洱海蓝藻爆发的时空特征及影响因子

湖泊生态环境对区域气候变化和流域人类活动十分敏感。随着流域的持续开发,洱海作为云贵高原第二大淡水湖泊面临着严重的生态与环境问题,主要包括水质恶化和生态功能的衰退,其中蓝藻水华问题尤为突出。针对湖泊现代监测数据存在时间序列较短、连续监测记录缺乏、监测位点不完全一致等问题,应用沉积物记录开展色素等多指标分析和环境变化重建研究,并对洱海湖区南、中、北3个湖盆的沉积物记录进行对比分析,从而探讨洱海富营养化与蓝藻爆发的历史与变化特征,并识别藻类响应模式的空间异同。沉积物色素记录结果表明,洱海蓝藻生物量变化具有明显的时空差异性,呈现由南至北,先后增加、最后呈现蓝藻水华全湖性持续爆发的模式。进一步的简约模型方差分解结果表明气候变暖和营养盐富集是洱海蓝藻生物量变化的主要驱动因子,此外相对较浅的南部湖盆还受到水位波动、水动力减弱、水生植物演化的综合影响。因此,在气候变暖的背景下,控制水体营养盐输入、合理调控湖泊水位、提高水体透明度并恢复水生植物是控制洱海蓝藻水华爆发和进行生态恢复的重要措施。

Spatio-temporal patterns and drivers of cyanobacteria blooms in Erhai Lake, Southwest China

Lake environments and ecosystems are known to be sensitive to climate change and human activities. Erhai, a large plateau lake (~250 km²), is characterized by complicated lake morphometry and has experienced multiple environmental stressors (such as eutrophication, water regulation, etc.) over the past few decades. These have led to the deterioration of its water quality and loss of ecosystem resilience, where cyanobacteria blooms have frequently occurred since the 1990s. To uncover the long-term history and spatio-temporal pattern of cyanobacterial blooms in Erhai Lake, multi-proxy analyses of lake sediments from three different parts of the lake basin were conducted and compared. Based on the high-resolution sedimentary pigment data from each core, we found that there existed a strong asynchrony in the long-term changes of algal production among the cores. The significant increase of cyanobacterial pigments in the shallower southern part of the basin started from the late 1980s, earlier than those of the central and northern parts of the lake basin (~1990 and 2000, respectively), with the whole-basin showing cyanobacteria blooms starting from ca. AD 2000. Furthermore, minimum adequate models built to explain the changes in the pigment concentration in the sediments, suggests that climate warming and eutrophication were the main factors that led to the cyanobacteria blooms across the lake basin.In addition, cyanobacteria bloom for the southern part of the lake basin was also related to the water-level fluctuation, hydrodynamics, and macrophyte changes over the last few decades. Overall, our sedimentary records showed that there existed strong heterogeneity in the spatio-temporal patterns of cyanobacterial blooms and the driving factors also varied across space and over the last century in Erhai Lake.. Therefore, taking the current global warming scenario into account, control of both nutrient input and water regulation should be highlighted for ecological restoration and sustainable management of Erhai Lake