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What Future for Saline Lakes?
Abstract
Some grow and others shrink as changing climate patterns and human demands for scarce water resources reshape the ecology of the world's salt lakes.
... A terminal lake is located at the mouth of an inland river [3]. Surface and underground runoff in terminal lake basins are not connected to other water catchment areas or to the ocean and have independent hydrological processes. ...
... Surface and underground runoff in terminal lake basins are not connected to other water catchment areas or to the ocean and have independent hydrological processes. The lake water in these areas accounts for approximately half of total global lake reserves [3]. The above-mentioned characteristics make terminal lakes among the most dynamic global hydrological systems. ...
... The above-mentioned characteristics make terminal lakes among the most dynamic global hydrological systems. Water level fluctuates rapidly and significantly due to the influence of natural climate change and human activities [3][4][5][6] and is an indicator of climate change and environmental variability in the lake area [7]. The alarmingly rapid shrinking of many terminal lakes due to global climate change and regional human activities [8][9][10] is one of the principal environmental problems facing mankind [11,12]. ...
Obtaining the water volume of small-and medium-sized lakes in enclosed watersheds with scarce data is a global focus of research. River flow into a lake is an important factor affecting the water volume. However, most river flow measurement methods involve long cycles, low efficiency , and transdisciplinary expertise, making rapid assessments in ungauged basins impossible. This paper proposes a remote sensing flow estimation method based on multi-source remote sensing data, which quickly assesses river flow and provides important input data for lake water volume simulation. The cross-section flow was estimated by extracting the river width. The calculated results were consistent with the measured data, with accuracy greater than 90%. The results compared with daily data measured at hydrological stations, and the Nash coefficient was greater than 0.9. Additionally, the simulation method for lake area, water volume, and water level was constructed using river inflow input data, greatly reducing the parameters required by the conventional lake water volume simulation method. Based on the remote sensing discharge estimation method, we quickly and conveniently obtained changes in river flow into the lake, simulated lake water volume, and provided the basis for water resource management in terminal lake basins with scarce data.
... Nearly 27% of the Earth's land-surface area is characterized by systems lacking an outlet for water drainage (de Martonne 1927). In some cases, the watershed will deliver water to a large single internal basin, forming an endorheic terminal lake (Williams 1993(Williams , 1996. These closed basins are by nature dynamic, responding to changes in input and output of water; water enters through direct precipitation, runoff, or groundwater seeps, and it leaves only through evaporation. ...
... Terminal lakes are sensitive to climate variation, both natural fluctuations and anthropomorphic climate change, as well as modifications to the land-surface hydrology such as damming and diverting flow (Williams 1996(Williams , 2002. In addition, these lakes, particularly larger ones in arid regions such as Great Salt Lake (GSL), present a great opportunity to study hydroclimatic change as they are superb recorders of regional conditions over time (Bowen et al. 2019). ...
... Decreases in water input in the context of rising temperature will certainly affect the biota of GSL. Much of this is driven by changes in salinity as organisms are adapted to particular salinity ranges, and the higher salinity predicted in drought conditions may have major effects on the plankton as well as the higher trophic levels of the lake (Williams 1996(Williams , 2002. ...
Terminal lakes are highly susceptible to climate change impacts since water that enters through precipitation, runoff, and groundwater must be balanced with water that leaves through evaporation. A change in this equation can lead to a decline in elevation, which can be tragic for the ecosystem, particularly if the closed basin is shallow. Great Salt Lake faces many threats that will impact the volume of water in the depression of the Bonneville Basin where it resides. If the lake’s level declines, salinity increases, and wetlands are altered. Salinity is a driver of microbial diversity and, as this foundation of the ecosystem is altered, so will be the rest of the food web, affecting large numbers of avian migrators along the Pacific and Central fly-ways. Human population growth and water diversions for agriculture have put a strain on Great Salt Lake, resulting in a terminal lake whose trajectory is downward in surface area. How might anthropogenic climate change impact this scenario? Alterations in temperature can influence the timing of snowmelt and change evapotranspiration. As temperatures increase and droughts persist, climate change will amplify the decline in lake elevation, creating more dust from the exposed lakebed. Dust blowing into inhabited valleys will worsen air quality with particulates and may be laden with the pollutants collected by the lake. Early melting of the snowpack in the Wasatch Mountains due to higher temperatures would be further impacted as airborne dust from the dry shorelines is deposited during storms and can reduce the albedo of snow, altering groundwater recharge of the watershed. The current status of Great Salt Lake, with no water rights of its own and increasing pressures for water use upstream, does not bode well for the survival of this critical ecosystem given climate change predictions for the southwestern United States.
... Terminal lakes are unique and dynamic hydrological systems that can experience relatively rapid changes in water surface elevation, lake area, and lake volume due to fluctuating lake water sources and sinks (Street 1980;Mason et al. 1994;Williams 1996). Because their water budget integrates multiple hydrological forcings, the paleolimnological record of lake-level variability has been proposed as a natural proxy indicator of historical climatic variation (Mason et al. 1994, Williams 1996. ...
... Terminal lakes are unique and dynamic hydrological systems that can experience relatively rapid changes in water surface elevation, lake area, and lake volume due to fluctuating lake water sources and sinks (Street 1980;Mason et al. 1994;Williams 1996). Because their water budget integrates multiple hydrological forcings, the paleolimnological record of lake-level variability has been proposed as a natural proxy indicator of historical climatic variation (Mason et al. 1994, Williams 1996. Terminal lakes are also sensitive to changes in basin hydrology, however, and their water budgets can be impacted by human alteration of basin land use/land cover, and human abstractions from or contributions to tributary discharge. ...
... Terminal lakes are also sensitive to changes in basin hydrology, however, and their water budgets can be impacted by human alteration of basin land use/land cover, and human abstractions from or contributions to tributary discharge. They require careful water management plans, and the assumed absence of human alteration of the lake water budget must be demonstrated before they can be used to monitor climate change (Williams 1996(Williams , 1998. ...
Devils Lake, a terminal saline lake in eastern North Dakota, has experienced catastrophic flooding over the past two decades producing direct damages in excess of $1 billion ($USD). We use three long-term datasets to examine the temporal coherence between historical lake fluctuations and basic hydroclimatic drivers. Monthly precipitation and mean monthly air temperature data are used to characterize long-term precipitation delivery and evaporative demand. Monthly water balance data for a representative location are used to assess basin soil moisture conditions. A lake volume time series documents lake volume fluctuation in response to long-term precipitation and regional soil moisture conditions. Three variables are derived from the datasets, each characterizing a different aspect of the region’s hydroclimatology. A rescaling technique is applied to each variable to examine the temporal coherence and relative patterns of the variables and to identify distinct homogeneous hydroclimatic regimes during the historical period. The three rescaled variables show strong temporal coherence and confirm 1980 as an abrupt transition year between two distinct long-term hydroclimatic modes. Mode 1, a longer and drier phase, runs from 1907 to 1980, while mode 2, a shorter and wetter phase, extends from 1981 to the present. Multi-decadal and century-scale fluctuations between these two modes are the key drivers of long-term lake volume fluctuations, upon which interannual- and interdecadal-scale climatic variability are superimposed. The similar rates of change among the rescaled variables provides evidence in support of the conclusion that long-term natural hydroclimatological variability is the primary driver of observed lake volume changes at Devils Lake during the Twentieth Century and provides a foundation upon which to evaluate the potential contributing effects of anthropogenic climate change, and human alterations of the land use hydrology.
... 00 S-0°24 0 34.91 00 S) situated within Lake Nakuru National Park approximately 160 km North-West of the Kenyan capital city-Nairobi (Fig. 1). The lake is shallow, with a mean depth of 1.5 m (Williams, 1996), covering an area of 40-60 km 2 at an altitude of 1,759 m asl. Three seasonal rivers (Njoro, Makalia and Enderit), the Baharini spring and water from the Nakuru town sewage treatment plant discharge into the lake. ...
... The variation in water volume results in large fluctuations of physico-chemical parameters such as water temperature and salinity (Okoth et al., 2009). For example, salinity ranges between 10 and 120% (Williams, 1996) and daily temperature fluctuations result in strong diurnal cycles of stratification and mixing (Melack & Kilham, 1974). Annual rainfall averages 1,000 mm. ...
... Physico-chemical parameters, namely water temperature, dissolved oxygen concentration, salinity, alkalinity, conductivity and pH were measured in situ at each of the sampling sites, using a calibrated JEN-WAY 3405 electronic probes (Barloword Scientific Ltd, Essex, UK), with independent probes for each variable. The following chemical analyses were performed: Total-P using a Lambda 20 Perkin Elmer Ò (Waltham MA, USA) spectrophotometer after mineralisation with potassium-peroxodisulfate (NF EN 1189, 1996; DOP using a Lambda 20 Perkin Elmer Ò spectrophotometer (NF EN 1189, 1996; Total-N using a RFA 300 Alpkem Ò (OI Analytical, College Station, TX, USA) continuous-flow analyser after mineralisation with potassium-peroxodisulfate (NF EN ISO 11905-1, 1997); nitrate nitrogen was determined using cadmium reduction methods; and dissolved organic nitrogen by Kjeldahl digestion. All chemical analyses was done following APHA (1998). ...
Rotifers dominate zooplankton biomass of many aquatic environments. However, their link to food web biomass has rarely been elucidated in alkaline-saline lakes. Variations in C content, C:N ratio and stable isotope composition (13C, 15N) of dominant rotifer species were studied from January to December 2008 in alkaline–saline Lake Nakuru to provide insights into their bioenergetics. We established that B. dimidiatus dominated in terms of abundance (80000‒100000×103 ind m─3) and C biomass. Also B. dimidiatus constituted about 60–75% of the rotifer biomass in the samples. All the rotifer species exhibited significant (p < 0.05) seasonal differences in biomass, C and C:N ratios. Rotifers had lower mean 13C than course particulate organic matter (CPOM), fine particulate organic matter (FPOM) and fish, but higher than mean 13C in the dominant phytoplankton species. In all species, 13C and 15N increased markedly during the rainy season reflecting the feeding onset on allochthonous food sources. The isotopic increase correlated with an increase in their C:N. Our results demonstrate that rotifers respond quickly to any increase in primary production and can cope with changes in its nature and timing.
