Evidence from isotopic geochemistry as an indicator of eutrophication of Meiliang Bay in Lake Taihu, China

In this paper, Lake Taihu, a large shallow freshwater lake in China, is chosen as an example of reconstruction of eutrophication through the comparison between stable isotopes from dissolved nutrients and plants and water column nutrient parameters and integration of multiple proxies in a sediment core from Meiliang Bay including TN, TP, TOC, C/N,δ15N,δ13C, etc. Differences in aquatic plant species and trophic status between East Taihu Bay and Meiliang Bay are indicated by their variations inδ13C andδ15N of aquatic plants andδ15N of NH4 . A significant influence of external nutrient inputs on Meiliang Bay is reflected in temporal changes inδ15N of NH4 and hydro-environmental parameters. The synchronous change betweenδ13C andδ15N values of sedi-mented organic matter (OM) has been attributed to elevated primary production at the beginning of eutrophication between 1950 and 1990, then recent inverse correlation between them has been caused by the uptake of 15N-enriched inorganic nitrogen by phytoplankton grown under eutrophication and subsequent OM decomposition and denitrification in surface sediments, indicating that the lake has suffered from progressive eutrophication since 1990. Based on the use of a combination of stable isotopes and elemental geochemistry, the eutrophication of Meiliang Bay in Lake Taihu could be better traced. These transitions of the lake eutrophication respectively occurring in the 1950s and 1990s have been suggested as a reflection of growing impacts of human activities, which is coincident with the instrumental data.     

改善中国太湖水生态环境的新对策—“如何解决太湖流域水质型缺水和环境自然资源退化问题？”

Taihu Lake is one of the famous five great freshwater lakes in China. Taihu Lxike Basin (TLB) is a densely populated and economic developed area in China. The surface water quality in TLB was deteriorated from I-Ⅱ grade in the history to IV-V grade at present. To develop a series of technology of most cost-effective and achievable for improving environment in a local water area of most sensitive for society and improving water quality for more and more areas step by step is the key point of the new strategy. Except the measures for reducing the industrial and domestic pollution load to the lake, some research topics are suggested to be emphasized.     

一种浅水湖耦合模式系统的发展与应用

Growing developments in lake basins in China, have adversely affected, the water quality of lake, in particular, the water bodies of many famous shallow lake are seriously polluted in recent years. Some projects have been built up to improve the water quality, for example, the sewage interception project (i.e. Xiyuan tunnel project) and four sewage treatment plants etc. have been built up in Dianchi Lake. In order to predict and evaluate the effects of projects on the water quality, it is necessary to develop a coupled model system, which should mainly include wind, circulation and water quality parameters. This paper describes the development and application of a coupled modeling system in a shallow lake, which include a 3D micro-meteorology model (3DMM), a 2D hydrodynamic model (2DHM) and a 2D water quality model(2DWM).The coupled modeling system has been applied to predict the ejfects of environmental protection projects on water quality in Dianchi Lake.     

通过望虞河引长江水济太湖的生态意义

Taihu Lake is the third largest fresh water lake in China, locating in Yangtze Delta as the richest area of China. At present, eutrophication problem is severe in Taihu Lake. This paper, in view of ecological system, presents analysis of the composition structural characteristics of Taihu Lake environment regarded as a whole ecological system, energy and substances circulation between ecological factors. The Taihu Lake ecological environment is proceeding a lake evolution period, i.e. middle-eutrophic to eutrophic. Therefore the diversion water''from Yangtze River to Taihu Lake through the Wangyu River acts to change external agent function for Taihu ecological system, i.e. increasing water quantity of Taihu Lake may rise water level and speed up flow exchanging. Moreover, with harnessing measures for pollution sources to reduce input of nutrients, natural evolution procedure of Taihu ecological environment may slow down to subsequently improve Taihu ecological environment.     

