Changes in the Aral Sea ichthyofauna and fishery during the period of ecological crisis

Aboriginal ichthyofauna of the Aral Sea consisted of 20 generative‐freshwater species from seven families. After acclimatization in 1927–1963, the number of species increased to 34. The regulation of Syr Dar’ya and Amu Dar’ya river water flows, and increasing water withdrawals, primarily for irrigation, resulted in a declining lake water level, increasing salinization and changing habitat conditions, especially for reproduction. As a result, the spawning areas were greatly reduced, and because of worsening conditions for natural reproduction, fish catches in 1961–1976 decreased more than 4‐fold. The first signs of the negative impacts of salinization on fishes appeared in the mid‐1960s. Natural reproduction ceased by the mid‐1970s, and indigenous commercial fish fauna were lost by the end of the 1970s. Flounder‐gloss was introduced from the Black Sea in 1979–1987 to preserve the fishery, and it was the only commercial fish left by 1991–2000. Because of the water level decline, the Aral Sea became divided in 1989 into the Large and Small Seas. By the end of the 1990s, flounder became extinct in the Large Aral because of high salinity, as did other fishes. Decreasing agriculture activity has resulted in stabilized run‐off of the Syr Dar’ya to the Small Aral since 1988, creating a freshened water zone where indigenous ichthyofauna returned from lacustrine systems and the river. The ecological state of the Small Aral is improving, with some aboriginal valuable commercial fishes having reached numbers making their commercial catch possible once again.     

Modern state of the Small (Northern) Aral Sea fauna

The Aral Sea is a terminal lake lying within the deserts of Central Asia in Kazakhstan and Uzbekistan, draining the Amu Darya and Syr Darya rivers. Before the 1960s, it was a large brackish water lake with an average salinity of 10.3 g L^?1. The anthropogenic regression and salinization of the Aral Sea at that time resulted from increasing water withdrawals from the Amu Darya and Syr Darya for irrigation purposes. The salinization resulted in the disappearance of most of its invertebrates and all freshwater fish. As a result of the water level decrease, the Aral Sea divided into a northern Small Aral and a southern Large Aral at the end of the 1980s, with the two having different hydrological regimes. After construction the first Kokaral Dam in 1992, the water level of the Small Aral Sea increased by >1 m, with a gradual decline in the salinity beginning. To date, the Small Aral has again become brackish. Its average salinity reached 5.3 g L^?1 by April–May 2013, with the highest salinity of 9.9 g L^?1 in Butakov Bay, whereas the salinity was very low at 1.2–2.0 g L^?1 in the estuary zone of the Syr Darya. There is an ongoing process of restoration of the former biodiversity, with many fresh water and brackish water invertebrate species reappearing due to the decreasing salinity. Freshwater fish species (bream, roach, carp, asp, zander, wels, etc.) returned into the Small Aral from the Syr Darya River and lakes in its lower reaches where they survived. Fisheries are recovering and catches are growing. Continuing salinity decreases, however, may cause decreases in the numbers, or even disappearance, of marine and halophilic invertebrate species. This study summarizes the results of studies of the Small Aral zooplankton, zoobenthos and ichthyofauna carried out in the spring of 2013. An historical review of changes in the Aral Sea and its fauna also is presented.     

The dying Dead Sea: The microbiology of an increasingly extreme environment

The Dead Sea, on the border between Israel and Jordan, currently contains around 348 g salt L^?1. Divalent cations (Mg²⁺, Ca²⁺) dominate over monovalent cations (Na⁺, K⁺), while Cl^? and Br^? are the main anions. The pH of the Sea is about 6. The water balance of the lake is negative, having dropped over 1 m year^?1 over the past decade. The water is supersaturated with Na⁺, with massive quantities of halite precipitating to the bottom of the lake. Biological monitoring since 1980 has indicated that blooms of the unicellular green alga Dunaliella and halophilic Archaea of the family Halobacteriaceae only develop following significant dilution of the upper water layers in the lake after very rainy winters. Such events occurred in 1980, and even more dramatically in 1992, when up to 3.5 × 10⁷ Archaea mL^?1 in the diluted upper 5–10 m of the water column coloured the lake red. Species isolated from the lake include Haloferax volcanii, Haloarcula marismortui, Halorubrum sodomense and Halobaculum gomorrense. Dunaliella was no longer observed in the lake after 1996, with prokaryote numbers remaining low. To characterize the residual microbial community in the lake, biomass was collected in February 2007 for environmental genomic analyses. The results were compared with the metagenome of microbial bloom material collected in 1992. The 16S rRNA archaeal phylotypes recovered from the 2007 sample were diverse, with phylotypes distantly related to the genera Halorhabdus, Haloplanus, Natronomonas and others. Halorhabdus sp. also was recovered in culture. The 1992 bloom sample was very homogeneous, however, with a single cluster remotely related to Halobacterium salinarum. These results illustrate that the microbial communities are dynamic, even in one of the most extreme environments on Earth, and exhibit strong shifts in species composition as conditions for life become increasingly adverse.     