... 1978). Anoaier importent feature which disdinguishes sait from freshwater lakes is that salt lakes are much more sensitive to climatic change (Williams, 1996). This enhanoed sensitivity reflects the nature of their existence. ...
... nanoe, atmospheric precipitation. and the evaporationprecipiteton proc8ss (Gibbs. 1970;Feth, 19'11 ;Kilham, 1975;Stallard. 1980;Stallard and 49 Edmond, 1981 1 983). In openpit lakes, pit-lake water chemistry is predominantly detemiined by proximal mck-dominanoe but the evaporaüong~pitaaon process also plays an influential role (Miller et al., 1998;Williams. 1996). ...
... A similar situation was found by Miller et al. (1996) who detbrmined that the conoentration of all constituents in a pit lake in a semi-arid dirnate inue~sed over time because of evapo-concentration. This also conairs with Williams (1996) who found that with a dight increase in aridity. less water enters a Iake. ...
... Saline and hypersaline lakes are globally widespread and constitute almost half of the total inland water surface area (30,31). With a wider salinity gradient from seawater salinity (35 g/L) to salt saturated (salinity . ...
... For SEM, each sample (900 mL) was fixed with 2.5% glutaraldehyde (100 mL) out of the glove box and left at 4°C overnight. The samples were dehydrated in ethanol (30,75,95, and twice at 100%) before embedding in hexamethyldisilazane (HMDS; Sigma-Aldrich, St. Louis, MO, USA) (111). The samples were platinum coated before imaging. ...
NRFeOx microorganisms are globally distributed in various types of environments and play a vital role in iron transformation and nitrate and heavy metal removal. However, most known NRFeOx microorganisms were isolated from freshwater and marine environments, while their identity and activity under hypersaline conditions remain unknown.
... Inland saline lakes are an important global water resource that provide important livelihood systems throughout the world (de Martonne, 1927;Langbein, 1961;Waiser and Robarts, 2009). The hydrological states of such terminal lakes -lake level, lake area, and lake volume − can exhibit large and rapid changes in response to natural forcings (Williams, 1996). Terminal lakes are also sensitive to human alterations in basin hydrology, including water diversion, water abstraction, crop cultivation, and deforestation/afforestation (Williams, 1996(Williams, , 2001, and increased demand for agricultural production has frequently led to declining lake levels (Gross, 2017;Williams, 2002). ...
... The hydrological states of such terminal lakes -lake level, lake area, and lake volume − can exhibit large and rapid changes in response to natural forcings (Williams, 1996). Terminal lakes are also sensitive to human alterations in basin hydrology, including water diversion, water abstraction, crop cultivation, and deforestation/afforestation (Williams, 1996(Williams, , 2001, and increased demand for agricultural production has frequently led to declining lake levels (Gross, 2017;Williams, 2002). ...
We use the Budyko framework to examine streamflow changes due to climate variation and human activities in the Mauvais Coulee Basin, a 1002 km2 sub-basin that contributes streamflow to Devils Lake, a terminal lake that has experienced catastrophic flooding over the past three decades. The basin lies within the northern glaciated prairies, contains innumerable wetland complexes that follow fill-spill hydrological principles, has undergone
extensive land use change to support dryland farming, and has experienced a drought to deluge hydroclimatic transition over the last century. We implement the Budyko framework to partition the runoff increase to the lake between its climatic or human components. Initial results attribute 45% of the streamflow increase to climate factors, and 55% to human activities. Implementation of the Budyko framework to examine streamflow partitioning, however, rests upon a series of assumptions that are usually not directly verified. We then examine each Budyko framework assumption to determine its suitability for our study site and study period. None of the required assumptions are fully satisfied. Our study site and study period encompass two distinct hydroclimatic modes, contain no clear single inflection point separating baseline and altered periods, experience root zone soil moisture storage changes during the study period, and exhibit a non-stationary precipitation-streamflow relationship during the transitional period between the two hydroclimatic modes. Streamflow attribution produced by the standard application of the Budyko framework is not applicable to our study site or study period. We recommend that local-scale investigations of streamflow partitioning based upon the Budyko framework be
more intentional in verifying model assumptions as a standard practice in implementing the method.
... With their current volume of 82,676 km 3 , they account for 44% of the total lake water storage on earth (Messager et al., 2016). These lakes play an important role in determining regional climate patterns, sustaining biotic productivity and diversity, maintaining environmental and human health, and providing recreational services, minerals, and other resources (Hammer, 1986;Williams, 1996). Therefore the dynamics of saline lakes are of great importance to a broad array of stakeholders. ...
... Some examples of the declining saline lakes around the world are provided in Fig. 1. In most cases, unsustainable upstream water withdrawals have been a primary factor in the lake shrinkage (Williams, 1996). Lake Urmia, the Aral Sea, and Owens Lake are some examples of the shrinkage as a result of anthropogenic interventions. ...
River flow reductions as a result of agricultural withdrawals and climate change are rapidly desiccating endorheic lakes, increasing their salinity and affecting the bio-diversity and human wellbeing in the surrounding areas. Here we present a new framework to guide eco-hydrological restoration of saline lakes and build their resilience to climate change by optimizing agricultural land use and related water withdrawals. The framework involves four steps: 1. selection of global circulation models for the basin under study; 2. establishment of a hydrological balance over the lake's area to estimate the amount of water required for its restoration; 3. water allocation modeling to determine the water available for restoration and allocation of the remaining water across different users in the lake's basin; and 4. basin-scale optimization of land use and cropping patterns subject to water availability. We illustrated the general applicability of the framework through the case of the second largest (by volume) hyper-saline lake globally, Lake Urmia, which lost 96% of its volume in only 20 years, primarily as a result of upstream water withdrawals. Through the application of the framework, we estimated the amount of water needed to restore the lake, either fully or partially, and proposed a sustainable land-use strategy, while protect farmers' income in the basin. Considering future climate change projections under two representative concentration pathways (RCP) 4.5 and 8.5, we found that an average annual surface inflow of 3,648 Mm3 (∼70% increase in RCP 4.5) and 3,692 Mm3 (∼73% increase in RCP 8.5) would be required to restore the lake by 2050, respectively. This would require the respective conversion of 95,600 ha and 133,687 ha of irrigated land to rain-fed cropland or grassland across the basin by 2050. The proposed framework can be used for building resilience to climate change and mitigating human-induced threats to other declining saline lakes.
... These closed basin lakes are normally saline and are often referred to as inland saline (salt) lakes. The total volume of water contained within saline lakes is comparable to that of freshwater lakes, and they form an important global water resource (Williams 1996(Williams , 2002. ...
... Lake level fluctuations are driven by short-term and longterm variations in climate, and also by lake bathymetry such that the lake area-lake volume relationship of a saline lake can have preferred states in lake level (Street 1980, Mohammed and Tarboton 2011, Haghighi et al. 2016. Terminal lake level fluctuation is also extremely sensitive to human modification of basin hydrology, including human abstraction or augmentation of surface or groundwater inflow, diversion of tributaries, and alteration of basin land use/land cover (Williams 1996, Coe and Foley 2001, Micklin 2007. ...
Devils Lake, a terminal lake in eastern North Dakota, has risen more than 9 m between 1992 and 2013, producing a 286% increase in lake area, and causing more than US$1 billion in direct damages. An annual volumetric lake water budget is developed from monthly hydroclimatological variables for the period 1951–2010 to investigate the rapid lake expansion. The lake is an amplifier terminal lake in which long-term climatic changes are amplified by positive feedback mechanisms, causing the lake to transition from a precipitation-dominated to a runoff-dominated water budget. Factors specific to the Devils Lake Basin further amplify this positive feedback relationship. These include principles of fill-spill hydrology that operate between individual sub-basins within the closed basin, and between the innumerable wetland complexes within each sub-basin. These factors create a pronounced non-stationary precipitation–runoff relationship in the basin during both long-term wetting and drying phases.
... Despite the large variety of services that saline lakes provide and their global extent in dry regions, they are shrinking worldwide as their hydrological balance is changed by both climatic and anthropogenic factors (Williams 1996;Wurtsbaugh et al. 2017). Using the Köppen-Trewartha (K-T) climate classification and analysing observations from 1900 to 2010, as well as simulations spanning 1900-2100 from 20 global climate models, Feng et al. (2014) demonstrated a significant redistribution of climate types in the most recent 15-year period (1996-2010) compared with the period . ...
The hypersaline Lake Urmia, located in Iran, has undergone a significant reduction in size and is currently facing the risk of desiccation. The decrease in water levels, coupled with elevated salinity levels, has initiated ecological degradation, leading to a substantial decline in the region’s waterbird population. This study employs breakpoint analysis to determine the year when the drought event affecting the lake commenced. Additionally, canonical correspondence analysis (CCA) is utilised to elucidate the interaction between environmental parameters and the waterbird assemblages in Lake Urmia over the period 1970–2018. Our investigation identifies the year 2000 as the initiation of the water crisis in Lake Urmia, synchronously coinciding with the decline in the waterbird populations. This finding highlights a significant connection between the majority of waterbird species and the axes of CCA, intricately linked with water availability within Lake Urmia. This revelation underscores the pivotal role of fluctuations in water levels in shaping the dynamics of the lake’s waterbird assemblages. Furthermore, our observations emphasise the importance of even minor improvements in hydrological conditions of the lake, resulting in substantial positive impacts on waterbird populations.
... Evaporite salts from saline lakes and playas have a profound influence on atmospheric cycles and the climate system. 1 Salt particles, originating from these terrestrial sources, can be introduced into the atmosphere through processes like wind erosion, human activities, or wave actions, and can be carried alongside mineral dust over extensive distances. 2 It had been confirmed that the salt dust particles from the Qaidam Basin can migrate eastward with strong cold air currents. ...
