, 陈光杰, 陈小林, 陈丽, 黄林培, 刘园园, 施海彬, 胡葵, 王教元, 康文刚云南师范大学旅游与地理科学学院高原地理过程与环境变化云南省重点实验室,昆明 650500
Long-term pattern of diatom community responses to water pollution and hydrological regulation in Yangzong Lake
TAOJianshuang, CHENGuangjie, CHENXiaolin, CHENLi, HUANGLinpei, LIUYuanyuan, SHIHaibin, HUKui, WANGJiaoyuan, KANGWengang通讯作者:
收稿日期:2016-04-7
修回日期:2016-07-4
网络出版日期:2016-10-26
版权声明:2016《地理研究》编辑部《地理研究》编辑部
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1 引言
持续增强的流域活动使得云南部分湖泊面临着水体富营养化与重金属污染的胁迫,导致了湖泊生态环境功能明显降低。阳宗海是云南省九大高原湖泊之一,为流域开发与社会经济持续发展提供了水源供给、渔业养殖、休闲旅游等重要的生态系统服务功能[1]。自然状态下湖泊的富营养化过程是极为缓慢的,但由于强烈的人类活动干扰,大量的污染物通过地表径流和点源排放等进入湖泊水体,加快了湖泊富营养化的进程和生态系统的演化,导致了蓝藻暴发等严重的环境问题。近年来,随着流域的大规模开发与工农业的迅速发展,阳宗海面临着富营养化和蓝藻暴发等胁迫[2,3]。同时,2008年6月阳宗海经历了严重的砷污染事件,导致了水质明显恶化并带来了居民健康、饮用水源等公共安全问题。大量研究表明,水体富营养化和重金属污染等环境压力会导致湖泊生物多样性的降低和湖泊生态系统稳定性的下降[4-6]。针对阳宗海水体砷污染的水质变化特征、砷的分布与迁移、健康风险评价等已有大量研究[1,7,8]。湖泊砷污染不仅是一个重要的全球公共健康问题[9],同时砷等重金属污染还会带来潜在的生态风险[10]。在生态风险评价上,徐永梅等通过水体砷浓度和藻类数量、种群数据的研究,发现阳宗海砷污染导致了藻类种群与数量的突变[11]。同时,砷等重金属污染物也能够通过食物链的传递过程在鱼类、水生植物等体内产生富集作用[12],从而危及生态系统的健康。目前针对阳宗海的生态评价主要以短时间尺度的水体监测和室内实验为主,缺乏长期和连续的湖泊监测资料,难以揭示阳宗海生物群落对不同类型污染物的长期响应特征与生态系统健康的变化模式。湖泊沉积物记录了连续的环境变化信息,可忠实地反映湖泊生态环境变化的历史与主要过程。因此,古湖沼学方法能够弥补湖泊研究中长期监测数据的不足,开展沉积物的多指标分析能够重建水体环境与生物群落变化的过程[13]。如沉积物物理、化学指标能够反映湖泊水文条件与营养状况的变化历史[14,15],生物群落指标能够反映湖泊生态系统的演化过程并用于长期的生态评价[16]。硅藻是湖泊水体中常见的淡水藻类,具有生命周期短、物种多样性高、能够快速响应环境变化等特征,由于其硅质组分使得硅藻壳体能较好地保存在湖泊沉积物中,因此硅藻已成为指示湖泊环境与生态变化的主要生物指标之一[17,18]。硅藻不仅能够有效地指示湖泊富营养化过程[19],其群落结构及形态特征对重金属污染的水体也十分敏感[20,21],如耐污染硅藻物种丰度的增加能够反映污染物质的输入增 加[20,22]。近年来沉积物硅藻记录已经被应用于云南湖泊的生态环境研究中,包括滇池[23]、星云湖[24]、洱海[25]、抚仙湖[26]、泸沽湖[27]等,然而已有研究主要集中于生物群落对湖泊富营养化以及气候变化的响应特征上,缺乏对重金属污染等其他环境压力的叠加影响与生态响应模式等过程的探讨。
拟应用沉积物记录开展阳宗海生态与环境变化的多指标分析,评价近百年来不同类型环境压力对硅藻群落结构的长期驱动影响,并比较其驱动强度的异同。结合湖泊监测数据与历史文献资料,在提取沉积物硅藻群落、砷浓度、营养元素与稳定同位素信号、粒度等记录的基础上,重建近百年来阳宗海水环境变化的历史,识别硅藻群落结构长期变化的特征和主要时段,诊断硅藻群落对湖泊污染的响应模式和生态系统的变化特征,可为阳宗海的综合治理与生态修复提供重要的科学依据和数据积累。
2 研究区概况与研究方法
2.1 研究区概况
阳宗海位于昆明市主城区以东30 km,属南盘江水系。湖区属亚热带高原季风气候,年平均气温14.5 ℃,流域面积192 km2,湖泊面积31.7 km2,海拔1770.8 m,最大水深30.0 m,平均水深19.5 m,主要入湖河流有阳宗河、七星河以及摆依河,湖东北汤池河为唯一出水口[3,28]。阳宗海是流域内主要的农业、工业、渔业及饮用水水源地,过去几十年来经历了多次水利改造,并出现了水质恶化的长期趋势。1960年,阳宗海水量减少、水位下降,经人工水渠引摆依河河水入阳宗海。1965年,摆依河入阳宗海的引水工程重新改造,渠道长2.3 km,最大引洪量增加到7 m3/s,平均年引水量2000万m3,1983年最多引水2700万m3。近几十年来,阳宗海周边新建了大量的工矿企业（大型火电厂、化肥厂、水泥厂、冶炼厂等）及旅游设施[29],同时流域土地利用强度的增加都导致了湖区承载的污染物总量逐渐增加,出现了明显的富营养化特征。阳宗海水质在1992年前总体能达到地面水质一类或二类标准[30],如1957年黎尚豪等对阳宗海的综合调查结果显示水体硝酸态氮、磷酸盐磷含量较低（部分水体低于检测限）,透明度可达6 m[31]。然而随着生活污水和工业废水的排放、网箱养鱼等影响的持续增强,1997-1998年阳宗海多次出现大面积水华现象,反映了20世纪90年代开始水体营养盐逐渐升高[30],湖水总体处于四类水质水平[32]。2002-2012年,阳宗海水体富营水平持续上升,且2006-2007年富营养化过程尤为明显[33]。1994-2013年的水质监测数据对比发现（表1）[34-36],水体总磷（TP）、总氮（TN）呈现升高的趋势,而透明度则由4.7 m下降到了2.2 m。水体营养盐升高外,阳宗海的砷污染问题突出。2007年9月以前阳宗海湖水砷浓度均值不到6 μg/L,2008年9月份水体As浓度监测值高达128 μg/L,超出国家饮用水标准（10 μg/L）的12倍以上,砷污染浓度值超过国家五类水标准[7]。近年来随着湖泊治理力度的加大,阳宗海水体砷浓度有所降低,但仍超出国家饮用水标准5倍左右（表1）。
Tab. 1
表1
表1阳宗海水质参数对比[
Tab. 1Time series of water quality changes in Yangzong Lake
| 年份 | TN（mg/L） | TP（μg/L） | As（μg/L） | pH | 透明度（m） |
|---|---|---|---|---|---|
| 2013 | 0.56 | 38.8 | 54.3 | 8.1 | 2.2 |
| 2008 | 0.80 | 59.7 | 128.0 | - | 2.6 |
| 2005 | 0.49 | 11.1 | - | 8.7 | 2.4 |
| 1994 | 0.25 | 2.0 | - | - | 4.7 |
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2.2 湖泊现代调查与样品采集
2013年对阳宗海进行了湖泊水质与沉积物调查,利用重力采样器在湖泊深水区提取了沉积物钻孔（长度41 cm）,采样点水深为28 m（24.907oN、103.005oE,图1）。将提取的沉积物柱芯避光密封后,在野外进行钻孔分样并放置低温保存。钻孔0~5 cm深度按0.5 cm间隔分样,5 cm以下深度按1 cm间隔取样,利用冻干机将样品冻干并密封避光保存。水质调查结果显示,Chl-a含量为3.7 μg/L,TN为0.56 mg/L,TP为38.8 μg/L,NO3-、NO2-、NH4+分别为88.0 μg/L、19.6 μg/L、167.4 μg/L。
显示原图|下载原图ZIP|生成PPT图1阳宗海采样点
-->Fig. 1Coring site of Yangzong Lake
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2.3 样品处理与数据分析
2.3.1 实验室处理 沉积物钻孔年代学序列的建立是基于210Pb和137Cs两种放射性同位素来测定的[37]。利用美国Canberra公司生产的高纯锗探测器、数字化谱仪及多通道分析系统对样品放射性核素210Pb与137Cs进行测试分析,并应用恒定补给速率CRS模型建立年代学序列[38]。沉积物砷（As）浓度、叶绿素a（Chl-a）含量、δ13C、δ15N同位素以及元素含量的测定均采用的是沉积物全样样品。沉积物As浓度分析采用X Series II ICP-MS电感耦合等离子体质谱仪（Thermo Fisher Scientific,USA）测定,湖泊沉积物国家标准样品（GBW 07309）的分析误差为±5%。沉积物Chl-a分析在加拿大女王大学生物系John Smol实验室完成,测定方法采用可见光反射光谱法（即VRS-Chl-a）。同时应用Thermo MAT-253质谱仪与元素分析仪测定碳、氮稳定同位素（δ13C、δ15N）组成和元素含量（TC、TN）,测量精度分别为±0.15‰和±1.0%。沉积物As浓度及TC、TN与δ13C、δ15N稳定同位素分析均由福建师范大学完成。
沉积物粒度的分布特征使用英国Malvern公司生产的马尔文激光粒度仪（MS2000）进行测定,具体步骤包括：将样品在加热条件下经H2O2和HCl溶液处理后,加入蒸馏水并静置24小时,除去上清液,加入六偏磷酸钠分散剂,并经超声波震荡后上机测定,粒径结果分成<2 μm、2~63 μm、>63 μm以及中值粒径4个组分进行数据分析。
硅藻分析采用国际标准方法对沉积物样品进行预处理[39]。主要步骤包括：在沉积样品中加入10%HCl去除碳酸盐等矿物,加入30%H2O2并置于80℃的水浴锅水浴4小时以去除沉积物中以及硅藻细胞壁上的有机质,反应完全后以1200 rpm速度离心样品4 min,抽出上层液后加入蒸馏水混合并重复上述步骤4次,最后加入几滴甲醛溶液密封低温保存。将预处理完成的硅藻浓缩液滴至玻片上,完全干燥后用Naphrax?树胶进行制片。硅藻鉴定主要参照Krammer等的分类系统[40],并在莱卡生物显微镜（1000倍油镜）下完成硅藻鉴定和计数,在分类学上鉴定到物种水平。其中0~5 cm与5~30 cm深度的钻孔分别按0.5 cm、1 cm间隔进行样品处理与硅藻鉴定,30 cm以下按4 cm间隔鉴定。每个样品的硅藻计数控制在400~450粒,出现半个以上壳体计数为一粒,每个样品中计算每种硅藻的个数与硅藻总个数的比值来表示硅藻的相对丰度（即百分含量）,从而指示硅藻群落结构的变化。
2.3.2 数理统计 在硅藻地层序列分析中,选择硅藻百分含量大于5%的常见属种来识别主要物种的变化特征。进一步通过主成分分析（PCA）识别近百年来硅藻群落结构变化的主要方向,同时应用限制性聚类分析（CONISS）与断棍（Broken-stick）模型来判识硅藻种群组合显著变化的主要时段。对环境数据进行标准化处理,采用冗余分析（redundancy analysis,RDA）识别驱动硅藻群落变化的主要环境因子,同时保留P<0.05的环境变量,并检查方差膨胀系数,剔除膨胀因子大于20的变量,对剩余的环境变量开展简约模型选择,最终得到能够解释硅藻群落变化的显著环境变量。同时采用物种丰富度指数来指示硅藻群落的生物多样性水平,应用回归分析来识别硅藻生物多样性对环境因子的响应模式。在回归分析中,对物种数据与环境数据分别进行了正态分布检验;在多变量统计分析中,对群落与环境数据进行平方根与log10转换。统计分析均在R（2.14.0）软件中完成,地层图使用C2软件制图。
3 结果分析
3.1 年代序列
基于沉积物210Pb、137Cs活度和CRS模型建立的钻孔年代—深度模型显示,210Pb比活度随深度的增加呈递减趋势且在30 cm深度左右衰减到背景值（图2a）。137Cs是一种人工放射性核素,主要产生于20世纪50-70年代的大气层核试验并通过大气沉降进入地球环境,其中1963年的137Cs沉积量最大,在中国湖泊沉积物剖面中1963年附近的137Cs峰值具有年代标志意义[41]。阳宗海钻孔中137Cs的峰值出现在18.5~20.5 cm附近,其中20.5 cm对应1963年左右,即为全球大气中137Cs沉降较集中的时期,与CRS模型推算的年代基本一致（图2b）。沉积物岩芯底部向上至10.5 cm的沉积速率呈上升的趋势,10.5 cm至表层呈现一定的波动,其中10.5~6.5 cm（1990-1997年）呈升高趋势,在4.5~2.5 cm深度附近沉积速率明显降低。
显示原图|下载原图ZIP|生成PPT图2沉积物柱芯210Pb和137Cs比活度深度剖面图（a）与CRS测年结果、沉积速率（b）
-->Fig. 2Depth profiles showing the results of sediment unsupported 210Pb and 137Cs radio activities (a), as well as the CRS dating model and sedimentation rate (b)
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3.2 硅藻群落结构变化特征与主要时段
阳宗海硅藻群落总体以浮游物种为主（图3）,其中浮游优势种主要有Cyclotella ocellata、C. rhomboideo-elliptica、C. comta、C. stelligera、C. pseudostelligera、Fragilaria crotonensis及Aulacoseira ambigua,底栖硅藻主要有F. ulna var. acus和Achnanthes minutissima。硅藻群落的长期变化特征主要体现在浮游类型硅藻向底栖类型硅藻的转变,如在3.5 cm处浮游硅藻百分比减少,而在~2008年浮游硅藻减少了约55%、底栖硅藻百分比增加到60%左右。
显示原图|下载原图ZIP|生成PPT图3阳宗海硅藻优势属种（>5%）百分含量变化的沉积物地层图
-->Fig. 3Sedimentary profile showing the stratigraphic changes of dominant diatoms (> 5%) at Yangzong Lake
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根据限制性聚类分析和Broken-stick模型检验结果将硅藻群落划分为4阶段（图3）,硅藻群落分别在~1965年、~1986年、~2006年出现了明显的转变。钻孔深度20 cm以下（即~1965年以前）,硅藻群落结构相对稳定并以C. ocellata和F. crotonensis为主要的优势种,物种丰度均>25%,而贫营养种C. rhomboideo-elliptica占10%左右。1965-1986年期间,C. rhomboideo-elliptica物种丰度逐渐增加到70%左右,替代了C. ocellata和F. crotonensis成为主要的优势种。然而,C. rhomboideo-elliptica在12 cm处（~1986年）丰度骤降为<5%甚至完全消失,并且在12~3.5 cm深度（1986-2006年）之间C. ocellata和F. crotonensis再次成为优势种,A. ambigua也逐渐增加,而在3.5 cm至表层（2006-2013年）阶段,这三个硅藻种迅速消失且其他浮游种硅藻（如C. stelligera,Stephanodiscus hantzschii）也开始减少,同期耐金属污染种A. minutissima和F. ulna var. acus成为主要的优势种,其中A. minutissima百分含量达到50%以上。
主成分分析（PCA）与Broken-stick模型检验表明,硅藻群落数据的PCA第1和第2主轴在统计学上是显著的,且分别解释了硅藻群落结构变化的44.8%和32.7%（图4）。阳宗海主成分分析双标图显示,主轴1正方向主要有F. crotonensis、C. ocellata和A. ambigua,主轴1负方向主要有C. comta、C. pseudostelligera以及耐金属污染种硅藻F. ulna var. acus和A. minutissima。而主轴2正方向上主要分布为云南地方种C. rhomboideo-elliptica。综上,主轴1主要反映了浮游硅藻种和耐污染底栖种的变化,主轴2可能代表了贫营养种C. rhomboideo-elliptica与富营养种之间的替换。
显示原图|下载原图ZIP|生成PPT图4阳宗海硅藻PCA双标图
-->Fig. 4The PCA biplot of diatom community data for Yangzong Lake showing the first two axes
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3.3 环境驱动因子硅藻多样性响应模式的识别
为进一步识别驱动硅藻群落变化的主要环境梯度,将PCA样品点得分与沉积物的多个环境指标（如Chl-a、沉积物As浓度、粒度、δ13C、δ15N、TC、TN）进行了对比分析（图5）。硅藻PCA第1轴与第2轴得分反映了硅藻群落发生明显变化的主要阶段分别为2006-2013年和1965-1986年。~1986年以前阳宗海沉积物Chl-a变化比较稳定且含量偏低（2.5~8 μg/g）,~1986年以后其含量逐渐升高,最高值达96.2 μg/g。沉积物元素化学指标显示,TC和TN含量均在20世纪90年代开始明显增加,δ15N呈先增加后减小的趋势,而δ13C值与C/N比值整体出现波动减小的变化。其中,δ13C在表层的最低值为-23.3‰,随着钻孔深度的减少C/N比值由25降低到8左右,δ15N值的变化范围为5.2‰~9.4‰。通过对比沉积物的不同粒径大小发现,20世纪80年代以前中值粒径与粗颗粒粒径（>63 μm）呈稳定变化,20世纪80年代初均出现了第一次峰值;而20世纪90年代初开始,二者变现为波动增加的趋势。沉积物As浓度背景值（如~1950年以前）大约为30~40 μg/g,20世纪90年代初开始逐渐增加,并且在2007-2008年左右达到450 μg/g以上。
显示原图|下载原图ZIP|生成PPT图5沉积物多指标环境记录与硅藻群落PCA第1和第2轴得分的对比
-->Fig. 5Comparison of multi-proxy sediment records with diatom PCA axis 1 and 2 scores
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进一步对硅藻数据与环境数据进行独立的RDA分析与简约模型分析（表2）。RDA的置换检验结果表明除了δ15N的P值大于0.05以外,其余变量均表现为显著。通过简约模型结果得到3个显著的环境因子As、中值粒径和TN,分别解释了27.1%、21.8%、29.6%,三者共同解释了39.1%,环境变量未解释的比例为60.9%（图6）。
Tab. 2
表2
表2主要环境变量在独立RDA分析中的解释能力与简约模型结果
Tab. 2Summary of individual RDA analyses and variation minimum adequate model showing the explanatory power of key environmental variables
| 环境指标 | 解释能力（绝对值） |
|---|---|
| 中值粒径 | 0.236*** |
| 细颗粒粒径<2 μm | 0.285*** |
| 中颗粒粒径2~63 μm | 0.276*** |
| 粗颗粒粒径>63 μm | 0.211*** |
| δ13C | 0.204*** |
| δ15N | 0.031 |
| TC | 0.232*** |
| TN | 0.315*** |
| C/N | 0.283*** |
| As | 0.288*** |
| 简约模型结果：As +中值粒径+TN | 0.391** |
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显示原图|下载原图ZIP|生成PPT图6简约模型的方差分解结果（数值小于0的未显示）
-->Fig. 6Summary of variance partitioning results for key environmental variables included in the minimum model (Values <0 not shown)
