Biodiversity Changes of Benthic Macroinvertebrates in Tamjin river system by Jangheung Dam Construction

Benthic macroinvertebrates in freshwater include Nematoda, Annelida, Mollusca, and Arthropoda etc. Insects in arthropoda are among the most conspicuous inhabitants of streams and rivers and occupy up to 95% of macroinvertebrates. In most cases, it is the larval stages of these insects that are aquatic, whereas the adults are terrestrial. Tamjin river system was surveyed seasonally for 13 years (1998–2010) to study the biodiversity changes of macroinvertebrtes by Jangheung Dam construction. Total macroinvertebrates consist of 139 species, 101 genera, 59 families, 19 orders, 6 classes in 4 phylums. To start 57 species in 1998 before the dam construction, 41 species were in 1999 which is the first year of construction. After the construction the number of species increased gradually and 73 species emerged in 2009 and 2010. The individual number fluctuated annually and it is difficult to infer the comprehensive results, but ephemerids decreased dramatically after the construction and then they increased gradually since 2006, whereas caddisflies increased rapidly and decreased. Among the studied taxa Ephemeroptera showed the highest diversity relatively, and the next was Trichoptera and Coleoptera. The species occurrence pattern was stable in Ephemeroptera as 15–24 species and fluctuated in Trichoptera ranged from 4 species (2001) to 15 species(2008). In Diptera, 8 species emerged up in 2003 and 2007 and 3 species in 1998 and 1999 and in Coleoptera, 3–6 species emerged in stable pattern.     

Surface–subsurface water exchange rates along alluvial river reaches control the thermal patterns in an Alpine river network

1. Water temperature is a key characteristic of stream ecosystems that is gaining scientific and managerial relevance as maximum temperatures in aquatic ecosystems increase worldwide.
2. To assess the effect of surface–subsurface water exchange on stream water temperature patterns, four alluvial reaches in the Tagliamento River basin (NE Italy), constrained by geomorphic knickpoints at the upper and lower end, and two to four hyporheic flowpaths within each reach, were continuously studied during summer 2007 and winter 2007–08. Water temperature was continuously monitored at the upstream and downstream knickpoints of the floodplains, as well as at discrete upwelling areas within each reach. Discharge and vertical hydraulic gradient were measured along the alluvial reaches, and the residence time and chemistry of upwelling water were assessed four times during the study.
3. Discharge variation along the study reaches revealed that massive hyporheic exchange occurred in all sites, ranging from 21% in reach 2–52% in reach 1. End member mixing analysis showed little influence of ground water, as almost all upwelling water was freshly infiltrated hyporheic water. Importantly, hyporheic exchange flows shaped surface temperature at the upwelling locations in all study reaches, providing potential thermal refugia for aquatic biota. At sites with highest hyporheic flow rates, net temperature change was also reflected at the floodplain scale.
4. The magnitude of the thermal change along a hyporheic flowpath was not related to the flowpath length but to the estimated ²²²Rn water age. Reduction in the diel thermal amplitude by hyporheic flows rather than net temperature change, reduced temperature extremes. Therefore, restoration activities to create thermal refugia should consider the role of hyporheic flows and enhance the exchange between surface and hyporheic waters.     

Ion exchange systems in proton-metal reactions with algal cell walls

Abstract: Algal cell walls contain acidic polysaccharides, e.g. alginic acid in many marine species, and in pectin fresh-water species. At neutral pH these provide anionic sites which bind ionically to metals, and acidification releases metals when covalent bonds to H are made. Added Cu releases an equivalent amount of Ca, Mg, H from Vaucheria , and protonated amines also displace metals. Interestingly, diamines, which function as efficient growth promoters, are sorbed more strongly than monoamines based on Langmuir adsorption constants. Sorption of Pb and Cd on Rhizoclonium from the solid hydroxides releases Na, Ca, Mg from the alga and OH from the hydroxide in essentially stoichiometric amounts. Sorbed heavy, metals can be removed by precipitation of the sulfide (Cd), hydroxide (Cm AI, and Pb), or as an EDTA complex (Pb) in ion exchange processes. Values of ion exchange constants for displacement of Ca by Mg, Zn, Cd, Pb, and Cu on Vaucheria are independent of pH and increase with the (charge)²/radius of metal ions, as also observed for K and AI. These results indicate a non-cooperative behavior of anionic sites which interact with these metals by electrostatic attractions. Rates of metal desorption and ion exchange constants with alginates as model systems were also investigated.     