加拿大内陆水的保护

Contrary to general international perception, Canada does not have an unlimited supply of freshwater. However, because Canada has a small population, it does have a generous water allocation on a per capita basis. Nor is Canada immune from water quality problems:its cold continental climate, urbanization and industrial activities all contribute to water quality concerns and deterioration. Generally, the authority to manage water in Canada is held by the country''s provincial governments. The Great Lakes basin is the world''s largest freshwater ecosystem and is located in Canada''s industrial heartland. Water issues, starting with phosphorus in the 1960''s, created international headlines. In the 1970''s toxics became the predominant issue and this led to the Great Lakes Water Quality Agreement which established the ecosystem approach to water quality management. This approach is now the standard approach to water quality management and has been successfully applied to a number of other lake and river ecosystems in Canada. While there have been improvements in the water quality of the Great Lakes much remains to be done on toxic elimination and the large contaminant stores in the sediments. Atmospheric deposition has become a significant source of chemicals from outside the basin The Canadian prairies, the agricultural heartland of Canada, is one major ecozone that has not been selected to have current and potential water quality problems examined by a federal government program. Both the quantity and quality of water in this region are potentially significant factors limiting economic diversification and sustainable development in this vast and ecologically disturbed region.     

太湖富营养化问题及其综合控制对策

On the basis of nine-time current situation investigation for eutrophication of Taihu Lake during 1991-1995, this paper evaluated the trophic levels in the different periods and analyzed the development of the main nutrient content in the nearest 35 years. The results show that the trophic level of Taihu Lake is in the transition state from meso-eutrophic to eutrophic. The eutrophhic and hypereutrophic waters account for 10% or so. The limiting nutrient, P, rises most rapidly, which causes the ratio of N:P to decrease. The increase of P content is still one of the main factors giving rise to the eutrophication of Taihu. LakeSome proposals of comprehensive countermeasure for the eutrophication are put forward. They include the pollution source control of the basin, the littoral multiple management, optimal dispatch of water conservancy facilities, the engineering of helping Taihu Lake with diversion of the Changjiang River, and as well as the setting of the water quality protection and legal system.     

综合治理太湖污染的一种方法：为环境目的而挖泥

The eutrophication of Lake Taihu is becoming more serious day by day and more urgent to be comprehensively harnessed. The lake sludge is considered as a important polluting factor. To control the internal pollution source of Lake Taihu and restore its water ecological environment, this paper put forward an idea of the dredging for environmental purposes. It was on the basis of the research on the sludge storage and physical/chemical characteristics. The technical keys are sludge-dredging depth, time, method and sludge treatment. The requirements and scheme for the environmental dredging work in Lake Taihu were also analyzed in detail.     

太湖：过去、现在和将来

The presence of roads, farm house foundations, wells and Liangzhu period cultural relics in the bottom of Lake Taihu attest to the fact that this shallow depression was probably dry between 4 and 5 thousand years ago. This interpretation is corroborated by the sudden disappearance of algal pigments at sediment depths carbon-14 dated at 4-5 thousand years before present.In winter, the stronger winds are predominantly from the northeast. These winds result in a powerful counterclockwise current that transports lake sediments and has altered the very shape of the lake over the last 300 years. Winds produce a complex mixing pattern in Lake Taihu with storm induced sediment deposition occurring near the lake''s center.During approximately 240 days of the year, the wind blows across Lake Taihu with sufficient force to mix it to its bottom. As a result, this polymictic lake rarely becomes anoxic and dissolved oxygen at the mud water interface is maintained at or above 4 mg·l^-1. The consequences of this high dissolved oxygen are quite impressive as high organic loading to the lake would otherwise render its bottom waters anaerobic killing many of its natural inhabitants.Because suspended solids reduce (attenuate) light penetration, the major primary production takes place in the top metre of the lake (mean Secchi Transparency-0.25 m). Suspended clays are slow to settle and wind mixing keeps fine-grained suspended solids in suspension in all but the most quiet backwaters of the lake.In the recent past about 23 000 metric tonnes of phytoplankton were produced in Lake Taihu. This large production represents only about 5% of the total influx of organic material entering the lake. In summer and fall, cyanobacteria such as Microcystis spp. and Anabaena spp. dominate most of the lake. Recently, however, mixotrophic flagellates displaced cyanobacteria as the dominant algae in parts of Lake Taihu with high bacteria and high suspended solids (e.g. Wuli and Meiliang Bay). In the future, facultative heterotrophs may come to dominate an ever larger portion of the lake waterc column.     