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为了识别生物多样性对湖泊污染的响应模式,以沉积物色素Chl-a来代表湖泊系统生产力来识别生物多样性的响应模式,同时分析砷污染对生物多样性的影响过程。结果表明,系统生产力与物种丰富度呈现单峰模式（R2=0.34,P<0.001）,而物种丰富度与沉积物As浓度呈显著的负相关（R2=0.29,P<0.001）（图7）。
显示原图|下载原图ZIP|生成PPT图7硅藻物种丰富度响应沉积物Chl-a（a）和As浓度（b）变化的模式
-->Fig. 7Changes of diatom species richness in response to lake sediment Chl-a (a) and As (b), respectively
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4 讨论
4.1 湖泊富营养化的长期过程与硅藻群落响应特征
阳宗海沉积物地球化学指标指示了水体富营养化的长期过程,并且与湖泊监测记录显示的湖泊富营养化过程基本一致。~1965年以前,沉积物Chl-a、TN、TC以及δ15N稳定同位素呈现数值低且稳定变化的状态,表明此阶段阳宗海营养水平较低,与1957年黎尚豪等的水质调查结果一致[31]。1965-1986年期间,各项沉积物指标值有所波动但变化并不明显,而沉积物营养元素明显升高的时期为1986-2013年。首先,~1986年开始沉积物记录的Chl-a与TC含量显著增加,指示了营养水平上升促进了湖泊初级生产力的提高。其次,沉积物TN含量于20世纪90年代后呈波动增加的长期趋势（图5）,且1994-2013年期间阳宗海水体监测记录中的TP浓度升高了近20倍（表1）,二者都指示了水体营养盐长期累积并增加的过程。此外,研究表明随着湖泊富营养化过程的加剧,沉积物δ15N为逐渐上升的趋势[42],~1998年以前阳宗海沉积物δ15N也呈现上升的趋势,同样表明营养盐长期累积增加的过程;但~1998年后δ15N以及δ13C明显降低,这可能与1997-1998年期间阳宗海出现多次蓝藻大面积暴发的事件有关。同时近百年来,沉积物C/N比值出现稳步降低的长期变化特征,也指示了湖泊营养水平的持续升高导致了藻类的大量繁殖[43]。硅藻群落变化的时间序列总体反映了湖泊富营养化的长期驱动过程,同时水文调控等环境压力也对硅藻群落的演替产生了叠加影响。方差分解结果显示,TN作为营养水平的指标解释了硅藻群落结构长期变化的29.6%,表明营养水平总体驱动了硅藻群落结构的长期变化。其中,~1965年前阳宗海硅藻的主要优势种为C. ocellata和F. crotonensis,同时C. rhomboideo-elliptica百分含量为10%左右。研究表明硅藻对水体中营养水平有显著的指示作用,如C. ocellata是中—富营养湖泊中常见的硅藻种[44],而Li等在抚仙湖的研究中发现C. rhomboideo-elliptica在营养水平较低的水体中物种丰度较高[45]。因此,硅藻群落组合与沉积物多指标记录都反映了~1965年前阳宗海水质在此阶段总体处于贫—中营养水平,与1957年黎尚豪等[31]对阳宗海水体调查的结果一致。在1965-1986年期间,贫营养种C. rhomboideo-elliptica由10%左右突增到70%,但此时间段上沉积物指标显示湖泊营养水平相对于~1965年前并没有降低。而流域开发资料显示1965年摆依河调水工程完成并正式开通,调水入湖能够为河流硅藻物种的扩散提供一个生态通道,从而使得部分硅藻物种（如C. rhomboideo-elliptica）在数量上占据优势并改变湖泊硅藻群落的构成。已有研究表明湖泊硅藻群落结构会受到湖泊水文连通性的影响,如20世纪初抚仙湖湖水的倒灌直接导致了星云湖硅藻群落中C. rhomboideo-elliptica的突然增加[46]。因此阳宗海河流调水工程可能导致了硅藻群落的改变与C. rhomboideo-elliptica的大量增加,湖泊的水文调控可以为物种的扩散提供生态通道从而影响生物群落的构建与组成。
自~1986年开始,阳宗海硅藻群落的变化特征与该时间段内营养盐的持续升高基本同步。如C. ocellata和F. crotonensis成为主要的优势种、喜营养属种A. ambigua、S. hantzschhii、C. stelligera等逐渐增加,而贫营养种C. rhomboideo-elliptica基本消失。已有研究表明,A. ambigua与S. hantzschii是长江中下游常见的富营养化指示性物种[19],高山湖泊研究表明F. crotonensis的增加与水体中N的富集相关[47,48]。而A. ambigua不仅能指示营养盐的富集,同时其较高的沉降速率也使得该物种能够在水动力增加的条件下具有竞争优势[49]。阳宗海的硅藻记录中A. ambigua显著增加的时间开始于~1998年,与沉积物中值、粗颗粒粒径波动上升的变化趋势一致。方差分解结果表明中值粒径的变化可以解释硅藻群落演替的21.8%,表明了湖泊水动力的增强也对硅藻群落的演替产生了驱动影响。在长期的富营养化背景下,阳宗海硅藻群落总体呈现了贫营养种逐渐被喜营养物种替代的特征,同时湖泊的水动力变化也进一步影响了生物群落结构。
4.2 砷污染与硅藻响应模式
阳宗海沉积物忠实地记录了湖泊砷污染的过程,且硅藻群落在砷污染时期发生了明显的转变。如与~1950年前的背景值（30~40 μg/g）相比,2007-2008年左右沉积物As浓度达到450 μg/g以上。此外,耐金属污染硅藻种A. minutissima的大量出现与阳宗海As浓度急剧的增加一致。来自其他地区的现代调查表明,随着水体重金属污染的持续增加,部分硅藻属种（如Cyclotella spp.和F. crotonensis）迅速减少,而耐金属污染硅藻（如A. minutissima）迅速增加并成为优势种[21,50]。在阳宗海硅藻群落的研究中同样发现了类似的特征,即~2006年后浮游硅藻C. ocellata和F. crotonensis百分含量由40%左右迅速降低且富营养物种A. ambigua、S. hantzschii、C. stelligera也开始减少或消失。同时,随着As浓度达到峰值,沉积物的沉积速率与Chl-a含量均出现了一个低值,表明高浓度的砷污染可能对部分藻类产生了一定的抑制作用。已有监测记录与研究表明随着水体重金属浓度的增加,硅藻群落会从浮游种转变为耐污染的底栖种[21]。从底栖硅藻和浮游硅藻百分比（图3）来看,阳宗海浮游硅藻种类在~2006年开始减少,表明~2006年后砷污染对硅藻群落的驱动作用最强。方差分解结果表明近百年来沉积物As浓度是显著的独立环境因子,解释了硅藻群落结构变化的27.1%,揭示了近十年来阳宗海砷污染对湖泊生物群落演替的驱动作用。4.3 多重环境压力与硅藻多样性的响应模式
进一步对硅藻多样性变化的分析表明,阳宗海水体的富营养化与砷污染都对硅藻多样性产生了影响但驱动模式不尽相同（图7）。生物多样性指数是指示生态系统健康与稳定性的重要指标[51,52]。张民等对云贵高原湖泊夏季浮游植物组成及多样性进行了研究,发现浮游植物物种丰富度与TP、TN显著正相关,表明湖泊水体的营养水平会影响浮游植物的物种丰富度[53],而Japesen等研究发现物种丰富度与富营养化湖泊的营养水平呈现单峰关系[54]。阳宗海水体营养盐的升高使得藻类的可获得性资源增加,可直接促进硅藻物种丰富度的增加;然而当水体营养水平升高到一定水平时,一些贫营养型硅藻（如C. rhomboideo-elliptica）的适应性降低则会导致硅藻物种丰富度降低,因此在时间尺度上阳宗海的硅藻群落物种丰富度与系统生产力呈现单峰模式（图7a）。这与该地区贫营养和重富营养湖泊（如抚仙湖和滇池）硅藻群落多样性随系统生产力分别呈现增加和减少的长期模式相一致[55]。而在重金属污染的水体中,较强的生态毒性效应会导致敏感的硅藻物种数量减小甚至完全消失,另一方面耐金属污染硅藻种（如A. minutissima）可以获得明显的资源竞争优势并成为优势物种,最终导致物种丰富度的降低,从而出现了阳宗海硅藻物种丰富度与As浓度之间呈显著的负相关（图7b）。邓洪平等在嘉陵江的研究中也发现由于下游受到城市及工业污水的影响导致硅藻群落物种丰富度、多样性指数数值从上游到下游逐渐减小[6]。因此在长期的营养盐富集以及砷污染的胁迫下,阳宗海生物多样性的降低趋势与生物群落结构的变化总体同步,都指示了阳宗海生态系统可能随着砷污染事件发生了明显的转变。5 结论
沉积物记录多指标分析表明了近百年来阳宗海生态环境出现了明显的变化,硅藻群落的演替特征反映了湖泊富营养化、重金属污染与水文调控等多个环境压力对湖泊生态系统的长期影响。近几十年来,随着水体营养盐的持续输入以及湖泊藻类生物量、初级生产力的升高,阳宗海硅藻群落中贫营养种逐渐被喜营养物种所替代,硅藻物种丰富度呈现先增加后减少的长期响应模式。湖泊引水工程直接导致了贫营养种C. rhomboideo-elliptica的突然增加,但随着水体营养水平的持续升高而迅速减少甚至消失。同时,工业砷污染是导致硅藻群落结构突变的主要驱动因素,表现为耐金属污染硅藻种A. minutissima随着沉积物As浓度的升高而迅速增加,同时硅藻物种的丰富度明显降低。因此,在阳宗海长期富营养化和水文调控的背景下,水体砷污染物浓度达到一定阈值后生物群落会出现明显的结构转变和物种丰富度的持续降低。并且硅藻是反映不同类型人类活动驱动湖泊生态系统的敏感指标,基于沉积物记录的多指标分析可为污染湖泊的综合治理与生态修复提供重要的研究手段和基础数据。The authors have declared that no competing interests exist.
参考文献 原文顺序
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文中引用次数倒序
被引期刊影响因子
| [1] | . 为掌握2008年阳宗海砷（As）污染事件后控制与修复过程中水质特征及变化，对湖水As含量、pH值、电导率、总硬度等水质参数，以及底质As含量和生物残毒进行全程监测和分析评价。结果表明：阳宗海As污染事件后水质恢复历时28个月；阳宗海湖水As质量浓度经历了先上下波动、后持续下降再到稳定在0．05mg／L以下的变化过程；底泥中As的质量浓度经历了先迅速升高后大幅下降，再小幅上涨后又回落至21．5～27．0mg／L的变化过程；pH值、电导率及总硬度等参数受到一定影响，湖水中贝类等水生生物对As的富集能力较强。最后从管理角度提出了保护阳宗海水资源的措施。 为掌握2008年阳宗海砷（As）污染事件后控制与修复过程中水质特征及变化，对湖水As含量、pH值、电导率、总硬度等水质参数，以及底质As含量和生物残毒进行全程监测和分析评价。结果表明：阳宗海As污染事件后水质恢复历时28个月；阳宗海湖水As质量浓度经历了先上下波动、后持续下降再到稳定在0．05mg／L以下的变化过程；底泥中As的质量浓度经历了先迅速升高后大幅下降，再小幅上涨后又回落至21．5～27．0mg／L的变化过程；pH值、电导率及总硬度等参数受到一定影响，湖水中贝类等水生生物对As的富集能力较强。最后从管理角度提出了保护阳宗海水资源的措施。 |
| [2] | . 以近年来阳宗海水体TP、TN、高锰酸盐指数、透明度、水体中N、P比和水生生物特性等湖泊富营养化要素综合评价了阳宗海水体水质变化特征。在总结阳宗海污染控制取得阶段性成果的基础上，针对目前仍然存在的富营养化威胁，建议将恢复湖泊生态系统、控制内外污染源以及强化流域环境管理作为新的控制对策。 以近年来阳宗海水体TP、TN、高锰酸盐指数、透明度、水体中N、P比和水生生物特性等湖泊富营养化要素综合评价了阳宗海水体水质变化特征。在总结阳宗海污染控制取得阶段性成果的基础上，针对目前仍然存在的富营养化威胁，建议将恢复湖泊生态系统、控制内外污染源以及强化流域环境管理作为新的控制对策。 |
| [3] | . 通过对 1997～ 2 0 0 1年阳宗海水质监测资料的分析 ,采用秩相关系数检验法得出结果表明 :总磷、总磷这 5年呈下降趋势 ,而高锰酸盐指数变化不明显 ,富营养化的威胁仍然存在。 通过对 1997～ 2 0 0 1年阳宗海水质监测资料的分析 ,采用秩相关系数检验法得出结果表明 :总磷、总磷这 5年呈下降趋势 ,而高锰酸盐指数变化不明显 ,富营养化的威胁仍然存在。 |
| [4] | Summary 1. Submerged plant richness is a key element in determining the ecological quality of freshwater systems; it has often been reduced or completely lost.2. The submerged and floating-leaved macrophyte communities of 60 shallow lakes in Poland and the U.K. have been surveyed and species richness related to environmental factors by general linearised models.3. Nitrogen, and more specifically winter nitrate, concentrations were most important in explaining species richness with which they were inversely correlated. Phosphorus was subsidiary. Such an inverse relationship is consistent with findings in terrestrial communities. Polish lakes, with less intensively farmed catchments, had greater richness than the U.K. lakes.4. The richest U.K. communities were associated with winter nitrate-N concentrations of up to about 1–265mg65Land may correspond with ‘good’ ecological quality under the terms of the European Water Framework Directive. Current concentrations in European lowlands are often much higher. |
| [5] | |
| [6] | . 于2006年11月, 2007年2月、5月和8月, 分别采集嘉陵江下游8个采样点藻类样品, 分析其硅藻群落结构及物种多样性, 并利用物种多样性指数及硅藻商等对水质进行了生物学评价。结果表明: (1)共发现89种硅藻, 硅藻细胞密度变幅为0.57×104—4.51×104 ind/L, 总平均2.31×104 ind/L; 多样性指数值变幅为0.72—3.12, 总平均2.20; 均匀度指数值变幅为0.15—0.52, 总平均0.36; 硅藻商变幅为0.66—9.48, 总平均3.24。 (2)硅藻群落结构呈现出季节和水平分布上的变化。在季节变化上, 物种丰富度、细胞密度及多样性指数等以温度较低的春(5月)、秋(11月)两季最高, 而以夏季(8月)最低。在水平分布上, 从上游到下游, 硅藻群落结构呈现出物种丰富度、多样性指数值逐渐减小, 而细胞密度和硅藻商逐渐增加的趋势。(3)嘉陵江下游水质总体为β-中污水体。其中位于城市上游的云门、沙溪、温塘峡、井口水质较好, 为微污或β-中污水体, 而位于城区及下游的合川、毛背沱、磁器口和朝天门水质较差, 为α-中污或污染水体。 于2006年11月, 2007年2月、5月和8月, 分别采集嘉陵江下游8个采样点藻类样品, 分析其硅藻群落结构及物种多样性, 并利用物种多样性指数及硅藻商等对水质进行了生物学评价。结果表明: (1)共发现89种硅藻, 硅藻细胞密度变幅为0.57×104—4.51×104 ind/L, 总平均2.31×104 ind/L; 多样性指数值变幅为0.72—3.12, 总平均2.20; 均匀度指数值变幅为0.15—0.52, 总平均0.36; 硅藻商变幅为0.66—9.48, 总平均3.24。 (2)硅藻群落结构呈现出季节和水平分布上的变化。在季节变化上, 物种丰富度、细胞密度及多样性指数等以温度较低的春(5月)、秋(11月)两季最高, 而以夏季(8月)最低。在水平分布上, 从上游到下游, 硅藻群落结构呈现出物种丰富度、多样性指数值逐渐减小, 而细胞密度和硅藻商逐渐增加的趋势。(3)嘉陵江下游水质总体为β-中污水体。其中位于城市上游的云门、沙溪、温塘峡、井口水质较好, 为微污或β-中污水体, 而位于城区及下游的合川、毛背沱、磁器口和朝天门水质较差, 为α-中污或污染水体。 |
| [7] | . 云南阳宗海砷污染事件引起社会广泛关注.为了解事件发生后阳宗海砷污染水平及变化趋势,分别于2008年12月、2009年2月、5月及9月四次采样,研究了阳宗海湖水、底泥、周边井水、土壤、农作物及水生生物中的砷含量及其变化趋势.研究结果显示:湖水平均砷浓度分别为176.9、147.3、159.3和161.1μg/L(算术平均),底泥平均浓度分别为32.87、62.41、62.99和46.96μg/g(算术平均).阳宗海湖水砷浓度经历了先升后降再到平稳的变化过程,底泥砷含量迅速升高后缓慢下降,湖水和底泥间砷交换还在进行.阳宗海附近土壤中砷最高浓度为23.33μg/g,未超过国家土壤环境质量三级标准.大米、玉米、花椰菜、小油菜等农作物可食用部分中砷的最高值为0.35μg/g,均未超过国家无公害食品标准.水生植物中砷水平大多在100～200μg/g之间,最高为苦草,砷含量超过300μg/g,说明该植物对砷有一定的富集能力.虾、鱼类等可食用水生动物砷浓度范围为1.52～11.4μg/g. 云南阳宗海砷污染事件引起社会广泛关注.为了解事件发生后阳宗海砷污染水平及变化趋势,分别于2008年12月、2009年2月、5月及9月四次采样,研究了阳宗海湖水、底泥、周边井水、土壤、农作物及水生生物中的砷含量及其变化趋势.研究结果显示:湖水平均砷浓度分别为176.9、147.3、159.3和161.1μg/L(算术平均),底泥平均浓度分别为32.87、62.41、62.99和46.96μg/g(算术平均).阳宗海湖水砷浓度经历了先升后降再到平稳的变化过程,底泥砷含量迅速升高后缓慢下降,湖水和底泥间砷交换还在进行.阳宗海附近土壤中砷最高浓度为23.33μg/g,未超过国家土壤环境质量三级标准.大米、玉米、花椰菜、小油菜等农作物可食用部分中砷的最高值为0.35μg/g,均未超过国家无公害食品标准.水生植物中砷水平大多在100～200μg/g之间,最高为苦草,砷含量超过300μg/g,说明该植物对砷有一定的富集能力.虾、鱼类等可食用水生动物砷浓度范围为1.52～11.4μg/g. |
| [8] | . 通过采集阳宗海水体、沉积物样品并测定砷的总量及形态组成,分析了水体、沉积物中砷的空间分布,评价了砷的污染现状,计算了人为贡献率与湖中砷的储存量,并调查了砷的来源.结果表明,2010年4月阳宗海水体中总砷含量介于71.96～101.2μg·L-1,且随着水深的增加而略有升高.溶解态砷在68.14～96.72μg·L-1之间,其中As(Ⅲ)占32%.水中砷的健康危害风险度在4.77×10-4～6.66×10-4a-1的范围内,对周围环境产生严重威胁.沉积物中砷含量介于6.05～396.49 mg·kg-1.0～2、2～4、4～6、6～8及8～10 cm沉积物中砷的平均含量依次为155.66、52.01、29.78、19.22、17.52 mg·kg-1.表层0～2 cm沉积物砷的累积程度最高,地累积指数最高达5级.随着深度增加,砷的累积程度显著降低.沉积物中砷的各种形态的平均含量由高到低依次为残渣态、腐殖酸结合态、铁锰氧化态、强有机结合态、离子交换态、水溶态、碳酸盐结合态.随着深度增加,砷的生物可利用态比重逐渐减小,残渣态的比重明显增大.表层0～2 cm沉积物砷的人为贡献率最大,平均为81.94%.随深度增加,人为贡献率显著降低.目前,阳宗海水体与沉积物中的砷储存总量为70.65 t,人为贡献量占砷总储存量的82.68%,这其中主要来自南岸的磷肥厂.同时,东岸的高尔夫球场及北岸的火电厂、温泉也对阳宗海砷的累积有所贡献. 通过采集阳宗海水体、沉积物样品并测定砷的总量及形态组成,分析了水体、沉积物中砷的空间分布,评价了砷的污染现状,计算了人为贡献率与湖中砷的储存量,并调查了砷的来源.结果表明,2010年4月阳宗海水体中总砷含量介于71.96～101.2μg·L-1,且随着水深的增加而略有升高.溶解态砷在68.14～96.72μg·L-1之间,其中As(Ⅲ)占32%.水中砷的健康危害风险度在4.77×10-4～6.66×10-4a-1的范围内,对周围环境产生严重威胁.沉积物中砷含量介于6.05～396.49 mg·kg-1.0～2、2～4、4～6、6～8及8～10 cm沉积物中砷的平均含量依次为155.66、52.01、29.78、19.22、17.52 mg·kg-1.表层0～2 cm沉积物砷的累积程度最高,地累积指数最高达5级.随着深度增加,砷的累积程度显著降低.沉积物中砷的各种形态的平均含量由高到低依次为残渣态、腐殖酸结合态、铁锰氧化态、强有机结合态、离子交换态、水溶态、碳酸盐结合态.随着深度增加,砷的生物可利用态比重逐渐减小,残渣态的比重明显增大.表层0～2 cm沉积物砷的人为贡献率最大,平均为81.94%.随深度增加,人为贡献率显著降低.目前,阳宗海水体与沉积物中的砷储存总量为70.65 t,人为贡献量占砷总储存量的82.68%,这其中主要来自南岸的磷肥厂.同时,东岸的高尔夫球场及北岸的火电厂、温泉也对阳宗海砷的累积有所贡献. |
