Climate-nutrient-morphology interactions drive algal blooms in Chinese lakes

Algal bloom proliferation in lakes has become a core manifestation of global aquatic ecosystem degradation, with their occurrence mechanisms driven by the interplay of multiple factors including climate change, human activities, and lake morphology. However, the combined effects of "climate-nutrient-morphology" on lake algal bloom remain unclear. To systematically reveal the spatiotemporal patterns and interactive effects of algal blooms in Chinese lakes, this study utilized multiple-source data from 1985 to 2019. Our results showed that algal bloom frequency remained high in lakes north of 35°N latitude (average bloom occurrence rate of 7.42 %), demonstrating algal adaptation to cold environments. The advancement of algal bloom phenology is associated with short-term fluctuations in water temperature and increased lake water temperature and agricultural inputs of nitrogen and phosphorus fertilizers collectively exacerbates the risk of algal bloom outbreaks. Moreover, the moderating effect of lake morphology can partially reduce algal bloom risk. This study clarifies the multi-threshold coupling mechanism of lake algal blooms and further reveals the regulatory capacity of lake morphology against climate and nutrient stress, providing scientific basis for establishing differentiated management strategies and zoned early warning systems.