Contributions of phosphatase and microbial activity to internal phosphorus loading and their relation to lake eutrophication

Phosphatase may accelerate the process of lake eutrophication through improving phosphorus bioavailability. This mechanism was studied in three Chinese eutrophic shallow lakes (Lake Taihu, Lake Longyang and Lake Lianhua). Phosphatase activity was related to the concentration of soluble reactive phosphorus (SRP) and chlorophyll a. Stability of dissolved phosphatase in reverse micelles may be attributed to molecular size, conformation and active residues of the enzyme. At the site with Microcystis bloomed in Lake Taihu, dissolved phosphatase activity was higher and more stable in micelles, SRP concentrations were lower in interstitial water, the contents of different forms of phosphorus and the amounts of aerobic bacteria were lower while respiration efficiency was higher in sediments. Phosphobacteria, both inorganic and organic and other microorganisms were abundant in surface water but rare in sediments. Therefore, internal phosphorus may substantially flux into water column by enzymatic hydrolysis and anaerobic release, together with mobility of bacteria, thereby initiating the bloom. In short, biological mechanism may act in concert with physical and chemical factors to drive the internal phosphorus release and accelerate lake eutrophication.     

太湖微囊藻的生长动力学

Following the development of local industries, agriculture and the increase of living standard of people, Lake Taihu is in the meso-eutrophication stage. The main eutrophication part in this lake is the Meiling Bay. The dominant phytoplankton species are Microcystis, Anabena, Melosira, Cyclotella and Cryptomonas. In summer, Microcystis spp. occupys 85% of algae biomass and form the water bloom. This causes the trouble for the people lived around the lake, especially for the drinking water of Wuxi City.The Microcystis intrinsic rate was high, the Max. growth rate 1.27. Besides Microcystis own characteristics, its growth depended on irradiation, temperature and nutrients, especially the phosphorus. This paper also discussed the possibility of biomanipulation for restoration of lake ecology and the control strategy of lake eutrophication.     

太湖富营养化现状及原因分析

根据2005-2006年太湖湖泊生态系统研究站的监测结果,结合历史监测记录,评价了近5年来太湖富营养化的趋势.结果显示,从2000年以来,太湖的富营养化状况有加重趋势.主要表现在:1)与历史监测资料对比,近5年来无论梅梁湾还是湖心区,夏季水体TN、TP含量均呈增高趋势,如1992-2001年,太湖湖心区夏季(6-8月份)水体TN的平均值为1.706 mg/L (范围1.238-2.266mg/L),而2002-2006这5年间该平均值为2.344mg/L(范围1.924-2.717mg/L),明显高于前10年(p=0.005),另外,同期湖心区夏季的水体透明度则明显下降(1992—2001年夏季平均值为0.63 m,而2002-2006年则为0.34 m,p=0.003); 2)从野外调查看,太湖夏季水华暴发的范围越来越大,从2000年以前的梅梁湾、竺山湾及部分湖西区为主,发展到2006年的整个西太湖,夏季暴发水华的面积占太湖总面积的一半以上,且一年中出现水华的时间越来越长,水华出现的频率越来越高,微囊藻水华为特征的藻型生态系统在大太湖似乎越来越稳定;3)近年来太湖沉水植物分布区的面积有所下降.研究表明,太湖近年来富营养化的现状不容乐观,原因可能与近几年异常的气候和水文条件有关,也可能与水草区的不断破坏而减弱了微囊藻水华的生态竞争有关,应引起有关部门重视.     