| [9] | This communication presents results of our 2-year survey on groundwater contamination in three districts , Varanasi and Gazipur of Uttar Pradesh (UP) in the upper and middle Ganga plain, India. Analyses of 4,780 tubewell samples revealed that concentrations in 46.5% exceeded 10 microg/L, in 26.7%, 50 microg/L and in 10% 300 microg/L limits. concentrations up to 3,192 microg//L were observed. The age of tubewells (n=1,881) ranged from less than a year to 32 years, with an average of 6.5 years. Our study shows that older tubewells had a greater chance of contamination. Depth of tubewells (n=3,810) varied from 6 to 60.5 m with a mean of 25.75 m. A detailed study in three administrative units within district, i.e. block, Gram Panchayet, and village was carried out to assess the magnitude of the contamination. Before our survey the affected villagers were not aware that they were suffering from arsenical toxicity through contaminated drinking . A preliminary clinical examination in 11 affected villages (10 from and 1 from Gazipur district) revealed typical arsenical ranging from , to Bowens (suspected). Out of 989 villagers (691 adults, and 298 children) screened, 137 (19.8%) of the adults and 17 (5.7%) of the children were diagnosed to have typical arsenical . Arsenical and adverse obstetric outcome were also observed, indicating severity of exposure. The range of concentrations in hair, nail and urine was 137-10,900, 764-19,700 microg/kg, and 23-4,030 microg/L, respectively. The urine, hair and nail concentrations of correlated significantly (r=0.76, 0.61, and 0.55, respectively) with drinking concentrations. The similarity to previous studies on contamination in West Bengal, Bihar and Bangladesh indicates that people from a significant part of the surveyed areas in UP are suffering and this will spread unless drives to raise awareness of toxicity are undertaken and an safe supply is immediately introduced. |
| [10] | This review deals with environmental origin, occurrence, episodes, and impact on human health of arsenic. Arsenic, a metalloid occurs naturally, being the 20th most abundant element in the earth's crust, and is a component of more than 245 minerals. These are mostly ores containing sulfide, along with copper, nickel, lead, cobalt, or other metals. Arsenic and its compounds are mobile in the environment. Weathering of rocks converts arsenic sulfides to arsenic trioxide, which enters the arsenic cycle as dust or by dissolution in rain, rivers, or groundwater. So, groundwater contamination by arsenic is a serious threat to mankind all over the world. It can also enter food chain causing wide spread distribution throughout the plant and animal kingdoms. However, fish, fruits, and vegetables primarily contain organic arsenic, less than 10% of the arsenic in these foods exists in the inorganic form, although the arsenic content of many foods (i.e. milk and dairy products, beef and pork, poultry, and cereals) is mainly inorganic, typically 65-75%. A few recent studies report 85-95% inorganic arsenic in rice and vegetables, which suggest more studies for standardisation. Humans are exposed to this toxic arsenic primarily from air, food, and water. Thousands and thousands of people are suffering from the toxic effects of arsenicals in many countries all over the world due to natural groundwater contamination as well as industrial effluent and drainage problems. Arsenic, being a normal component of human body is transported by the blood to different organs in the body, mainly in the form of MMA after ingestion. It causes a variety of adverse health effects to humans after acute and chronic exposures such as dermal changes (pigmentation, hyperkeratoses, and ulceration), respiratory, pulmonary, cardiovascular, gastrointestinal, hematological, hepatic, renal, neurological, developmental, reproductive, immunologic, genotoxic, mutagenetic, and carcinogenic effects. Key research studies are needed for improving arsenic risk assessment at low exposure levels urgently among all the arsenic research groups. |
| [11] | . 通过对2007—2011年阳宗海砷浓度和藻类数量、种类变化数据的研究,分析砷浓度对藻类的影响。 通过对2007—2011年阳宗海砷浓度和藻类数量、种类变化数据的研究,分析砷浓度对藻类的影响。 |
| [12] | In this study the biotransference of selenium copper, cadmium, zinc, arsenic and lead was measured in a contaminated seagrass ecosystem in Lake Macquarie, NSW, Australia, to determine if biomagnification of these trace metals is occurring and if they reach concentrations that pose a threat to the resident organisms or human consumers. Selenium was found to biomagnify, exceeding maximum permitted concentrations for human consumption within carnivorous fish tissue, the highest trophic level examined. Selenium concentrations measured within carnivorous fish were also above those shown to elicit sub-lethal effects in freshwater fish. As comparisons are made to selenium concentrations known to effect freshwater fish, inferences must be made with caution. There was no evidence of copper, cadmium, zinc or lead biomagnification within the food web examined. Copper, cadmium, zinc and lead concentrations were below concentrations shown to elicit adverse responses in biota. Copper concentrations within crustaceans M. bennettae and P. palagicus were found to exceed maximum permitted concentrations for human consumption. It is likely that copper concentrations within these species were accumulated due to the essential nature of this trace metal for many species of molluscs and crustaceans. Arsenic showed some evidence of biomagnification. Total arsenic concentrations are similar to those found in other uncontaminated marine ecosystems, thus arsenic concentrations are unlikely to cause adverse effects to aquatic organisms. Inorganic arsenic concentrations are below maximum permitted concentrations for human consumption. |
| [13] | Summary 1. One of the greatest challenges faced by limnologists, as well as most ecologists and environmental scientists, is finding data with time scales appropriate to their questions. Because of the general lack of reliable long-term monitoring data, it is often difficult to determine the nature and timing of ecosystem changes. In lieu of direct monitoring data, palaeolimnologists have developed a variety of physical, chemical and biological approaches to track past changes in aquatic ecosystems using proxy data archived in lake and river sediments. This article summarises a few of our recent palaeolimnological programs that have studied the effects of multiple stressors on lake ecosystems and demonstrates how palaeolimnological approaches can circumvent this common problem of data availability.2. Lakewater calcium concentrations are declining in many softwater lake regions because logging and acid precipitation have lowered calcium levels in soils. In many cases, however, the onset of lakewater calcium decline predates direct observation, and so documenting the effects on freshwater ecosystems may be complex. By combining laboratory, field and palaeolimnological approaches, it is now evident that keystone taxa (e.g. spp.) have been severely affected by these calcium declines. 3. Some of the most common complaints received by lake managers concern the smell and taste of water. Although the root causes of taste and odour problems vary, compounds released by certain species of algae are often responsible. In nutrient-poor or mesotrophic lakes, colonial chrysophytes are often the culprits, including scaled taxa of the genus . Palaeolimnological approaches can be used to assess the various multiple stressors that influence the abundance of these phytoplankton. 4. : recent climatic warming is affecting a wide range of lake ecosystems in diverse and often complex ways across vast geographical regions, and this has added to the complexities of limnological responses to other stressors. As more palaeolimnological studies are completed, meta-analyses of sedimentary profiles can now be used to help disentangle the effects of climate warming from other environmental variables to determine how various components of lake ecosystems are responding to these multiple stressors. |