... Human activities, particularly agricultural irrigation, have played a significant role in the desiccation of the Aral Sea and, indeed, saline lakes globally (Williams, 1996;Wine & Laronne, 2020). Similar to the Aral Sea, Lake Urmia in Iran has also faced a rapid decline in its water levels (Darehshouri et al., 2023;Feizizadeh et al., 2023), mirroring the situation of many other saline lakes across continents (Wurtsbaugh et al., 2017). ...
The rapid shrinkage and salinization of the Aral Sea over the last few decades has precipitated an environmental disaster, with widespread implications for people whose livelihoods depend on it. Although debated extensively, few viable strategies have yet been identified for reviving the Aral Sea. Here, we propose a hydro‐eco‐social framework to develop a viable, sustainable solution and explore its feasibility to resolve the Aral Sea problem. Based on eco‐environmental indicators, we contend that it is feasible to raise the Aral Sea by 40 m above the Baltic Sea level, while maintaining salinity levels tolerable for aquatic organisms, simultaneously reducing sandstorm risk by 58%. Basin‐wide water balance under climate change scenarios shows that this level can be supported through management interventions that reduce water usage by 22.0–23.2 km³/year and ensure sufficient recharge into the lake, without compromising socio‐economic opportunities. To implement this solution, we propose establishing a socio‐ecologically aligned water governance network for basin‐scale water management that has potential application for other, similarly declining, major lake systems.
... Saline lakes account for around half of the global volume of inland surface water bodies and emit 0.28-0.32 GT C y − 1 of CO 2 (Duarte et al., 2008;Wen et al., 2019;Williams, 1996). Recent studies have determined that salinity affects microbial activities and hydrochemical processes as well as GHG emissions from saline lakes (Xun et al., 2022). ...
Although saline aquatic ecosystems are significant emitters of greenhouse gases (GHGs), dynamic changes in GHGs at the sediment-water interface remain unclear. The present investigation carried out a total of four sampling campaigns in Daihai Lake, which is a eutrophic saline lake situated in a semi-arid area of northern China. The aim of this study was to investigate the spatio-temporal dynamics of carbon dioxide (CO2) and methane (CH4) fluxes at the sediment-water interface and the influencing factors. The mean concentrations of porewater CO2 and CH4 were 44.98 ± 117.99 μmol L-1 and 124.36 ± 97.00 μmol L-1, far exceeding those in water column of 11.14 ± 2.16 μmol L-1 and 0.33 ± 0.23 μmol L-1, respectively. The CO2 and CH4 fluxes at the sediment-water interface (FS-WCO2 and FS-WCH4) exhibited significant spatial and temporal variations, with mean values of 9.24 ± 13.84 μmol m-2 d-1 and 3.53 ± 4.36 μmol m-2 d-1, respectively, indicating that sediment is the source of CO2 and CH4 in the water column. However, CO2 and CH4 fluxes were much lower than those measured at the water-air interface in a companion study (17.54 ± 14.54 mmol m-2d-1 and 0.50 ± 0.50 mmol m-2d-1, respectively), indicating that the diffusive flux of gases at the sediment-water interface was not the primary source of CO2 and CH4 emissions to the atmosphere. Regression and correlation analyses revealed that salinity (Sal) and nutrients were the most influential factors on porewater gas concentrations, and that gas fluxes increased with increasing gas concentrations and porosity. The microbial activity of sediment is greatly affected by nutrients and Sal. Additionally, Sal has the ability to regulate biogeochemical processes, thereby regulating GHG emissions. The present investigation addresses the research gap concerning GHG emissions from sediments of eutrophic saline lakes. The study suggests that controlling the eutrophication and salinization of lakes could be a viable strategy for reducing carbon emissions from lakes. However, further investigations are required to establish more conclusive results.
... Saline lakes are distributed globally, and their surface area accounts for 45% of total area of inland water bodies (Jellison et al., 2008;Williams, 1996). Microorganisms are one important component of saline lake ecosystems (Oren, 2008) and contribute significantly to the biogeochemical cycles of carbon, nitrogen and sulfur elements (Wang W D et al., 2019;Paul Antony et al., 2013;Kuznetsov, 1975) and biomass production (Cole et al., 1988;Hammer, 1981). ...
Assembly processes of prokaryotic and microeukaryotic community is an important issue in microbial ecology. However, unclear remains about the relative contribution of deterministic and stochastic processes to the shaping of prokaryotic and microeukaryotic communities in saline lake water. Here, we systematically investigated the assembly processes governing the prokaryotic and microeukaryotic communities in Qinghai Lake with the use of Illumina sequencing and a null model. The results showed that both deterministic and stochastic processes play vital roles in shaping the assemblies of prokaryotic and microeukaryotic communities, in which stochastic processes appeared to dominate (> 70%). Prokaryotic communities were mainly governed by non-dominant processes (60.4%), followed by homogeneous selection (15.8%), variable selection (13.6%) and dispersal limitation (10.2%), whereas microeukaryotes were strongly driven by non-dominant processes (68.9%), followed by variable selection (23.6%) and homogenizing dispersal (6.3%). In terms of variable selection, nutrients (e. g., ammonium, dissolved inorganic carbon, dissolved organic carbon and total nitrogen) were the major factors influencing prokaryotic and microeukaryotic community structures. In summary, prokaryotes and microeukaryotes can be predominantly structured by different assembly mechanisms, in which stochasticity is stronger than deterministic processes. This finding helps to better comprehend the assembly of prokaryotic and eukaryotic communities in saline lakes.
... Saline lakes account for around half of the global volume of inland surface water bodies and emit 0.28-0.32 GT C y − 1 of CO 2 (Duarte et al., 2008;Wen et al., 2019;Williams, 1996). Recent studies have determined that salinity affects microbial activities and hydrochemical processes as well as GHG emissions from saline lakes (Xun et al., 2022). ...
... Saline lakes are typical extreme environments and are widely distributed on Earth, accounting for nearly half of the total inland water area (Williams, 1996). Xinjiang is the largest province in China, located in the center of Eurasia, with a large area of saline and alkaline environments, which contain rich microbial resources, such as halophilic bacteria (Zhang et al., , 2016Liu et al., 2020) and halophilic archaea . ...
The microbial diversity and ecological function in different saline lakes was reduced or disappeared as the influence of climate change and human activities even before they were known. However, reports about prokaryotic microbial of saline lakes from Xinjiang are very limited especially in large-scale investigations. In this study, a total of 6 saline lakes represented three different habitats, including hypersaline lake (HSL), arid saline lake (ASL), and light saltwater lake (LSL) were involved. The distribution pattern and potential functions of prokaryotes were investigated by using the cultivation-independent method of amplicon sequencing. The results showed that Proteobacteria was the predominant community and was widely distributed in all kinds of saline lakes, Desulfobacterota was the representative community in hypersaline lakes, Firmicutes and Acidobacteriota were mainly distributed in arid saline lake samples, and Chloroflexi was more abundant in light saltwater lakes. Specifically, the archaeal community was mainly distributed in the HSL and ASL samples, whereas it was very rare in the LSL lakes. The functional group showed that fermentation was the main metabolic process of microbes in all saline lakes and covered 8 phyla, including Actinobacteriota, Bacteroidota, Desulfobacterota, Firmicutes, Halanaerobiaeota, Proteobacteria, Spirochaetota, and Verrucomicrobiota. Among the 15 functional phyla, Proteobacteria was a distinctly important community in saline lakes, as it exhibited wide functions in the biogeochemical cycle. According to the correlation of environmental factors, SO42-, Na+, CO32-, and TN were significantly affected in the microbial community from saline lakes in this study. Overall, our study provided more detailed information about microbial community composition and distribution from three different habitats of saline lakes, especially the potential functions of carbon, nitrogen, and sulfur cycles, which provided new insight for understanding the complex microbiota adapt to the extreme environment and new perspectives on evaluating microbial contributions to degraded saline lakes under environmental change.
... Salt lakes are an important part of the global terrestrial aquatic ecosystem, accounting for about half of the world's total inland surface water [1]. They are mainly distributed in arid and semi-arid regions on all continents of the world, such as the rain-shadowed regions of California and Nevada, the Caribbean Plateau of British Columbia (Canada), and the middle belt of the Asia-Africa-European salt lake region (including the Tibetan Plateau in China, the Dead Sea in Palestine and the salt lakes in southwestern Russia). ...
The extreme geographical and climatic conditions of the Tibetan Plateau result in lakes spanning a diverse range of environmental conditions. Studying microbial response to extreme environmental conditions is important for understanding their adaptation and evolution in the natural environment. In this study, the microbial community composition in the surface sediments from 12 lakes with different salinities on the Tibetan Plateau were analyzed using the Illumina high-throughput sequencing platform. The results showed that the phyla Proteobacteria and Bacteroidota were the major bacteria, and Crenarchaeota was the major group of archaea in low and moderately saline lakes (salinity 0.64–33.88PSU), whereas Firmicutes and Halobacterota increased significantly in high saline lakes (salinity 44.25–106.9PSU). Salinity was the most important factor impacting bacterial α-diversity, characterized by a significant decrease in microbial diversity indices with increasing salinity. Salinity was also the main driving factor determining the microbial community composition of these lakes. Other factors, including Chl-a, OM and glacial meltwater, also had important effects to some extent. In contrast, geographic factors had no remarkable effect on microbial community composition.
... Species were collected from localities in the south and southeast of Spain (Table 1), a region with an arid Mediterranean climate where inland saline waters are very common (Millán et al., 2011;Williams, 1996). ...
The immune response represents a suite of evolved traits that can involve energetic and evolutionary trade‐offs with other energy‐demanding and fitness‐related processes. Here, we tested the hypothesis that aquatic beetles living in inland hypersaline habitats have lower immune capacity than freshwater congeners.
Phenoloxidase activity, encapsulation response and antimicrobial peptide activity were compared in freshwater/hypersaline species pairs with differing osmoregulatory capacity and cuticular waterproofing properties in the genera Nebrioporus (Dytiscidae) and Enochrus (Hydrophilidae), independent evolutionary lineages that have colonised saline media separately.
