西藏玛旁雍错和拉昂错水深、水质特征及现代沉积速率

基于2009年和2010年分别在玛旁雍错和拉昂错开展的2次野外湖泊调查,本文简要报道这2个藏南内流水系湖泊的水深分布、湖水理化特征及湖泊现代沉积速率.测深结果显示玛旁雍错湖盆形状规则,深水区坡度平缓,最大水深为72.6 m;拉昂错北部为较浅的河流冲积扇,通过狭长的水道与开阔的南部湖区相连,南部湖区中心平坦,实测最深处49.03 m;根据水深数据计算的玛旁雍错和拉昂错水量分别为1.462×10¹⁰m³和5.711×10⁹m³.玛旁雍错湖水剖面水质在垂直方向上呈现明显的分层结构,温跃层介于25~35 m之间,温度梯度为0.17℃/m,水体pH、电导率和溶解氧在温跃层具有同步变化特征;拉昂错湖水温跃层与玛旁雍错相比不明显,5~15 m间温度梯度为0.16℃/m,湖水pH与溶解氧呈反相变化,这可能与水生植物呼吸作用有关.2个湖泊湖水的主要离子组成特征除Ca²⁺外基本相同,拉昂错主要离子浓度约为玛旁雍错的3倍,而Ca²⁺则约为玛旁雍错的1/2;利用²¹⁰Pb和¹³⁷Cs方法对玛旁雍错和拉昂错的短岩芯进行了测试,结果表明2个湖泊近代沉积速率分别约为0.31 mm/a和0.65 mm/a.     

CLM4-LISSS模型对太湖多时间尺度水热通量模拟性能的评估

湖泊模型为数值天气预报模型提供热量通量、水汽通量和动量通量等下边界条件,但是不同时间尺度上湖泊水热通量变化的控制因子不同,因此有必要对湖泊模型进行多时间尺度上的离线评估.本文利用2012-2016年太湖中尺度通量网避风港站的气象资料和辐射数据驱动CLM4-LISSS模型(Community Land Model version 4-Lake,Ice,Snow and Sediment Simulator),并与涡度相关观测(Eddy Covariance,EC)结果进行对比,以年平均潜热通量模拟结果最佳为目标调整了模式中的消光系数、粗糙度长度方案,研究了该模型从半小时到年尺度上对湖表温度和水热通量的模拟性能.结果表明:模型对湖表温度的模拟在各时间尺度上均比较理想,但是模拟的日较差较小;从半小时到年尺度上潜热通量的变化趋势都能被很好地模拟出来,但在季节尺度上,潜热通量的模拟出现了秋冬季偏高、春夏季偏低的情况,季节变化模拟不准确.湖表温度和潜热通量模拟偏差的原因可能是消光系数的参数化方案.相比之下,感热通量尽管年际变化趋势的模拟值与观测值一致,但是从半小时到年尺度均被高估.特别地,冷锋过境期间,模型能较好地模拟出潜热通量和感热通量的变化趋势,但对于高风速条件下的感热通量模拟效果不佳.本文的研究结果能为湖泊模式的应用与发展提供有用信息.     

喜马拉雅造山带西部拉昂错蛇绿岩带区域地壳深部结构及其可能构造归属研究

前人研究表明喜马拉雅造山带西部出露的拉昂错蛇绿混杂岩为新特提斯洋壳岩石圈的一部分,代表了新特提斯洋的关闭及其随后大洋岩石圈物质的仰冲.鉴于拉昂错蛇绿岩的构造演化历史尚不明确,前期对于拉昂错蛇绿岩带构造归属的研究主要基于岩石学研究和地表地质调查等,缺少精细的深部地壳结构进行运动学指示,因此证明拉昂错蛇绿混杂岩体的构造归属并非易事.本次研究中,我们对前期获得的一条南北向延伸穿过雅鲁藏布江缝合带和喜马拉雅造山带西部拉昂错蛇绿岩体的112 km长的深反射地震剖面进行了构造解释.高分辨率的深反射地震剖面清晰地显示了喜马拉雅山脉西部造山带内发育良好的地壳双冲构造几何结构,该地壳尺度双冲构造将印度俯冲地壳物质从底部运移到上部.同时,地震剖面还显示拉昂错蛇绿岩体和雅鲁藏布江蛇绿岩体在上地壳深处呈倾向相反但底部相通的结构构造.结合前人的岩石学/地球化学/地表地质研究成果,我们认为拉昂错蛇绿岩体为雅鲁藏布江缝合带蛇绿岩体的一部分.印度俯冲前缘的双冲构造折返将深部物质带到地表过程的同时,还将部分雅鲁藏布江蛇绿混杂岩携带至南侧距主缝合带位置大约20 km的拉昂错蛇绿岩区域.     