太湖流域水环境变化及缘由分析

太湖水环境质量在最近的十年中下降1－2个等级,1990年86．5％的水体为Ⅱ、Ⅲ类,到2000年太湖水体87％Ⅳ类;1990年太湖水体为中－富营养化,2000年太湖水体以富营养化为主,本文通过分析经济社会发展和水环境变化,认为太湖流域工业化与城市化及居民生活水平的提高,吧及不合理的农业生产方式,使水环境面临巨大的压力,环保意识落后、治理能力不足、管理体制不合理是太湖目前水环境恶化的根本原因。     

1980年以来太湖总磷变化特征及其驱动因子分析

磷是湖泊生态系统物质和能量循环的重要组成部分,是湖泊富营养化防治的重要控制性指标.为分析太湖富营养化与人类活动的关系,掌握总磷（TP）的时空变化规律及驱动因子,本文收集整理了1980—2020年太湖TP浓度数据并分析了TP的时序、时空和年内变化特征.结果表明,1980s经济社会快速发展之初,伴随着工业和三产用水量激增,废污水排放量和入湖负荷大增,1985—1995年太湖TP浓度急剧升高.随着治理与保护措施的实施,到1995年达到峰值后逐步走低,2009年后进入了窄幅波动期.从空间上看,不同时段TP浓度分布格局较好地反映了入湖污染物的输入分布.通过分时段对比分析可能影响太湖TP浓度变化的驱动因子,分别讨论了经济社会发展、用水量、废污水排放量,入湖水量、入湖河流TP浓度、入湖TP负荷,蓝藻水华、水温,高等水生植物,底泥释放,太湖换水周期变化等.结果表明,近10年来入湖TP负荷增加,蓝藻水华强度加大,水温升高,高等水生植物面积减少,这些因素会导致太湖TP浓度上升.2008—2019年净入湖TP负荷比1998—2007年增加了33.9%,而近10年太湖换水周期缩短了17.7%,在一定程度上抵消了影响太湖TP浓度升高的驱动因子的不利影响,太湖TP浓度不升反降.为此建议在新一轮太湖治理中积极开展控源截污、节水减排、水资源调控、高等水生植被恢复、重点污染湖区清淤疏浚等针对性措施以期获得更好的太湖TP浓度控制效果.     

湖北长湖富营养化状况及时空变化(2012-2013年)

为评估长湖水体富营养化程度,2012-2013年分4个季度对全湖区20个采样点的物理、化学和生物要素进行监测,在评价水质现状的基础上采用综合营养状况指数法和浮游植物细胞丰度指数法综合评价水体营养状况,并应用典型相关分析(CCA)方法揭示水体富营养化状况与湖泊理化要素之间的典型相关性.结果显示:4个季节长湖全湖区的水质均处于地表水IV类~劣V类水标准;综合营养状态指数值在49.54~82.55之间,浮游植物细胞丰度在2.88×106~61.73×106cells/L之间,均显示其处于富营养化状态;长湖富营养化状况的分布呈现一定的时空差异性;CCA分析显示,长湖理化要素变量可解释68.6%的水体富营养化状况变量的变异,影响其富营养化状况的主要理化因素有水体总磷、总氮、溶解氧、亚硝态氮、硝态氮浓度,水深和沉积物总磷、总氮含量.长湖水体富营养化主要是由于外源的磷污染,其次是氮污染,富营养化最严重的夏、秋季浮游植物的生长主要受氮营养限制,而冬、春季则部分受磷营养限制,部分属于过渡类型.因此,建议大力削减围网/围栏养殖量,同时考虑结合水生植物栽种等生态工程建设措施以降低长湖水体发生严重富营养化的风险,并进一步改善长湖的水质现状.     