Hypersaline species ( N. ceresyi and E. jesusarribasi ) showed significantly lower phenoloxidase activity and antimicrobial peptide responses than their freshwater relatives ( N. clarkii and E. salomonis ). Encapsulation responses in freshwater species also appeared to be higher than in hypersaline relatives.
Our results reinforce the complex nature of immune responses and suggest that adaptation to saline environments may have involved a trade‐off between osmoregulation and investment in immune defences, but also are consistent with relaxed selection pressures on basal immune responses resulting from lower microbial infection load in saline habitats. In addition, the more resistant cuticle of species occupying such habitats may protect against the entry of parasites, reducing selection pressure on immunity.
Because the evolution of salinity tolerance is associated with reduced immune capacity, saline specialists may be particularly vulnerable to the dilution of saline waters and consequent changes in pathogen communities and load following colonisation by more generalist microorganisms.
... However, the Salton Sea is not a unique case worldwide. Inland saline lakes account for around 44% of the volume (and 23% of the area) of all lakes on our planet (Messager et al., 2016), and many of them are similarly shrinking due to a combination of increased water demand and changes in local climate (Williams, 1996). For example, the Aral Sea in central Asia has seen massive reductions in both lake area (by 74%) and volume (by 90%), turning its freshly exposed surrounding lakebed into new dust sources. ...
The ongoing desiccation of California's Salton Sea has led to increasing concerns about air quality and health for its surrounding communities, including the nearby Coachella Valley – a region already experiencing severe air quality and health disparities. Here we explore spatial air pollution and human health disparities in the Coachella Valley with particular attention to disparities arising across population characteristics including both socioeconomic and demographic vulnerabilities. We use two different measures of respiratory and cardiovascular health outcomes at the individual and census tract levels – one measure based on a randomly sampled telephone survey and the other measure based on emergency room visitation data – to investigate the degree to which these health outcomes are connected to air pollution and socioeconomic metrics. We further investigate biases and differences between the health outcome metrics themselves and suggest opportunities to address them in future analyses and survey efforts. We find that more vulnerable communities are associated with higher levels of fine particulates, but lower levels of ozone. While emergency visit rates show a significant positive correlation with both pollutants, no such association is found when using surveyed health outcome data. The ratio of emergency visits versus survey rates shows a positive relationship with socioeconomic and demographic vulnerability, indicating that vulnerable communities are less likely to self-report diagnoses despite higher rates of respiratory or cardiovascular hospitalization. Additionally, survey respondents tend to show less vulnerability relative to their surrounding census-based demographics. These findings suggest the need for greater attention to health issues specifically within disadvantaged communities in the Coachella Valley, building upon and working within existing community networks and local resources, to better address current and projected health needs. Our findings also highlight disparities in air pollution exposure, health outcomes, and population characteristics in the Coachella Valley, providing context for crucial pollution reduction efforts in the face of increasing environmental threats.
... They occur throughout the arid (25-200 mm annual precipitation) and semi-arid (200-500 mm) regions of the world (Jellison et al., 2004;Oren et al., 2009). They include a vast array of different sizes, ages, salinity, ionic composition, flora and fauna; from ephemeral playa lakes to ancient lakes (Hammer, 1986;Williams, 1996). The global volume of inland saline water (85,000 km 3 ) is only slightly less than that of freshwater (105,000 km 3 ) (Shiklomanov, 1990). ...
Changes in land use/land cover (LULC) are the key factors driving biodiversity and ecosystem services decline globally. This study examines spatiotemporal LULC changes in a Ramsar coastal temporary wetland (Larnaca Salt Lake) on the island of Cyprus between 1963 and 2015. LULC changes in the area are related to variations in the provision of ecosystem services (ES) namely food provision, climate regulation, avifauna support and landscape aesthetics. LULC mapping was performed based on the interpretation of aerial photos taken in 1963, while 2015 mapping was based on CORINE classification validated by satellite image analysis and fieldwork. We used the following indicators for the ES examined: (1) crops’ yield for the estimation of food supply, (2) carbon storage potential for climate regulation, (3) land cover potential to support avifauna richness and (4) naturalness as a proxy for landscape aesthetics. Quantifications were based on a mixed-methods approach with the use of statistical data, expert opinion and bibliography. Estimates for every service were assigned to CORINE land use classes (CLC) present in the area. Landscape structure was measured using a suite of commonly employed landscape metrics. The results showed that between 1963 and 2015 there has been a significant reduction in food provisioning service by 75%, a 37% reduction in carbon storage capacity, an 11% reduction in the capacity to support avifauna, and a 13% reduction in landscape aesthetics. Increased soil surface sealing, mainly with the construction of the international airport, which resulted in the conversion of natural or semi-natural to artificial surfaces, has been the main reason for the decrease in ES supply over the last fifty years in the study area. The character of the area in terms of land use types richness and diversity remains fairly stable but the dominant land use types have experienced fragmentation. The study sets the basis for a monitoring scheme to evaluate the state of the temporary wetlands with emphasis placed on spatial processes as a link to ES provision.
... Saline lakes are an important part of the global terrestrial aquatic ecosystem, which account for about half of the total volume of inland surface water in the world (Williams, 1996). They are mainly distributed in arid and semi-arid regions of all continents in the world, such as the Rift Valley in East Africa, the rain-shadowed regions of California and Nevada (USA), the Cariboo Plateau in British Columbia (Canada), the Kulunda Steppe in South Siberia (Russia) and the Tibetan Plateau (China). ...
Badain Jaran Desert (BJD), characterized by extremely arid climate and tallest sand dunes in the world, is the second largest desert in China. Surprisingly, there are a large number of permanent lakes in this desert. At present, little is known about the composition and distribution of microbial communities in these desert lakes, which are an important bioresource and play a fundamental role in the elemental cycles of the lakes. In this study, the physicochemical characteristics and microbial communities of water samples from 15 lakes in BJD were comparatively investigated. The results showed that the lakes were rich in Na⁺, Cl⁻, CO3²⁻ and HCO3⁻ while Ca²⁺ and Mg²⁺ were scarce, with pH 8.52-10.27 and salinity 1.05-478.70 g/L. Bacteria dominated exclusively in low saline lakes (salinity < 50 g/L) while archaea were predominant in hypersaline lakes (salinity > 250 g/L), which abundance increased along salinity gradient linearly. Genera Flavobacterium, Synechocystis and Roseobacter from phyla Bacteroidetes, Cyanobacteria, Alphaproteobacteria were the major members in low saline lakes whereas Halomonas, Aliidiomarina and Halopelagius from Gammaproteobacteria and Euryarchaeota were abundant in moderately saline lakes (salinity 50-250 g/L). The hypersaline lakes were predominated by extreme halophiles such as Halorubrum, Halohasta and Natronomonas from Euryarchaeota. The correlation among the microbes in the lakes was mainly positive, suggesting they can survive in the harsh environments through synergistic interactions. Statistical analyses indicated that physicochemical characteristics rather than spatial factors shaped the microbial communities in the desert lakes. The pH was the most important environmental factor controlling alpha diversity, while salinity was the major driver determining microbial community structure in BJD lakes. In contrast, geographic factors had no significant impact on the microbial community compositions.
... Because terminal lakes exhibit such great interannual and long-term variations in L L and L A it is critical to examine their volumetric water budget budgets (Williams 1996;Todhunter 2018). Table 2 and Figure S8 present the lake water budget variables in units of depth (mm). ...
Devils Lake, a terminal lake in northeast North Dakota (USA), has experienced catastrophic flooding since 1993. From January 31, 1993, to December 31, 2014, lake level rose from 433.62 to 442.44 m, lake area expanded from 179.9 to 653.5 km², and lake volume increased from 0.70 to 3.80 km³. More than $1 billion ($USD) has been spent in government payments to mitigate direct, primary, tangible flood damages. This paper provides a case study of the hydrological basis of the Devils Lake flood disaster. The unique geomorphic setting, paleoclimatic record, and hydroclimatic conditions of the region are summarized, and a wide range of hydroclimatic data is examined to provide a broad understanding of the physical basis of the flood disaster. The primary cause of the disaster was a transition to a sustained wetter climate that resulted in a dramatic response in basin hydrological variables in 1993. The transition from a long-term dry period to a long-term wet period caused the lake water budget to begin to change from an atmosphere-controlled water budget dominated by precipitation input to an amplifier lake water budget dominated by surface runoff input to the lake. Other important hydrological factors include a nonlinear precipitation–runoff relationship following the long-term drought, fill-spill and fill-merge hydrological behavior that is characteristic of wetland complexes, an increase in the lake area-to-basin area ratio, and the critical role of frozen soils in controlling infiltration and runoff production of spring snowmelt. Engineering works to manage lake volume through two outlets have reduced, but not entirely eliminated, future flood risk.
... There are many examples of endorheic saline lakes severely affected by human activities due to uncalibrated consequences of the actions done (Williams, 1996(Williams, , 2002Moore, 2016). Lessons learnt from these hydrological systems show that simplistic regulation of the lakes water may led to changes in the lake salinity that may destroy the singularity of the hydrological systems. ...
Most of the athalassic saline and hypersaline lakes are located in arid and semiarid regions where water availability drives the hydrological dynamics of the lake itself and the associated ecosystems. This is the case of the Salada de Chiprana Lake, in the Ebro River basin (Spain). It is the only athalassic permanent hypersaline lake in Western Europe, and where rare and endangered bacterial mats exist. This work presents a robust hydrogeological conceptual model for the lake system. The model evaluates the contribution of groundwater discharge to the whole water budget and explains the hydrological behaviour of the lake system. The lake behaves as a flow-through system rather than a closed basin. About 40% of total water outflow from the lake occurs as groundwater, whereas evaporation accounts for the remaining 60%. The surface water inflows are variable, but the groundwater contribution seems almost constant, amounting to 13% of the average total water inflow and contributing 1.9% of salt income. The high water salinity of the lake is controlled by evaporation, by saline water inflows from irrigation return flows, and the by groundwater outflows. The role of groundwater should be taken into account when drafting the water and land planning, once the conditions for the conservation of the algal mats are defined. A major contribution of this study is the water balance in the Salada de Chiprana Lake, which is consistent with a robust hydrogeological conceptual model defined upon scarce hydrogeological, hydrochemical and isotopic data in the local context as conditioned by the regional behaviour. The water balance is a key tool to help to correctly manage this unique athalassic saline lake, and the approach used here can be extrapolated to other similar ecosystems around the world.
