North Aral Sea Research Articles

An insight into effect of soil salinity on vegetation dynamics in the exposed seafloor of the Aral Sea

The desiccation of the Aral Sea has precipitated significant ecological degradation, resulting in the progressive development of vegetation on the exposed seafloor. Soil salinity emerges as a pivotal determinant in this ecological succession process. Employing a comprehensive methodology integrating multi-source datasets spanning from 1986 to 2023, this study elucidates the temporal changes in vegetation dynamics and soil salinity levels. Satellite imagery (Landsat-4/5/7/8), field soil samplings, hydrological and topographic data were analyzed to understand their interactions with regression analysis. The results reveal a consistent increasing trend in the Normalized Difference Vegetation Index (NDVI) across the exposed seabed since 1986. However, NDVI demonstrates a non-linear relationship with elevation in the North Aral Sea region. Interestingly, NDVI levels near an elevation of 42 m on the exposed seabed approximate those observed during the pre-recession period in the 1960s. Conversely, in the South Aral Sea region, NDVI demonstrates a linear upward trend with increasing elevation. Furthermore, the spatial distribution of soil salinity on the exposed seabed was delineated with linear regression analysis. It revealed water salinity levels at the time of sea recession can serve as a proxy for soil salinity in cases where direct soil data is unavailable. Through establishing a robust correlation between NDVI and soil salinity, the range of stable NDVI values on the exposed seabed was delineated. Lastly, three hypothetical scenarios of rising water levels were considered to evaluate changes in stable NDVI across different elevation gradients. If the water level returns to 45 m, the salt-desert area would decrease by 4.5 × 104 km2, accounting for 23 % of the total area in 1960. At this water level, it is anticipated that lake hydrological conditions and ecological environments may restore to those observed in 1981. This study provides a long-term perspective on environmental changes in the Aral Sea region by integrating multiple data sources and analytical methods. The predictive insights from the scenario analysis offer valuable guidance for future water management and ecological restoration efforts. Compared with previous studies, it presents a detailed and comprehensive picture of the interplay between vegetation dynamics and soil salinity, highlighting the critical impact of water level changes on the region's ecosystem.

Gender roles in the fisheries of North Aral Sea in Kazakhstan

The purpose of this study is to contribute to the existing research on the Aral Sea from a gender perspective, with a specific focus on women's roles in the fishery sector.The methodology employed in this study involved the use of a semi-structured in-depth interview instrument, which was developed to document the role of women in the fisheries value chain, as well as the challenges and opportunities they face.Originality / value of the research. This article aims to fill the gap in the lack of recognition of women's roles in fisheries in Kazakhstan and start a conversation about gender considerations in the ecologically and economically vulnerable coastal community of Kazakhstan.Findings. The study's findings highlight the prevalent gender roles in the fishery sector in the research area, where men are primarily responsible for catching fish, while women process and add value to it, both at home and in processing plants. However, despite their significant presence in the fish processing industry, women lack representation in fisheries associations. The study also identified pikeperch as a key export-oriented fish and highlighted the potential for women to contribute to farmed fish production. Finally, the study identified women's interest in skills training, particularly in marketing and sales, and recommended that stakeholders in the fishery sector jointly design and organize training programs to facilitate women's access to these skills.

Water Balance of the Regulated Arid Lake as an Indicator of Climate Change and Anthropogenic Impact: The North (Small) Aral Sea Case Study

Inland waters in the endorheic basins of the arid zone are especially vulnerable to both climate-induced changes and anthropogenic influence. The North Aral Sea, which previously suffered a drastic shrinkage and partially recovered with the launch of the human-made Kokaral dam, is currently subject to significant inter-annual variability of its water volume. This study aimed to obtain insight into the modern water balance condition of the lake and to project the possible changes in it. A series of model simulation experiments were implemented based on three representative concentration pathway (RCP) scenarios with varying maximum lake surface levels, determined by the dam. Present-day dam conditions showed the possibility to retain the lake volume above 26 km3 under the RCP 2.6 and 6.0 scenarios. Simulations under the RCP 8.5 scenario revealed significant instability of the lake volume and a well-shown decrease in the outflow amount. A possible human-made increase in terms of the lake surface level up to 48.5 m.a.s.l. may allow for the retention of the volume in the range of 48–50 km3 in the RCP 2.6 case. The RCP 6.0 and 8.5 scenarios revealed a lake volume decrease and almost full cessation of the Kokaral outflow toward the end of the 21st century.