云南程海和阳宗海季节性分层及其消退对冬季水华的潜在影响

基于2014年10月2016年7月在云南程海和阳宗海开展了4个季度(秋季,10月;冬季,1月;春季,4月;夏季,7月)的调查,研究了两个湖泊的水体分层特征,探讨了热力分层及其变化与其他环境因子对浮游植物生物量的潜在影响,结果显示:程海和阳宗海水体分层的特征均为冬季混合、春季形成分层、夏秋季分层稳定,两湖均属暖单次混合型湖泊;程海分层期温跃层的平均深度(顶界)、厚度和强度分别为17.70±3.89 m、5.54±4.44 m和0.67±0.43℃/m,阳宗海的分别为12.53±3.35 m、8.25±4.85 m和0.53±0.43℃/m.在热力分层稳定期,两湖底层达到缺氧甚至厌氧状态,底层的电导率总体较表层高.调查期间,两个湖泊水柱表层浮游植物生物量(以叶绿素a浓度表征)均在冬季出现峰值,程海和阳宗海的分别为19.22±11.08和45.82±9.41μg/L;进一步分析发现,热力分层的消退可能是导致水体表层无机营养盐升高(底层供给)的重要原因,加之适宜的光热条件可诱导两湖冬季水华的发生;在其他季节转化期间,浮游植物生物量变化的主要影响因子亦具有一定的共性及湖泊与季节异质性.     

南方水库热分层消亡期混合层深度及缺氧区时空变化特征——以南宁市天雹水库为例

湖库热分层消亡引起的突发性水质恶化现象引起了广泛的关注,我国南方水库大多是暖单次混合型湖泊,每年混合一次,导致水库水质周期性下降,但目前对南方水库热分层消亡过程的高频监测研究较少。为探究我国南方水库热分层消亡期水体混合过程的时空变化规律及驱动因素,以广西南宁天雹水库为例,于冬季热分层消亡期(2019年11月—2020年2月)对水库多点位水体理化指标开展原位监测,并利用自建气象站获取气象水文数据。结果表明:(1)水库热分层消亡期间,过渡区水深较浅可在短期内达到完全混合状态且缺氧区同步消失;而湖泊区混合过程整体滞后于过渡区,混合层深度由6.85 m增加至13.65 m,缺氧区逐渐减小,缺氧指数(AI)由0.40减小至0.07,直至水体完全混合后缺氧区消失;水库过渡区较湖泊区提前约40 d达到完全混合状态。(2)气象因子是引起热分层结构变化的主要因素,气温(T)、辐射(R)与混合层深度(MLD)呈现显著负相关(R_T=0.927、R_R=0.925,P<0.01),风速(WS)与MLD呈现显著正相关(R_WS=0.728,P&...     

西藏当惹雍错和扎日南木错现代湖泊基本特征

湖泊现代特征的调查和对比研究是湖泊学和古湖泊学研究工作的基础,青藏高原大部分湖泊目前仍缺少详细的基本特征考察资料.基于2009年9月实地考察,本文报道藏北高原腹地的两个内陆封闭大湖——扎日南木错和当惹雍错的水深分布和现代湖水基本特征.测深结果显示扎日南木错大部分湖区水下地形较为平坦,最大水深为71.55m;当惹雍错实测最大水深为214.48m,是青藏高原上已知最深的湖泊,也是我国已知的第二深水湖.湖水理化性质显示在垂直方向上两湖都呈现明显的分层结构,温跃层的温度梯度分别为1.1℃/m和0.57℃/m,当惹雍错底层水温最低仅为1.6℃;两湖表水层的电导率分别高达18500μS/cm和12900μS/cm;两湖表水层pH都超过10,而底层水的pH都降低到5左右,上下层湖水显示了不同的酸碱性质.湖水电导率和溶解氧在温跃层都具有同步跃变特征,反映了温度对湖水性质的影响.     