... The Soan-Sakesar valley, in the Salt Range (Pakistan) is a semi-arid area (Figure 1) where groundwater and wetlands (saline lakes) are the major water resources for daily consumption, explaining their large utilization to meet the regional growing demand. Saline lakes, which provide a large number of services to water birds, mineral extraction, environmental conservation or to industrial use, are shrinking worldwide [3,4] due to their overexploitation by humans, particularly for agricultural irrigation and other domestic purposes [5,6]. As such, the chemistry of this water resource changes quickly and its salinity usually increases significantly [1,7,8]. ...
The surfaces of saline lakes are shrinking at a threatening rate worldwide. Likewise, the Uchhali complex (formed by three saltwater lakes located in the Salt Range, Pakistan) that serves as a major regional source of water for humans and as a habitat for water birds must be monitored. With this objective in mind, we conducted a study coupling hydrochemistry and stable isotope compositions (δ 37 Cl, δ 18 O and δD) in order to characterize its hydrochemical properties and the main processes controlling them. Results showed that the Uchhali complex salinity has dramatically increased compared to other similar lakes in the world. While the Uchhali (UL) and Khabbeki (KL) lakes present a sodium-chloride hydrofacies, the Jahlar (JL) is of a sodium-bicarbonate type. Hydrochemistry parameters indicate that the weathering of surrounding rocks is the major vector for the increase of total dissolved solids in the water. On the other hand, the observed enrichment in heavy isotopes of the water stable isotope compositions implies that the different lakes are undergoing a long history of intense evaporation. The study of the corresponding δ 37 Cl isotope compositions supports the conclusion that evaporation, along with weathering, are the main driving processes. Besides climate effects that result in the decrease of annual precipitation and the increase of evaporation, water consumption for domestic purposes (household and agriculture) aggravates the rise of the lakes' salinity.
... Closed (also called endorheic or terminal) lakes are confined within land with no outflow (De Martonne, 1927). Because of that, water balance of a closed lake only depends on water inflow, precipitation, and evaporation (Bengtsson and Malm, 1997;Williams, 1996), making the lake a good indicator of climate and land use changes in the entire watershed. Kharel and Kirilenko (2015) provided an overview of observed changes in closed lakes worldwide. ...
Flood control is one of the most important ecosystem services provided by wetlands. Large-scale loss of wetlands, combined with more intensive precipitation under changing climate, increases flood risks, to which closed watersheds are particularly susceptible. In the Devils Lake (North Dakota, USA) watershed, a prolonged wet condition since early 1990s has caused a nearly 10 m rise in water level, resulting in over $1 billion losses. While studies have shown the changing climate is the major driver of this flooding, it is still unclear how much contribution could be due to the historical conversion of wetlands in the upper basin. We developed a Soil and Water Assessment Tool (SWAT) model for the Devils Lake watershed and simulated various scenarios representing present and possible past and future wetland area. We estimated the changes in flood risks under the historical and CMIP-5 future climates with these wetland scenarios. We found that while currently wetland restoration does not significantly change flood risks, under the modified climate it presents a good complementary measure reducing the negative impacts of current flood management strategies.
... Lakes are globally distributed aquatic ecosystems, and they are also "sentinel" ecosystems that can sensitively respond to either anthropogenic perturbations or global climate change (Adrian et al. 2009;Tranvik et al. 2009). Half of the total surface of all terrestrial aquatic ecosystems (including lakes, rivers, wetlands, reservoirs, etc.) are occupied by saline and hypersaline lakes (William 1996), which significantly contribute to global carbon budget (Duarte et al. 2008). Frequently reported archaea in lakes are dominated by phyla of Euryarchaeota, Crenarchaeota, Thaumarchaeota, Pacearchaeota, and Woesearchaeota Jiang et al. 2008;Jiang et al. 2009a;Liu et al. 2016;Najjari et al. 2015; Ortiz-Alvarez and Casamayor 2016; Pagaling et al. 2009). ...
Uncovering microbial diversity and their influencing factors is a primary goal for microbial ecology. In comparison with studies on bacterial diversity, limited is known about archaeal diversity and its response to influencing factors in lakes. Here, we investigated the archaeal community compositions (ACCs) and their correlation with spatial/environmental factors in the sediments from 38 Chinese lakes with a large range of salinity (0.2–363.1 g/l) and pairwise geographic distance (3–3656 km). Illumina-Miseq sequencing was employed to characterize the ACCs in the lakes samples. The results showed that Euryarchaeota, Bathyarchaeota, Thaumarchaeota, and Woesearchaeota were the dominant archaeal phyla in the studied samples, and they each can occur in the samples with a wide range of salinity (0.2–363.1 g/l) although their abundance was relatively low (<1%) in certain samples. The Thaumarchaeota and Woesearchaeota phyla dominated (up to 90% of total sequences) some lake sediments. Mantel test indicated that compositions of total archaeal community and the Euryarchaeota and Woesearchaeota populations were significantly (p < 0.05) correlated with geographic distance in the studied lake sediments. Salinity was the most important environmental factor influencing the compositions of the total archaeal community and the Euryarchaeota population, while it did not show significant influence on the distribution of the Woesearchaeota and Thaumarchaeota populations. Taken together, this survey expands our current knowledge on the ecology of lacustrine archaea and give clues for studying the archael role in biogeochemical cycles in lakes.
... Saline and hypersaline lakes are import components in inland aquatic ecosystems (accounting for up to half of the total surface of all terrestrial aquatic ecosystems (Williams 1996), and thus they contribute significantly to global carbon budget (Duarte et al. 2008). Saline and hypersaline lakes host abundant dissolved organic and inorganic carbon and other nutrition, which sustain highly active microbial communities (Anderson and Stedmon 2007). ...
The Gammaproteobacteria are widely and abundantly distributed in various environments, and they play important roles in the geochemical cycles of biogenic elements (e.g., C, N and S) in the ecosystems. Previous studies showed that Gammaproteobacteria dominate in saline and hypersaline lakes. However, little is known on how salinity influences gammaproteobacterial community composition and their ecological functions (i.e., organic carbon degradation). In this study, we investigated the gammaproteobacterial diversity and carbon utilization and their response to salinity in six saline/hypersaline lakes and one freshwater lake on the Qinghai–Tibetan Plateau (QTP). The results indicated that the gammaproteobacterial community composition was mainly influenced by the salinity of the studied QTP lakes. Salinity was also a key environmental factor influencing the carbon utilization ability of Gammaproteobacteria: within one genus (e.g., Halomonas, Pseudoalteromonas, Vibrio) the strains retrieved from low-salinity environments had stronger carbon utilization ability than their counterparts from high-salinity environments; within one genus, the strains isolated from lakes with different salinity shared similar carbon utilization preference, indicating that species belonging to the same genus may execute similar ecological functions in the environments regardless of salinity.
... Examples of such environments include the paleolake basin in the Great Salt Lake Desert, Utah (Litchfield 1998), and several lakes in Western Australia (Mormile, Hong and Benison 2009). Among the several unique similarities between Earth analogues Williams (1996). Shading indicates major areas of distribution of saline lakes. ...
Saline and hypersaline environments are known for their unique geochemical properties, microbial populations and aesthetic appeal. Microbial activities and a spectrum of diversity seen in hypersaline environments are distinct with many novel species being identified and reported on a regular basis. Many distinguishing characteristics about the adaptation, morphology, evolutionary history, and potential environmental and biotechnological applications of these organisms are continually investigated. An abundance of interdisciplinary activities and opportunities exist to explore and understand the importance of these environments that potentially hold promising solutions for current and future global issues. Therefore, it is critical to conserve these unique environments and limit the damage inflicted by anthropogenic influences. Increased salinization due to water diversions, undesired freshening, extensive mineral extraction, sewage effluents, pollution due to agricultural runoff and industrial processes, urbanization, and global climate change are factors negatively affecting hypersaline lakes and their surrounding environments. If these harmful effects continue to proceed at the current or even accelerated rates, irrevocable consequences for these environments will occur, resulting in the loss of potential opportunities to gain new knowledge of the biogeochemistry as well as beneficial microbial populations closely associated with these unique and interesting environments.
... Saline lakes across the globe are shrinking 1,2 (Fig. 1a). Increasing water use by humans, especially for agricultural irrigation 3 , is a significant factor in lake desiccation. For example, agricultural water development in the Aral Sea watershed 2 has reduced lake area by 74% and volume by 90% (ref. ...
Many of the world's saline lakes are shrinking at alarming rates, reducing waterbird habitat and economic benefits while threatening human health. Saline lakes are long-term basin-wide integrators of climatic conditions that shrink and grow with natural climatic variation. In contrast, water withdrawals for human use exert a sustained reduction in lake inflows and levels. Quantifying the relative contributions of natural variability and human impacts to lake inflows is needed to preserve these lakes. With a credible water balance, causes of lake decline from water diversions or climate variability can be identified and the inflow needed to maintain lake health can be defined. Without a water balance, natural variability can be an excuse for inaction. Here we describe the decline of several of the world's large saline lakes and use a water balance for Great Salt Lake (USA) to demonstrate that consumptive water use rather than long-term climate change has greatly reduced its size. The inflow needed to maintain bird habitat, support lake-related industries and prevent dust storms that threaten human health and agriculture can be identified and provides the information to evaluate the difficult tradeoffs between direct benefits of consumptive water use and ecosystem services provided by saline lakes.