A systems approach to validating the water vision of the Aral Sea Basin

Abstract:

The governments of the Aral Sea Basin countries, in cooperation with international organizations (UNESCO and World Bank) came up with a “water vision “for the region until 2025. The landlocked Aral Sea has been suffering from an imbalance in water evaporation, and, water inflow from its two main sources — Amu Darya and Syr Darya rivers, when the planners in the former Soviet Union from the 1960s diverted the river waters for irrigation. The irrigated area has increased from the 1960s by two‐thirds to 7 million hectares and the population by three‐fold to 50 million in the basin countries. Consequently the inflow to the Aral Sea from these two rivers decreased from 55 km³ in 1960 to a few km³ during the 1980s and 1990s. This has resulted in one of the worst man‐made ecological disasters of the century. In this paper, we examine different scenarios to achieve the vision goals and whether it is indeed feasible. Using IWMI basin‐oriented water accounting principles, we have shown that significant amount of water is being wasted in the region. Our analysis concludes that though not all the vision goals are likely to be met over the next 25 years, the inflow into the Aral Sea can be increased to over 20 km³ through better management and use of water resources.     

The past,present, and future Aral Sea

The Aral Sea, a once vast brackish terminal lake in the heart of Central Asia, has been rapidly drying since the 1960s. It had separated into four separate waterbodies by September 2009. The maximum water level decline was more than 26 m, whereas the lake surface area decreased 88% and the water volume 92%. The lake salinity increased by more than 20‐fold. Prior to the modern recession, the Aral Sea experienced a number of water level declines and subsequent recoveries over the last 10 millennia. The main causative factor until the 1960s was the periodic westward diversion of the Amu Dar’ya, the main influent river, towards the Caspian Sea by both natural and human forces. The post‐1960 recession, however, was overwhelmingly the result of unsustainable irrigation development. The lake’s modern recession has caused a broad range of severe negative ecological, economic and human welfare problems. To restore the Aral Sea to its 1960s’ size and ecological condition would be very difficult, if not impossible, in the foreseeable future. The plight of the Aral Sea, however, is far from hopeless. Partial restoration of portions of the lake is still feasible. A project to raise the Small (northern) Sea was completed in Fall 2005, raising its water level by 2 m, and lowering its salinity to a level not much higher than the early 1960 levels. Its ecological recovery has been dramatic, and a new project to improve further the Small Aral was recently announced. Improving the Large (southern) lake would be much more difficult and expensive. A project to save the deep Western Basin partially is technically feasible, however, and should be given careful evaluation. It is important to repair and preserve what is left of the deltas of the two tributary rivers, Syr Dar’ya and Amu Dar’ya, as these two rivers are of great ecological and economic value, and act as biological refugia for endemic species of the Aral Sea.     

Politics of the Dead Sea Canal: a historical review of the evolving discourses,interests, and plans

This article explores how the idea of a canal connecting the Dead Sea with either the Red Sea or the Mediterranean Sea has evolved. It analyzes the proposals, the official interests, and the undeclared reasons. It provides a critical understanding of the discourses behind the complex hydro-political dynamics in a changing and contested topography within the context of a wider geopolitical conflict. This study sheds lights on the relations between interests, discourses, and the canal project. This study contributes to the literature on water history by shedding light on the evolving relations between interests, discourses, and the canal project.     

黄海和东海的环流数值模拟研究

本文从海洋三维原始动力学方程出发,考虑真实地形及(1/4)°×(1/4)°的水平网格,同时考虑黑潮和潮流,数值模拟黄海和东海的环流系统,主要结论是:1)模拟调和常数与分布于该区的81个台站的实测调和常数相比,日分潮振幅和位相的平均绝对误差分别为1.7cm和5.2°,半日分潮M_2振幅和位相的平均绝对误差分别为4.1cm和3.7°;2)模拟的黑潮路径与长期观测结果相吻合;3)黑潮进入研究区域后,一分支从台湾东北部分离出来后进入东海,影响可达29°N,这与海洋普查的调查结果以及文献中的结果一致;4)黑潮的一个分支北上形成对马暖流的一部分,且对马暖流是多源的,对马暖流通过对马海峡进入日本海,同时模拟结果显示一支由日本海进入研究区域的海流,后者需进一步调查和研究;5)黄海表层流主要沿南下方向,在近底层。中国和朝鲜的沿岸流为南下,黄海底层海盆由一顺时针方向的环流控制着,在中国成山头以外的北黄海底层,存在一较弱的逆时针环流。     