1975-2013年西藏佩枯错湖面变化及分析

根据1975年地形图、1970s末至2013年19期Landsat（MSS、TM、ETM⁺）陆地资源卫星和20032009年ICESat卫星数据,以及近40年气象资料,对西藏佩枯错湖泊面积变化进行分析.结果表明,湖泊面积、湖泊高度变化波动较大,均呈减少和退缩趋势.19752013年间湖泊面积减少10.68 km²,减幅为3.79%.从空间动态变化来看,变化较明显的区域位于该湖的南岸和东北岸,南岸、东北岸湖岸线分别向北、向西南萎缩.20032009年湖面高度和湖泊面积均呈现出下降趋势,分别下降了0.17 m和4.4 km².19992013年之间对该流域湖泊有影响的冰川变化分析显示,冰川呈现出退缩、面积减少趋势.数据显示冰川面积总共减少了17.17 km²,减少率为7.91%.自1971年以来,流域气温总体呈上升趋势,2000年以后升温显著.佩枯错43 a来降水量年际变化波动较大,年降水量呈减少趋势,总的来说降水量每10 a减少6.99 mm.虽然佩枯错属于降水和冰雪融水补给湖泊,但该流域湖面增减与周围冰川变化的关系并不明显,与温度变化呈负相关,而与流域内降水量呈正相关.综合分析表明,佩枯错流域湖泊变化与冰川退缩关系不密切,降水量是湖泊变化的主要原因.     

乌梁素海冰封期分层与混合特征及对氧代谢速率的影响

为探究寒旱区浅湖冰封期分层动态与其对湖泊新陈代谢速率的影响,于2016-2019年对乌梁素海气象与冰雪条件、冰下水体环境开展原位观测,分析水温和溶解氧变化特征、冰下混合层的出现与发展动态及其对代谢速率的影响.结果显示:观测期内乌梁素海整体水温较高(可接近10℃),冻结期水温结构主要由稳定的上部逆温层和下部弱逆温层构成,...     

青藏高原达则错近1000年来生态系统变化及可能机制

在全球变化的背景下,厘清湖泊生态系统对气候环境以及人类活动的响应机制对制定社会的适应政策非常重要.目前的研究手段如现场观测和围隔实验等可以很好地揭示湖泊生态系统在有观测记录以来的演替和变化过程,但是不能提供历史时期湖泊生态系统的变化及其对气候环境变化和人类活动的响应.古湖沼学可以为探讨湖泊生态系统的长期变化及其对气候环境变化的响应提供重要信息.本文以青藏高原中部无鱼湖泊达则错为研究对象,利用沉积物岩芯西藏拟溞（Daphnia tibetana）残体丰度和总烯酮含量重建该区过去1000年的浮游生物记录;利用总氮、总磷以及总有机碳含量重建过去1000年湖泊营养盐以及有机质变化记录;结合烯酮不饱和度重建的古温度记录,探讨达则错过去1000年生态系统变化及其对气候环境演变的响应机制.研究发现达则错湖泊生态系统尤其是生产力在自然状况和人类活动影响下存在显著变化.在自然状况下,较高的湖泊初级和次级生产力发生在温度较低和湖水营养盐浓度较高时;而在过去150年,达则错湖泊环境受到人类活动影响显著,湖泊生产力发生相应变化,较高的湖泊生产力发生在温度较高时期,其主要受由人类活动带来的营养盐元素浓度控制.研究结果表明达则错湖泊生态系统在人类活动影响下发生了显著的改变.     

青海湖热力状况的模拟与未来情景之研究

运用基于湖泊热量收支与湍流扩散的湖泊热力学模型模拟了青海湖近３０年来湖水热力状况,内容包括湖泊水面温度,温度沿深度的垂直分布,冬季结冰与融冰的起迄时间,冰盖厚度;积雪深度与天数等。在此基础上,运用４个ＧＣＭｓ模型输出的ＣＯ２倍增情景下该地区的气候状况,评价了湖泊热力状况在未来的可能变化情况。     

纳木错水温变化及热力学分层特征初步研究

水温变化是湖泊的重要物理特性,对湖泊的水质特征、湖水能量循环、水生生态系统研究具有重要意义.基于不同季节的实地观测资料,分析青藏高原高海拔、深水大湖纳木错的水温变化特征及季节差异,并着重分析湖水热力学分层的季节变化.结果显示纳木错中部、东部两个湖盆冬季封冻,夏季存在稳定分层,春、秋季混合,是一个典型双季对流、完全混合型湖泊.但两个湖盆水温变化与热力学分层又有各自的特征,东部浅湖盆湖水在春季升温快,夏季分层与秋季翻转均比中部湖盆早,且秋季翻转时水温也比中部湖盆高.初步分析认为两个湖盆不同的湖盆形状及水深分布可能是造成其热力学特征差异的主要原因.     

