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1.
Data are presented on the composition and biomass of the Aral Sea zooplankton in August and October, 1989. As salinity gradually increased, a decrease in zooplankton species composition occurred at a salinity of 25–30 g L−1. Because the Aral has now divided into two water-bodies, the zooplankton communities in these lakes have begun to conform with their individual hydrological and biological regimes.  相似文献   

2.
Lake Balkhash is one of the many closed lakes in Central Asia. Mechanisms of demineralization in Lake Balkhash were considered from results of surveys undertaken on the lake and along the Ili River. Electrical conductivity (EC) values at the eastern coast in south-western Lake Balkhash were higher than those of the western coast. The Ili River enters at the south-western corner of the lake, so that EC values of this area are low. This water flows westwards. The distribution of Ca2+ concentrations showed that these were lower value in Lake Balkhash than along the Ili River, implying Ca2+ removal by the lake. Amongst suspended mineral matter in the lake occur calcite and dolomite. Thus, a possible mechanism of calcium removal is that it is removed as crystals of calcite or dolomite. SO 4 2– concentration within the lake has increased for the past 37 years. This may be caused by the discharge into the lake from the city of Balkhash of waste water from a copper smelter.  相似文献   

3.
An overview of recent changes in salinity in the surface waters of the Aral sea basin is given. Total dissolved salts (salinity) in most waters are higher than admissible values for drinking water, and ionic composition has changed with time. Salinity of the ‘Big Sea’ of the Aral was 48 g L−1 in 1998, but has decreased to below 21 g L−1 in the ‘Small Sea’ due to the building of a new dam between the two parts of the Aral Sea.  相似文献   

4.
抚仙湖-星云湖水生生物与水环境研究综述   总被引：3，自引：0，他引：3  
抚仙湖与星云湖两湖相连,构成一个相连湖泊的微生态系统,这在云南九大高原中具有唯一性,且二者分别属于不同的营养状态,属于生态系统研究的敏感区域。本文通过对近年来相关文献的系统回顾,分析、评价了抚仙湖-星云湖水环境指标与水生生物研究现状的内容、方法及其成果;概述了自1980年以来抚仙湖-星云湖各项水环境因子（物理因子和化学因子）及生物因子（浮游植物、沉水植物、浮游动物等）的相关特征及其演化规律;提出在相关研究中存在的一些亟待解决的问题。  相似文献   

5.
咸海流域水资源利用的区域合作问题分析   总被引：5，自引：1，他引：4  
咸海的主要水源为阿姆河和锡尔河,自20世纪60年代以来由于人口的增加和农业政策导致的灌溉面积的迅速扩大,河流径流被大量引入且消耗于农业灌溉,使得入湖地表径流大幅度减少。原本是地球上的第四大湖泊的咸海,目前面积已缩小到只有原来的十分之一,并分离形成三个主要的残留湖,湖泊及湖滨的生态环境极度恶化。同时,巨大的干涸裸露湖床已成为盐尘和有毒物的发源地,严重威胁周边地区的人类健康。中亚五国自独立后于1992年签订了《中亚五国水协定》,旨在通过协定和后续协议加强区域合作扭转咸海流域严重的水危机与生态危机。但事与愿违,危机事态未得到抑制且有扩大趋势。通过对相关事态进行的深入分析,认为除改变该地区经济发展模式以减少农业用水外,在公平合理分配水资源的基础上加强国家间的合作,开展全流域水资源的综合开发、利用与管理才是扭转目前危机的最有效的途径。  相似文献   