黄、渤海近海海浪环境测量与分析

利用近海海浪环境开展大尺度船模试验是一种有效的船舶性能试验技术,了解近海海浪环境特征对该试验的开展具有重要意义。文中对黄、渤海多个海域近海海浪进行实地测量,采用谱分析法得到测量海浪的有义波高、特征周期、波能谱等参数,并将实测波浪谱与大洋谱进行无因次化比较,讨论了实测波浪谱与大洋谱的相似性。分析结果表明特定风向与潮汐条件下近海海浪谱与大洋谱具有相似性。     

The effect of marine and Aral Sea water on the salinity tolerance of three Paramecium species (Ciliophora)

The shift of salinity tolerant ranges in three species of ciliates Paramecium caudatum, P. primaurelia and P. jenningsi was studied in waters containing a composition of salts resembling those in the Aral Sea, in comparison with composition of salts in marine waters. The results indicate that the salt values of tolerant ranges are increasing in water with the Aral Sea composition. The ratio among values of tolerant ranges is described by a linear function. A similar ratio connecting the same tolerant ranges exists in ciliates, but leads to reliable values of tolerant ranges when expressed in terms of chlorine concentration. Thus, the connection between the tolerances of aquatic organisms obtained for water of marine composition and water of continental composition might be described by the equation , where S_m = tolerance of organisms in marine water, whereas S_k = tolerance of organisms in continental saline water. The term α indicates the portion of chlorine ion continental saline water, while β indicates the portion in marine water.     

The effects of riprap in enhancing the abundance and coexistence of Gobiidae along the southern Caspian Sea coast

Many natural coastal habitats around the world are being replaced by hard coastal defense structures as a result of rising sea levels and increasing intensity of storms. To examine the potential effects of riprap on gobies in the nearshore zone of the southern Caspian Sea, we used angling to compare their abundance and diversity in 13 riprap and natural habitats (sandy and gravel shores) from April 2012 through April 2013. In total, 819 gobies of three species, Caspian sand goby Neogobius pallasi (N?=?433), round goby Neogobius melanostomus (N?=?206), and Caspian goby Neogobius caspius (N?=?180) were collected. No round gobies were caught from sandy shores and only two Caspian gobies were caught from gravel habitats, while all three species were abundant in riprap shores. A significant difference was observed in CPUE of all three goby species among shore types, with riprap sites having the highest abundance. PERMANOVA and nMDS demonstrated differences in goby assemblages among all three habitats. There were significant differences in round goby and Caspian goby sizes among riprap and natural habitats, while there were no significant differences in Caspian sand goby size among habitat types. In general deployment of riprap, especially in an area characterized as having natural shores with low structural complexity, could enhance the abundance and coexistence of nearshore gobies and act as a dispersal vector.     

Climate change: A potential risk to cage culture and genetic structure of native fisheries in fish cage‐installed inland lakes

Fish cage aquaculture (FCA) in lakes is a viable climate change (CC) mitigation approach; however, deficiencies in monitoring, early warning and risk planning could threaten its sustainability. Thus, the present study focused on examining the experiences with CC and its risks to cage fish culture, and phenotypic structure of a typical endemic fishery in fish cage‐installed (FCI) and fish cage‐free (FCF) lakes. Using a structured questionnaire, fisherfolks of typical FCI and FCF lakes in southwestern Nigeria were consulted for their local experiences regarding CC variables, effects on cage aquaculture and the occurrence of caged fish in their fish catches. For phenotypic structure analysis, size cohorts of cage‐cultured (CCU) and wild‐caught (WC) Oreochromis niloticus from FCI (CC_UFCI and WCFCI), and WC from FCF (WCFCF) were obtained and analysed for phenotypic differences (p < .05) and mix‐up through cluster/linkage analysis. Respondents experienced unpredictable climatic conditions, increased rainfall fluctuations and declining rainfall (86.4; 47.1%, 50.0; 64.7%, 100.0; 88.2%, in FCI and FCF lakes, respectively), indicating that CC affects cage culture, induces cage damage and floods, and results in caged fish escapes (40.9; 35.3%, 81.8; 11.8%, 95.5; 41.2% in FCI and FCF lakes, respectively), while caged fishes occur in fisherfolks’ catches (63.6% FCI). Phenotypically, WCFCF and WCFCI were similar, but differed from CC_UFCI for pre‐dorsal length. WCFCF and WCFCI differed for caudal peduncle lengths. In addition, some individuals of CC_UFCI clustered with WCFCI and WCFCF, rather than their population cohorts. Climate change impacts on FCA lakes have implications regarding caged fish escapes. Phenotypic structures indicated a possible mix‐up of caged and wild O. niloticus populations. Thus, monitoring, control and surveillance (MCS) of cage culture in lakes is necessary, and development of genetic markers for endemic species would also facilitate MCS.     

