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Published on: December 19, 2019
Multi-component dissolved gas dynamics as early warning indicators for algal bloom development in the three gorges
Chenyu Wei1, Dian Li2, Hao Li3
1State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan 430072, China; Hubei Field Observation and Scientific Research Stations for Water Ecosystem in Three Gorges Reservoir, China Three Gorges University, Yichang 443002, Hubei, China.
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Harmful algal blooms (HABs) threaten global freshwater ecosystems, yet reliable early warning indicators remain elusive, as traditional nutrient and temperature models often fail to capture the metabolic transition to explosive proliferation. This study investigates multi-component dissolved gas dynamics (O₂, CO₂, N₂, Ar, and TDG) as novel early warning indicators that directly reflect algal physiological activity rather than static environmental conditions, thereby bridging the gap between favorable conditions and bloom realization. We conducted continuous in-situ monitoring in the Pengxi River of the Three Gorges Reservoir, China, across five periods between 2023 and 2024. The results revealed three sequential gas-based indicators reflecting bloom progression. First, the Argon-Oxygen (Ar-O₂) correlation shifted from positive to negative, signaling the transition to algae-favorable conditions where photosynthetic oxygen production overrides temperature-driven solubility controls. Second, Photosynthetic Quotient (PQ) spikes exceeding 1.5 revealed cryptic subsurface algal accumulation before significant surface biomass appeared. Third, Total Dissolved Gas (TDG) supersaturation exceeding 105% marked a biophysical tipping point where micro-bubble formation accelerated bloom intensification through buoyancy-mediated aggregation. Unlike static environmental parameters, these gas dynamics directly reflect algal physiological activity and spatial distribution. Critically, the PQ‑spike stage defines the optimal intervention window, enabling reservoir operations to disrupt subsurface accumulation before surface manifestation and TDG‑driven escalation. Integrating these dissolved gas patterns into existing frameworks bridges the gap between environmental favorability and actual bloom occurrence. Our mechanism-based framework offers a transformative pathway for proactive HAB management in reservoir systems worldwide under intensifying climate pressures.
