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引用本文:钱福明,张恺,陈光杰,尹永鑫,王教元,胡葵.云南杞麓湖沉积物记录的近现代生态环境变化及影响因子识别.湖泊科学,2018,30(4):1109-1122. DOI:10.18307/2018.0423
QIAN Fuming,ZHANG Kai,CHEN Guangjie,YIN Yongxin,WANG Jiaoyuan,HU Kui.Sediment-inferred recent pattern and drivers of environmental and ecological changes at Lake Qilu, Yunnan Province. J. Lake Sci.2018,30(4):1109-1122. DOI:10.18307/2018.0423
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云南杞麓湖沉积物记录的近现代生态环境变化及影响因子识别
钱福明1, 张恺1, 陈光杰1,2, 尹永鑫1, 王教元1,2, 胡葵1,2
1.云南师范大学旅游与地理科学学院, 昆明 650500;2.云南师范大学高原地理过程与环境变化云南省重点实验室, 昆明 650500
摘要:
随着云南社会经济的持续发展与极端气候事件的频发,高原大中型湖泊面临着水质恶化、生态与环境功能退化的长期胁迫.为识别亚热带大型湖泊面临的主要环境压力,以杞麓湖为研究对象,在对沉积物钻孔进行物理(粒度、烧失量)、生物(色素、硅藻)等指标分析的基础上,结合现代监测和湖泊调查数据,重建了近两百年来湖泊水文条件、富营养化和环境变化的历史,并对硅藻群落结构的演化进行了驱动过程识别.沉积物粒度在1958年之前变化总体较为稳定且有较高的黏土含量;随着围湖造田等流域开发的增强,沉积物粒度组成自1960s开始频繁波动且粗颗粒组分快速增加.1981-2000年期间,随着落水洞泄水工程的修建杞麓湖的水位控制与水文调控得到加强,沉积物砂质含量降低且粒度组成变化较小;2000-2013年期间,湖泊疏浚工程的开展和区域降水的持续减少都导致了沉积物粒度组成波动较大、粗颗粒组成较高.沉积物色素记录了湖泊初级生产力的缓慢上升出现于19世纪中后期,并自1960s开始总叶绿素与蓝藻色素含量总体出现了较大幅度的增加趋势并持续至今.而在2000-2005年期间,湖泊浅水区的疏浚清淤导致了内源营养盐输入量的降低与藻类生物量的明显下降;沉积物蓝藻色素含量在1998、2008和2012-2013年左右出现明显的峰值,指示杞麓湖可能出现了较大范围的蓝藻暴发事件.统计分析结果显示,湖泊硅藻群落结构出现了多次明显转变且呈现底栖硅藻百分比长期降低的特征,水体富营养化的持续是驱动硅藻群落结构演替的主要因子,而水生植物退化、水文条件与气候变化也对硅藻群落的构建产生了重要的叠加影响.本文的沉积物分析结果表明,亚热带大型湖泊的生态治理与环境保护需要重点围绕营养盐负荷控制、水文调控优化与底栖生境恢复,并需应对全球变暖与极端气候事件产生的叠加影响.
关键词:  杞麓湖  湖泊沉积物  藻类色素  硅藻  富营养化  水文调控
DOI:10.18307/2018.0423
分类号:
基金项目:国家重点研发计划项目(2017YFA0605202)、国家自然科学基金项目(41771239,U1133601,41171048)、教育部科学技术研究项目(213034A)和云南师范大学施源大学生科技创新基金项目联合资助.
Sediment-inferred recent pattern and drivers of environmental and ecological changes at Lake Qilu, Yunnan Province
QIAN Fuming1, ZHANG Kai1, CHEN Guangjie1,2, YIN Yongxin1, WANG Jiaoyuan1,2, HU Kui1,2
1.School of Tourism & Geography, Yunnan Normal University, Kunming 650500, P. R. China;2.Provincial Key Laboratory of Plateau Geographical Processes & Environmental Change, Yunnan Normal University, Kunming 650500, P. R. China
Abstract:
With the socio-economic development and increased occurrence of extreme climate, many lakes in Yunnan Province have experienced severe threats such as water quality deterioration and degradation of ecological and environmental functioning. To identify the main environmental stressors threatening the subtropical large and shallow lakes, we conducted multi-proxy sediment analyses for Lake Qilu, including the application of physio-chemical (grain size, nutrients) and biological (pigments, diatoms) indicators. Combined with modern meteorological monitoring and lake survey data, we reconstructed a two-century history of hydrodynamic changes, cyanobacteria bloom and lake eutrophication, and identified the driving factors for the succession in diatom community structure. The composition of sediment grain sizes generally remained stable until 1958 with a relatively high content of fine clays before showing frequent fluctuations and a rapid increase of coarse particles after the 1960s. The construction of a catavothre draining project led to a stronger control of water level and hydrological fluctuation in Lake Qilu, resulting in a smaller magnitude of grain size fluctuation and a lower content of sandy components during the period of 1981-2000. More recently, both lake dredging and a continuous decrease of regional precipitation caused strong fluctuations of grain size components and a higher content of sandy sediments. The sediment pigment content, an indicator for lake production, increased slowly since the middle 19th century before showing an accelerating trend after the 1960s. During the period of 2000-2005, the dredging of the shallow lake basin significantly decreased the nutrient release from lake sediments, resulting in an abrupt drop of algal production. The spike of cyanobacterial pigments may suggest the existence of massive cyanobacterial blooming in Lake Qilu around the years of 1998, 2008 and 2012-2013. Multivariate analyses further showed that diatom community composition has significantly shifted several times with a sustained decreasing trend in the percentage of benthic diatoms. While nutrient enrichment played a major role in structuring diatom assemblages over time, the anthropogenic regulation of lake hydrology and habitat availability were also found to synergistically affect the community succession of diatoms. Our multi-proxy results revealed that a combination of increased nutrient control, reduced hydrological regulation and enhanced climate mitigation should be applied altogether for sustainable management and ecological restoration of subtropical large lakes in Southwest China.
Key words:  Lake Qilu  lake sediments  algal pigments  diatoms  eutrophication  hydrological regulation
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