Impacts of lake water change on vegetation development in the retreat area of the Aral Sea

The Aral Sea has been persistently shrinking in past decades, and the influence of the lake water level changes on vegetation in the lake retreat areas is uncertain. In this study, we quantitatively assessed the vegetation development due to relevant hydrological changes in the retreat area of the Aral Sea. The results showed that the normalized difference vegetation index (NDVI) in the retreat area displayed an overall increase from 1986 to 2020. The increasing vegetated area accounted for 84 % of the total area of the South Aral Sea, which was caused by an increase in the exposed lakebed area. However, about 40 % of the area in the North Aral Sea was the increasing vegetated area due to the improved water environment. When the depth to water table (DTW) was larger than 7–8 m, vegetation development was more dependent on precipitation than groundwater. When DTW was less than 7–8 m, groundwater had a more significant impact than precipitation on vegetation development. The negative impacts of groundwater salinity exceed the positive contributions of water supply on vegetation development, which differs to the common understanding under conditions of fresh or brackish groundwater in arid climates. Water level recovery is an effective option for improving vegetation establishment on the exposed seabed; otherwise, the exposed seabed area observed during the period 1990s–2010s in the eastern basin may remain a saline desert for a long period in the future. Finally, an empirical relationship between NDVI and water levels was established, which can be used for lake water level management that considers vegetation development in the retreated area of the Aral Sea.

Monitoring and Mapping of Soil Salinity on the Exposed Seabed of the Aral Sea, Central Asia

The incredible drying of the Aral Sea has resulted in a large area of exposed seafloor with saline soils, which has led to catastrophic consequences. This study investigated ground-truth soil salinity data and used Landsat data to map the soil salinity distribution of the exposed seabed of the Aral Sea from 1960 onwards. The soil salinity distribution, with the depth from 0 cm to 100 cm, was analyzed. The correlation analysis was applied to find the best performance index in describing soil salinity changes. The results showed that ground-truth data of topsoil salinity (depth of 0−5 cm) exhibited a significantly strong correlation with soil salinity index 4 (SI4) among seven indices, where the Pearson correlation coefficient (r) was up to 0.92. Based on the relationship between soil salinity sampling data and SI4, a linear regression model was employed to determine the capability of evaluating the soil salinity distribution of the Aral Sea with the coefficient of determination (R2), root mean squared error (RMSE), and ratio of performance to deviation (RPD) values of 0.84 and 0.86 dS m−1 and 2.36, respectively. The SI4 performed well and was used to predict the soil salinity distribution on the exposed seabed. The distribution showed that soil salinity increased from the former to current shoreline. In the North Aral Sea, compared to 1986, the water area remained stable, accounting for 50.3% in 2020, and the soil salinization level was relatively low. However, the moderately and slightly saline areas dominated 73.8% and 7.5% of the South Aral Sea in 2020, with an increase of 53% and 6% transformed from the water area. The area of salinized soils dramatically increased. The strongly and extremely saline areas were mainly located in the northeastern part of the eastern basin and western part of Vozrozhdeniya Island, respectively, and were the main source of salt-dust storms. These results support the dynamic monitoring and distribution patterns of soil salinization in the Aral Sea.

Organic Carbon Burial in the Aral Sea of Central Asia

The burial of organic carbon in lake sediments plays an important role in the terrestrial carbon cycle. Clarifying the current status of carbon burial in the lakes of Central Asia is of great significance for the application of carbon balance assessments. With the analysis of the total organic carbon and nitrogen and the carbon isotope and organic carbon burial rate in the core sediment of the North Aral Sea, the status and influencing factors of organic carbon burial over the past 70 years can be revealed. The results showed that the main source of organic carbon was predominantly from lacustrine aquatic plants. However, the contribution of terrigenous organic carbon increased from the 1950s to the 1960s. The burial rate of organic carbon in North Aral Sea sediments was consistent with the overall change in the regional temperature. The burial rate of organic carbon showed an upward trend as a whole with an average of 28.78 g·m−2·a−1. Since 2010, the burial rate of organic carbon has stood at the highest level in nearly 70 years, with an average of 55.66 g·m−2·a−1. The protection of a lake by human beings can not only significantly improve the lake’s aquatic ecosystem but also help to increase the burial rate of the lake’s organic carbon.