洋口港开发建设与江苏“江海联动”战略研究

江苏沿江港口水深不足、布点密集、重复建设、盲目竞争,长期未得到充分开发,江苏沿海地区在很大程度上影响了江苏经济的发展。"江海联动"战略是以提高港口经济的整体竞争力为基点,以提升江苏省综合竞争力为目标,重新审视"整合沿江",高度重视"开发沿海",对于江苏经济社会全面发展,特别是苏中、苏北地区实现跳跃式发展有着重大的现实意义。研究江苏区域经济发展战略,就要使苏中、苏北的发展有突破口,突破口就在港口。洋口港是江苏建港条件最好的深水海港,现在经济论证、技术论证都取得了很多成果,应加快洋口港的开发,以此拉动长江北岸港口的整合,带动江苏沿海经济的开发开放,进而辐射整个长江流域。     

汽轮机的级内损失及减小措施

以节约能源,提高电厂汽轮机生产效率为目的,通过对电厂常用的300MW汽轮机的运行参数及能量转换过程等的分析,将汽轮机的损失分为两大类,一类是汽轮机的外部损失,一类是汽轮机的内部损失。重点总结出了汽轮机内部的七项主要级内损失:喷嘴损失、动叶损失、余速损失、鼓风摩擦损失、扇形损失、漏汽损失及湿汽损失,同时从不同角度分析了这七项级内损失产生的原因,并从汽轮机的结构设计与选择、增加相应的辅助装置或部件等方面阐述了减小各项级内能量损失的措施,以提高机组运行效率。     

Correlation between sea surface temperature and wind speed in Greenland Sea and their relationships with NAO variability

The North Atlantic Oscillation (NAO) is one of the major causes of many recent changes in the Arctic Ocean. Generally, it is related to wind speed, sea surface temperature (SST), and sea ice cover. In this study, we analyzed the distributions of and correlations between SST, wind speed, NAO, and sea ice cover from 2003 to 2009 in the Greenland Sea at 10°W to 10°E, 65°N to 80°N. SST reached its peak in July, while wind speed reached its minimum in July. Seasonal variability of SST and wind speed was different for different regions. SST and wind speed mainly had negative correlations. Detailed correlation research was focused on the 75°N to 80°N band. Regression analysis shows that in this band, the variation of SST lagged three months behind that of wind speed. Ice cover and NAO had a positive correlation, and the correlation coefficient between ice cover and NAO in the year 2007 was 0.61. SST and NAO also had a positive correlation, and SST influenced NAO one month in advance. The correlation coefficients between SST and NAO reached 0.944 for the year 2005, 0.7 for the year 2008, and 0.74 for the year 2009 after shifting SST one month later. NAO also had a positive correlation with wind speed, and it also influenced wind speed one month in advance. The correlation coefficients between NAO and wind speed reached 0.783, 0.813, and 0.818 for the years 2004, 2005, and 2008, respectively, after shifting wind speed one month earlier.     

Invasive Neogobius melanostomus in the Lithuanian Baltic Sea coast: Trophic role and impact on the diet of piscivorous fish

