Dynamics Of Phytoplankton Community And Its Relationship With Environmental Factors In Three Large Reservoirs For Drinking Water Supply, Guangdong Province

To know phytoplankton community and its relationship with environmental factors in three reservoirs, Gaozhou reservoir, Nanshui reservoir and Dashahe reservoir, we monthly investigated phytoplankton community structure and environmental factors from January to Desember in 2010. Correlation analysis and Canonical correspondence analysis are used for exploring the relationship between phytoplankton comminuty and environmental factors.The average total nitrogen concentration in Gaozhou, Nanshui and Dashahe reserivors were less than 1 mg/L. Total nitrogen concentration was higher in dry season than in wet season. Total phosphorus concentration in Dashahe and Gaozhou reserviors were higer in dry season than in wet season, and it was low without seasonal dynamics in Nanshui reservoir.Eighty seven taxons in 7 phylas were identified in the three reservoirs. Chlorophyta contributed to most phytoplankton species in Dashahe and Gaozhou reservoirs. Most species of phytoplankton belonged to Bacillariophyta and Chlorophyta in Nanshui reservoir.Cyanophyta dominated the phytopalnkton assemblage from March to Apirl and Chlorophyta dominated in wet season in Gaozhou reservoir. Anabaena mucosa and Microcystis flos-aquae were the predominant species from January to May and Cosmarium sp. staurastrum sp. and Cyclotella sp. were predomomant species in the other periods. Chlorphyta dominated phytoplankton assemblage from June to September and Cyanophyta dominanted phytoplankton assemblage in the other period in Dashahe reservoir. Staurastrum sp. was the predominant species from June to September but Microcystis sp. in the other periods. Bacillariophyta and Chlorphyta were dominant classes in Nanshui reservoir, and Cyclotella sp. and Melosira sp. were the predominant species.The environmental factors primarily regulating the dynamics of phytoplankton community were different between three reservoirs. In Gaozhou Reservoir, Canonical correspondence analysis showed that nitrate concentration was the most important factor for determing Cyanophyta abundance, while Chlorophyta abundance was mainly affected by water temperature. Conductivity and phosphate concentration were the main environment factors structuring the phytoplankton community in Nanshui reservoir; Ammonium, phosphate concentrations and conductivity were the critical environment factors for structuring phytoplankton community in Dashahe reservoir.Low precipitation, low water level and storage capacity, and decreasing water transparency and temperature Gaozhou reservoir in dry season, contributed to Anabaena mucus turning into the dominant species and forming cyanobacterial blooms. In flood season, increase of precipitation resulted in high water level, and thermal stratification occurred in water column. Microcystis flos-aquae dominated the phytoplankton community gradually replacing Anabaena mucus, the blooms finally disappeared with a dramatic decrease of total cyanobacteral biomass.