Aquatic EcoHealth Group, Key Laboratory of Urban Environment and Health, Fujian Key Laboratory of Watershed Ecology, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Sci Total Environ. 2020 Jun 15;721:137684. doi: 10.1016/j.scitotenv.2020.137684. Epub 2020 Mar 5.
Deep high-altitude mountain lakes can act as a natural laboratory, and have the potential to contribute ecological data for understanding the way natural climate and anthropogenic changes that can affect the ecosystems. We present a multi-proxy record from a sediment core from such a lake (Lake Lugu) in southwest China with emphasis on the changes in the testate amoebae community, along with sedimentological data (magnetic susceptibility, total organic carbon/TOC and total nitrogen/TN) over the last 2500 years. In total, 29 testate amoebae species belonging to eight genera (Arcella, Centropyxis, Cyphoderia, Difflugia, Netzelia, Phryganella, Pseudodifflugia and Zivkovicia) were identified. Three stages were clearly defined for the lake based on testate amoebae community. The first stage dated to about 500 BCE-800 CE, with the testate amoebae community dominated by Centropyxis and influenced by soil erosion. The second stage (about 800-1920 CE) was characterized by a gradual increase of TOC and TN and an abrupt shift from Centropyxis-dominated to Difflugia-dominated communities. The third stage (about 1920-2010 CE) showed the pronounced impact of environmental change, high proliferation of Difflugia and a strong influence of human activities. Our results suggest that the testate amoebae assemblages in this high-altitude mountain lake are sensitive paleoenvironmental indicators that can help to monitor alpine lake ecosystem change and model lake succession under changing climate and environment. The potential causes of changes in the testate amoebae species composition and three stages of Lake Lugu succession were soil erosion and pollutants. The soil erosion led to the inwash of terrestrial particles and few testate amoebae species into Lake Lugu showing the importance of stochastic processes. The nutrient enrichment from soil erosion generated disturbances in the environment and species competition that led to the proliferation of some species and disappearance of others through niche based deterministic processes.
深高山湖泊可以作为一个天然实验室，并有潜力为了解自然气候和人为变化如何影响生态系统提供生态数据。我们展示了来自中国西南部这样一个湖泊（泸沽湖）的沉积物岩芯的多代用记录，重点是有壳变形虫群落的变化，以及过去 2500 年来的沉积学数据（磁化率、总有机碳/TOC 和总氮/TN）。总共鉴定出 29 种有壳变形虫，属于 8 个属（Arcella、Centropyxis、Cyphoderia、Difflugia、Netzelia、Phryganella、Pseudodifflugia 和 Zivkovicia）。根据有壳变形虫群落，该湖明显分为三个阶段。第一阶段可追溯到大约公元前 500 年至公元 800 年，有壳变形虫群落以 Centropyxis 为主，受土壤侵蚀影响。第二阶段（约公元 800-1920 年）的特点是 TOC 和 TN 逐渐增加，Centropyxis 为主的群落突然转变为 Difflugia 为主的群落。第三阶段（约公元 1920-2010 年）显示出环境变化的显著影响，Difflugia 的大量繁殖以及人类活动的强烈影响。我们的结果表明，这种高山湖泊中的有壳变形虫组合是敏感的古环境指标，可以帮助监测高山湖泊生态系统变化，并在气候变化和环境变化下模拟湖泊演替。泸沽湖演替的三个阶段和有壳变形虫物种组成变化的潜在原因是土壤侵蚀和污染物。土壤侵蚀导致陆地颗粒和少数有壳变形虫物种进入泸沽湖，显示出随机过程的重要性。土壤侵蚀产生的养分富集会对环境造成干扰和物种竞争，导致一些物种的繁殖和其他物种的消失，这是通过基于生态位的确定性过程实现的。