| [14] | . 位于青藏高原东北部的希门错为一冰川深水湖,流域面积小,受人类 活动影响较小,忠实地记录了湖泊的自然演化过程.结合希门错湖区特点,对沉积物的粒度特征进行了详细分析.希门错岩心的黏土含量在20%～60%之间,粗 砂含量在0～10%之间,粉砂含量在20%～80%之间.粒度参数用矩值法求得,平均粒径(φ值)为6.0～8.5,标准偏差为0.8～3.0,偏度分布 范围在-1.0～1.0之间,峰度为1.0～25.0.频率分布曲线存在众数粒径为0.6、1.0、8、30和200μm的次总体.众数粒径为1μm的次 总体在7.3～6.0 m成为沉积物的主体,显示了极弱的水动力条件,为湖面结冰的情况下形成.众数粒径为8和30 μm的次总体为沉积物的主体,分别代表了弱的水动力环境和强的水动力环境,指示了深水和浅水两种环境.结合有机质含量和磁化率两个指标,对整段岩心的沉积 特征进行了分析,发现整段岩心经历了5次较大的环境变化:12.80～7.30 m有机质含量最低,磁化率最高,粗砂含量几乎为零,黏土含量较高,湖水较深,水动力条件较弱;7.30～6.25 m有机质含量低,磁化率下降,沉积物主要由黏土组成,湖面结冰时间更长,沉积环境更加稳定;6.25～5.00m有机质含量和磁化率剧烈波动,粗砂明显增 多,湖水较浅,水动力条件较强;5.00～3.55 m有机质含量快速升高,磁化率下降,粗砂含量仍然较高,水动力条件较强,但水位比前一阶段有所升高;3.55～0 m有机质含量最高,磁化率最低,粗砂含量降低,湖水较深,降水量较大,水动力条件减弱. 位于青藏高原东北部的希门错为一冰川深水湖,流域面积小,受人类 活动影响较小,忠实地记录了湖泊的自然演化过程.结合希门错湖区特点,对沉积物的粒度特征进行了详细分析.希门错岩心的黏土含量在20%～60%之间,粗 砂含量在0～10%之间,粉砂含量在20%～80%之间.粒度参数用矩值法求得,平均粒径(φ值)为6.0～8.5,标准偏差为0.8～3.0,偏度分布 范围在-1.0～1.0之间,峰度为1.0～25.0.频率分布曲线存在众数粒径为0.6、1.0、8、30和200μm的次总体.众数粒径为1μm的次 总体在7.3～6.0 m成为沉积物的主体,显示了极弱的水动力条件,为湖面结冰的情况下形成.众数粒径为8和30 μm的次总体为沉积物的主体,分别代表了弱的水动力环境和强的水动力环境,指示了深水和浅水两种环境.结合有机质含量和磁化率两个指标,对整段岩心的沉积 特征进行了分析,发现整段岩心经历了5次较大的环境变化:12.80～7.30 m有机质含量最低,磁化率最高,粗砂含量几乎为零,黏土含量较高,湖水较深,水动力条件较弱;7.30～6.25 m有机质含量低,磁化率下降,沉积物主要由黏土组成,湖面结冰时间更长,沉积环境更加稳定;6.25～5.00m有机质含量和磁化率剧烈波动,粗砂明显增 多,湖水较浅,水动力条件较强;5.00～3.55 m有机质含量快速升高,磁化率下降,粗砂含量仍然较高,水动力条件较强,但水位比前一阶段有所升高;3.55～0 m有机质含量最高,磁化率最低,粗砂含量降低,湖水较深,降水量较大,水动力条件减弱. |
| [15] | . 通过210Pb测年、历史事件记载和沉积记录,对钻孔岩芯沉积物年代进行了确定.利用花粉、硅藻、磁参数、色素及结合态磷等多环境代用指标分析,讨论了近0.3ka来龙感湖流域植被、土壤侵蚀变化与湖泊环境演化之间的关系,特别是龙感湖营养态的变化.湖泊经历了两次由贫营养向中等营养的转变,两次富营养化的发生（1770AD后和1906AD后）与人类活动增强导致的湖泊营养外负荷的增加密切相关.历史时期降水的变化又是决定该区人类活动强度变化的诱因.近0.04ka来,湿地的严重破坏和流域化学肥料的使用,使得湖泊富营养化程度呈现明显加重趋势. 通过210Pb测年、历史事件记载和沉积记录,对钻孔岩芯沉积物年代进行了确定.利用花粉、硅藻、磁参数、色素及结合态磷等多环境代用指标分析,讨论了近0.3ka来龙感湖流域植被、土壤侵蚀变化与湖泊环境演化之间的关系,特别是龙感湖营养态的变化.湖泊经历了两次由贫营养向中等营养的转变,两次富营养化的发生（1770AD后和1906AD后）与人类活动增强导致的湖泊营养外负荷的增加密切相关.历史时期降水的变化又是决定该区人类活动强度变化的诱因.近0.04ka来,湿地的严重破坏和流域化学肥料的使用,使得湖泊富营养化程度呈现明显加重趋势. |
| [16] | There is a recognized need to anticipate tipping points, or critical transitions, in social-ecological systems(1,2). Studies of mathematical(3-5) and experimental(6-9) systems have shown that systems may 'wobble' before a critical transition. Such early warning signals(10) may be due to the phenomenon of critical slowing down, which causes a system to recover slowly from small impacts, or to a flickering phenomenon, which causes a system to switch back and forth between alternative states in response to relatively large impacts. Such signals for transitions in social-ecological systems have rarely been observed(11), not the least because high-resolution time series are normally required. Here we combine empirical data from a lake-catchment system with a mathematical model and show that flickering can be detected from sparse data. We show how rising variance coupled to decreasing autocorrelation and skewness started 10-30 years before the transition to eutrophic lake conditions in both the empirical records and the model output, a finding that is consistent with flickering rather than critical slowing down(4,12). Our results suggest that if environmental regimes are sufficiently affected by large external impacts that flickering is induced, then early warning signals of transitions in modern social-ecological systems may be stronger, and hence easier to identify, than previously thought. |
| [17] | CiteSeerX - Scientific documents that cite the following paper: Pollution of Lakes and Rivers: A Paleoenvironmental Perspective |
| [18] | For almost a century biogeographers have used paleoecological methods, including tree-ring, pollen, macrofossil, and charcoal analysis, to reconstruct climate and environmental conditions for the late Quaternary, but paleolimnological proxies and approaches provide new opportunities for biogeographers. In the last two decades, paleolimnology has grown rapidly as a result of several technical advancements: (1) the development of new proxies, (2) improved coring, sampling, and dating techniques that provide finer temporal resolution, and (3) more sophisticated statistical techniques and greater computing power, which allow for enhanced quantitative calibration of climate and environmental signals from paleolimnological proxies. These advances have led to a plethora of research projects, many using novel approaches, on climate change, anthropogenic impacts, conservation and restoration, aquatic/terrestrial links, resource management, succession, biodiversity, and introduced species. Paleolimnologists are working at the frontiers of biogeographical research, particularly contributing to research on climate change, biogeochemical cycles, and anthropogenic impacts on Earth systems. |
| [19] | . 在对长江中下游地区45个湖泊表层沉积硅藻属种分布及多次季节性水样调查的基础上,研究了57个常见硅藻属种对总磷指标的生态学特征.利用加权平均回归方法,计算出常见属种对总磷指标响应的生态最佳值及忍耐幅度.根据生态学理论得出,属种Cyclotellameneghiniana、C.atomus、Stephanodiscusparvus、S.minutulus、Naviculasubminiscula是长江中下游湖泊富营养化发生的很好的指示性属种;而Aulacoseiraalpigea、Cyclostephanosdubius、C.tholiformis、C.invisitatus、Stephanodi 在对长江中下游地区45个湖泊表层沉积硅藻属种分布及多次季节性水样调查的基础上,研究了57个常见硅藻属种对总磷指标的生态学特征.利用加权平均回归方法,计算出常见属种对总磷指标响应的生态最佳值及忍耐幅度.根据生态学理论得出,属种Cyclotellameneghiniana、C.atomus、Stephanodiscusparvus、S.minutulus、Naviculasubminiscula是长江中下游湖泊富营养化发生的很好的指示性属种;而Aulacoseiraalpigea、Cyclostephanosdubius、C.tholiformis、C.invisitatus、Stephanodi |
| [20] | <a name="Abs1"></a>We examined changes at the community and population level of sedimentary diatoms over a wide temporal and spatial gradient of metal pollution encountered in cores from three lakes in the Abitibi mining region (Québec, Canada). Diatom communities on the whole appeared to be very tolerant of metal contamination, as shown by diatom cell accumulation rates decreasing only under the most severe conditions of contamination, which were found from the 1930s to the 1980s in Lac Dufault (cadmium, up to 94 μg/g dry sediment; Cu, up to 8600 μg/g; Zn, up to 9000 μg/g). Under the moderate conditions of contamination observed in the other two lakes and in the most recent sediment of Lac Dufault, diatom cell accumulation rates tended to increase over values typical of the pre-mining period. However, there were increasing rearrangements of the community composition along the contamination gradient. Under moderate metal enrichment, the diatom community of Lac Vaudray experienced only subtle changes, with <i>Cyclotella stelligera</i>, albeit decreasing, remaining the dominant taxon. In the intermediately contaminated Lac Caron, several benthic taxa, noticeably <i>Cymbella silesiaca</i> and several <i>Fragilaria</i> species, rose in taxonomic importance. The most extreme contamination observed in Lac Dufault led to a severely impoverished community almost entirely represented by <i>Achnanthes minutissima</i> and <i>Brachysira vitrea</i>. With increasing levels of contamination, there was a shift from planktonic to benthic taxa and morphotypes and a consistent decrease in the siliceous stomatocysts/diatom frustules ratio. These trends suggest that littoral zones may represent an important refugium under conditions of high contamination. Responses to metal stress were in general more evident at the population than at the community level. <i>Cyclotella stelligera</i> and <i>B. vitrea</i> had a consistent negative and positive response, respectively, along the gradient and are the most promising indicators of metal pollution for this region. |
| [21] | Diatom remains were analysed in two short sediment cores from a subalpine Italian lake (Lake Orta), known for its major industrial pollution dating from the late 1920s, which has only recently been stopped. Copper was recognised as the main toxic agent for diatoms during the first 30 years of pollution (peak value: 100 渭g l-1 in the late 1950s). A diatom community similar to other deep subalpine lakes existed in the past, and was disrupted by the pollution events. Acute and long-term effects of Cu contamination were tracked by changes in three distinct groups of species around the sharp boundary corresponding to the onset of the pollution. These groups were respectively composed of: (1) Species quickly extirpated by the discharge, mostly belonging to Fragilaria and Cyclotella and never reappearing; (2) Species apparently not affected, or not immediately affected, by the pollution, showing no definite trends with time. Synedra species, with various deformities, were conspicuous among these; (3) Species with accumulation rates increasing with time irrespective of pollution, mostly belonging to Achnanthes. Properties and tolerances of these groups (e.g. Synedra and Achnanthes) are discussed in detail. |