6.
Recent rapid salinity rise in three East Antarctic lakes   总被引：1，自引：0，他引：1  
Research in East Antarctica has shown several recent environmental changes that may be linked to human impacts on climate. In order to detect the influence and context of these changes on coastal aquatic ecosystems we examined lake sediment cores from three lakes in the Windmill Islands, East Antarctica; Beall Lake, Holl Lake and ȁ8Lake Mȁ9. Cores were sectioned at␣2.5 mm intervals. Their diatom species composition was examined to detect changes in lake salinity using a diatom-salinity transfer function, and their algal pigment content was examined to detect photoautotrophic community responses to environmental change. Results showed that Holl Lake originated in a depression exposed by Holocene recession of the continental ice sheet and that Beall Lake and Lake M originated as isolated marine basins formed by changes in relative sea level. A general late Holocene trend of declining lake salinity was evident in all three lakes, interrupted by one short-term high salinity event in Beall Lake. This is consistent with a long-term positive moisture balance. This general decline in salinity has been followed by a remarkable recent rapid increase in salinity in all three lakes in the last few decades. We speculate that this rapid increase in salinity might be linked to changes taking place in the region including feedbacks resulting from decreasing sea ice extent as recorded in the nearby Law Dome ice core, and positive feedbacks in the catchments whereby reduced snow cover has led to decreased albedo, which in turn has caused increased evaporation and sublimation. Collectively these changes have shifted the lakes across a threshold from positive to negative moisture balance. A minor, but not rapid shift in the abundance of diatom pigments relative to pigments from green algae and cyanobacteria was also detected suggesting that some changes in photoautotrophic community composition have occurred. Measurements of modern nutrient levels are also higher than would be expected in Beall Lake and Holl Lake, given the extremely low sediment accumulation rates. This may be associated with a c. 300% increase in the population of Adélie penguins in the Windmill Islands recorded since the 1950s, or may a first signs of a rapid increase in catchment development and associated lake productivity as experienced in Antarctic and Arctic lakes subject to recent rapid regional warming. The most marked feature of the records is the rapid increase in salinity in all three lakes in␣the last few decades, which has occurred in lakes both with and without resident penguin populations.Dominic A. Hodgson and Donna Roberts contributed equally to this work  相似文献   

7.
Long-term water quality monitoring data from two riverine lakes in the Upper Mississippi River basin, Lakes St. Croix and Pepin, were analyzed to compare the long-term average water quality conditions and land use distributions, water quality trends and loads at lake inlets and outlets, trends from long-term versus short-term monitoring records, and the ability of paleolimnological cores to accurately infer lake water quality conditions. During the 1976–2004 period, the long-term average concentrations of nutrients, suspended solids, and chlorophyll-a were consistently lower at the Lake St. Croix inlet versus the Lake Pepin inlet, which drains a greater proportion of urban and agricultural runoff. Despite these differences, nutrient trends were similar at the inlets to both lakes; reductions in total phosphorus and ammonium concentrations were attributed to improvements in point source technologies, whereas increasing nitrate concentrations were attributed to both point source changes and nonpoint source increases. Despite improvements in several water quality variables, nitrate concentrations are increasing in both lakes, sediment trends indicate persistent nonpoint source inputs to Lake Pepin, and current total phosphorus concentrations remain well above pre-1950s levels in both lakes. Since urban development and agriculture are increasing in the Lake St. Croix and Lake Pepin Watersheds, continued point source regulation and additional nonpoint source control efforts will be needed to further improve water quality in these lakes. The 1976–2004 trends for most water quality variables were similar at inlet versus outlet sites on Lake St. Croix. Trends at Lake Pepin inlet versus outlet sites were less similar, but data availability limited the comparison to the 1993–2003 period. While the truncated data record highlighted short-term trends in both lakes, the full data record was most useful for exploring general patterns in water quality. Length of monitoring record affected our ability to detect trends at the inlets to both lakes, and altered the magnitude of detected trends. During the two decades of the 1980s and 1990s, paleolimnological estimates of retained phosphorus loads were similar to those estimated from recent water quality monitoring. These similarities support the use of paleolimnological approaches to infer past water quality conditions in Lakes St. Croix and Pepin. This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this special issue of the Journal of Paleolimnology. D. R. Engstrom served as guest editor of the special issue.  相似文献   

