structure of rotifers in Hainan Province,seven typical reservoirs were sampled in December of 2006 and May of 2007.32 species were identified,among which the majority was eurythermal or mesophilic species. In the two sampling periods,the dominant species and their relative dominance in abundance varied between different reservoirs, almost all the dominant species were small sized ones with armor.The dominant species were Brachionusforficula and Brachionus falcatus in the early flood season and Filinia camasecla in the late dry season.The average abundance and biomass of rotifers were 66.8ind./L and 21.61μg/L,respectively,which both were lower than those in the subtropics and temperate zones.In general,the rotifers were characterized by low species diversity,small body size and low abundance.Although the relative abundance of the dominant rotifers varied slightly between the dry and flood seasons,the consistent species composition indicates that the rotifers keep a steadily community structure in the tropical reservoirs.