| [22] | <a name="Abs1"></a>We studied diatom taxonomic composition and the presence of morphological alterations (size and deformations) along a sediment core collected in Lac Dufault, Abitibi, whose watershed has a long history of mining pollution presently undergoing mitigation. According to sediment dating with <sup>210</sup>Pb and metal profiles along the core, we could identify four periods in the contamination history of the lake, which were characterized by different diatoms. <i>Tabellaria flocculosa</i> was dominant in the pre-mining period but was drastically reduced at the onset of pollution when <i>Fragilaria</i> cf. <i>tenera</i> became important. This diatom, together with other <i>Fragilaria</i> species and cysts of <i>Chaetoceros muelleri</i>, typified the transition period in which Cu reached its maximum value and other metals started to increase. During the period of maximum contamination with Zn, Cd, and Fe accompanied by acid mine drainage, <i>Achnanthes minutissima</i> and <i>Brachysira vitrea</i> were dominant. These taxa started to wane in the most recent sediments representing a partial chemical recovery. <i>Asterionella formosa</i>, which almost vanished at mining onset, reappeared with high abundance in these superficial sections. Beside these taxonomical shifts, we observed during the contamination period significant reduction in valve length together with increased percentages of valve deformations. Because available data on water chemistry and a diatom-based pH reconstruction suggest that Lac Dufault escaped severe acidification, diatom patterns observed in the core can be mostly ascribed to metal contamination. Individual diatom abundance and valve length had strong statistical relationships with the different metals identified in the core. Diatom changes both taxonomic and morphological can be excellent specific indicator of metal contamination and early recovery. |
| [23] | <a name="Abs1"></a>Fish introduction, eutrophication and disappearance of aquatic vegetation are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. Fish were introduced to Lake Dianchi, a eutrophic plateau lake in southwest China, in the late 1950s and 1970s. After the introduction, invasive fish became the dominant species, and the total fish yield increased. Meanwhile, the trophic level of Lake Dianchi had a tendency to increase in the past decades because of the increases in human activities in the watershed area. In addition, the area of aquatic vegetation decreased from more than 90 to 1.8% of the lake area from the 1950s to 2000. This study investigated the effects of fish introduction, eutrophication and aquatic vegetation on the diatom community of Lake Dianchi by examining the changes of microfossil diatom assemblage and abundance. Results showed that the absolute abundance and diatom assemblages changed after fish were introduced. The endemic species, <i>Cyclotella rohomboideo-elliptica</i>, disappeared with the introduction of fish and increasing trophic levels after 1958. <i>Fragilaria crotonensis</i> entered into the lake with the introduction of fish and gradually thrived in the lake after 1958. Diatom species numbers also decreased gradually from 21 to 9 from the past to present. Epiphytic diatoms disappeared with the decrease of aquatic vegetation after 1985. Our study indicated that eutrophication was the most important process determining diatom abundance, and fish introduction was a secondary process determining diatom abundance, while aquatic vegetation had a more important role in structuring the diatom community in this eutrophic plateau lake. |
| [24] | Eutrophication, disappearance of aquatic vegetation and fish introduction are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. This study investigated the effects of eutrophication, aquatic vegetation and fish introduction on the diatom community of Lake Xingyun by examining the changes of microfossil diatom assemblage. Results showed that diatom assemblages changed with increasing trophic level, decreasing aquatic vegetation and fish introduction. A mesotrophic, alkaliphilous species, Aulacoseira ambigua, was dominant in Lake Xingyun before 1950, which indicated the lake was mesotrophic in the period. Epiphytic diatom species (Achnanthes minutissima, Denticula sp., Gomphonema pumilum) presented high relative concentration between 1950-1980, which indicated aquatic vegetation had a higher cover in this period. The number of diatom species varied from 20 to 66, and to 52 with the change of aquatic vegetation from the past to present. Epiphytic diatoms except Achnanthes minutissima disappeared with the decrease of aquatic vegetation after 1980. Since 1980, with the sharply rising of TP and TN concentration, mesotrophic species (Aulacoseira ambigua) disappeared and eutrophic species (Cyclostephanos dubius, Fragilaria crotonensis, Aulacoseira granulata, Nitzschia palea) were dominant. It indicates the lake has evolved towards eutrophication after 1980. Our study indicated that change of trophic status and aquatic vegetation are important driving factors affecting diatom community composition in Lake Xingyun, but that fish introductions have also been an additional factor. |
| [25] | . 于2004-2005年间对洱海水体的硅藻群落进行逐月监测及研 究,共发现71个种,分属于18个属.硅藻群落结构的季节变化显著,主要优势种为耐营养的属种.不同季节的硅藻优势种类有明显区别,冬季的主要优势种为 Fragilaria crotonensis,春季Aulacoseira ambigua与F.crotonensis的组合占优势地位,夏季以Cyclotella ocellata为主,秋季则A.ambigua与Cyclostephanos dubius组合为优势种.空间上除1*点外,硅藻分布虽然在相对丰度上存在一定的南北差异,但优势属种在全湖具有较好的一致性.说明洱海全湖的水质都已 处于中富营养状态.对除1*点外的11个采样点的硅藻及水化学数据进行平均,得到逐月数据,通过数理统计分析的手段,探讨硅藻群落变化与环境因子之间的关 系,结果表明影响季节尺度硅藻群落发生变化的最主要因子是气象条件,其次是营养盐. 于2004-2005年间对洱海水体的硅藻群落进行逐月监测及研 究,共发现71个种,分属于18个属.硅藻群落结构的季节变化显著,主要优势种为耐营养的属种.不同季节的硅藻优势种类有明显区别,冬季的主要优势种为 Fragilaria crotonensis,春季Aulacoseira ambigua与F.crotonensis的组合占优势地位,夏季以Cyclotella ocellata为主,秋季则A.ambigua与Cyclostephanos dubius组合为优势种.空间上除1*点外,硅藻分布虽然在相对丰度上存在一定的南北差异,但优势属种在全湖具有较好的一致性.说明洱海全湖的水质都已 处于中富营养状态.对除1*点外的11个采样点的硅藻及水化学数据进行平均,得到逐月数据,通过数理统计分析的手段,探讨硅藻群落变化与环境因子之间的关 系,结果表明影响季节尺度硅藻群落发生变化的最主要因子是气象条件,其次是营养盐. |
| [26] | One new species, four newly recorded genera, and two newly recorded species of diatoms are de-scribed from China. They are Sellaphora fuxianensis sp. nov. Li, Sellaphora Mereschkowsky, Karayevia Round & Bukhtiyarova, Placoneis Mereschkowsky, Fallacia Stickle & Mann, Placoneisprespanensis Levkov, Krstic & Nakov, and Fallacia lucinensis (Hustedt) D. G. Mann. All taxa were collected from Lake Fuxian in Yunnan Province, China. These species were observed with light and scanning electron microscopes, and their taxonomic characters are discussed. |
| [27] | A mean annual temperature increase has been recorded on the Yunnan-Guizhou Plateau of China during the last century. This temperature increase has been significantly greater since the 1950s. Thus, paleolimnological analyses may be utilized to better understand ecological responses to recent changing climate over decadal to centennial timescales, especially in regions with sparse lake monitoring data. Here, we present paleolimnological results from a Pb-210/Cs-137-dated sediment core spanning approximately the last similar to 250 years from a remote, alpine, semi-closed oligotrophic lake (Lugu Lake) on the northwestern Yunnan-Guizhou Plateau. Sediment profiles of diatoms, geochemical variables (LOI550, TOC and C/N) and median grain size were analyzed and compared with the climate data (1951 AD-2010 AD) from the Lijiang weather station. Endogenous productivity of Lugu Lake has increased gradually over the last 30 years. The majority of diatom taxa encountered in the core are typical of alkaline oligotrophic lakes. Diatom assemblages were dominated by Cyclostephanos dubius, Cyclotella taxa, and fragilarioid taxa. Diatom species composition has changed significantly with three assemblage shifts at different scales over the similar to 250-year period. Diatom species diversity reveals a distinct increase before similar to 1970 AD, followed by a decline. In addition, a decreasing trend in diatom cell-size was consistent with recent warming trends. Redundancy analysis (RDA) shows that regional air temperature trends (annual, spring, summer, and winter) have played a significant role (p < 0.05) in determining diatom compositional changes over the past six decades. Results of this study suggest that regional warming is the main driving force behind recent changes in diatom composition at Lugu Lake, while nutrients may also have impact on the diatom change in recent 10 years. |
| [28] | |
| [29] | . |
| [30] | . 由于近年Ｎ、Ｐ输入、输出失衡，大量营养盐滞留湖中，加以电厂温排水影响，阳宗海水体恶化加剧，两年出现大面积水华；且湖中鱼类结构不合理，数量偏少，导致水质变化。为此，必须取缔网箱及高密度堰塘养鱼，实施环湖截污，降低电厂排水温度，调整鱼类种群结构。 由于近年Ｎ、Ｐ输入、输出失衡，大量营养盐滞留湖中，加以电厂温排水影响，阳宗海水体恶化加剧，两年出现大面积水华；且湖中鱼类结构不合理，数量偏少，导致水质变化。为此，必须取缔网箱及高密度堰塘养鱼，实施环湖截污，降低电厂排水温度，调整鱼类种群结构。 |
| [31] | . |
| [32] | . 阳宗海为云南省小江西支断裂控制形成的天然淡水湖泊,距昆明市约40km.当湖面控制水位为黄海高程1769.904m时,湖泊面积约为31km2,最大水深为29m,平均水深约20m,蓄水量约6.17亿m3;阳宗海的天然补给水源主要为流域内天然降水,年均产水量约为6800万m3. 阳宗海为云南省小江西支断裂控制形成的天然淡水湖泊,距昆明市约40km.当湖面控制水位为黄海高程1769.904m时,湖泊面积约为31km2,最大水深为29m,平均水深约20m,蓄水量约6.17亿m3;阳宗海的天然补给水源主要为流域内天然降水,年均产水量约为6800万m3. |
| [33] | . 分析2002—2012年阳宗 海TN、TP、Chl-a、氮磷比的动态变化特征及相互关系,并用综合营养状态指数法评价阳宗海的富营养化状态。结果表明:阳宗海富营养化呈上升趋 势,2007年从之前的贫营养级上升为中营养级;Chl-a、TN、TP浓度在2007年后均呈快速上升趋势。Chl-a浓度与TN、TP浓度呈正相关, 且氮磷比越接近阈值16∶1,Chl-a浓度上升就越快。指出若营养盐输入得不到有效控制,预测阳宗海将在2017年前后达到富营养级水平,水质将进一步 下降。 分析2002—2012年阳宗 海TN、TP、Chl-a、氮磷比的动态变化特征及相互关系,并用综合营养状态指数法评价阳宗海的富营养化状态。结果表明:阳宗海富营养化呈上升趋 势,2007年从之前的贫营养级上升为中营养级;Chl-a、TN、TP浓度在2007年后均呈快速上升趋势。Chl-a浓度与TN、TP浓度呈正相关, 且氮磷比越接近阈值16∶1,Chl-a浓度上升就越快。指出若营养盐输入得不到有效控制,预测阳宗海将在2017年前后达到富营养级水平,水质将进一步 下降。 |