8.
Lake Balkhash,Kazakhstan   总被引：2，自引：0，他引：2  
Lake Balkhash is a large (18,000 km3), closed, and slightly saline lake in the south-west of Kazakhstan. It is divided into two basins, a south-western and an eastern basin. These have somewhat different limnological conditions, but the most obvious one is that the south-western basin has a salinity of <2 g L−1 whereas the salinity of the eastern basin is ∼4 g L−1. Numerous fish and invertebrate introductions, many successful, have been made. In 1969, a dam impounding the Kapchagay reservoir was constructed on the River Ili, the major river flowing into the lake. The impoundment of water in this reservoir caused a fall of some 1.5 m in the water-level of the lake. This fall, together with other events on the catchment, caused considerable damage to reedswamps in the lake, to the fishery and to conservation values. A number of suggestions has been made on how to prevent further damage. Some, particularly those involving a moratorium on further filling of Kapchagay reservoir and irrigation, have been implemented, at least in part. This has caused some remission in environmental damage and provides for cautious optimism with regard to the lake’s future. Even so, the environmental status of the lake remains vulnerable and many dangers persist.  相似文献   

9.
Environmental change in Lake Taihu and its catchment since the early to middle part of the twentieth century has left a clear geochemical record in the lake sediments. The human activities in the lake and its catchment responsible for the change include agriculture, fishery, urbanisation, sewage and industrial waster disposal. Sediment cores were collected from Meilian Bay of northern Lake Taihu to investigate the record of anthropogenic impacts on the lake’s ecosystem and to assess its natural, pre-eutrophication baseline state. Two marked stratigraphic sediment units were identified on the basis of total phosphorus concentration (TP), pigments, total organic carbon (TOC)/total nitrogen (TN), δ13C and δ15N corresponding to stages in the lake history dominated by phytoplankton, and by aquatic macrophytes. Results show that as TP loading increased from the early 1950s the lake produced sediments with increasing amounts of organic matter derived from phytoplankton. In the early 1950s, the first evidence for eutrophication at the Meilian Bay site is recorded by an increase in C/N values and in sediment accumulation rate, but there is little change in phosphorus concentrations, pigments, δ13C and δ15N at this time. After 1990 a more rapid increase in trophic status took place indicated by increased levels of phosphorus, pigments, δ15N and by decreased δ13C and TOC/TN values in the lake sediments. The first increase in trophic status of the early 1950s results mainly from agricultural development in the catchment. In contrast, the acceleration from ca. 1990 originates from the recent development of fisheries and the urbanisation and industrialisation of the catchment.  相似文献   

10.
淀山湖太湖形成的古生物证据   总被引：3，自引：0，他引：3  
闵秋宝 《地理研究》1987,6(4):26-35
通过对湖泊周围钻孔样品的微体古生物分析,根据化石群的生态特征,结合岩性、孢粉、14C等资料探讨晚更新世中期以来淀山湖、太湖沉积环境的演变过程,并比较其异同。现代湖泊的形成于全新世晚期。  相似文献   

11.
白杨河-艾里克湖水现状分析   总被引：3，自引：0，他引：3  
根据白杨河、艾里克湖的地表水以及周围地下水的电导率的监测资料,结合不同时期地下水位、土壤水分的变化特点,阐述了地下水埋深和水质的时空分布规律,以及对植被分布的影响.分析结果表明:地下水埋深从白杨河河道至湖岸表现为龙口地带最深、中游河段最浅、入湖口和湖岸居中;土壤水分是湖岸区最高,其次是入湖口,河段中部最低;地表水和地下水电导率的变化均是龙口最低,其次是河段中部,入湖口和湖边最高;在湖区内从湖边到湖心水的电导率依次减小,冰的电导率最低.环湖岸地带,由湖及远地下水位埋深逐渐增加、电导率依次增加、土壤水分依次减少,与其相对应的植被类型依次为芦苇、柽柳苗、柽柳林、盐穗木.同时,研究结果表明艾里克湖将会出现水质盐化趋势,而增加入湖河水水量、疏通排盐通道,促进湖水循环活化是缓解湖水咸化的主要措施.  相似文献   

