Phytoplankton functional groups in a high spatial heterogeneity subtropical reservoir in China

Traditional classification of phytoplankton assemblages does not adequately reflect their ecological function in aquatic ecosystems. Therefore, we used a functional group approach based on the Q index to analyze the spatial and temporal patterns, environmental factors and the ecological status of phytoplankton in the Danjiangkou Reservoir (DJKR) of China in July 2011 to April 2012. Groups B (Cyclotella species), C (Asterionella formosa and Cyclotella meneghiniana), D (Stephanodiscus hantzschii, Synedra acus and Nitzschia sp.), Lo (mainly Peridiniopsis spp.), P (Fragilaria capucina and Aulacoseira spp.) and Y (Cryptomonas ovata and Cryptomonas erosa) were classified as dominant phytoplankton functional groups. We ran redundancy analysis and Pearson correlation analysis to assess the relationship between functional groups and environmental factors. Total phosphorus, pH and soluble silicate were apparently the key factors driving variation in phytoplankton functional groups. The analyses suggest P-limitation of phytoplankton growth. The Q index based on functional groups indicated the relatively good ecological status of the DJKR which varied as a function of the mixing regime; most samples were scored as medium or high quality according to the Q index evaluation (Q > 2). This is the first application of the assemblage index to a water supply reservoir for the Middle Route Project (MRP) for South-to-North Water Transfer (SNWT) in China.