滇池底栖无脊椎动物群落结构及水质评价

滇池位于云南省昆明市西南郊,海拔1885m的高原面上,受纳盘龙江、宝象河等21条入湖水源,湖水出口南流转北注入金沙江。滇池南北长39．0km^2,东西最宽12．5km^2,最窄2．44km^2,湖岸线151．2km^2,面积为330．0km^2,属于高原构造型亚热带石灰岩富营养型湖。     

青龙河底栖无脊椎动物群落结构及其水质评价

本文论述了青龙河底栖生物种类、数量、分布和结构等特点及其与环境因子间的关系。应用Beck、Gleason、Shannon、Simpson等生物指数对水质状况进行评价。结果表明青龙河除个别断面受污染外,大部分河段属尚清洁水。     

饮用水处理流程中的微藻及其去除率

为了解某市饮用水处理流程中的藻类状况,对某市饮用水源及自来水厂各主要处理过程中的水样进行藻类检测鉴定。在各水样中共检测到藻类72种,蓝藻、绿藻和硅藻为优势藻群,并检出微囊藻、颤藻和鱼腥藻等潜在产毒的种类,其中微囊藻在源水中的细胞密度为1.9×106cell·L-1。源水中藻类细胞密度为2.8×106cell·L-1,处理后自来水中藻类的细胞密度为4.6×104cell·L-1,藻类总去除率为98.3%,其中滤池对藻类的去除率为82.7%,但其对蓝藻的去除率仅为11.8%。研究结果表明,该市水源可能已受到藻毒素的污染;现有自来水处理工艺中的滤池难以对个体较小的有毒蓝藻有效去除。针对该地区水源藻类的分布情况提出了优化过滤工艺的建议。     

Trace metal fractionation in water and sediments of an urban river stretch

Abstract

In this study, the fractionation and ecotoxic potential of Cr, Ni, Cu and Pb in water and sediments of the river Yamuna (Delhi stretch) is presented. The river water is used for various purposes such as irrigation, industrial, domestic and drinking. The investigations suggest that the availability of metals in water follows the sequence Ni>Cr>Pb>Cu whereas a different pattern (Pb>Cu>Ni>Cr) is observed in sediments. Statistically significant spatial variations are indicated by two-way ANOVA in different geochemical forms of the metals and physicochemical parameters of water and sediments of the river Yamuna. Principal component analysis (PCA) suggests a similar source for all four metals probably from the sewage from municipal drains. PCA also indicates some independent sources of Cu and Pb. The hot spots were identified using hierarchical cluster analysis considering bioavailable forms of the metals in water and sediments as objects and the sampling sites as variables. Risk assessment code analysis indicates that metals generally pose medium to high risk at different sites. However, at a few locations either Ni or Pb cross the level of very high ecological risk.     

Physiological control of water exchange in anurans

Research on water exchange in frogs has historically assumed that blood osmotic potential drives water exchange between a frog and its environment, but here we show that the “seat patch” (the primary site of water exchange in many anurans), or other sites of cutaneous water uptake, act as an anatomic “compartment” with a water potential controlled separately from water potential of the blood, and the water potential of that compartment can be the driver of water exchange between the animal and its environment. We studied six frog species (Xenopus laevis, Rana pipiens, R. catesbeiana, Bufo boreas, Pseudacris cadaverina, and P. regilla) differing in ecological relationships to environmental water. We inferred the water potentials of seat patches from water exchanges by frogs in sucrose solutions ranging in water potential from 0 to 1000‐kPa. Terrestrial and arboreal species had seat patch water potentials that were more negative than the water potentials of more aquatic species, and their seat patch water potentials were similar to the water potential of their blood, but the water potentials of venters of the more aquatic species were different from (and less negative than) the water potentials of their blood. These findings indicate that there are physiological mechanisms among frog species that can be used to control water potential at the sites of cutaneous water uptake, and that some frogs may be able to adjust the hydric conductance of their skin when they are absorbing water from very dilute solutions. Largely unexplored mechanisms involving aquaporins are likely responsible for adjustments in hydric conductance, which in turn, allow control of water potential at sites of cutaneous water uptake among species differing in ecological habit and the observed disequilibrium between sites of cutaneous water uptake and blood water potential in more aquatic species.     

延河流域植物群落功能性状对环境梯度的响应

研究群落水平上的植物功能性状特征及其随环境梯度的变化规律,对认识不同环境梯度下植物群落的形成及其对环境的适应机制具有重要意义。以延河流域不同环境梯度下的稳定的自然植物群落为对象,测量了植物群落组成物种的叶厚度、比叶面积、叶组织密度、比根长、根组织密度、单位质量叶氮含量、单位质量根氮含量、种子质量、种子体积等9个性状,然后以物种重要值为基础加权平均得到各个性状在群落水平上的平均值(即群落性状值);以现有的环境因子栅格图为基础,利用ArcGIS提出各群落对应的环境因子值,同时测定各个群落的土壤水分,分析群落各性状值与环境因子的关系,并建立关系模型。结果表明:在群落水平上,9个植物功能性状分别与13个环境因子存在不同程度的相关性,同时这9个植物功能性状对8个环境因子梯度(土壤水分、年4-10月平均气温、年7-9月总降雨量、降雨季节变化、年平均降雨量、年平均蒸发量、坡度、坡向)的响应特征较好,不同植物功能性状间具有较好相关性。群落水平上植物功能性状及其组合随环境梯度的规律性变化,反映了延河流域植被群落构建过程中环境对功能性状的筛选效应。该研究结果对该区的植被恢复重建的物种选择及植被布局规划具有重要的实践意义。     

