Environmental Variability and its Impact on Phytoplankton Communities in Taiwan's Aogu Wetland

Abstract

The Aogu Wetland Forest Park in Taiwan, a vital ecological hotspot within the East Asian-Australasian Flyway, faces significant threats from anthropogenic activities, agricultural runoff, and climate variability. This study integrated multiple analytical approaches, including Hierarchical Cluster Analysis (HCA), Canonical Correspondence Analysis (CCA), and Generalized Additive Mixed Models (GAMMs), to investigate the spatial and temporal variability of phytoplankton communities across six sites over an eight-year monitoring period (2015–2023). Phytoplankton diversity, assessed using Shannon–Wiener and Margalef indices, revealed distinct patterns driven by environmental gradients, with diversity indices ranging from 0.06 (DS2, May) to 2.21 (CS, July). HCA grouped sites into distinct clusters based on nutrient dynamics and salinity, indicating the influence of site-specific conditions. CCA identified ammonia (NH₄-N), nitrate (NO₃-N), temperature, and salinity as the most significant environmental drivers affecting genera-level distributions. GAMM analyses further quantified nonlinear interactions between phytoplankton abundance and key parameters, such as total dissolved solids (TDS), total phosphorus (TP), NH₄-N, and NO₃-N, providing detailed insights into how these factors vary across seasons and sites. The dominance of Cyanobacteria during colder months, with an average winter temperature of 27.8 °C, indicates the heightened risk of harmful algal blooms associated with nutrient enrichment. Seasonal dynamics showed that warmer summer months intensified the effects of nitrate and total phosphorus, driving site-specific phytoplankton proliferation. Adaptive wetland management strategies, including enhanced hydrological connectivity, nutrient runoff reduction, and targeted restoration, are essential to mitigate eutrophication and sustain ecological resilience. This approach provided practical insights for balancing conservation goals with ecosystem services in one of Taiwan’s key wetlands.