| [34] | Yungui Plateau lakes in southwesterm China are economically important. Water and Sediments of 24 lakes throughout Yunnan Province were sampled in Octobel 1994. We describe chemical and ptysical characteristics of Yunnan lakes, and address effects of regional geology, human influences on water quality and sediment type, also we inquired into the geochemical information of sediments,Water quality differs between deep Yunnan lakes of tectonic origin and shallow solution basins. Shallow lakes generally have higher nutrient concentrations and appear more susceptible to riparian disturbance than deeper lakes. Shallow lakes with high macrophyte standing crops, nerertheless, exhibit nutrient -poor wates. Principal ions Ca+2, Mg+2, and HCO3-1 reflect regional carbonate geology, except in cheng Hai, whict is a sedium blcarbonate lake.Specific conductance and 未18O are positively correlated indicating that evaporation concentrates both solufes and 18O Large, shallow lakes in soulheastern Yunnan exhibit 18Oenriched waters because of substanfial evaportion, whereas small, deep lakes are 18O -deplered. Lakewater are 18O-depleted in small, shallow basins that receive substantial rain water inputs relative to their small volumes. 18O enrichment in Cheng Hai suggests that a recent 5-m water-level decline in this lake was caused by increased evaporation or diversion of freshwater inflow.Yunnan watersheds have undergone substantial deforestation, agriculture, soil erosion, and inclustrialization, Limnetic nutrient concentrations indicate that human activities have affected water quality. Organic matter content is low in sediments because of increasecl non -carbonate, clastic sediment yield from watersheds. Environmental policies are needed to balance ecological contraints with economic activities that impact water quality. |
| [35] | . 利用2008年云贵高原13个湖泊丰水期的全面水质调查数据,系 统分析云贵高原湖泊水质现状,通过与历史资料对比,揭示20年来的水质变化,并分析水质变化的原因.同时利用主成分分析将23个水质参数概括为6个主要成 分,除程海外所有湖泊水质均与第一主成分密切相关.人类活动影响下的水体富营养化、有机污染以及农业面源污染等是除程海外湖泊污染的主要驱动因子,程海水 质变化主要受水体的矿化度增加所驱动.另外,根据各主成分得分,本文也对13个湖泊水质进行了综合评价,并在评价的基础上就湖泊的保护和治理提出建议. 利用2008年云贵高原13个湖泊丰水期的全面水质调查数据,系 统分析云贵高原湖泊水质现状,通过与历史资料对比,揭示20年来的水质变化,并分析水质变化的原因.同时利用主成分分析将23个水质参数概括为6个主要成 分,除程海外所有湖泊水质均与第一主成分密切相关.人类活动影响下的水体富营养化、有机污染以及农业面源污染等是除程海外湖泊污染的主要驱动因子,程海水 质变化主要受水体的矿化度增加所驱动.另外,根据各主成分得分,本文也对13个湖泊水质进行了综合评价,并在评价的基础上就湖泊的保护和治理提出建议. |
| [36] | <a name="Abs1"></a>The increase of ultraviolet radiation (UVR, 280–400 nm) caused by stratospheric ozone depletion has profound effects on aquatic ecosystems. High-altitude lakes in the Yunnan Plateau are exposed to high intensities of UVR and contain low concentrations of chromophoric dissolved organic matter (CDOM). Thirty-eight lakes in the Yunnan Plateau with elevations from 1291 to 3809 m above sea level were investigated to study CDOM concentrations and possible effects of UVR on the lake ecosystem. The attenuation of UVR in the Yunnan Plateau lakes was calculated from the absorption coefficient of CDOM based on an empirical relationship from lakes in the Alps and Pyrenees mountains. Absorption coefficients [<i>α</i>(<i>λ</i>)] at 320 nm [<i>α</i>(320)] ranged from 0.52 to 14.05 m<sup>−1</sup> (mean ± standard deviation, 4.40 ± 3.85 m<sup>−1</sup>) and at 380 nm [<i>α</i>(380)] from 0.05 to 4.51 m<sup>−1</sup> (1.40 ± 1.30 m<sup>−1</sup>). The exponential slope coefficient for the relationship of wavelength to <i>α</i>(<i>λ</i>) ranged from 16.2 to 41.4 μm<sup>−1</sup> (21.74 ± 4.93 μm<sup>−1</sup>) over the 280–400 nm interval. Normalized fluorescence emission (NFLU) at 450 nm from an excitation wavelength of 355 nm, <i>F</i> <sub>n</sub>(355), averaged 7.93 ± 3.22 NFLU. A significant positive relationship was found between <i>α</i>(355) and <i>F</i> <sub>n</sub>(355). The estimated diffuse attenuation coefficients of UV-B (320 nm) and UV-A (380 nm) ranged from 0.55 to 15.77 m<sup>−1</sup> and from 0.24 to 6.73 m<sup>−1</sup>; the corresponding 1% attenuation depths ranged from 0.29 to 8.44 m and from 0.68 to 19.12 m. Twenty-five of 38 lakes had 1% UV-B attenuation depths of 1.5 m or more. The median 1% attenuation depth was 28.8% of the sampling depth for UV-B radiation and 60% for UV-A. In addition to CDOM, chlorophyll <i>α</i> (Chla) and total suspended matter (TSM) also may contribute to attenuation of UVR. |
| [37] | . |
| [38] | |
| [39] | Phytolith [opal phytolith] analysis of lake records is an important and currently underutilized tool of palaeoenvironmental reconstruction. If investigators choose to undertake the time-consuming task of constructing modern phytolith reference collections for their study regions, their efforts are likely to be rewarded because phytoliths can be useful in the identification of specific taxa. Ide... |
| [40] | 05ubat 2008-Ocak 2009 tarihleri aras03nda K02prü04ay Nehri’nde se04ilen 7 02rnekyerindan al03nan ayl03k 02rneklerle akarsuyun fizikokimyasal 02zellikleri ile epilitik diyatomelerinin mevsimsel da0603l03mlar03 ve geli06imleri incelenmi06, fizikokimyasal veriler ile diyatomeler aras03ndaki ili06ki belirlenmi06tir. Fizikokimyasal parametrelerin ortalama de06erleri; s03cakl03k 13,94 oC, pH 8,09, E.C 501,08 μS/cm, bulan03kl03k 26,95 NTU, bikarbonat (HCO-3) 197,99 mg/L,02 karbonat (CO-3) 5,74 mg/L, klorür (Cl-) 68,52 mg/L, amonyum azotu (NH4-N) 0,09 mg/L, nitrit azotu (NO-2-N) 0,005 mg/L, nitrat azotu (NO-3-N) 0,42 mg/L, orta fosfat fosforu (PO4-3-P) 0,12 mg/L, 0402zünmü06 oksijen 8,92 mg/L, organik madde 1,25 mg/L, biyolojik oksijen ihtiyac03 (BO025) 3,10 mg/L, toplam sertlik 223,54 CaCO3 mg/L, sülfat (SO42-) 27,39 mg/L,02 kalsiyum (Ca+2) 57,35 mg/L, magnezyum (Mg+2) 19,93 mg/L, tuzluluk 0,25ppt olarak tepit edilmi06tir. K02prü04ay Nehri’nde epilitik olarak Bacillariophyta’dan 119 takson saptanm0306t03r. Navicula, Nitzschia, Cymbella, Gomphonema en 04ok tür say03s03na sahip takson olmu06, akarsuda sürekli g02zlemlenen bentik türler 02rnekyerleri ve mevsimlere g02re farkl03l03k g02stermi06, ancak Achnanthidium minutissimum , Cymbella affinis , Cocconeis placentula , Diatoma vulgaris , Ulnaria ulna sürekli olarak g02zlenmi06tir. Nitszchia en 04ok tür say03s03 ile temsil edilen takson olmu06tur. Fizikokimyasal de06erlere ve alglere g02re su kalitesi de06erlendirmesi yap03larak birbirleriyle kar0603la06t03r03lm0306t03r. K02prü04ay Nehri su kalitesinin diyatomelere g02re belirlenmesi i04in Saprobi 02ndeksi (SI), Trophi Diyatom 02ndeksi (TDI) kullan03lm0306, 1., 2., 3., 4., 5., ve 6. 02rnekyerlerinin organik olarak az kirli, 7. 02rnekyerinin ise organik olarak kirli oldu06u belirlenmi06tir. Fizikokimyasal de06i06kenler Klee (1991)’nin metoduna g02re de06erlendirilmi06, ilk alt03 02rnekyerinin organik olarak 04ok az kirli, 7. 02rnekyerinin az kirli oldu06u saptanm0306t03r. Akarsuda epilitik olarak geli06en alglerin bask03nl03klar03 belirlenmi06, 02rnekyerleri ve aylara g02re bask03n taksonlar de06i06iklik g02stermi06tir Akarsu boyunca 02rnekyerleri aras03 benzerli06in saptanabilmesi i04in S03rensen benzerlik indeksi kullan03lm0306, 04al0306ma alan03nda 3. ve 4. 02rnekyeri birbirine en 04ok, 1. ve 6., 1. ve 7. 02rnekyerleri en az benzeyen alanlar olmu06tur. |
| [41] | . <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>是湖泊沉积物断代常用的两种核素,沉积物中核素的深度分布,不但随核素的大气沉降量变化,也与流域环境变化和沉积后核素的再分布有关。我国环境复杂,人类活动强烈,<sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>深度分布的非理想曲线常见于我国一些湖泊的沉积物。本文简要介绍了湖泊沉积物 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>深度分布理想曲线和断代基本原理,在参阅大量有关中国湖泊沉积物 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>断代文献的基础上,讨论了 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>非理想深度分布曲线的解译和沉积物断代的几个常见问题。主要观点如下: 1)我国湖泊沉积物不存在所谓的1974年和1986年蓄积峰;2)一些湖泊沉积出现的非单峰型 <sup>137</sup> Cs深度分布曲线,可能与人类活动或湖流扰动湖泊底泥、流域侵蚀产沙环境变化和 <sup>137</sup> Cs主要来源于冰川融水补给等因素有关;3)沉积物中的核素垂向运移,不改变剖面中1963年 <sup>137</sup> Cs蓄积峰的位置,不影响其断代标志意义;4)流域环境突发事件引起的沉积剖面中的 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>明显异常,是断代的可靠标志等。最后介绍了根据沉积剖面 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>总量与本底值对比,求算沉积速率的核素质量平衡法。 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>是湖泊沉积物断代常用的两种核素,沉积物中核素的深度分布,不但随核素的大气沉降量变化,也与流域环境变化和沉积后核素的再分布有关。我国环境复杂,人类活动强烈,<sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>深度分布的非理想曲线常见于我国一些湖泊的沉积物。本文简要介绍了湖泊沉积物 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>深度分布理想曲线和断代基本原理,在参阅大量有关中国湖泊沉积物 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>断代文献的基础上,讨论了 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>非理想深度分布曲线的解译和沉积物断代的几个常见问题。主要观点如下: 1)我国湖泊沉积物不存在所谓的1974年和1986年蓄积峰;2)一些湖泊沉积出现的非单峰型 <sup>137</sup> Cs深度分布曲线,可能与人类活动或湖流扰动湖泊底泥、流域侵蚀产沙环境变化和 <sup>137</sup> Cs主要来源于冰川融水补给等因素有关;3)沉积物中的核素垂向运移,不改变剖面中1963年 <sup>137</sup> Cs蓄积峰的位置,不影响其断代标志意义;4)流域环境突发事件引起的沉积剖面中的 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>明显异常,是断代的可靠标志等。最后介绍了根据沉积剖面 <sup>137</sup> Cs和 <sup>210</sup> Pb<sub>ex</sub>总量与本底值对比,求算沉积速率的核素质量平衡法。 |
| [42] | . |
| [43] | Sediment trap material collected at five depths from two locations in Lake Michigan has been studied to determine the sources of particulate organic matter and the early diagenetic changes which occur during sinking of particles. Aquatic material dominates in shallower depths whereas land-derived material is more important in near-bottom depths. Organic carbon concentrations decrease with depth as a result of remineralization of organic matter by microbial activity and dilution by resuspended bottom sediments. Preferential remineralization of algal organic matter and downslope transport of particulate matter from coastal areas create differences in the lipid biomarker characteristics of settling particles found at different depths in the water column. Calculations of apparent decomposition rate constants from lipid distributions at different depths show that shorter chainlength n -alkanoic acids are degraded faster than longer components. Carbon and nitrogen isotopic compositions of total organic matter are nearly unaffected by large-scale amounts of remineralization during sinking. |
