Combined effects of nutrient loadings and warming on algal blooms in a plateau lake: Dianchi, China
摘要
Under the influence of anthropogenic activities and global warming, imbalanced nutrient inputs (specifically the total nitrogen (TN):total phosphorus (TP) ratio in loading inputs for lake restoration) and lake warming are becoming crucial factors influencing algal blooms. Yet their effects on lake eutrophication are not fully understood. Here, we applied the PCLake+ model to investigate the interactive effects of nutrient loading, nutrient imbalance (varied TN:TP ratios in loading inputs), and surface warming on eutrophication of Lake Waihai, the biggest part of Lake Dianchi, which has experienced long-term eutrophication under significant anthropogenic and natural disturbances. Results showed that increasing TN:TP ratio from 5:1 to 15:1 accelerated algal growth, resulting in a 33.1% increase in chlorophyll-a (Chl-a) concentration during summer. Rising annual lake temperatures (from 16.87 ℃ to 18.09 ℃) promoted algal biomass accumulation, leading to a 30.9% increase in Chl-a concentration during summer. The combined effects of high TN:TP ratio (≥ 15:1) and elevated water temperature (annual average of 18.09 ℃) exhibited antagonism in high-nutrient-input conditions (TP ≥ 1.47 mg·m−2·d−1) but synergism under low-nutrient-input scenarios (TP < 1.09 mg·m−2·d−1). These findings suggest that global warming and elevated TN:TP ratios could significantly hinder lake restoration efforts, highlighting the urgency of reducing nitrogen inputs to mitigate the negative impacts on lake ecosystems in a warming climate.