Ammonia 1 Biochemical oxygen demand 1 Biological integrity 1 Biological integrity index China 1 Dissolved oxygen 1 Drought 1 Dry and wet 1 Dry periods 1 Ecosystem health assessment 1 Ecosystems 1 Gehu Lake 1 Health 1 Hydrological period 1 Integrity indices 1 Jiangsu 1 Lakes 1 Nitrogen 1 Phytoplankton 1 Quality control 1 Redundancy 1 Redundancy analysis 1 Water quality 1 Water quality factor 1 Wet period 1 Yangtze Delta 1 community dynamics 1 environmental factor 1 index method 1 phytoplankton 1