全球变化下青藏高原湖泊在地表水循环中的作用

青藏高原是地球上最重要的高海拔地区之一,对全球变化具有敏感响应.青藏高原作为"亚洲水塔",其地表水资源及其变化对高原本身及周边地区的经济社会发展具有重要的影响.然而,在气候变暖的情况下,构成高原地表水资源的各个组分,如冰川、湖泊、河流、降水等水体的相变及其转化却鲜为人知.湖泊是青藏高原地表水体相变和水循环的关键环节.湖泊面积、水位和水量对西风和印度季风的降水变化非常敏感,但湖泊面积和水量变化在不同区域和时段的响应也不尽相同.湖泊水温对气候变暖具有明显响应,湖泊水温和水下温跃层深度的变化能够对水—气的热量交换具有明显影响,从而影响了区域蒸发和降水等水循环过程.由于湖泊水量增加,高原中部色林错地区湖泊盐度自1970s以来普遍下降.根据60多个湖泊实地监测建立的遥感反演模型研究发现,2000—2019年湖泊透明度普遍升高.对不同补给类型的大湖水量平衡监测发现,影响湖泊变化的气象和水文要素具有较大差异.在目前的暖湿气候条件下,青藏高原的湖泊将会持续扩张.为了深入认识湖泊变化在青藏高原区域水循环和气候变化中的作用,需要全面了解湖泊水量赋存及连续的时间序列变化,需要深入了解湖泊理化参数变化及对湖泊大气之间热量交换的影响,需要更多来自大湖流域的综合连续观测数据.     

Differences and cause analysis of changes in lakes of different supply types in the north‐western Tibetan Plateau

Most lakes of the Tibetan Plateau were experiencing quick expansion in recent decades; a detailed study on the changes in lakes of different supply types will help to understand the cause of the changes by analysing area change of 34 lakes and water level change of eight lakes in the north‐western Tibetan Plateau. All lakes are classified into three types: non‐glacier‐fed lakes, upstream lakes and glacier‐fed lakes. The glacier‐fed lakes are separated into glacier‐fed_P1 (quick expansion region) and glacier‐fed_P2 (slow expansion region). Combining the changes in precipitation, temperature and evaporation, less precipitation may be the main reason for lake shrinkage from 1976 to 1996 and quickly increasing precipitation led to the lakes' expansion from 1996 to 2000. However, after 2000, upstream lakes remained in a stable state with slight variation, non‐glacier‐fed lakes and glacier‐fed_P2 lakes exhibited a slightly increasing rate with high precipitation and high evaporation, and glacier‐fed_P1 lakes still expanded quickly. On the basis of the assumption of same precipitation and evaporation, glacial meltwater may make an important contribution (>52%) to the increase in water storage of Bangdag Co and Meima Co. The results suggest that glacial meltwater augments the increased rate of glacier‐fed_P2 lakes and plays a much more important role in the expansion of glacier‐fed_P1 lakes compared to other lakes.     

Discovery of bacteriopheophytin-a in lacustrine deposits from Lake Zigetang on the central Tibetan Plateau and its paleoenvironmental significance

Lake Zigetang is located on the central Tibetan Plateau(TP) and represents a rare but typical meromictic lake in China.The lake's stable meromixis sustains microflora communities, and changes in these communities are relatively independent of climate. Therefore, these communities can be used as paleoclimate proxies. In this paper, the stratification properties and their relationships with the microflora of Lake Zigetang were analyzed. We found that water depth and climate conditions were two important factors for maintaining meromixis in Lake Zigetang. Generally, stratification was enhanced during warm periods, while temperature differences between the mixolimnion and monimolimnion were decreased during cold periods. The presence of anoxygenic phototrophic bacteria(APB) was demonstrated by the discovery of bacteriopheophytin-a(Bph-a) in the sediments.This bacterial community is mainly concentrated at the bottom of the chemocline and the top of the monimolimnion, where it forms a thin APB layer. Moreover, total APB productivity is mainly affected by the light intensity penetrating to the APB layer,which exponentially increases as the thermocline becomes shallow. Therefore, high Bph-a values in the lake corresponded to a shallow thermocline and warm periods, low Bph-a values corresponded to cold periods, and zero changes indicated that the water was completely mixed and reflected an extreme cold climate or low lake level period. Thus, Bph-a can be used as a climate proxy to reconstruct the history of lake stratification and climate changes.     