Saving the Aral Sea: A cross-cultural communication success

The Aral Sea was once the fourth-largest salt lake in the world. With a drainage basin crossing seven middle-Asian countries, it nearly disappeared at the end of the past century due to human activities. Since the ‘80s, an international mobilization emerged, carried out by leading hydrologists and biologists from around the world. Prof. Dr. Nikolai Aladin from the Zoological Institute of St. Petersburg is one of them, having dedicated the last decades to saving the Aral Sea. Combining a shrewd academic talent with an empathic communication style, he managed to talk culturally and politically distant leaders into acting together to save this common good. Today, if the North Aral Sea is considered saved, it is not only an engineering and political achievement but essentially a cross-cultural communication success. This short paper is reviewing and analyzing this exceptional success, with the ambition to inspire others.

Analysis of water balance in Aral Sea and the influencing factors from 1990 to 2019

咸海地处中亚，气候和人类的双重影响下湖面急剧萎缩引发区域生态危机，定量解析其水量平衡互动关系及影响因素对咸海地区水资源管理和生态保护有重要意义.基于1990—2019年密集时序Landsat影像、T/P卫星、Jason1/2测高卫星及咸海数字测深模型（DBM），提取近30年咸海面积、水位变化信息，重建咸海水位-面积-库容曲线，探明咸海水量变化特征；建立水量平衡模型，定量分析研究区水量平衡要素变化及时空差异，探讨其互动关系与影响机制.结果表明：（1）1990—2019年间，咸海水量减少了2271.6×10⁸ m³（约75.15%），年平均变化率达-78.3×10⁸ m³/a；南咸海水量变化趋势与咸海整体基本一致，北咸海除1999年出现了极小值外，其余年份水量变化趋势均呈波动上升状态，至2019年水位已恢复至1984年水平.（2）1990s以来，南、北咸海水量平衡结构变化时空差异显著，阿姆河入湖径流量呈波动减少趋势，随着咸海持续退缩水体蒸发不断减小，区域水量支出收入比由1990年的2.46降低到2015年的0.87；近年来丰水年份南咸海地下水可由亏损转化为盈余状态，水域变化进入相对平缓的状态.北咸海入湖径流量波动增加，蒸散发随水域面积增加而增加，1990s初以来水量收入超过水量支出，区域地下水盈余，湖泊水位不断抬升.（3）湖区尺度上，入湖径流量和水域蒸发量是咸海水量变化的主导因素.流域尺度上，气候变化与人类活动共同影响咸海入湖水量，南咸海入湖水量与阿姆河上游来水、流域耕地面积显著相关，而北咸海入湖水量主要与锡尔河上游来水相关.;The Aral Sea is located in Central Asia. Under the impact of climate change and human activity, the lake surface has shrunk sharply and triggered a regional ecological crisis. It is of great significance to study the changes of water balance and their driving factors for water resources management and ecological protection in the Aral Sea region. Based on the dense time-series Landsat imagery from 1990 to 2019, T/P satellite, Jason1/2 altimetry satellite, and digital bathymetry model (DBM) of the Aral Sea, time serieses of the Aral Sea area and water level in the past 30 years were extracted, to reconstruct the Aral Sea water level-area-volume capacity curve and explore the characteristics of the Aral Sea volume changes. A water balance equation was also established to quantitatively analyze the spatiotemporal changes of the water balance elements in the study area and their impacts on the Aral Sea volume. The results show that the water volume decreased by 2271.6×10⁸ m³ (about 75.15%) with an average decreasing rate of 78.3×10⁸ m³/a from 1990 to 2019 in the Aral Sea, a similar variation trend was detected in the South Aral Sea. Except for the minimum value in 1999, the water volume in other years showed a fluctuating and rising state in the North Aral Sea. By 2019, the water level had returned to the level of 1984. Since the 1990s, the inflow from the Amu Darya River to the Aral Sea showed a decreasing trend, and the spatiotemporal differences in the water balance structure of the South and the Nouth Aral Sea are significant. As the Aral Sea continues to shrink, and water evaporation continues to decrease, the regional water expenditure and income ratio decreases from 2.46 in 1990 to 0.87 in 2015. In recent years, the groundwater in the South Aral Sea changed from deficit to surplus, and the water area changed into a relatively stable state. The evapotranspiration of the North Aral Sea increased with the increase of the water area. Since the early 1990s, the water income has exceeded its expenditure, regional groundwater has bacome surplus, and the lake water level has been constantly rising. On the regional scale of the Aral Sea, the inflow and evaporation are the main factors affecting the change of the water volume in the Aral Sea. On the catchment scale, climate change and human activities jointly affect the inflow of the Aral Sea. The inflow of the South Aral Sea is significantly correlated with the runoff from the upper Amu Darya River and the cultivated land area of the basin, while the inflow of the North Aral Sea is mainly correlated with the runoff from the upper Syr River.