... Inland water ecosystems (e.g., rivers, lakes, and wetlands) contribute significantly to global carbon budget ( Battin et al. 2009). Saline and hypersaline lakes occupy about a half of the total inland water surface area (Williams 1996), and thus studying microbial populations involved in carbon cycling in saline/ hypersaline lakes is of great importance to understand global carbon cycling. Aerobic anoxygenic phototrophic bacteria (AAPB) are a group of heterotrophic prokaryotes capable of harvesting light for ATP production (energy supplement) without molecular oxygen generation (Beatty 2002;Kobl ı zek et al. 2010;Kobl ı zek 2011;Okamura et al. 1986;Beatty 1998a, 1998b). ...
Aerobic anoxygenic phototrophic bacteria (AAPB) are widespread and play important roles in carbon cycling in the lakes of the Qinghai-Tibetan Plateau. However, little is known about how free-living and particle-attached AAPB distribute with salinity in the Qinghai-Tibetan lakes. In the present study, the abundance and diversity of free-living and particle-attached of AAPB were investigated in seven Qinghai-Tibetan lakes with salinity ranging from freshwater to almost saturation (1.2 g/L-241.1 g/L). An integrated approach was employed including pufL-M gene (encoding the photosynthetic reaction center of AAPB)-based quantitative polymerase chain reaction (QPCR) and PCR-cloning phylogenetic analysis. The QPCR data showed that the ratio between particle-attached and free-living AAPB was positively correlated (R² = 0.73, P <0.01) with increasing salinity. The pufL-M gene phylogenetic analysis showed that the AAPB population composition varied with salinity in the studied Qinghai-Tibetan lakes. These results suggested that salinity may be the important factor shaping the AAPB distribution in the studied Qinghai-Tibetan lakes, and AAPB may be adapted to the harsh conditions in the Qinghai-Tibetan lakes by attaching to particles.
... Hydrologic systems across the globe are highly sensitive to and affected by climate and land-use change (Legesse et al., 2003;Bouraoui et al., 2004;Heuvelmans et al., 2005;Gosain et al., 2006;Rosenzweig et al., 2007). These modifications are probably the most visible in endorheic (also called terminal or closed) lakes, which are confined within the land with no outflow (de Martonne, 1927), as their levels only depend on the balance of water inflow, precipitation, and evaporation (Williams, 1996;Bengtsson and Malm, 1997). Over the last few decades, significant fluctuations in lake levels due to the combined effect of climate change and human activities have been reported; however, no consistent global trend has been observed (Rosenzweig et al., 2007). ...
Terminal lakes are impacted by regional changes in climate. Devils Lake (DL), North Dakota, United States (U.S.), is a case in which a prolonged shift in the precipitation pattern resulted in a 10-m water-level rise over the past two decades, which cost over one billion U.S. dollars in mitigation. Currently, DL is 1.5 m from an uncontrolled overspill to the nearby Sheyenne River, which could lead to unprecedented environmental , social, and economic costs. Water outlets recently implemented in the lake to slow the water-level rise and prevent an uncontrolled overspill are subject to significant concerns over the introduction of invasive species and downstream water quality. We developed a hydrological model of the DL basin using the soil and water assessment tool and analyzed DL's overspill probability using an ensemble of statistically downscaled General Circulation Model (GCM) projections of the future climate. The results indicate a significant likelihood (7.3-20.0%) of overspill in the next few decades in the absence of outlets; some members of the GCM integration ensemble suggest an exceedance probability of over 85.0 and 95.0% for the 2020s and 2050s, respectively. Full-capacity outlets radically reduce the probability of DL overspill and are able to partially mitigate the problem by decreasing the average lake level by approximately 1.9 and 1.5 m in the 2020s and 2050s, respectively.
... Terminal lakes are among the world's most dy namic natural hydrological systems, with water surface elevation (WSE) often changing rapidly in response to variations in the volume of lake water sources and sinks (Williams 1996). They are also ex tremely sensitive to human modification of basin hydro logy and can experience significant WSE changes due to alteration of basin land use/land cover and river hydrology (Coe & Foley 2001, Williams 2002, Micklin 2007. ...
Since the spring of 1993, the water surface elevation at Devils Lake, a terminal lake in eastern North Dakota, USA, has risen by 8.8 m, producing more than 1 billion USD in direct flood damages. We examine the relationship between weather-type frequencies at Bismarck, North Dakota, and lake volume changes from 1965 to 2010 using the Spatial Synoptic Classification (SSC) system. First, we find statistically significant changes in the frequency of selected weather types over both annual and seasonal time periods. This indicates a trend toward in -creased advection of more humid weather types that is consistent with the historical rise in lake level. Second, a comparison of weather type frequencies between a subset of years with extreme large and small lake surges, and extreme large and small lake drawdowns, shows that weathertype frequency plays an important role in explaining annual lake volume fluctuations. The results support a climatic explanation for the historical lake rise at Devils Lake, but the relationships are not as strong as might have been anticipated given the unprecedented lake rise that occurred during the study period. A more detailed examination of the complex and non-linear nature of the lake water balance may be needed to further clarify how precipitation input is translated into lake volume changes.
... Several processes can be implied in lake water salinity. The salinity of lakes is conventionally considered to be the result of the input salt content concentrated by evaporation (Crowe, 1993;Williams, 1996;Barjaktarovic and Bendell-Young, 2002;Yechieli and Wood, 2002). Other solute sources in lake salt budget coming from surface and underground soils or rocks catchment weathering through many processes such as solution, oxidation-reduction, acidity and the formation of organic complexes (Gibbs, 1970;Kilham, 1990;Barjaktarovic and Bendell-Young, 2002) can also be involved. ...
Located on the triple rift junction hosting the Karonga-Usungu depression in Tanzania, Lake Ngozi is the second largest crater lake of the East African Rift. The lake has a number of peculiar features: it has a near constant water level, no permanent surface inlets and outlets, it is vertically well-mixed, with homogeneous distribution of temperature and chemical composition, and it is characterised by near neutral to slightly acid Na–Cl waters of comparatively high salinity and high P–CO2. Based on the different chemical signature of surface and ground waters (low-Cl type) from lake waters, mass balance methods have been applied to investigate lake dynamics. Water enters the lake mainly by precipitation and groundwater inflow, and leaves by groundwater outflow and evaporation. A large groundwater outflow of 2.4 m yr−1 has been estimated. The high salinity, Na–Cl signature of Lake Ngozi waters, together with 3He/4He ratios measured on dissolved gases (between 7 and 8.3 Ra) and high-PCO2 values estimated all along the water vertical column indicate the inflow of deep-seated fluids, likely magmatic in origin, into the lake. The existence of a hydrothermal system possibly at 250 °C in the root of the volcanic edifice is also hypothesised on the basis of solute geothermometry. Despite the current lack of vertical stratification, the lake is suspected to act as condenser for CO2 and other gases of deep magmatic origin, and should be then further monitored for the risk of limnic eruptions as well as for environmental and climatic concerns.
Saline lakes across the globe have experienced severe reduction in their surface area as a result of climate change and human-induced perturbations like water diversion and extraction. The changing lake volume is predicted to have large-scale implication on the in-lake biogeochemistry. This study explores the carbon (C) and nitrogen (N) cycling in a desiccating hypersaline lake (Sambhar Lake, India) along with adjacently located brine reservoir and salt pans by measuring concentrations and stable isotopic ratios of different C and N pools during winter and monsoon. Incubation experiments to estimate the net nitrification and mineralization rates in lake sediments were also performed. The Lake witnessed a large decrease in surface area and showed a clear signature of desiccation on lake biogeochemistry. Both particulate and dissolved fractions of C and N in the lake increased as the lake desiccated from monsoon to winter. Low N isotopic composition (δ15N) of particulate organic matter during winter suggested the presence of N2 fixers in this nutrient-rich saline environment. Taken together, significant difference in C and N concentrations and isotopic compositions were observed across the lake, brine reservoir, and salt pans, suggesting considerable modulation of in-lake processes due to human interventions.
Saline and hypersaline environments are classified as wetlands and constitute the largest ecosystems on the planet (a half of inland aquatic ecosystems), they are widely distributed all over the continental zones (Africa, America, Europe, Australia, and Asia). African salt lakes are located in the arid northern and southern regions. Some of the African saline and hypersaline lakes are Natron, chott Melghir, chott El Jerid, Zahrez Chergui and Guerbi. Microbial diversity within salt lakes is restricted to a few extremely salt-tolerant species. Certain microorganisms can thrive in salty and extreme environmental conditions. These microorganisms can be found over the three domains (Archeae, Bacteria, and Eukarya). The microbial biodiversity of African salt lakes is of great interest not only to have an overview of halophilic microorganisms flourishing in these extreme ecosystems but also for their potential applications in different fields. Extremophiles are a group of microorganisms with high biotechnological and industrial potential, especially for their ability to produce biopolymers, pigments, antibiotics, and enzymes. Most African salt lakes are unexploited; a few studies were published on microbial diversity which is an excellent opportunity for scientists to discover new genera and/or species and also news molecules of biotechnological interest. This chapter reviews African salt lake distribution and the microbial diversity, with an emphasis on the North of Africa. An overview of microbial, diversity which can contribute to the development of African countries is also provided by presenting a prominent investigation of the bioactive molecules from salt lakes with potential application in biotechnology.
Key Words: Salt lakes, Microbial diversity, African countries, Biotechnology, Metabolites.