Quantitative comparison of river inflows to a rapidly expanding lake in central Tibetan Plateau

The recent rapid expansion of inland lakes on the Tibetan Plateau (TP) are a good indicator of the consequences of climate change. Quantifying the hydrological cycle of the lake basin is fundamentally important to understand the causes of lake growth. However, the hydrological processes of the TP interior are very complex and difficult to investigate because of the lack of observations. This is especially true for estimating the lake changes when run‐off inflows are affected by small lakes located in the flow routes within drainage areas. We used an integrated hydrological model, in combination with glacier melt and lake retention models, to analyse the run‐off inflows to Lake Siling Co, the largest endorheic lake in Tibet. It includes four subdrainage basins: Zhajiazangbu, Zhagenzangbu, Alizangbu, and Boquzangbu. Lake Siling Co was characterized by considerable increases during warm season from 1981 to 2012, due to the increased run‐off from Zhajiazangbu accounting for about 51–62% of the total run‐off inflows. Moreover, the dramatic increases exhibited during cold seasons were related to the increased retention water released from the small lakes within Zhagenzangbu and Alizangbu. Of the studied subdrainage basins, Boquzangbu contributed the least during both warm and cold seasons. On average, the annual amount of evaporation from lakes within the drainage area was about 2 times greater than that of glacier melt run‐off. Our results suggest that the retention effects of lakes on river inflows should receive more attention, because understanding these effects is potentially crucial to improved understanding of lake variations in the TP.     

Discovery of bacteriopheophytin-<Emphasis Type="Italic">a</Emphasis> in lacustrine deposits from Lake Zigetang on the central Tibetan Plateau and its paleoenvironmental significance

Lake Zigetang is located on the central Tibetan Plateau (TP) and represents a rare but typical meromictic lake in China. The lake’s stable meromixis sustains microflora communities, and changes in these communities are relatively independent of climate. Therefore, these communities can be used as paleoclimate proxies. In this paper, the stratification properties and their relationships with the microflora of Lake Zigetang were analyzed. We found that water depth and climate conditions were two important factors for maintaining meromixis in Lake Zigetang. Generally, stratification was enhanced during warm periods, while temperature differences between the mixolimnion and monimolimnion were decreased during cold periods. The presence of anoxygenic phototrophic bacteria (APB) was demonstrated by the discovery of bacteriopheophytin-a (Bph-a) in the sediments. This bacterial community is mainly concentrated at the bottom of the chemocline and the top of the monimolimnion, where it forms a thin APB layer. Moreover, total APB productivity is mainly affected by the light intensity penetrating to the APB layer, which exponentially increases as the thermocline becomes shallow. Therefore, high Bph-a values in the lake corresponded to a shallow thermocline and warm periods, low Bph-a values corresponded to cold periods, and zero changes indicated that the water was completely mixed and reflected an extreme cold climate or low lake level period. Thus, Bph-a can be used as a climate proxy to reconstruct the history of lake stratification and climate changes.     

Changes in the thermal structure of moderate to large sized lakes in response to changes in air temperature

Interannual variability in the thermal structure of lakes is driven by interannual differences in meteorological conditions. Dynamic or mechanistic models and empirical or statistical methods have been used to integrate the physical processes in lakes enabling the response of the thermal structure to changes in air temperature to be determined. Water temperature records for Lake Mendota, WI., are possibly the most extensive for any dimictic lake in the world and allowed both approaches to be used. Results from both techniques suggest the mixed layer temperature increases with increasing air temperature. Results from the empirical approach suggested epilimnion temperatures increase 0.5 to 1.0°C per 1.0°C increase in air temperature compared to 0.4 to 0.85°C estimated from a dynamical model (DYRESM). Increased air temperatures are related to significant warming in deep water temperatures in the absence of stratification; however, mid summer hypolimnion temperatures are expected to change very little or increase only slightly in response to climatic warming. Both approaches suggest increases in air temperatures increase the length of summer stratification; results from the dynamic model suggest an increase of approximately 5 days per 1°C increase in air temperature. Longer stratification is reflected in shallower late summer thermocline depths. With these quantitative relationships and forecast increases in air temperature for the 2 × CO₂ climatic scenario (Greenhouse Effect) from three General Circulation Models, projections are made describing the changes in the future mean thermal structure of moderate to large sized lakes.     