12.
Studies addressing within-lake variability of fossil chironomid assemblages are very few, and all deal with hydrologically stable temperate lakes where the question of spatial integration mostly relates to the mixing of faunal assemblages associated with shallow, warm-water habitat and those associated with deeper, cold-water habitat. Here we study within-lake variability of surface-sediment chironomid assemblages in the fairly large (∼100–170 km2 since 1983) and shallow (Z max = 5–8 m) fluctuating tropical lake basin of Lake Naivasha, Kenya, and compare the patterns observed with those in two smaller adjacent basins, one similarly shallow (Lake Oloidien, 5.1–5.7 km2, 5–8 m), the other deep and stratified (Crescent Island Crater, 1.9 km2, 14–17 m). Chironomid assemblages were analysed in core-top samples and surface sediments along inshore to offshore transects, and how well individual samples represented the total (basin-wide mean) subfossil assemblage was considered both in terms of taxon richness and taxon percent composition. Within-lake variability of subfossil chironomid concentrations (with generally higher absolute values in nearshore samples) could be explained by effects of sediment winnowing and focusing, whereas between-lake variability reflected their relative susceptibility to wind-driven sediment disturbance or bottom anoxia. In all study lakes, but most significantly in lakes Naivasha and Oloidien, species distribution in the subfossil chironomid assemblages showed a strong nearshore to offshore gradient, which in these shallow lakes, reflects the dominant control of substrate and food quality on species distribution in the living community. Particularly in the larger basins, nearshore samples better represented the total lake assemblage than offshore samples, because the former always contained a component of mud-dwelling species whereas the latter often lacked a component of macrophyte-dwelling species. Our results show that although sedimentation dynamics in the shallow, wind-stressed Lake Naivasha is dominated by frequent resuspension and random sediment redistribution, the near- to offshore gradient in chironomid habitat remains imprinted on subfossil assemblages. We conclude that also in shallow fluctuating lakes, given sufficient size, incomplete pre-burial spatial integration of habitat-specific chironomid assemblages can be exploited for within-lake calibration of environmental gradients.  相似文献   

13.
Primary producer community structure (PPCS) in shallow lakes isinfluenced by phosphorus (P) load and water column P concentration.Theoretically PPCS may shift between phytoplankton and macrophyte states withintermediate P loading, but phytoplankton dominate when P loading exceeds acritical threshold. We analyzed sediment cores from five shallow, eutrophiclakes (size range: 0.6 to 125 km2) that arephytoplankton dominated to determine whether the development of the currentstate was associated stratigraphically with an increase in sediment total P(TP) and a shift in PPCS. We used sponge biogenic silica(BSiSponges) concentrations and total carbon to total nitrogenratios (TC:TN) as proxies for macrophyte abundance and sediment organic mattersource, respectively. Three stratigraphic groups of sediments were identifiedwith k-means cluster analysis. These samples were grouped by increasing TPconcentrations and decreasing age and identified as macrophyte, transitionaland phytoplankton sediments. Results show that as P loading increased in thelate 19th and early 20th centuries, the lakes producedsediments with an increasing contribution from phytoplankton. Four of our lakesmay represent a subset of shallow lakes because of their large size (30 to 125km2) and relatively rapid historic P enrichment. Inthese Florida lakes, PPCS shifted to phytoplankton dominance with nopaleolimnological record of lake-wide alternating stable states or of lake-widephytoplankton dominance before anthropogenic P enrichment.  相似文献   