Evidence from isotopic geochemistry as an indicator of eutrophication of Meiliang Bay in Lake Taihu,China

In this paper, Lake Taihu, a large shallow freshwater lake in China, is chosen as an example of reconstruction of eutrophication through the comparison between stable isotopes from dissolved nutrients and plants and water column nutrient parameters and integration of multiple proxies in a sediment core from Meiliang Bay including TN, TP, TOC, C/N, δ ¹⁵N, δ ¹³C, etc. Differences in aquatic plant species and trophic status between East Taihu Bay and Meiliang Bay are indicated by their variations in δ ¹³C and δ ¹⁵N of aquatic plants and δ ¹⁵N of NH₄ ⁺. A significant influence of external nutrient inputs on Meiliang Bay is reflected in temporal changes in δ ¹⁵N of NH₄ ⁺ and hydro-environmental parameters. The synchronous change between δ ¹³C and δ ¹⁵N values of sedimented organic matter (OM) has been attributed to elevated primary production at the beginning of eutrophication between 1950 and 1990, then recent inverse correlation between them has been caused by the uptake of ¹⁵N-enriched inorganic nitrogen by phytoplankton grown under eutrophication and subsequent OM decomposition and denitrification in surface sediments, indicating that the lake has suffered from progressive eutrophication since 1990. Based on the use of a combination of stable isotopes and elemental geochemistry, the eutrophication of Meiliang Bay in Lake Taihu could be better traced. These transitions of the lake eutrophication respectively occurring in the 1950s and 1990s have been suggested as a reflection of growing impacts of human activities, which is coincident with the instrumental data.

     

VCS柱状采样及其在中国太湖富营养化评价中的应用

The lake sediments, especially in recent years, genuinely record human being''s activities upon the lake environment. The top 30cm sections are of significance in the process of advanced cultural eutrophication and water quality deterioration. Based on the data of 4 core sam-ples obtained in June 19-22, 1997, with VCS in northern, western and southern Taihu Lake, some preliminary results are reported. Further analyses on the physico-chemical items as well as element content may reveal more information of the accelerating cultural eutrophication.     

太湖与流域治理

太湖流域是中国最重要的经济区.流域面积36500km~2,六分之五为平原,有上海、无锡、苏州、杭州等重要城市.以太湖为中心和其周围的河网构成了流域水系的特点.治理和开发的目标是防洪、供水、水资源保护和航运.治理的方案充分发挥太湖的调蓄作用,规划了十项骨干工程,可使流域内收到十分显著的综合效益.其中以望虞河和太浦河最为重要,可以解决80％上游洪水的出路和从长江引水2.8km~3,缓解防洪和水污染的压力,建议及早兴建.     

太湖不同生态型湖区枝角类组成和丰度长期变化的差异性

枝角类作为淡水湖泊生态系统中的初级消费者之一,对生存环境的改变极为敏感.本文分析了太湖西、中和东部等湖区的钻孔沉积物、表层沉积物以及春夏秋季活体枝角类的组成与丰度.结果表明:活体枝角类组成以象鼻溞(Bosmina spp.)为优势种,秋季枝角类属种数量最多.太湖不同生态型湖区表层沉积物枝角类组成均以象鼻溞为优势种,其中西部与中心湖区的枝角类组成与丰度较为相似,种类单一,枝角类绝对丰度高;东部湖区枝角类属种较为丰富,绝对丰度低,优势种由浮游种象鼻溞以及沿岸种圆形盘肠溞(Chydorus sphaericus sl)和西方笔纹溞(Graptoleberis testudinaria)等种属构成.百年以来,太湖枝角类组成与丰度随着营养水平增加而改变,富营养指示种(Bosmina longirostris)丰度的增加与贫营养指示种(Bosmina longispina)丰度的下降,响应了湖区生态环境的演变过程.1970s末期,太湖西部与中心湖区在进入富营养化阶段,枝角类组成单一,象鼻溞占有绝对优势,与东部湖区相比,沿岸种、底栖种稀少.东部湖区在1960s以后,枝角类属种数量增加,但丰度下降,响应了1960s以来该区域营养水平提高、沉水植被生物量增加以及沼泽化加剧的环境过程.