| [44] | We studied the trophic development of the past 30–10002years in eight moderately deep Dutch lakes based on their sedimentary fossil diatom assemblages. The dominant diatoms indicating meso- to eutrophic conditions were Aulacoseira subarctica , Cyclotella ocellata , C. cyclopuncta , C. meneghiniana, Puncticulata bodanica , Aulacoseira granulata , Cyclostephanos dubius , C. invisitatus , Stephanodiscus hantzschii , S. medius , and S. parvus . Ordination of diatom data separated the lakes into four groups according to their total phosphorus concentrations (TP), water supply, water management, and origin. The first group consists of dike-breach lakes, which were in stable eutrophic to hypertrophic conditions throughout the past century with diatom-inferred TP (DI-TP) concentrations of between 70 and 30002μg02l 611 . The main factors influencing these dike-breach lakes are river management, ground water supply of riverine origin, and local land use. The second group are artificial lakes of fluctuating oligo- to mesotrophic conditions and DI-TP concentrations of 10–3002μg02l 611 . Only one of the artificial lakes showed a DI-TP increase due to changes in catchment agricultural practice. A third group includes an artificial moat and an inland dike-breach lake with DI-TP concentrations of 50–10002μg02l 611 . The fourth group contains an individual dike-breach lake with stable mesotrophic conditions of 5002μg02l 611 throughout the past century. Rather than showing a regional pattern, the studied lakes behave very individualistically with regard to their trophic history, reflecting changes in the local hydrology and in their nutrient sources. |
| [45] | An endemic diatom, Cyclotella rhomboideo-elliptica Skuja, from the Yunnan Plateau, has been disappearing gradually from some lakes of the plateau. This study investigated the diatom's distribution in 30 lakes and documents long-term population changes in the paleolimnological record of a deep lake, Lake Fuxian. Living cells of C. rhomboideo-elliptica were found in five Yunnan Plateau lakes in 1957, but cells were restricted to Lake Fuxian in 2005. Its absolute abundance fluctuated from low to high to low. Our study suggests that nutrient concentrations correlate with C. rhomboideo-elliptica's s abundance and survival. We infer that the disappearance of C. rhomboideo-elliptica in some lakes may be due to increased nutrient concentrations and the species may be indicators of low nutrients. During the study, we also found that decreased in the diatoms average long axis length after the early 1990s. This morphological change was likely due to higher nutrient concentrations or to the increase in temperature, or a combination of the two. |
| [46] | . 随着人类活动的增强与全球气候变暖的持续,近年来云南湖泊的生态系统功能持续退化,而目前对云南湖泊生态系统的研究还主要集中于单一环境压力的生态效应。以星云湖为研究对象,通过沉积物记录与现代监测资料,识别在湖泊富营养化、气候变化以及人类强烈干扰下硅藻群落结构响应的过程,并甄别驱动群落变化的主要环境压力及其强度。结果显示随着湖泊生产力水平(如沉积物叶绿素a浓度)的增加,硅藻物种组成发生了明显的变化,主成分分析表明了水体富营养化是驱动群落变化的主要环境因子(<i>r</i>=-0.63, <i>P</i>< 0.001)。简约模型与方差分解的结果表明近200年来(钻孔长度38cm),湖泊营养水平和水动力是驱动星云湖硅藻群落变化的主要环境因子,分别解释了群落变化的18.8%和2.9%;而1951年以后,湖泊营养水平和温度分别解释了硅藻群落结构变化的31.4%和26.8%。研究结果表明了硅藻群落长期变化的主控因子是湖泊营养水平,而人类活动及气候变化等可以通过改变湖泊水动力及湖水温度来驱动硅藻群落的演替,同时抚仙湖-星云湖的连通性也对硅藻群落的演替产生了一定影响。 随着人类活动的增强与全球气候变暖的持续,近年来云南湖泊的生态系统功能持续退化,而目前对云南湖泊生态系统的研究还主要集中于单一环境压力的生态效应。以星云湖为研究对象,通过沉积物记录与现代监测资料,识别在湖泊富营养化、气候变化以及人类强烈干扰下硅藻群落结构响应的过程,并甄别驱动群落变化的主要环境压力及其强度。结果显示随着湖泊生产力水平(如沉积物叶绿素a浓度)的增加,硅藻物种组成发生了明显的变化,主成分分析表明了水体富营养化是驱动群落变化的主要环境因子(<i>r</i>=-0.63, <i>P</i>< 0.001)。简约模型与方差分解的结果表明近200年来(钻孔长度38cm),湖泊营养水平和水动力是驱动星云湖硅藻群落变化的主要环境因子,分别解释了群落变化的18.8%和2.9%;而1951年以后,湖泊营养水平和温度分别解释了硅藻群落结构变化的31.4%和26.8%。研究结果表明了硅藻群落长期变化的主控因子是湖泊营养水平,而人类活动及气候变化等可以通过改变湖泊水动力及湖水温度来驱动硅藻群落的演替,同时抚仙湖-星云湖的连通性也对硅藻群落的演替产生了一定影响。 |
| [47] | ABSTRACT Dated sediment cores from five alpine lakes (>3200聽m asl) in Rocky Mountain National Park (Colorado Front Range, USA) record near-synchronous stratigraphic changes that are believed to reflect ecological and biogeochemical responses to enhanced nitrogen deposition from anthropogenic sources. Changes in sediment proxies include progressive increases in the frequencies of mesotrophic planktonic diatom taxa and diatom concentrations, coupled with depletions of sediment N and C聽:聽N values. These trends are especially pronounced since approximately 1950. The most conspicuous diatoms to expand in recent decades are and . Down-core species changes are corroborated by a year-long sediment trap experiment from one of the lakes, which reveals high frequencies of these two taxa during autumn and winter months, the interval of peak annual limnetic [ ]. Although all lakes record recent changes, the amplitude of stratigraphic shifts is greater in lakes east of the Continental Divide relative to those on the western slope, implying that most nitrogen enrichment originates from urban, industrial and agricultural sources east of the Rocky Mountains. Deviations from natural trajectories of lake ontogeny are illustrated by canonical correspondence analysis, which constrains the diatom record as a response to changes in nitrogen biogeochemistry. These results indicate that modest rates of anthropogenic nitrogen deposition are fully capable of inducing directional biological and biogeochemical shifts in relatively pristine ecosystems. |
| [48] | <a name="Abs1"></a>With the development of quantitative transfer functions to relate community structure to physicochemical variables, reconstructions of past environmental conditions have been possible and have enhanced our understanding of various ecosystem processes. There are cases, however, in which this approach is not applicable, or does not provide enough information for the questions being asked. In these cases, some alternatives are to conduct experiments or to examine the distribution of species at a finer spatial resolution. These two approaches have been used as alternatives to or in conjunction with the development of transfer functions. In this review, I discuss the ways in which these two approaches are now being used in paleolimnological studies to enhance our understanding of the ecology of the species found in sediment records and thus refine interpretations of environmental change. My focus is primarily on studies that deal with establishing clearer relationships between environmental variables and the growth or distribution of organisms. I present examples of how these approaches have been integrated in a variety of studies, including those designed to: (1) refine and enhance reconstructions that are based on transfer functions; (2) develop new paleolimnological tools to reconstruct environmental change; (3) explore mechanistic links in the relationships between organisms and commonly reconstructed environmental variables; and (4) pose and test hypotheses based on patterns in the sediment record. These cases demonstrate that the use of these approaches was essential to clarify species-environment relationships as well as lake responses to disturbance. As in all disciplines, however, there are many challenges in this area of research. In particular, the quantitative integration of these approaches with the sediment record is a major challenge, due to disparate spatial and temporal scales. This research can also be quite labor-intensive, and provides information on fewer taxa than in the calibration set approach. It also requires interdisciplinary training and/or collaboration in fields that have historically been less integrated, hence they may require greater effort. These issues may hinder the use of these approaches because of the perceived difficulty. I discuss these challenges and address possible solutions. |
| [49] | Transects of surface sediment samples were taken in 4 lakes from the Sylvania Wilderness Area, Upper Peninsula of Michigan. These surface samples were compared with diatom samples from a core taken in the Northwest basin of Crooked Lake, also from the Sylvania Wilderness Area. Weighted Averaging calibration was used to reconstruct lake depths in Crooked Lake using the diatom microfossils from the core and the surface samples to infer past lake depth. During the early Holocene the lake was dominated by planktonic species and diatom-inferred water depth was large approx. 13 m. At about 6700 BP inferred water depth was 2 m and samples were dominated by Fragilaria construens var. venter a species characteristic of shallow parts of the surface sample transects. From 6700 to 5000 BP reconstructed water level was at its shallowest. From 5000 to 3000 BP it increased. This rise in water level was marked by increasing abundances of Aulacoseira ambigua and occurred at the same time increasing percentages of hemlock pollen indicate increasing available moisture. Modern water depth was reached about 3000 BP. The water level changes at Crooked Lake are consistent with regional climate changes in the Upper Midwest during the Holocene. The lake was shallowest during the mid-Holocene warm period documented by other investigators. It deepened as the Midwestern climate became cooler and wetter during the late Holocene. |