Historical Change and Ecological Risk of Potentially Toxic Elements in the Lake Sediments from North Aral Sea, Central Asia

The Aral Sea has received worldwide attention for the deterioration of its biological and chemical status. The accumulation of potentially toxic elements (PTEs) in the lake sediments reflects changes in the surrounding watershed and represents a potential hazard for the lake ecosystem. In conjunction with existing environmental records from the Aral Sea basin, sedimentary records of PTEs in North Aral Sea covering a short time scale, anno Domini (AD) 1950–2018, were used to reveal historical changes in PTE concentrations and potential risks to lake functioning. The results suggested that the levels of PTEs in lake sediments from North Aral Sea changed abruptly around 1970 AD, which is concurrent with the intensification of human activities within the basin. After 1970 AD, with the exception of As, which remained at unpolluted-to-moderately polluted levels, the geo-accumulation indices of the remaining PTEs studied (V, Cr, Zn, Co, Pb, Ni, Cu and Cd) inferred a moderately polluted status. Before 1970 AD, the total ecological risk was low, but since 1970, the total ecological risk index has exceeded 150, indicating moderate risk. Historical changes in PTE levels of lake sediments from North Aral Sea and their potential ecological risks are reported for the first time. The conclusions provide an important reference for the protection of lake ecosystems and will provide data for regional/global comparisons of environmental change during the Anthropocene.

Changes in area and water volume of the Aral Sea in the arid Central Asia over the period of 1960–2018 and their causes

The Aral Sea (68,478 km2 in 1960) was the world’s fourth largest inland lake in 1960s. However, it shrank sharply over the past six decades, and its changes caused a series of severe environmental issues. In this paper, we reconstructed its variations over the period of 1960 to 2018 by using observation data and remote sensing data, and analyzed their influencing factors. The results show that the area of the Aral Sea shrank dramatically by 60,156.50 km2 (about 87.85%) and the total loss of water volume was approximately 1,000.51 km3 over the study period. In 1986, the Aral Sea broken up into the south and the north parts. Since then, the South Aral Sea has shrunk continuously, while both the area and the water volume of the North Aral Sea have had a little change and shown a very slightly increasing trend. Through comprehensive analysis, it was found that human activities, especially damming and irrigation, are the dominant factors influencing the long-term variation of the Aral Sea. The increased precipitation and glacier meltwater could not compensate for the water loss of the Aral Sea.

Drying Lakes: A Review on the Applied Restoration Strategies and Health Conditions in Contiguous Areas

