Convergence And Divergence Of Phytoplankton Communities In Succession: An Enclosure Experiment

A community is considered a biological unit of an ecosystem. Its assembly is an essentialand dynamic issue in community ecology study. However, the pattern of community assemblyremains controversial. One viewpoint holds that there is a consistent match between theenvironment and community. Species composition should converge towards the certainconfiguration in a system with similar environmental (or ecological) conditions. The alternativeview holds that historical sequences should be considered in community assembly and differenthistorical sequences of populations occurring in a community can lead to final distinctcommunity compositions.Phytoplankton is the main primary producer in pelagic water. All the species are sensitive toexternal conditions because of their small size and high reproductive rate. Phytoplanktoncommunities can be easily affected by disturbances that result in succession. Therefore, thephytoplankton is an ideal model for community succession study.In the present thesis, an enclosure experiment system (fifteen enclosures) was designed andconducted, comprising three treatments (control, nutrient enrichment and fish stocking) inLiuxihe Reservoir, Guangdong Province. Each treatment had five replications. Three, four orfive replications are randomly selected in each treatment for data analysis. The results showedthat the successions of phytoplankton communities are very similar in spite of the differentreplication number used in the treatment for data analysis. That means the succession ofphytoplankton community converge and three replications are enough for community studyalthough the standard error became lower when the more replications were used. That impliesthe accuracy can be improved by increasing the number of replications. In addition, nutrientenrichment and fish stocking also led to a lower standard error in this experiment. It can beinferred that enrichment and fish stocking tend to facilitate convergence in the succession ofphytoplankton communities.