Seasonal succession of phytoplankton community and its relationship with environmental factors of North Temperate Zone water of the Zhalong Wetland,in China

A data set of phytoplankton community and environmental parameters in a hydrological integrity period, i.e. a poor water term, a medium term and a rich water term of North Temperate Zone climate, was analyzed in order to describe seasonal variation of phytoplankton community and its relationship with environmental variables in the Zhalong Wetland of China. The algal population of the Zhalong Wetland was not abundant, with a mean density of 5.08 × 10⁷ cell/L (ranged from 4.54 × 10⁷ cell/L in a poor term to 5.56 × 10⁷ cell/L a medium term). However, its diversity was essentially limited to Cryptophyta, Bacillariophyta, Chlorophyta, Euglenophyta being the group with highest densities. There were considerable seasonal variations in phytoplankton composition. In general, the dominance of Bacillariophyceae was found in a medium term, which was higher than the other period (p < 0.05). The rich water period also showed Bacillariophyceae and Chlorophyta dominance while the phytoplankton was dominated by Cryptophyta erosa in a poor water term. 10 environmental variables, which were significant (p < 0.05) during the studied periods in one-way analysis of covariance, were selected to explore the relationship between phytoplankton structure and environmental factors by canonical correspondence analysis (CCA). The results of the CCA applied to the environmental factors indicated that water temperature (WT) and ammonia (NH₃-N) significantly influenced the phytoplankton community (p < 0.05; Monte Carlo test of first constrained axis). Besides WT and NH₃-N, the most discriminate physic-chemical variables were nitrite (NO₂-N), suspend solid, nitrate (NO₃-N), silicon dioxide (SiO₂) and all the 10 physical–chemical parameters had a higher marginal effect and λ_A in the series of constrained CCAs though they were not significant.