Decrease of saline lakes, which comprise 44% of all available lake water, is a major concern. It additionally accelerates the desertification process of the region. Thus, various countries have taken different actions in protecting their lake water levels. The aim of this paper is to assess different strategies directed to tackle the decreased lake water levels in Lake Urmia and the Aral Sea, which split into the North Aral Sea and South Aral Sea. These are among the world’s largest and fastest drying saline lakes observed in the past 50 years and have both reduced to 10% of their original size. The paper presents a thorough review of academic reports, official documents, and databases. Although the dry-up of a lake is a natural process, it has been sped up by human interventions in the hydrological cycle. Dust storms (strong winds) cause problems in the surroundings. In the case of the Aral Sea, they transmit the pollutants from the dry lake bed causing severe health issues. Various strategies were implemented to manage the socio-economic conditions caused due to the drying of lakes. The strategy implemented for the North Aral Sea was to restore the lake by reducing the water withdrawals from the Syr Darya river, which lead to increased water inflow to the sea. The suggested strategy for Lake Urmia was to restore the lake by water transfer activities from various water sources. These projects have not yet been realized. The strategy implemented for the South Aral Sea was to use a dry lake bed to diversify the economy by oil and mineral extraction along with developing a tourist industry based on the considerable interest to come and observe an ecological disaster of such monumental proportions. These findings show that there is no common best solution for this type of problem. The best fit depends on the local context and it is strongly path-dependent.

White-tailed lapwing (Vanellochettusia leucura) in lake Cartma (lake systems of Syrdarya river's delta, Kyzylorda region, republic of Kazakhstan)

This article generalizes data of authors collected in course of birds count at Lake Cartma Lake Systems of Syrdarya river's delta of the territory of Kyzylorda region, Republic of Kazakhstan, in period of 2014-2019. Distribution, quantity, ecology and areal of white-tailed lapwing (Vanellochettusia leucura) is considered in details. White-tailed lapwing is a medium-sized wader; body structure largely resembles black-sided lapwing but the size is slightly lesser. At present time, on territory of Kazakhstan, the white-railed lapwing is nesting at wetland stations of middle and downstream (from border with Uzbekistan to North Aral sea), system of lakes in delta of Syr-Darya river, in the north part of Caspian sea. Quantity of white-tailed lawing on studied Cartma lake is determined in limits of 30-150 specimen; this is the result of season nature of countings, fluctuation of area of studied water body surface. A characteristic feature of this species is a peculiar voice, descriptively translated as “chetyre, chetyre” ("four, four” in Russian),  increasing at approach to nesting sites. Analysis of special literature on ornithology of eastern site of Aral sea and lakes of Syr-Darya river delta showed that for two hundred years period, white-tailed lapwing mostly adheres to constant habitats. Nesting station is located in shore zone, at sandbars and isles. Key words: Cartma lake, wetlands, white-tailed lapwing, distribution of avifauna, trophic specialization of birds, E.A. Eversmann

Remote Detection of Varying Water Storage in Relation to Surfacial Temperature of Aral Sea

Lake monitoring by remote sensing is of significant importance to understanding the lake and ambient ecological and environmental processes. In particular, whether lake water storage variation could predict lake surfacial temperature or vice versa has long fascinated the research community, in that it would greatly benefit the monitoring missions and scientific interpretation of the lake change processes. This study attempted to remotely detect the dynamics of the Aral Sea and pursue the relationships between varying lake water storage attributes and surface water temperature by using MODIS LST (Moderate-resolution Imaging Spectroradiometer Land Surface Temperature) 8-day composite products, satellite altimeter data, and actual meteorological measurements. Their associations with lake Surface Water Temperatures (SWT) were then analyzed. Results showed the lake water surface areas and elevations of the North Aral Sea tended to increasing trend from 2001 (2793.0 km2, 13.6 m) to 2015 (6997.8 km2, 15.9 m), while those of the South Aral Sea showed a decreasing trend during 2001 (20 434.6 km2, 3.9 m) and 2015 (3256.1 km2, 0.9 m). In addition, the annual daytime and nighttime lake SWT both decreased in the North Aral Sea, while only the daytime SWT in the South Aral Sea exhibited an increase, indicating a rising deviation of diurnal temperatures in the South Aral Sea during the past 15 yr. Moreover, a lower correlation was found between variations in the daytime SWT and storage capacity in the South Aral Sea (R2 = 0.33; P < 0.05), no fair correlations were tested between lake water storage and daytime SWT in the North Aral Sea nor between lake water storage and nighttime SWT in either part of the sea. These results implied that climate change, if any at least during the research period, has no significant effects on lake dynamics over the two sectors of the Aral Sea with anthropogenic disturbances. However, climate change and human activities may overlap to explain complex consequences in the lake storage variations. Our results may provide a reference for monitoring the spatiotemporal variations of lakes, increasing understanding of the lake water storage changes in relation to the lake SWT, which may benefit the ecological management of the Aral Sea region, in the effort to face the likely threats from climate change and human activities to the region.