The Tibetan Plateau (TP) hosts more than one thousand lakes (>1km2) in its endorheic basins. The changing climate in recent decades has led to significant modifications in the endorheic hydrologic system. Most TP lakes experienced dramatically expanding areas, rising water levels, and increasing storage, which inevitably influenced the lake salinity. This study provides a regional-scale investigation of water salinity changes of the TP lakes (for 83 lakes with two-epoch salinity records, among the approximately 160 lakes >50km2) by synthesizing multi-source data around the 1970s and 2010s. Our results reveal lake salinity has considerably declined for most expanding lakes across the endorheic basins. The mean salinity of 62 terminal lakes dropped from 92.76g/L to 42.00g/L during the 1970s-2010s, in contrast to the slight variations (3.42g/L to 1.48g/L) of the 21 exorheic or upstream lakes. As a result, many hypersaline lakes have become polysaline or oligosaline lakes, such as Cedo Caka, Norma Co, etc. In particular, some large lakes (e.g., Siling Co, “Twin Lakes”, and Ayakkum Lake) also experienced significant drops in water salinity, with the exceptional cases for Nam Co and Qinghai Lake probably due to the relatively low ratios of increased water mass to their net storages. The widespread declining water salinities could greatly influence bacterial richness, diversity, and evenness, and affect the aquatic carbon cycle and utilization in the high-altitude endorheic lakes. More attention should be paid on understanding the saline lake ecosystem evolution and the regional carbon cycle in response to changing water salinity of the TP lakes.
The distribution of nitrite- and N2O-reducing bacteria is key to potential N2O emission from lakes. However, such information in highland saline lakes remains unknown. Here, we investigated the abundance and community composition of nitrite- and N2O-reducing bacteria in the sediments of six saline lakes on the Qing-Tibetan Plateau. These studied lakes covered a wide range of salinity (1.0-340.0 g/L). Results showed that in the studied saline lake sediments nitrite-reducing bacteria were significantly more abundant than N2O-reducing bacteria, and their abundances ranged 7.14×103-8.26×108 and 1.18×106-6.51×107 copies per gram sediment (dry weight), respectively. Nitrite-reducing bacteria were mainly affiliated withα-, β-, and γ- Proteobacteria, with β- and α-Proteobacteria being dominant in low- and high-salinity lakes, respectively; N2O-reducing bacterial communities mainly consisted of Proteobacteria (α-, β-, γ-, and δ-subgroups), Bacteroidetes, Verrucomicrobia, Actinobacteria, Chloroflexi, Gemmatimonadetes and Balneolaeota, with Proteobacteria and Bacteroidetes/Verrucomicrobia dominating in low- and high-salinity lakes, respectively. The nitrite- and N2O-reducing bacterial communities showed distinct responses to ecological factors, and they were mainly regulated by mineralogical and physicochemical factors, respectively. In response to salinity change, the community composition of nitrite-reducing bacteria was more stable than that of N2O-reducing bacteria. These findings suggest that nitrite- and N2O-reducing bacteria may prefer niches with different salinity.
Climate induced drought is a prominent threat to natural saline aquatic ecosystems by modifying their hydrology and salinity, which impacts the biodiversity of these ecosystems. Lake Nyamithi is a naturally saline lake in South Africa that experienced the effects of a two-year supra-seasonal drought (2015–2016). This study aimed to determine potential effects of the drought and accompanying increased salinity (between 9.8 and 11.5 g L−1) on aquatic invertebrate communities of Lake Nyamithi, and assess their potential recovery following the drought. Aquatic invertebrates and water were collected for biodiversity and chemical assessments during predrought conditions (2014), the peak of the drought (2016) and after the site had received water (2017). Taxon richness was considerably reduced during the peak of the drought as many biota could not tolerate the increased salinity. Ecological resilience and recovery was evident in the lake since numerous biota (re)colonized the lake promptly after the site received water and salinity decreased (<8 g L−1). By the end of 2017, invertebrate biodiversity exceeded that of predrought conditions. Although some biota may be able to temporarily cope with extreme weather conditions, frequent or prolonged periods of drought and increased salinity pose a threat to naturally saline lakes such as Nyamithi and dilution with fresh water is vital for the persistence of species diversity and ecological integrity.
Lakes are of fundamental importance in the Earth system as they support essential environmental and economic services, such as freshwater supply. Streamflow variability and temporal evolution are impacted by the presence of lakes in the river network; therefore, any change in the lake state can induce a modification of the regional hydrological regime. Despite the importance of the impact of lakes on hydrological fluxes and the water balance, a representation of the mass budget is generally not included in climate models and global-scale hydrological modeling platforms. The goal of this study is to introduce a new lake mass module , MLake (Mass-Lake model), into the river-routing model CTRIP to resolve the specific mass balance of open-water bodies. Based on the inherent CTRIP parameters, the development of the non-calibrated MLake model was introduced to examine the influence of such hydrological buffer areas on global-scale river-routing performance. In the current study, an offline evaluation was performed for four river networks using a set of state-of-the-art quality atmospheric forcings and a combination of in situ and satellite measurements for river discharge and lake level observations. The results reveal a general improvement in CTRIP-simulated discharge and its variability, while also generating realistic lake level variations. MLake produces more realistic streamflows both in terms of daily and seasonal correlation. Excluding the specific case of Lake Victoria having low performances , the mean skill score of Kling-Gupta efficiency (KGE) is 0.41 while the normalized information contribution (NIC) shows a mean improvement of 0.56 (ranging from 0.15 to 0.94). Streamflow results are spatially scale-dependent, with better scores associated with larger lakes and increased sensitivity to the width of the lake outlet. Regarding lake level variations, results indicate a good agreement between observations and simulations with a mean correlation of 0.56 (ranging from 0.07 to 0.92) which is linked to the capability of the model to retrieve seasonal variations. Discrepancies in the results are mainly explained by the anthropiza-tion of the selected lakes, which introduces high-frequency variations in both streamflows and lake levels that degraded the scores. Anthropization effects are prevalent in most of the lakes studied, but they are predominant for Lake Victo-ria and are the main cause for relatively low statistical scores for the Nile River However, results on the Angara and the Neva rivers also depend on the inherent gap of ISBA-CTRIP process representation, which relies on further development such as the partitioned energy budget between the snow and the canopy over a boreal zone. The study is a first step towards a global coupled land system that will help to qualitatively assess the evolution of future global water resources, leading to improvements in flood risk and drought forecasting .
There is limited knowledge of microbial carbon fixation rate, and carbon-fixing microbial abundance and diversity in saline lakes. In this study, the inorganic carbon uptake rates and carbon-fixing microbial populations were investigated in the surface sediments of lakes with a full range of salinity from freshwater to salt saturation. The results showed that in the studied lakes light-dependent bicarbonate uptake contributed substantially (> 70%) to total bicarbonate uptake, while the contribution of dark bicarbonate uptake (1.35–25.17%) cannot be ignored. The light-dependent bicarbonate uptake rates were significantly correlated with pH and turbidity, while dark bicarbonate uptake rates were significantly influenced by dissolved inorganic carbon, pH, temperature, and salinity. Carbon-fixing microbial populations using the Calvin-Benson-Bassham (CCB) pathway were widespread in the studied lakes, and they were dominated by the cbbL and cbbM gene types affiliated with Cyanobacteria and Proteobacteria, respectively. The cbbL and cbbM gene abundance and population structures were significantly affected by different environmental variables, with the cbbL and cbbM genes being negatively correlated with salinity and organic carbon concentration, respectively. In summary, this study improves our knowledge of the abundance, diversity and function of carbon-fixing microbial populations in the lakes with a full range of salinity.
Lakes are of fundamental importance in the Earth system as they support essential environmental and economic services such as freshwater supply. They also modify the local hydro-meteorological continuum as a lower boundary of the atmosphere. Sentinels of climate change and anthropization, these open water bodies are facing disruptions of their equilibrium generally leading to a notable reduction of their levels worldwide. Stream-flow variability and temporal evolution are impacted by the presence of lakes in the river network, therefore any change in the lake state can induce a modification of the regional hydrological regime. Despite the importance of the impact of lakes on hydrological fluxes and the water balance, a representation of the mass budget is generally not included in climate models and global scale hydrological modeling platforms. The goal of this study is to introduce a new lake mass module, MLake (Mass-Lake model), into the river routing model CTRIP to resolve the specific mass-balance of open water bodies. Based on the inherent CTRIP parameters, the development of the non-calibrated MLake model was introduced to examine the influence of such hydrological buffer areas on the global scale river routing performances.
Proxy variables from palaeolimnological studies of lakes in the Prairie Pothole Region of North America have been used to infer large oscillations during the late Holocene between longer periods of high-salinity–dry conditions and shorter periods of low-salinity–wet conditions producing a normative pattern marked by the absence of hydrological stability. Studies of the historical rise in lake level at Devils Lake have identified 1980 as a transition point between two such hydroclimatic modes. This study uses multiple datasets to characterize the mean hydroclimatological and hydrological conditions of these two climatic modes. Mode 1 is a cool and dry phase, and mode 2 is a warmer and wetter phase. Precipitation onto the lake increased by 24% from mode 1 to mode 2. This small, but sustained, increase produced significant changes in the mean hydroclimatic and hydrological states for the basin, including a 383% increase in surface run-off to the lake, and a 282% increase in the basin run-off ratio. Devils Lake Basin is located along a hydrotone (region of strong hydroclimatic gradients) where small changes in hydrological drivers are amplified into large changes in regional moisture. The effects of the fluctuating climatic modes and strong hydroclimatic gradients are probably further amplified by the unique fill–spill hydrology of the northern glaciated plains, which can result in nonlinear precipitation–run-off relationships. This natural pattern of extreme hydrological variations for Devils Lake produces enormous challenges for lake management.
Hydrogeochemistry investigations have been carried out in the Pergusa Basin, located in central Sicily ( Italy), where Pergusa Lake represents a rare example of natural endorheic lake. In the area, agriculture and tourism are the main anthropic activities and, for this reason, groundwater is exploited for agricultural and domestic purposes. Samplings of lake water and groundwater have been carried out with the aim of characterizing the main physicochemical parameters, such as pH, electrical conductivity ( EC), sodium ( Na+), potassium ( K+), calcium ( Ca2+), magnesium ( Mg2+), chloride ( Cl-), bicarbonate ( HCO3), sulfate ( SO42+) and total dissolved solids ( TDS). Major hydrochemical facies were identified using Piper trilinear diagram. Furthermore, the results of the groundwater analysis were compared with historical measurements, showing changes in the chemical facies. Results highlight the possible irreversible negative effects on the ecosystem due to the geochemical evolution of lake water and groundwater.
