滇西北地区高山湖泊沃迪错近两百年来环境变化及枝角类群落响应

区域增温和大气氮沉降作用已成为高山湖泊面临的重要环境胁迫,已有高山湖泊生物群落响应的长期模式研究主要集中于藻类而缺乏更高营养级生物(如浮游动物)的系统调查。本研究选择滇西北地区深水型的高山湖泊沃迪错开展沉积物调查,通过多指标分析(总氮、总磷、叶绿素a、氮稳定同位素等)并结合区域气候重建记录,识别近两百年来该湖泊及流域环境的变化历史,进一步利用枝角类群落指标(物种组成、生物量等)定量评价了湖泊生物群落的响应模式与驱动因子。结果表明,湖泊营养水平(如总氮浓度)和初级生产力(叶绿素a浓度等)在过去近两百年总体呈上升趋势。相关分析显示,大气氮沉降和流域外源输入是影响总氮上升的主要因素,同时区域增温和营养盐富集促进了湖泊初级生产力的不断上升。自1960s以来区域升温明显,湖泊营养水平和叶绿素a浓度呈现加速上升的趋势。钻孔中枝角类群落以浮游属种(Daphnia longispina等)为优势种,在1900AD以前D.longispina相对丰度较为稳定(40.83%±8.02%),之后出现下降趋势且在1948—1965年间明显下降,之后再次明显上升并成为主要优势种。排序分析显示,气温、叶绿素a和总...

Environmental changes and cladoceran community responses during the past 200 years in an alpine lake of Wodi Co, Northwest Yunnan

Climate warming and atmospheric deposition have become the main environmental stressors for alpine lakes, however, the long-term response of biotic community in alpine lakes has been predominantly derived from algae rather than from biota at higher trophic levels (e.g., zooplankton). Here, a deep-water alpine lake, i.e., Wodi Co, was selected for a paleolimnological survey through multi-proxy sediment analyses (total nitrogen (TN), total phosphorus (TP), chlorophyll-a (Chl.a), stable isotopes of nitrogen, etc.) in combination with published records on regional climate change. With the historical reconstruction on the changes in lake and catchment environment, cladoceran remains were analyzed for taxonomic composition and production in quantifying the temporal pattern of community responses and environmental drivers in this alpine lake over the past two centuries. The time series showed that the nutrient level (e.g., TN) and primary productivity (i.e., Chl.a) generally showed a temporal trend of continuous increase. Correlation analysis showed that atmospheric nitrogen deposition and exogenous organic matter input were the main factors for the increase in TN, while both climate warming and nutrient enrichment led to a continuous increase of lake primary production. Since the 1960s there was an obvious warming of regional climate, meanwhile there was an accelerating increase in both lake nutrient level and Chl.a concentration. Regarding the sediment cladoceran assemblages, the planktonic species was found to be the dominant taxa such as Daphnia longispina. The relative abundance of D. longispina was relatively stable (40.83%±8.02%) before 1900 AD, but it decreased noticeably from 1948 to 1965 before it increased again and became the dominant species more recently. The Ordination analysis showed that, climate change, variation of nutrient level (TN) and Chl.a concentration were the main driving factors for the cladoceran community change before 1960s, thereafter, lake-water nutrition level (TN) and primary productivity became the main factors in driving cladoceran community shifts. In all, this study reveals the long-term effects of regional climate, atmospheric deposition and catchment surface processes on zooplankton communities in alpine lake and its stronger coupling with algae more recently. These findings can help evaluate key processes in driving ecological and environmental changes, and predict the future trajectories of their responses in alpine lakes under global change.