The Spatial Evolution Characteristics of Phytoplankton and the Impact of Environmental Factors in a Harbor-Construction-Formed Reservoir

Phytoplankton are an important part of aquatic ecosystems and substantially contribute to primary productivity. Under certain conditions, phytoplankton can grow or cluster in large numbers, resulting in enormous economic losses and serious threats to human life and health. In this study, complex causative species of algal blooms were examined and regulatory factors were determined in a reservoir formed by harbor construction. The reservoir is isolated from the harbor by sluice gates, forming a separate water region. Twelve species of phytoplankton, including normally and abnormally blooming species, were identified to be causing blooms in this continuous water. Different from the areas where simple algae caused blooms, multiple bloom-causative species, which were completely different, occurred at several stations. In this study area, whereas the abundance of algal cells was above 10 million cells/L, the total phosphorus concentration was higher than 0.2 mg/L. When the total phosphorus concentration was lower than 0.2 mg/L, there was no algal bloom. In waters with total algal cell abundance over 10 million, the N/P ratios were all ˂8. This study indicates that the occurrence of algal blooms in this water was influenced by the concentrations of total nitrogen and phosphorus, and total phosphorus plays a more important role.