| [50] | Diatom assemblages in sediments from two subalpine lakes in the Uinta Mountains, Utah, show asynchronous changes that are related to both anthropogenic and natural inputs of dust. These lakes are downwind of sources of atmospheric inputs originating from mining, industrial, urban, agricultural and natural sources that are distributed within tens to hundreds of kilometers west and south of the Uinta Mountains. Sediment cores were retrieved from Marshall and Hidden lakes to determine the impacts of atmospheric pollution, especially metals. Paleolimnological techniques, including elemental analyses and Pb and Pu dating, indicate that both lakes began receiving eolian inputs from anthropogenic sources in the late 1800s with the greatest increases occurring after the early 1900s. Over the last century, sediments in Marshall Lake, which is closer to the Wasatch Front and receives more precipitation than Hidden Lake, received twice the concentrations of metals and phosphorus as Hidden Lake. Comparison of diatom and elemental data reveals coeval changes in geochemistry and diatom assemblages at Marshall Lake, but not at Hidden Lake; however, a major shift in diatom assemblages occurs at Hidden Lake in the seventeenth century. The change in diatoms at Marshall Lake is marked by the near disappearance of and and an increase in benthic, metal-tolerant diatoms. This change is similar to changes in other lakes that have been attributed to metal pollution. The marked change in diatom assemblages at Hidden Lake indicates a shift in lake-water pH from somewhat acidic to circumneutral. We hypothesize that this change in pH is related to drought-induced changes in input of carbonate-rich desert dust. |
| [51] | Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and how science impacts upon all aspects of society and life. |
| [52] | 1. Using a palaeolimnological approach in shallow lakes, we quantified the species richness responses of diatoms and Cladocera to phosphorus enrichment. We also examined differences in species richness responses between littoral and pelagic assemblages of our focal communities. To address both spatial and temporal relationships, our study includes an analysis of both surface sediments from 40 lakes and of a lake sediment record spanning c. 120 years. The objective of our study was to determine whether similar species richness patterns occurred across trophic levels, as well as along spatial and temporal gradients. 2. We found that both diatom and Cladocera species richness estimates significantly declined with increasing phosphorus across space and through time. When the assemblages were subdivided according to known habitat preferences, littoral biodiversity maintained a negative trend, whereas pelagic species richness tended to show no relationship with phosphorus. 3. Negative productivitydiversity patterns have been observed across almost all palaeolimnological studies that span large productivity gradients. This congruence in patterns is most likely due to the similarity in data collection methods and in focal communities studied. The contrasting responses between littoral and pelagic assemblages may be explained by the differences in physical habitat and the pool of taxa in each of these environments. Consistent with the literature, we found statistical support for the idea that littoral diversity declines could be explained by an interaction between macrophytes and nutrients along strong trophic gradients. The general lack of a diversity response in our pelagic assemblages could be attributable to the limited pool of subfossil taxa. The response of the pelagic diatom could also be related to their broad range of nutrient tolerances. 4. The observed negative response of species richness to phosphorus enrichment, particularly in the littoral assemblages, has implications for ecosystems functioning because communities with reduced biodiversity often are less resilient to anthropogenic change. |
| [53] | . 浮游植物是水生生态系统中重要的初级生产者,对维持水生态系统的平衡起着十分重要的作用.根据2008年云贵高原湖泊丰水期浮游植物调查数据,系统地分析了云贵高原13个湖泊中浮游植物的种群密度、生物量、组成及其多样性.云贵高原13个湖泊中共鉴定出浮游植物7门109种(绿藻52种、蓝藻23种、硅藻20种、其他14种).13个湖泊浮游植物Shannon-Wiener指数在0.5-2.2之间,其值大小与单个环境因子无显著相关.相关分析发现浮游植物总量与总氮、总磷、CODMn、硝态氮含量显著正相关,物种丰富度与总氮、总磷(0.1mg/L范围内)、CODMn含量亦显著正相关.另外,研究也发现各湖泊间浮游植物组成的相似性与各湖泊间营养状态差异显著负相关.由此可见,湖泊的营养状态不仅影响浮游植物的总量、组成以及物种丰富度,而且也影响各湖泊物种组成的相似性. 浮游植物是水生生态系统中重要的初级生产者,对维持水生态系统的平衡起着十分重要的作用.根据2008年云贵高原湖泊丰水期浮游植物调查数据,系统地分析了云贵高原13个湖泊中浮游植物的种群密度、生物量、组成及其多样性.云贵高原13个湖泊中共鉴定出浮游植物7门109种(绿藻52种、蓝藻23种、硅藻20种、其他14种).13个湖泊浮游植物Shannon-Wiener指数在0.5-2.2之间,其值大小与单个环境因子无显著相关.相关分析发现浮游植物总量与总氮、总磷、CODMn、硝态氮含量显著正相关,物种丰富度与总氮、总磷(0.1mg/L范围内)、CODMn含量亦显著正相关.另外,研究也发现各湖泊间浮游植物组成的相似性与各湖泊间营养状态差异显著负相关.由此可见,湖泊的营养状态不仅影响浮游植物的总量、组成以及物种丰富度,而且也影响各湖泊物种组成的相似性. |
| [54] | 1.68Using data from 71, mainly shallow (an average mean depth of 3 m), Danish lakes with contrasting total phosphorus concentrations (summer mean 0.02–1.065mg P65L61l), we describe how species richness, biodiversity and trophic structure change along a total phosphorus (TP) gradient divided into five TP classes (class 1–5: 0.465mg P65L611). 2.68With increasing TP, a significant decline was observed in the species richness of zooplankton and submerged macrophytes, while for fish, phytoplankton and floating-leaved macrophytes, species richness was unimodally related to TP, all peaking at 0.1–0.465mg P65L611. The Shannon–Wiener and the Hurlbert probability of inter-specific encounter (PIE) diversity indices showed significant unimodal relationships to TP for zooplankton, phytoplankton and fish. Mean depth also contributed positively to the relationship for rotifers, phytoplankton and fish. 3.68At low nutrient concentrations, piscivorous fish (particularly perch, ) were abundant and the biomass ratio of piscivores to plankti-benthivorous cyprinids was high and the density of cyprinids low. Concurrently, the zooplankton was dominated by large-bodied forms and the biomass ratio of zooplankton to phytoplankton and the calculated grazing pressure on phytoplankton were high. Phytoplankton biomass was low and submerged macrophyte abundance high. 4.68With increasing TP, a major shift occurred in trophic structure. Catches of cyprinids in multiple mesh size gill nets increased 10-fold from class 1 to class 5 and the weight ratio of piscivores to planktivores decreased from 0.6 in class 1 to 0.10–0.15 in classes 3–5. In addition, the mean body weight of dominant cyprinids (roach, , and bream, ) decreased two–threefold. Simultaneously, small cladocerans gradually became more important, and among copepods, a shift occurred from calanoid to cyclopoids. Mean body weight of cladocerans decreased from 5.165 g in class 1 to 1.565 g in class 5, and the biomass ratio of zooplankton to phytoplankton from 0.46 in class 1 to 0.08–0.15 in classes 3–5. Conversely, phytoplankton biomass and chlorophyll increased 15-fold from class 1 to 5 and submerged macrophytes disappeared from most lakes. 5.68The suggestion that fish have a significant structuring role in eutrophic lakes is supported by data from three lakes in which major changes in the abundance of planktivorous fish occurred following fish kill or fish manipulation. In these lakes, studied for 8 years, a reduction in planktivores resulted in a major increase in cladoceran mean size and in the biomass ratio of zooplankton to phytoplankton, while chlorophyll declined substantially. In comparison, no significant changes were observed in 33 ‘control’ lakes studied during the same period. |
| [55] | . 目前国内对生产力-生物多样性关系(productivity-diversity relationship, PDR)的研究主要集中于陆地生态系统和空间尺度，少量关于湖泊系统的研究也主要集中于现代调查，缺乏较长时间尺度上的模式探讨。本文应用沉积物色素记录首先重建了抚仙湖和滇池初级生产力变化历史，对硅藻群落的主成分分析(PCA)表明湖泊初级生产力是驱动硅藻群落变化的主要环境梯度(PCA第一主轴得分)。进一步分析硅藻群落α与β多样性响应湖泊生产力水平的模式，发现滇池硅藻群落表现为随着系统生产力的上升物种丰度减少、β多样性降低，而抚仙湖呈现相反的变化模式。而且两个湖泊β多样性与生产力平均水平的关系均表现出与α多样性相似的特征；但在与生产力变化幅度的关系上，滇池表现出显著的负相关，而抚仙湖则没有显著的变化。滇池硅藻群落生产力随硅藻多样性的降低显著增加(R2 = 0.597, P < 0.01)，而在抚仙湖无显著变化，表明了滇池群落多样性的维持作用对群落生产力的影响较弱(如与营养盐富集的促进作用相比)。滇池明显的富营养化过程与强烈的人类扰动带来的环境异质性降低可能对群落多样性-生产力的关系产生了明显的控制作用。 目前国内对生产力-生物多样性关系(productivity-diversity relationship, PDR)的研究主要集中于陆地生态系统和空间尺度，少量关于湖泊系统的研究也主要集中于现代调查，缺乏较长时间尺度上的模式探讨。本文应用沉积物色素记录首先重建了抚仙湖和滇池初级生产力变化历史，对硅藻群落的主成分分析(PCA)表明湖泊初级生产力是驱动硅藻群落变化的主要环境梯度(PCA第一主轴得分)。进一步分析硅藻群落α与β多样性响应湖泊生产力水平的模式，发现滇池硅藻群落表现为随着系统生产力的上升物种丰度减少、β多样性降低，而抚仙湖呈现相反的变化模式。而且两个湖泊β多样性与生产力平均水平的关系均表现出与α多样性相似的特征；但在与生产力变化幅度的关系上，滇池表现出显著的负相关，而抚仙湖则没有显著的变化。滇池硅藻群落生产力随硅藻多样性的降低显著增加(R2 = 0.597, P < 0.01)，而在抚仙湖无显著变化，表明了滇池群落多样性的维持作用对群落生产力的影响较弱(如与营养盐富集的促进作用相比)。滇池明显的富营养化过程与强烈的人类扰动带来的环境异质性降低可能对群落多样性-生产力的关系产生了明显的控制作用。 |
