Radiation dimming and decreasing water clarity fuel underwater darkening in lakes  

辐射变暗和透明度降低共同加剧湖泊水下变黑

作　　者：Yunlin Zhang Boqiang Qin Kun Shi Yibo Zhang Jianming Deng Martin Wild Lin Li Yongqiang Zhou Xiaolong Yao Miao Liu Guangwei Zhu Lu Zhang Binhe Gu Justin D.Brookes 张运林;秦伯强;施坤;张毅博;邓建明;Martin Wild;Lin Li;周永强;姚晓龙;刘淼;朱广伟;张路;Binhe Gu;Justin D.Brookes(Taihu Laboratory for Lake Ecosystem Research,State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,China;University of Chinese Academy of Sciences,Beijing 100049,China;Institute for Atmospheric and Climate Science,Zurich CH-8001,Switzerland;Department of Earth Sciences,Indiana University-Purdue University,Indianapolis IN 46202,USA;Soil and Water Science Department,University of Florida,Gainesville FL 32611,USA;Water Research Centre,Environment Institute,School of Biological Science,University of Adelaide,Adelaide 5005,Australia)

机构地区：[1]Taihu Laboratory for Lake Ecosystem Research,State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]Institute for Atmospheric and Climate Science,Zurich CH-8001,Switzerland [4]Department of Earth Sciences,Indiana University-Purdue University,Indianapolis IN 46202,USA [5]Soil and Water Science Department,University of Florida,Gainesville FL 32611,USA [6]Water Research Centre,Environment Institute,School of Biological Science,University of Adelaide,Adelaide 5005,Australia

出　　处：《Science Bulletin》2020年第19期1675-1684,M0004,共11页科学通报（英文版）

基　　金：supported by the National Natural Science Foundation of China(41621002,41790423,41930760);the Key Program of the Chinese Academy of Sciences(ZDRW-ZS2017-3-4);the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(QYZDB-SSW-DQC016)。

摘　　要：Long-term decreases in the incident total radiation and water clarity might substantially affect the underwater light environment in aquatic ecosystems.However,the underlying mechanism and relative contributions of radiation dimming and decreasing water clarity to the underwater light environment on a national or global scale remains largely unknown.Here,we present a comprehensive dataset of unprecedented scale in China’s lakes to address the combined effects of radiation dimming and decreasing water clarity on underwater darkening.Long-term total radiation and sunshine duration showed 5.8%and 7.9%decreases,respectively,after 2000 compared to 1961–1970,resulting in net radiation dimming.An in situ Secchi disk depth(SDD)dataset in 170 lakes showed that the mean SDD significantly decreased from 1.80±2.19 m before 1995 to 1.28±1.82 m after 2005.SDD remote sensing estimations for 641 lakes with areas≥10 km^2 showed that SDD markedly decreased from 1.26±0.62 m during 1985–1990 to 1.14±0.66 m during 2005–2010.Radiation dimming and decreasing water clarity jointly caused an approximately 10%decrease in the average available photosynthetically active radiation(PAR)in the euphotic layer.Our results revealed a more important role of decreasing water clarity in underwater darkening than radiation dimming.A meta-analysis of long-term SDD observation data from 61 various waters further elucidated a global extensive underwater darkening.Underwater darkening implies a decrease in water quality for potable water supplies,recession in macrophytes and benthic algae,and decreases in benthic primary production,fishery production,and biodiversity.人类活动和气候变化造成到达地表太阳辐射降低(即辐射变暗)和水体透明度下降,两者共同作用深刻影响到水生生态系统水下光环境.全国116个太阳辐射观测站和839个日照时数观测站长期观测数据显示,2000年之后年均地表太阳辐射和日照时数比20世纪60年代分别下降了5.8%和7.9%,呈现显著下降趋势.与此同时,20世纪80年代和2006~2010年两次全国湖泊调查和历史文献数据分析发现,170个湖泊透明度平均值由1995年之前的1.80±2.19 m下降到2005年之后的1.28±1.82 m,遥感反演发现641个面积大于10 km2的湖泊透明度平均值由1985~1990年的1.26±0.62 m降低到2005~2010年的1.14±0.66 m.辐射变暗和透明度降低共同造成全国湖泊平均真光层深度范围内可利用的光合有效辐射量降低10%左右,并且透明度降低对湖泊水下光合有效辐射降低的贡献超过80%.文献综合分析进一步显示,全球湖库、海湾和近海水体均普遍存在透明度下降,水下变暗甚至变黑的事实,其势必深刻影响到水生生态系统各种物理、化学和生物过程以及生物多样性、生态系统服务功能和服务价值.

关 键 词：Radiation dimming Underwater darkening Secchi disk depth Remote sensing Aquatic ecosystems 

分 类 号：P343.3[天文地球—水文科学]