14.
The main limnological features of Lake Issyk-kul are described. The lake is a large (6,236 km2), deep (zm, 668 m), closed lake in eastern Kirgizia. It lies at ∼1,607 m above sea level, but water-levels have been dropping since the last century. It is slightly saline (salinity, ∼6g L−1), with Na+, Mg2+, Cl− and SO 4 2− the dominant ions. Nutrient levels are low and the lake is considered ultra-oligotrophic. Characeae dominate the macrophytes. About 300 and 117 taxa of, respectively, phytoplankton and zooplankton have been identified, withArctodiaptomus salinus the most numerous in the zooplankton. Chironomids dominate the benthos. Several endemic taxa of fish occur, of whichLeuciscus bergi was dominant until the 1970s. The fish fauna has been supplemented by many introduced species. Three mysids were introduced in 1965–8 and are now a significant part of the ecosystem. The present annual fish catch permitted is 320 t. The most important value of the lake is as a recreational resource. To promote and sustain this value requires careful, ongoing management. The most significant threats to the lake are local pollution, visitor pressure, and declining water-levels.  相似文献   

15.
Dust/sand storms are common events in the arid and semi-arid regions of Central Asia. The region is characterized by strong winds, scarcity of vegetation cover, continental climate with long and dry summers, frequent soil and atmospheric droughts. Central Asian drylands, covered by a great variety of desert types, represent a powerful source of mineral and salt aerosols.The main objectives of this study are to monitor and assess the spatial and temporal distribution of dust storms over the Central Asian region during the last seven decades. The identified active source areas of dust storms are located mainly in the sandy deserts and other types of deserts where the sensitive ecosystems suffered from human impact. The main persistent sources of dust storms are located in the large “dust belt” that extends from west to east over the southern deserts, north of Caspian Sea deserts, south of Balkhash Lake, and Aral Sea region. The results of the analysis show a significant decrease in dust/sand storm frequency during the last decades and considerable changes in the active source areas.  相似文献   

16.
The macrozoobenthos was investigated at eight sites in the Aral Sea inshore zone and in the lower reaches of the Syrdaria river. In the sea, the benthos comprised bivalve molluscsSyndosmya segmentum Recluz andCerastoderma isthmicum Issel, gastropods fromCaspiohydrobia Starob., the polychaeteNereis diversicolor O.F. Müller and the crabRhithropanopeus harrisii tridentatus (Maitland). In the Syrdaria, MysidaeParamysis lacustris (Czern.) and GammaridaeDikerogammarus aralensis (Uljanin) were found. These taxa have not been recorded from the Sea since the 1970s. The total zoobenthos biomass and density varied between the investigated Sea areas from 92 to 582 g/m2 and from 1,600 to 39,000 ind./m2, respectively. Spatial and temporal salinity changes within the range 20–41 g/L did not affect macrozoobenthos composition and structure. The conclusion is that the benthic ecosystem of the Aral Sea was in a state of comparative stability from the middle of the 1980s to the middle of the 1990s. Analysis of the zoobenthos in the inshore zone is proposed as a convenient and accessible method for monitoring the status of the zoobenthos of the entire Aral Sea.  相似文献   

17.
We examine the current ecological problems of the Balkhash region. An assessment is made of the ecological status of the territory and water resources among which Lake Balkhash and the Ili, Karatal and Lepsy were assessed as the most severely polluted rivers. Lake Balkhash is represented not only as a fishery water body but also as the unique center of the region’s ecological integrity. A rationale is provided for the need to carry out a geoecological monitoring as well as comprehensive measures for maintaining stability of the Lake Balkhash level, preventing the water bodies from pollution, the protection of the lakes’ floodplains, the preservation of tugai forests and saxaul vegetation, and a monitoring of desertification processes. Based on studying and analyzing the spatiotemporal physical-geographical characteristics of the territory of the Balkhash region, we constructed a fragment of the geoecological regionalization map. A study into the spatialregular distribution revealed the region’s dominant plant communities. The main pollution sources have been identified: mining industries, housing and communal facilities, influences from settlements, and agrocenoses, specifically irrigated agriculture. As a result of our investigations, it was found that all landscapes of the region have been undergoing changes due to anthropogenic impacts to become anthropogenic modifications of natural landscapes. It was further found that irrational consumption and ill thought-out strategies for utilization of biological resources, coupled with an inadequate scientific regulation of anthropogenic impacts, continue to inflict damage to the region’s bioresources.  相似文献   