An Effective Low-Cost Remote Sensing Approach to Reconstruct the Long-Term and Dense Time Series of Area and Storage Variations for Large Lakes.

Inland lakes are essential components of hydrological and biogeochemical water cycles, as well as indispensable water resources for human beings. To derive the long-term and continuous trajectory of lake inundation area changes is increasingly significant. Since it helps to understand how they function in the global water cycle and how they are impacted by climate change and human activities. Employing optical satellite images, as an important means of lake mapping, has been widely used in the monitoring of lakes. It is well known that one of the obvious difficulties of traditional remote sensing-based mapping methods lies in the tremendous labor and computing costs for delineating the large lakes (e.g., Caspian Sea). In this study, a novel approach of reconstructing long-term and high-frequency time series of inundation areas of large lakes is proposed. The general idea of this method is to obtain the lake inundation area at any specific observation date by referring to the mapping relationship of the water occurrence frequency (WOF) of the selected shoreline segment at relatively slight terrains and lake areas based on the pre-established lookup table. The lookup table to map the links of the WOF and lake areas is derived from the Joint Research Centre (JRC)Global Surface Water (GSW) dataset accessed in Google Earth Engine (GEE). We select five large lakes worldwide to reconstruct their long time series (1984–2018) of inundation areas using this method. The time series of lake volume variation are analyzed, and the qualitative investigations of these lake changes are eventually discussed by referring to previous studies. The results based on the case of North Aral Sea show that the mean relative error between estimated area and actually mapped value is about 0.85%. The mean R2 of all the five lakes is 0.746, which indicates that the proposed method can produce the robust estimates of area time series for these large lakes. This research sheds new light on mapping large lakes at considerably deducted time and labor costs, and be effectively applicable in other large lakes in regional and global scales.

Waders of Lake Cartma (The Systems of Coastal Lakes of the North Aral Sea, Kyzylorda, Kazakhstan)

Waders of Lake Cartma (The Systems of Coastal Lakes of the North Aral Sea, Kyzylorda, Kazakhstan)

Monitoring lake level changes by altimetry in the arid region of Central Asia

The study of lake level changes in arid region of Central Asia not only has important significance for the management and sustainable development of inland water resources, but also provides the basis for further study on the response of lakes to climate change and human activities. Therefore, in this paper, eleven typical lakes in Central Asia were observed. The lake edges were obtained through image interpretation using the quasi-synchronous MODIS image, and then water level information with long period (2002-2015) was acquired using ENVISAT/RA-2 and Cryosat-2 satellite borne radar altimeter data. The results show that these 11 lakes all have obvious seasonal changes of water level in a year with a high peak at different month. During 2002 – 2015, their water levels present decreased trend generally except Sarygamysh Lake, Alakol Lake and North Aral Sea. The alpine lakes are most stables, while open lakes’ levels change the most violently and closed lakes change diversely among different lakes.

Hydrologic Controls and Water Vulnerabilities in the Naryn River Basin, Kyrgyzstan: A Socio-Hydro Case Study of Water Stressors in Central Asia

Water vulnerabilities in Central Asia are affected by a complex combination of climate-sensitive water sources, trans-boundary political tensions, infrastructure deficiencies and a lack of water management organization from community to federal levels. This study aims to clarify the drivers of water stress across the 440 km Naryn River basin, headwater stem to the Syr Darya and the disappearing North Aral Sea. We use a combination of human and physical geography approaches to understand the meltwater-controlled hydrology of the system (using hydrochemical mixing models) as well as the human-water experience (via community surveys). Surveys indicate that current water stress is primarily a function of water management and access issues resulting from the clunky transition from Soviet era large-scale agriculture to post-Soviet small-plot farming. Snow and ice meltwaters play a dominant role in the surface and ground water supplies to downstream communities across the study’s 4220 m elevation gradient, so future increases to water stress due to changes in volume and timing of water supply is likely given frozen waters’ high sensitivities to warming temperatures. The combined influence of social, political and climate-induced pressures on water supplies in the Naryn basin suggest the need for proactive planning and adaptation strategies, and warrant concern for similar melt-sourced Central Asian watersheds.

