[Spatiotemporal Variations of Chlorophyll a and Its Relationship to Environmental Factors in Shiyan Reservoir].

The spatial-temporal characteristics of chlorophyll a concentration[(Chla)] were analyzed in Shiyan Reservoir, based on the monthly monitoring data from April 2013 to June 2014. The correlation between (Chla) and key environmental factors were also studied using correlation analysis and canonical correspondence analysis.The results showed that (TChla) was 9.59-123.29 μg·L, with an average of 52.03 μg·L. The (Chla) of cyanobacteria was 4.54-76.30 μg·L, with an average of 28.39 μg·L. The (Chla) of bacillariophyta was 3.16-46.09 μg·L, with an average of 15.02 μg·L. The (Chla) of chlorophyta was 0.77-26.2 μg·L, with an average of 8.62 μg·L. Cyanobacteria was the primary species from April to December in 2013 and May, June in 2014 while bacillariophyta was the primary species in other months. The spatial heterogeneity of (Chla) was unconspicuous and (Chla) decreased gradually from south to north. There was a risk of algal blooming for the whole reservoir during flood season and south part of reservoir in autumn. The storm runoff pollutant washout was the leading cause of the spatial heterogeneity of (Chla) in Shiyan Reservoir. Analysis revealed that water temperature was the most important driving factor for seasonal succession of phytoplankton. Significant correlation was found between (Chla) and surface runoff in flood season. TN:TP was negatively related to phytoplankton biomass and phosphorus was the restrictive factor for phytoplankton. Cyanophyta were affected water temperature, TOC, TN, pH, transparency, turbidity and NO-N. However silicate, TOC, NO-N, and COD were the main environmental factor of bacillariophyta while TOC, COD, pH, transparency and NO-N were the main factor of chlorophyta.