The partitioning of trophic niches is central for understanding the ecosystem processes associated with biological invasions. The recent successful establishment of Neogobius melanostomus in the Baltic Sea posed questions whether this invader found its own trophic niche, to what extent it competes with native benthivores, and if commercially important fish could be affected. In this study conducted along the Lithuanian Baltic coast, we used the stable isotope approach to identify potential trophic competitors of N. melanostomus. We also employed gut content analysis to quantify the incorporation of N. melanostomus into the diet of native piscivores. Furthermore, pre-invasion gut content data enabled us to check if there were any changes in the piscivorous fish diet after the invasion. We found N. melanostomus to be a subdominant benthivorous fish during the warm season of 2012–2013. It occupied a higher trophic position in spring (3.9) than in autumn (2.9), but spring specimens were also larger. The invader exploited a narrow (standard ellipse area 0.3–0.5‰²) and distinct core isotopic niche, but total niche area overlaps indicated potential trophic competition with Pleuronectes platessa, Platichthys flesus, Pomatoschistus minutus and Gasterosteus aculeatus in spring, and with P. minutus in autumn. The invader dominated the warm season (spring–autumn) diet of piscivorous fish (Gadus morhua, Myoxocephalus scorpius, Perca fluviatilis, Scophthalmus maximus) and its invasion was generally associated with decreased crustacean and increased fish-prey content. Therefore, it is plausible that N. melanostomus has created novel trophic links within the food web.     

Lakes and society: The contribution of lakes to sustainable societies

Lake management is typically approached from a biophysical perspective. Lake managers ask how lakes can be managed to sustain their ecological functions. The social value of lakes is usually given less attention. The present paper begins the analysis at the other end of the lake and society connection by posing the question: what social needs must be met to sustain society? The primary social needs of sustainable societies are outlined and then the contribution of lakes to each need is discussed. Lakes can only provide optimal social benefits if management decisions recognize the full set of potential contributions lakes can make to society and those management decisions are integrated to provided balanced attention to all values that lakes provide. The present paper expands the domain of values beyond the traditional environmental and recreational contributions of lake management to also include aesthetics, education, economic opportunity, emotional security, cultural opportunity, individual freedom and spirituality. Citizen involvement is essential in broadening the conceptualization of the lake values and in implementing integrated management plans.     

The changing face of the Ethiopian rift lakes and their environs: call of the time

The Ethiopian rift is characterized by many perennial rivers, and a chain of lakes that vary in size, and hydrological and hydrogeological settings. The water resources of the Rift lakes are one of the focal points for large‐scale development in Ethiopia over the last few decades. Some of the lakes and their influent rivers are used for irrigation, soda abstraction, fish farming and recreation, and also support a wide variety of endemic birds and wild animals. Ethiopia's major mechanized irrigation farms and commercial fishery are confined within the Rift region. A few of the lakes have shrunk in surface area because of excessive water abstractions, while others have expanded because of increased surface run‐off and groundwater inflows from percolated irrigation water. Excessive land degradation, deforestation and over‐irrigation have changed the hydrological setting of a few Rift lakes. Human activities, in combination with changes in climate and geology, have influenced the hydrological setting and the water quality of the lakes, with the salinity and major ion composition dramatically changed in some of them. This study tries to address the challenges associated with development of these surface‐water resources, focusing on environmental problems arising over the past few decades on three lakes (Abiyata, Beseka and Ziway) situated along the tectonically active Rift floor. The methods utilized in this study include field hydrological and hydrogeological mapping, supported by aerial photographs and satellite imagery interpretations, as well as hydrometeorological and hydrochemical data analysis, and catchment hydrological modeling. A converging‐evidence approach was adapted to reconstruct the temporal and spatial variations of the lake water levels and surface areas. The study results revealed that the major changes in the Rift Valley are related primarily to recent improper use of water from the large rivers draining the Rift Valley floor and the lake catchments, and from direct lake water abstractions aggravated intermittently by climatic and land use changes. These changes represent grave environmental consequences on the fragile Rift ecosystem that demands urgent intervention in the context of an integrated, basin‐wide water management approach. This study emphasizes lake water level changes and human influences on these changes. It also assesses human interactions and water quality changes, including land use changes and environmental repercussions on the lakes, as well as providing recommendations on how these issues should be addressed.     

基于GIS的POM模型及其在渤海潮流模拟中的应用

地理信息系统(GIS)作为对蕴含空间位置信息的数据进行采集、存储、管理、分发、分析、显示和应用等的新兴技术,显示出在海洋领域研究的重要性.做为目前海洋研究比较流行的数值模拟技术,集成GIS在空间数据处理和解析等的强大功能,以此扩展和开发基于GIS的数值模型的工程耦合形式,成为海洋GIS发展的前沿领域.将GIS在POM潮流模型前处理和后处理中应用,进行了GIS的功能性扩展编程,以文件交换形式,形成GIS和POM模型的分散式结合,并用此方法在渤海潮流模拟中进行了测试,其中在前处理中自动剖分网格和数据的自动提取等技术极大地提高了建模、调试和后处理的效率,而后处理显示等技术的使用为以后的集成一体化开辟了途径.