气候变化可以诱导全球富营养化湖泊中的浮游植物水华(PBs),这些水华严重威胁着湖泊生态系统和人类健康。然而,目前还不清楚城市化及其与气候的相互作用如何影响PB,这对湖泊的管理有影响。这里,我们使用多源遥感数据,并结合虚拟基线浮动巨藻高度(VB-FAH)指数和OTSU阈值自动分割算法来提取滇池的PB面积,中国,在其附近经历了频繁的PB和快速的城市化。我们进一步探讨了PB的物候和严重程度指标的长期趋势(2000-2021年),并量化了城市化的贡献,气候变化,以及这些趋势的营养水平。在比较2011-2021年至2000-2010年的数据时,我们发现PB的启动显着提前(28.6天)和明显更长的持续时间(51.9天),但消失时间的趋势不明显。提高藻类养分利用效率,可能是由水温升高和养分浓度降低引起的,推测是导致PBs的更早启动和更长持续时间的原因,春季风速与PBs的开始呈负相关。幸运的是,我们发现,无论是地区的面积和严重的水华(覆盖超过19.8平方公里)的频率表现出下降的趋势,这可能归因于风速增加和/或营养水平降低。此外,城市化引起的地表温度升高改变了土地和湖泊之间的热力学特征,which,反过来,可能导致当地风速和水温升高,这表明城市化可以不同地调节PBs的物候和严重程度。我们的发现对于理解城市化对PB动态的影响以及改善湖泊管理实践以促进全球变化下的可持续城市发展具有重要意义。
Climate change can induce phytoplankton blooms (PBs) in eutrophic lakes worldwide, and these blooms severely threaten lake ecosystems and human health. However, it is unclear how urbanization and its interaction with climate impact PBs, which has implications for the management of lakes. Here, we used multi-source remote sensing data and integrated the Virtual-Baseline Floating macroAlgae Height (VB-FAH) index and OTSU threshold automatic segmentation algorithm to extract the area of PBs in Lake Dianchi, China, which has been subjected to frequent PBs and rapid urbanization in its vicinity. We further explored long-term (2000-2021) trends in the phenological and severity metrics of PBs and quantified the contributions from urbanization, climate change, and also nutrient levels to these trends. When comparing data from 2011-2021 to 2000-2010, we found significantly advanced initiation of PBs (28.6 days) and noticeably longer duration (51.9 days) but an insignificant trend in time of disappearance. The enhancement of algal nutrient use efficiency, likely induced by increased water temperature and reduced nutrient concentrations, presumably contributed to an earlier initiation and longer duration of PBs, while there was a negative correlation between spring wind speed and the initiation of PBs. Fortunately, we found that both the area of the PBs and the frequency of severe blooms (covering more than 19.8 km2 ) demonstrated downward trends, which could be attributed to increased wind speed and/or reduced nutrient levels. Moreover, the enhanced land surface temperature caused by urbanization altered the thermodynamic characteristics between the land and the lake, which, in turn, possibly caused an increase in local wind speed and water temperature, suggesting that urbanization can differently regulate the phenology and severity of PBs. Our findings have significant implications for the understanding of the impacts of urbanization on PB dynamics and for improving lake management practices to promote sustainable urban development under global change.