Although extremely important to migrating waterfowl and shorebirds, and highly threatened globally, most saline lakes are poorly monitored. Lake Abert in the western Great Basin, USA, is an example of this neglect. Designated a critical habitat under the Western Hemisphere Shorebird Reserve Network, the lake is at near record historic low levels and ultra-high salinities that have resulted in ecosystem collapse. Determination of the direct human effects and broader climate controls on Lake Abert illustrates the broader problem of saline lake desiccation and suggests future solutions for restoration of key habitat values. A 65-year time series of lake area was constructed from Landsat images and transformed to lake volume and salinity. "Natural" (without upstream withdrawals) conditions were calculated from climate and stream flow data, and compared to measured volume and salinity. Under natural conditions the lake would have higher volume and lower salinities because annual water withdrawals account for one-third of mean lake volume. Without withdrawals, the lake would have maintained annual mean salinities mostly within the optimal range of brine shrimp and alkali fly growth. Even during the last two years of major drought, the lake would have maintained salinities well below measured values. Change in climate alone would not produce the recent low lake volumes and high salinities that have destroyed the brine shrimp and alkali fly populations and depleted shorebird use at Lake Abert. Large scale withdrawal of water for direct human use has drastically increased the imbalance between natural runoff and evaporation during periods of drought in saline lakes worldwide but could be offset by establishing an "environmental water budget" to lay a foundation for the conservation of saline lake habitats under continued threats from development and climate change.
In many arid regions, lakes often lose significant amounts of water through evaporation, leading to alkaline and saline aquatic systems. The water in terminal lakes (i.e. lakes with no outlet) may contain from 0.3–30% NaCl and higher (Williams 1998). Saline lakes are globally distributed and account for approximately half of the total volume of all inland surface water in the world (Williams 1998). The alkaline-saline lakes are a special class of saline lakes, with a pH from 9 to almost 12 in addition to high salinity (Duckworth et al. 1996). Lake Magadi (Kenya), Mono Lake (California, USA) and Soap Lake (Washington, USA) are examples of such lakes.
Cyanobacteria and eukaryotic algae are important primary producers in a variety of environments, yet their distribution and response to environmental change in saline lakes are poorly understood. In this study, the community structure of cyanobacteria and eukaryotic algae in the water and surface sediments of six lakes and one river on the Qinghai-Tibetan Plateau were investigated with the 23S rRNA gene pyrosequencing approach. Our results showed that salinity was the major factor controlling the community composition in these aquatic water bodies and the algal community structures of water and surface sediment samples grouped according to salinity. In subsaline-mesosaline lakes (salinity: 0.5-50 g L−1), Cyanobacteria (Cyanobium, Synechococcus) were highly abundant, while in hypersaline lakes (salinity: >50 g L−1) eukaryotic algae including Chlorophyta (Chlorella, Dunaliella), Bacillariophyta (Fistulifera), Streptophyta (Chara), and Dinophyceae (Kryptoperidinium foliaceum) were the major members of the community. The relative abundance ratio of cyanobacteria to eukaryotic algae was significantly correlated with salinity. The algae detected in Qinghai-Tibetan lakes exhibited a broader salinity range than previously known, which may be a result of a gradual adaptation to the slow evolution of these lakes. In addition, the algal community structure was similar between water and surface sediment of the same lake, suggesting that sediment algal community was derived from water column.
Water is an invaluable resource, and equitable access to it is a fundamental human right. Disenfranchised groups often lose access to water resources because their interests are not well represented by decision makers. Excluding these groups from resource management policy often results in myopic decisions that contribute to further ecosystem damage. We describe the ecological degradation of Lake Urmia in Iran, which has recently experienced increased salinity and declining water quantity. The lake is a UNESCO Biosphere Reserve and Ramsar site, and supports unique biodiversity in the region. The lake's decline is driven by the destruction of Zagros forests and the government's water policies, which diverted water to more politically connected agricultural land users, increasing social inequity and prompting more deforestation. The most straightforward restoration solution is to discontinue the diversions and allow critical inflows to recharge Lake Urmia, preserving the lake and wetlands for migratory birds, tourists, and local communities.
The delta lakes represent highly dynamic aquatic systems that have been undergoing
continuous and pronounced changes through the late Holocene to the present time.
General information on a biotic features as well as its fauna and flora are discussed. The
lakes margins are extensively vegetated, mainly by Phragmites and Typha. These plants
are also frequent on the islands and everywhere water hyacinth (Eichhornia crassipes) is
proliferating. The considerable variation in the composition and distribution of the
phytoplankton, zooplankton, macrobenthos and fish assemblages among these lakes was
mainly related to differences in the water quality, salinity, the concentration of nutrients
and climatic changes. Urbanization and industrial development during the last four
decades led to increased pollution (direct or indirect) from various sources, such as
industry, agriculture and sewage. These inputs create unique areas within the lakes.
Ecological changes have reduced fish yield and greatly impacted the local fishery.
Furthermore, insects and pests have increased, and have impacted human health.
Physical, chemical and biological variables were measured in the Great Salt Lake during 1985–87, when salinity in the mixolimnion was near 50 g/L, much lower than the 250 g/L maxima recorded in 1963. Decreased salinity has been accompanied by a change in macrozooplankton from one species (Artemia franciscana), to an assemblage with one rotifer, two copepods, Artemia, and the corixid Trichocorixa verticalis. Predation by the corixid may now limit Artemia to low densities (<100∙m−3). The low biomass of Artemia and other zooplankton has reduced grazing pressure on the algal community so that high chlorophyll levels (5-44 mg∙m−3) and low Secchi depths (0.8–2.7 m) are now present throughout the year. The algae presently reduce soluble reactive phosphorus and inorganic nitrogen in the mixolimnion to below 5 and 50 μg∙L−1, respectively. Shading in the 7-m thick mixolimnion by algae, and by purple-sulfur bacteria in the chemocline, decreases light penetration so that the monimolimnion now maintains a nearly constant temperature (9–11 °C) throughout the year. The data support the hypothesis that the effects of corixid predation have cascaded through the Great Salt Lake, affecting herbivores, nutrients and thermal stratification.
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
42− 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.
Reasons why Lake Elmenteita and rivers flowing into it decreased in volume during 1958–1987 were investigated. The effects of changing climate, landcover and landuse were considered. The study suggested that falling lake water-levels are not due to climate change alone: landuse changes and river abstraction and damming may also be important. Long-term trends in rainfall and evaporation reveal various patterns: monthly evaporation has slightly decreased recently but with no effect on lake levels; rainfall has remained more or less constant in total amount, but monthly falls show increased variability. Although flows in rivers and streams are primarily determined by rainfall, other factors operate near the lake so discharge into the lake cannot be predicted from rainfall. Increased settlement and farming on former forested areas within the catchment and irrigation along rivers also indirectly affect discharge values. Additionally, accelerated soil erosion from farmed lands has led to a reduced lake volume following soil deposition in the lake. It is noted that landuse changes need to be carefully monitored because of their effect on lake levels.
Sedimentology and Geochemistry of Modern and Ancient Saline Lakes (Tulsa, Okla.: Society for Sedi-mentary Geology
- See
- R W Example
- W M Renaut
- Last
See, for example, R. W. Renaut and W. M. Last, eds., Sedimentology and Geochemistry of Modern and Ancient Saline Lakes (Tulsa, Okla.: Society for Sedi-mentary Geology, 1994 [Special Publication no. 501).
Weil-er, compilers, Regional Assessment of Freshwater Ecosystems and Climatic Change in North America (Report of symposium organized by the
- See
- D M Example
- C S Mcknight
See, for example, D. M. McKnight and C. S. Weil-er, compilers, Regional Assessment of Freshwater Ecosystems and Climatic Change in North America (Report of symposium organized by the American Society of Limnology and Oceanography and the North American Benthological Society, 1995).
Caspian and Aral Seas: Two Different Paths of Envi-ronmental Degradation, " krhandlungen der interna-tionale Vereinigung f i r theoretische und angewandte Limnologie 26
- G N Golubev
For a modern account of the changes that have occurred in the Caspian Sea, see G. N. Golubev, " Caspian and Aral Seas: Two Different Paths of Envi-ronmental Degradation, " krhandlungen der interna-tionale Vereinigung f i r theoretische und angewandte Limnologie 26 (in press).
Once More on the Water Level Changes of the Caspian Sea
- G S Golytsin
- G N Panin
G. S. Golytsin and G. N. Panin. " Once More on the Water Level Changes of the Caspian Sea, " Vestnik Akademii Nauk SSSR 9 (1989): 59-63.
Changes in the Ionic Compo-sition of a Saline Lake Mar Chiquita, Province of Cor-doba, Argentina International Journal of Salt Lake Aral Sea Enclosed Seas and Large Lakes of Eastern Europe and Middle Asia (Am-sterdam The latter presents the proceedings of a NATO-sponsored meeting held in Tashkent
- D E See
- Martinez
See D. E. Martinez, " Changes in the Ionic Compo-sition of a Saline Lake, Mar Chiquita, Province of Cor-doba, Argentina, " International Journal of Salt Lake " Aral Sea, " in A. F. Mandych, ed., Enclosed Seas and Large Lakes of Eastern Europe and Middle Asia (Am-sterdam: SPB Academic Publishing, 1995); and P. Micklin and W. D. Williams, eds., AralSea Basin (Hei-delherg, Germany: Springer, 1996). The latter presents the proceedings of a NATO-sponsored meeting held in Tashkent in 1994 to discuss critical scientific issues concerning the lake.
Some Problems of Lake Manage-ment in Kenya
- F See
- Mwaura
See F. Mwaura, " Some Problems of Lake Manage-ment in Kenya, " in I. Salanki and V. Istvanovics, eds.. Limnological Buses of Lake Management [Proceedings of the ILECRTNEP (International Lake Environment CommitteelUnited Nations Environment Programme) International Training Course held at Tihany, Hungary, 24 May-5 June 19931, 178-80.