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引用本文:张运林,秦伯强,朱广伟.过去40年太湖剧烈的湖泊物理环境变化及其潜在生态环境意义.湖泊科学,2020,32(5):1348-1359. DOI:
ZHANG Yunlin,QIN Boqiang,ZHU Guangwei.Long-term changes in physical environments and potential implications for the eco-environment of Lake Taihu in the past four decades. J. Lake Sci.2020,32(5):1348-1359. DOI:
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过去40年太湖剧烈的湖泊物理环境变化及其潜在生态环境意义
张运林, 秦伯强, 朱广伟
中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室, 南京 210008
摘要:
过去40年,全球气候变暖、辐射变暗和变亮、风速减弱、气候异常波动等自然环境变化以及筑坝建闸、岸堤硬质化和调水引流等强烈人类活动势必会深刻改变太湖湖泊物理环境和过程,驱动湖泊生态系统演化.基于历史文献、档案数据以及气象水文和透明度等长期观测数据,本文系统梳理了太湖气温、水温、风速、水位和透明度等物理环境空间分布和长期变化特征,探讨了气温和风速、水位和透明度相互协同作用机制及其潜在生态环境意义.受全球变化和城市化等影响,过去40年太湖气温和水温呈现显著升高趋势,而近地面风速则表现为持续下降,湖泊增温和风速下降有利于藻类生长和蓝藻水华漂浮聚集,某种程度上增加了蓝藻水华出现频次和集聚的面积.为防洪和满足流域日益增长的水资源需求,闸坝管控和调水引流使太湖水位呈现缓慢增加趋势,而入湖污染物增加和富营养化则造成水体透明度逐渐下降,致使透明度与水位(水深)的比值明显降低,减少了湖底可利用光强,恶化水下光环境,在一定程度上驱动了太湖水生植被和草型生态系统退化.湖泊物理环境长期变化逐渐拓展了太湖藻型生境空间而压缩了草型生境空间,加剧了草型生态系统向藻型生态系统转化和增强了藻型生态系统的自我长期维持.太湖湖泊物理环境的显著变化也会部分抵消流域营养盐削减和湖体营养盐下降对藻类生物量和蓝藻水华的控制,增加了太湖蓝藻水华防控和湖泊富营养化治理的难度.这意味着未来流域控源截污需要更加严格的标准,而湖泊水位等物理环境的有效管控是应对藻华加剧和恢复草型生态系统的适应性管理策略.
关键词:  长期观测  物理环境  藻类水华  水生植被  湖泊增温  水位  透明度  太湖
DOI:
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基金项目:国家水体污染控制与治理科技重大专项(2017ZX07203)和国家自然科学基金项目(41930760,41621002,41771514)联合资助.
Long-term changes in physical environments and potential implications for the eco-environment of Lake Taihu in the past four decades
ZHANG Yunlin, QIN Boqiang, ZHU Guangwei
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China
Abstract:
The global environment has experienced rapid changes over the past four decades, including global climate warming, radiation dimming and brightening, wind stilling, and abnormal climate fluctuations. Meanwhile, strong human activities such as dam construction, bank hardening and water diversion and drainage have happened in Lake Taihu catchment. All these changes of natural environments and human activities have profoundly reshaped the physical environments and processes of Lake Taihu, which have further strongly driven the evolution of lake ecosystem structure and function. Based on historical literatures and documents, as well as long-term observations of meteorology, hydrology and Secchi disc depth (SDD), this study aims to systematically explore the spatial distribution and long-term change characteristics of physical environment in Lake Taihu, such as air temperature, water temperature, water level, wind speed and SDD. Meanwhile, we will elucidate the synergistic effects of air temperature and wind speed, water level and SDD and their potential ecological environmental significances for algal bloom outbreaks and aquatic macrophytes loss. Due to the global changes and rapid urbanization, the air temperature and water temperature of Lake Taihu have been increasing continuously in the past 40 years, while the wind speed near the ground has been decreasing continuously. Lake warming and decreasing wind speed facilitate the growth of algae and the floating accumulation of cyanobacteria bloom, which to some extent increases the observation frequency and area of cyanobacteria bloom. In order to control the flood and meet the increasing demand of water resources in the basin, the water level of Lake Taihu is increasing slowly due to dam control and water diversion. However, the increase of pollutants entering the lake and the development of eutrophication gradually decrease SDD. Therefore, the significant decrease of the ratio of SDD to water level (water depth) was observed in Lake Taihu, which significantly decreased the available light intensity at the bottom of the lake, and deteriorate the underwater light environment. All these changes have resulted in the loss of aquatic macrophytes and greatly driven the degradation of macrophyte-dominated ecosystem in Lake Taihu. The long-term changes of lake physical environment have gradually expanded the algae habitat space of Lake Taihu, compressed the macrophyte habitat space, accelerated the shift from a clear macrophyte-dominated state to a turbid algal-dominated state, and enhanced the long-term maintenance of algal-dominated ecosystem. Therefore, our findings highlight the importance of long-term physical environment monitoring data for deeply understanding ecosystem response to global climate change and human activities. The profound changes in physical environment has also partially offset the control of algal biomass and cyanobacteria bloom caused by the reduction of nutrients in the basin and the decrease of nutrients in the lake, which will increase the difficulty of prevention and control of cyanobacteria bloom and lake eutrophication in Lake Taihu. This means that in the future, more strict standards are needed for controlling pollution and nutrients, and the effective control of lake physical environment such as water level is the adaptive management strategy to deal with the aggravation of algal bloom and the restoration of macrophyte-dominated ecosystem.
Key words:  Long-term observations  physical environment  algal bloom  aquatic macrophytes  lake warming  water level  Secchi disc depth  Lake Taihu
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