Structure And Migration Patterns Of The Phytoplankton Community At Dashahe Reservoir

To improve the understanding of the mechanism and process of water eutrophication, it is necessary to know the phytoplankton species structure and the impact of multiple environmental factors to them. This is helpful to prevent and control the occurrence of water bloom, and to provide important reference to reservoir water quality management. In this study, we conducted continuous monitoring on Dashahe Reservoir in Jiangmei, Guangdong monthly from September 2012 to August 2014. We investigated the phytoplankton species structure in Dashahe Reservoir, and explored the impact of multiple environmental factors to the species with multivariate method. During August 2014(wet season) and December 2014(dry season), we performed 24 hour continuous monitoring to figure out the phytoplankton migration patterns and the main influence factors to them in Dashahe Reservoir. Our research results are concluded as the following:1. A total of 77 phytoplankton genera belonging to 7 phyla were identified. Specifically, 33 genera of them belong to Chlorophyta. 19 genera are classified to Bacillariophyta, 15 from Cyanophyta, and the others account for only a small proportion, which are from Pyrrhophyta, Euglenophyta and Chrysophyta.2. The seasonal variation of species composition generally followed a pattern that Cyanophyta and Chlorophyta were dominated in winter, the amount of Chlorophyta and Bacillariophyta increased in spring, and that Cyanophyta was dominated in summer and autumn.3. The diurnal variation of species is remarkable in the wet season. Specifically, from 8:00 to 14:00, and from 22:00 to 2:00, phytoplankton in the upper layer migrate downward. From 14:00 to 22:00, and from 2:00 to 6:00, phytoplanktons migrate upward. In the dry season, the migration pattern is different. From 8:00 to 10:00, and from 18:00 to 2:00, phytoplankton in the upper layer migrate downward, while from 10:00 to 18:00, and from 2:00 to 8:00, they migrate inversely.4. The seasonal variation of species is mostly affected by temperature. The diurnal variation of species influenced by light and dissolved oxygen. In the wet season, it is also influenced by ammonia nitrogen, while in the dry season, temperature is the dominant factors that affect the species composition.