Variations in glacier volume and snow cover and their impact on lake storage in the Paiku Co Basin,in the Central Himalayas

Glaciers and snow cover are important constituents of the surface of the Tibetan Plateau. The responses of these phenomena to global environmental changes are sensitive, rapid and intensive due to the high altitudes and arid cold climate of the Tibetan Plateau. Based on multisource remote sensing data, including Landsat images, MOD10A2 snow product, ICESat, Cryosat-2 altimetry data and long-term ground climate observations, we analysed the dynamic changes of glaciers, snow melting and lake in the Paiku Co basin using extraction methods for glaciers and lake, the degree-day model and the ice and lake volume method. The interaction among the climate, ice-snow and the hydrological elements in Paiku Co is revealed. From 2000 to 2018, the basin tended to be drier, and rainfall decreased at a rate of −3.07 mm/a. The seasonal temperature difference in the basin increased, the maximum temperature increased at a rate of 0.02°C/a and the minimum temperature decreased at a rate of −0.06°C/a, which accelerated the melting from glaciers and snow at rates of 0.55 × 10⁷ m³/a and 0.29 × 10⁷ m³/a, respectively. The rate of contribution to the lake from rainfall, snow and glacier melted water was 55.6, 27.7 and 16.7%, respectively. In the past 18 years, the warmer and drier climate has caused the lake to shrink. The water level of the lake continued to decline at a rate of −0.02 m/a, and the lake water volume decreased by 4.85 × 10⁸ m³ at a rate of −0.27 × 10⁸ m³/a from 2000 to 2018. This evaluation is important for understanding how the snow and ice melting in the central Himalayas affect the regional water cycle.     

Isotopic variation in the lake water balance at the Yamdruk‐tso basin,southern Tibetan Plateau

The use of stable isotopes is a practical tool in the study of the lake water budget. This is an one way to study the hydrological cycle in the large numbers of inland lakes on the Tibetan Plateau, in which the isotope record of the sediment is believed to reflect the climatic and environmental changes. The monitoring of stable isotopes of the precipitation, river and lake waters during 2004 in the inland Yamdruk‐tso basin, southern Tibetan Plateau, reveals the lake water δ¹⁸O is over 10‰ higher than the local precipitation. This high difference indicates strong isotope enrichment due to lake water evaporation. The simulation results based on the isotope technique show that the present lake water δ¹⁸O level corresponds to an average relative humidity of around 54–58% during evaporation, which is very close to the instrumental observation. The simulation results also show that the inland lakes on the Tibetan Plateau have a strong adjustability to the isotope shift of input water δ¹⁸O. On average, the isotope component in the inland lake water is to a large extent controlled by the local relative humidity, and can also be impacted by a shift of the local precipitation isotope component. This is probably responsible for the large consistence in the isotope component in the extensive inland lakes on the Tibetan Plateau. Copyright © 2008 John Wiley & Sons, Ltd.     

藏北色林错流域的水文特征

本文报道了1997年降1998年夏季对藏北色林错等水体水文特征的考察情况,结果表明,色林错是一个大型深水湖泊,表层水温在下午4：30左右达到最高,清晨7：30左右时最低,浅水区域表层湖水在6月份的极端最高水温为21．2℃,极端最低水温为11．0℃,而日平均水温变幅仅5．6℃,其幅度大于在同一时段湖区内不同区域之间表层水温的变化,色林错湖水的pH值较高咪9．19－9．66;表层水的pH昼夜变化较小,仅0．15,最高值出现在凌晨,同时水体不同区域及深度的pH值基本一致,其溶解氧变化在4．62－5．12mg/L,而且不同深度水层之间的变幅较小,仅0．03－0．35mg/L;但其湖汊浆东如瑞溶解氧的昼认变幅为4．58－5．59mg/l;盐度的日变幅为1．60％－2．20％,考察表明,藏北水体的盐分有一个从河流到湖泊、以及由流水向静水富集的趋势;鱼类的分布与水体盐分的含量密切相关,即鱼类随着水体盐分的增加而消失,代之以嗜盐性卤虫的出现及大量繁衍。