Impact of Environmental Factors on the Distribution Characteristics of Phytoplankton Functional Groups in Beijing

Rapid urbanization has significantly influenced urban aquatic ecosystems, with impacts manifested primarily in phytoplankton communities. However, the mechanisms driving the spatiotemporal dynamics of phytoplankton functional group (FGs) dynamics within megacities remain limited. In this study, Chaoyang District in Beijing was selected as the research site, the spatial-temporal patterns of physicochemical parameters, phytoplankton density, and FGs across 17 sites in summer and autumn were investigated. 116 species spanning 7 phyla and 57 genera were identified. Phytoplankton density peaked in autumn (4.7 × 107 cells L-1) versus summer (3.5 × 107 cells L-1), driven by Bacillariophyta dominance (58.5-61.9%). Synedra sp. and Microcystis sp. were perennial dominants (dominance: 0.4-0.9). Nutrient gradients governed FG succession: COD and TP peaked in summer (34.7 and 0.5 mg L-1), while inorganic nitrogen surged in autumn (TN: 3.4 mg L-1, NH4+-N: 1.4 mg L-1) due to temperature-mediated shifts in nitrogen cycling. The Redundancy analysis and partial least squares path modeling suggested that NH4+-N was the primary driver of FG dynamics (β = 0.6, p < 0.01), with water temperature indirectly modulating communities via nutrient cycling. This study presents an FGs-based framework to guide water use management and ecological resilience in rapidly developing cities.