Decadal changes of water properties in the Aral Sea observed by MODIS-Aqua

Twelve-year satellite observations between 2002 and 2013 from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the satellite Aqua are used to quantitatively assess the water property changes in the Aral Sea. The shortwave infrared (SWIR) atmospheric correction algorithm is required and used to derive normalized water-leaving radiance spectra nLw(λ) in the Aral Sea. We used radiance ratio nLw(555)/nLw(443) as a surrogate to characterize the spatial and temporal variations of chlorophyll-a (Chl-a) in the Aral Sea. Both seasonal variability and significant interannual changes were observed when the Aral Sea desiccated between 2002 and 2013. All three separated regions of the Aral Sea show increased nLw(555)/nLw(443) ratio (a surrogate for Chl-a) and the diffuse attenuation coefficient at the wavelength of 490 nm (Kd(490)) during the fall season. Of the three regions, the North Aral Sea has had the least interannual variability, while South-East (SE) Aral Sea experienced drastic changes. Waters in the SE Aral Sea are the most turbid with significantly higher Kd(490) than those in the other two subregions. Kd(490) gradually increased from ∼2 m−1 in 2002 to ∼3.5 m−1 after 2008 in the SE Aral Sea. In comparison, both radiance ratio nLw(555)/nLw(443) and Kd(490) were relatively stable for the North Aral Sea. In the South-West (SW) Aral Sea, however, nLw(555)/nLw(443) values reached peaks in the fall of 2007 and 2010. A possible link between the Aral Sea water property change and the regional climate variation is also discussed.

Genetic study of pike perch Sander lucioperca (Linnaeus, 1758) and bersh Sander volgensis (Gmelin, 1789) from the fishery water-bodies of Kazakhstan

The genetic polymorphism of the pike perch Sander lucioperca, sampled on the territory of the Republic of Kazakhstan (Lake Balkhash, Urals River, Syrdarya River and Shardara water reservoir, North Aral Sea) and in the Volga River, and the bersh Sandler volgensis (Lake Balkhash, Volga River) populations was examined at six microsatellite loci and the mitochondrial DNA cytochirome b gene. All examined loci were successfully amplified in both species and produced quite different allele profiles, whichallows them to be used for accurate species identification of pike perch and bersh. At the same time, neither nuclear nor mitochondrial markers revealed statistically significant differentiation betweenthe examined pike perch samples, excluding some isolation of the population from Volga River.

Long‐term hydrological changes of the Aral Sea observed by satellites

AbstractThe Aral Sea has been shrinking since the former Soviet Union constructed irrigation projects to divert water from its main rivers in the 1960s. The diminishing of the Aral Sea is “one of the worst environmental disasters in the world” (from United Nations Secretary‐General Ban Ki‐moon). In this study, 33 years of satellite observations from Advanced Very High Resolution Radiometer (AVHRR) and 21 years of satellite altimetry sea level data from TOPEX/Poseidon, Jason‐1, and Jason‐2 are used to quantify the long‐term hydrological changes in the Aral Sea. A simple algorithm with AVHRR channels 1 and 2 albedo is developed to identify and discriminate the water pixels from land and cloud. Thus, monthly water coverage in the region can be reliably generated. The water coverage maps since 1981 show constant decline of the Aral Sea. The coverage dropped from ∼4.7–4.8 × 104 km2 in 1981 to about ¼ of this value in the recent years. In fact, drastic hydrological change was observed in the main Aral Sea during the 2000s. In the South Aral Sea, sea level shows a steady decrease from 35 m above sea level to &lt;26 m since 1993. Total loss of water storage since 1993 is estimated to be ∼2.0 × 102 km3 for the South Aral Sea with a rate of ∼16−20 km3/yr before 2002, and a smaller value after 2002. In 1990, the North Aral Sea was observed to separate from the main Aral Sea. Water coverage, sea level, and total water storage were kept relatively stable for the period between 1993 and 2013 in the North Aral Sea. A water level increase and coverage expansion occurred during the 2005−2006 period when a dam was built in 2005 between the North Aral Sea and the South‐East Aral Sea.