18.
In a recent paper, Nof et al. (J Paleolimnol 35:417–439, 2006) suggest a physical mechanism which could account for the formation of ice on Lake Kinneret (Sea of Galilee) in northern Israel. Based on the sea surface temperature record of sediment cores from the Mediterranean Sea the authors argue that centennial-scale cold events had the potential to trigger local ‘springs ice’ formation on the lake in the past. Here, we demonstrate that a closer inspection of the paleoceanographic record in combination with correlation and regression analyses of meteorological data provides no evidence for such cold events in the lake region during the last 10,000 years. Thus, the formation of ‘springs ice’ on Lake Kinneret was unlikely at least since the beginning of the Neolithic.  相似文献   

19.
Saline lakes in the lower Grand Coulee,Washington, USA   总被引：1，自引：0，他引：1  
Changes in the limnology of two saline lakes, Lake Lenore and Soap Lake, in the lower Grand Coulee, Washington, between 1949 and the present are described. This paper is an abbreviated version of Chapter 11 in: W.T. Edmondson,The Uses of Ecology: Lake Washington and Beyond, pp. 209–226. University of Washington Press, Seattle. The book is based upon lectures given by the author inthe Jessie and John Danz Lectures. The considerable interest of studies on Lake Lenore and Soap Lake in the lower Grand Coulee, the authoritative account of these studies in the book, and the possibility that this account would not easily attract the attention of limnologists who study salt lakes were behind the decision to reproduce the chapter. Its reproduction has been graciously permitted by the author and the University of Washington Press. This permission is gratefully acknowledged. Whilst only Chapters 11 and 5 (Mono Lake) directly concern salt lakes, the book as a whole is an outstanding account of how limnological studies (with focus on those of Lake Washington) can serve humanity Ed.  相似文献   

20.
In Lake Constance, phosphorus concentrations and the seasonal development of phytoplankton communities in water samples from the pelagic zone were regularly recorded since the 1950's. Before the 1950's, there were occasional investigations of plankton communities since 1896. We compared these data with the sedimentary record in two sediment cores. Then, the eutrophication history of Lake Constance was inferred from diatoms. The record of biogenic silica in the cores is discussed with respect to diatom biomass increase.Diatom assemblages in the sediment cores precisely reflected the pelagic diatom development for the period 1971--1992. Both sediment cores and the water samples have a high interannual variability of diatom assemblages. Below a sediment depth of 27 cm (AD 1920), more than 50% of the diatoms were partly corroded, and we limited the reconstruction of trophic state changes to the interval of 1920--1993. Oligotrophic conditions of Lake Constance were indicated by the dominance of various Cyclotella taxa from 1920 to 1940. Since 1939/1940, increasing abundance of it Tabellaria fenestrata showed oligotrophic to mesotrophic conditions. Between 1953 and 1956, increasing Stephanodiscus hantzschii and disappearing Cyclotella indicated advanced eutrophication and total phosphorus values ranged between 8--10 mg m-3 during turnover in late winter. Further eutrophication was shown by disappearing T. fenestrata and increasing S. minutulus in 1963. Maximum TP concentrations of 87 mg m-3 occurred in 1979/80 and was accompanied by increasing abundances of Aulacoseira granulata. From 1986 to 1992, reoccurrence of Tabellaria fenestrata and Cyclotella indicate some recovery of Lake Constance.Biogenic silica and diatom abundances were similar among cores but indicate a 3--4 fold increase of diatom biomass only. This was far below the estimate of biomass increase from sedimentary pigment data (25 fold) and the estimate of phytoplankton data from the literature (70 fold).  相似文献   

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