Phytoplankton and Zooplankton Community Dynamics in an Alpine Reservoir: Environmental Drivers and Ecological Implications in Daqing Reservoir, China

To elucidate the structural characteristics and environmental drivers of plankton communities in alpine reservoirs, we examined phytoplankton and zooplankton in the Daqing Reservoir (China) across 13 sampling sites. Redundancy analysis (RDA) and Pearson correlation analysis were employed to explore the relationships between plankton density and environmental factors, as well as between plankton diversity indices and environmental conditions. Key findings include: (1) A total of 80 phytoplankton species were identified, with Chlorophyta (37 species) as the dominant group, while 52 zooplankton species were primarily represented by Rotifera. (2) Phytoplankton diversity indices (Shannon: 3.07–4.21) suggested oligotrophic conditions, whereas zooplankton indices (Shannon: 1.40–3.08) indicated meso- to oligotrophic states. (3) RDA analysis revealed that phytoplankton distribution was influenced by chemical oxygen demand and total phosphorus, while zooplankton distribution was related to ammonia nitrogen. These results highlight the importance of targeted nutrient management strategies to protect water quality in alpine reservoirs.