Responses of ecosystem carbon exchange to multi-level water addition in an alpine meadow in Namtso of Qinghai-Xizang Plateau,China

高寒草甸是青藏高原的主要草地类型, 对青藏高原生态系统碳收支具有重要的调节作用。目前, 有关高寒草甸生态系统碳交换对气候变化的响应所知甚少, 尤其是降水变化会如何影响高寒草甸碳交换过程的相关研究非常匮乏。该文作者于2013和2014年的生长季(5-9月)在青藏高原纳木错地区高寒草甸进行多梯度人工增水实验, 设置对照和5个水分添加梯度, 分别增加0%、20%、40%、60%、80%和100%的降水, 以研究高寒草甸生态系统在不同降水量条件下的碳交换变化。增水处理后, 各处理梯度之间的土壤温度没有显著差异, 而土壤含水量在不同增水处理后出现显著变化, 相对于对照, 增水幅度越大, 对应的土壤含水量越高。综合2013和2014年的观测结果, 高寒草甸生态系统整体表现为碳吸收, 在20%增水处理中, 净生态系统碳交换(NEE)达到最大值, 随着模拟的降水梯度进一步增加, NEE逐渐下降; 增水处理对生态系统呼吸(ER)无显著影响; 总生态系统生产力(GEP)的变化趋势与NEE一致, 即随着增水梯度增大, GEP先增加, 并在增水20%处理达到最大值, 随后GEP开始降低。研究表明, 在高寒草甸生态系统, 水分是影响GEP和NEE的重要因素, 对ER影响较弱; 未来适度的增水(20%-40%)能促进高寒草甸生态系统对碳的吸收。     

Comparison of response of two C3 species to leaf water relation,proline synthesis,gas exchange and water use under periodic water stress

Water relations, proline content and gas exchange of leaf were investigated under periodic water stress for two C3 plants (eggplant and tomato) in a greenhouse to study comparative adaptive responses. Although both species showed reduced water content of leaf and increased osmolality and proline content under low soil water potential, the recovery capacity after the stress was better in eggplant than tomato. Both species over-accumulated proline under low soil water potential and returned to its initial concentration during the recovery, indicating that proline may act as an osmoprotectant during drought. Proline was directly corresponding with osmolality during stress, and dehydration stress reduced the gas exchange parameters such as transpiration rate (ET), stomatal conductance (GS), and photosynthesis rate (Pn). At the final stage of the experiment both species showed 2.6 and 3.3 times lower Pn and 27 and 19 times lower GS for eggplant and tomato, respectively, as compared to control. But after stress was relieved by rewatering, both plants increased GS for 2 to 3 times and Pn for 4.5 times. Eggplant showed better water use efficiency (WUE) in relation to fruit production under the stress than tomato. Higher biomass allocation at root and fruit parts in eggplant indicated more efficient recovery than that of tomato. These findings inferred that both C3 plants developed internal complementary drought survival mechanism by lowering relative water content, increasing proline, and decreasing stomatal conductance but eggplants withstood the periodic draughting better than tomato, mainly due to its ability to recover from a water stress condition.     

青藏高原纳木错高寒草甸生态系统碳交换对多梯度增水的响应

高寒草甸是青藏高原的主要草地类型, 对青藏高原生态系统碳收支具有重要的调节作用。目前, 有关高寒草甸生态系统碳交换对气候变化的响应所知甚少, 尤其是降水变化会如何影响高寒草甸碳交换过程的相关研究非常匮乏。该文作者于2013和2014年的生长季(5-9月)在青藏高原纳木错地区高寒草甸进行多梯度人工增水实验, 设置对照和5个水分添加梯度, 分别增加0%、20%、40%、60%、80%和100%的降水, 以研究高寒草甸生态系统在不同降水量条件下的碳交换变化。增水处理后, 各处理梯度之间的土壤温度没有显著差异, 而土壤含水量在不同增水处理后出现显著变化, 相对于对照, 增水幅度越大, 对应的土壤含水量越高。综合2013和2014年的观测结果, 高寒草甸生态系统整体表现为碳吸收, 在20%增水处理中, 净生态系统碳交换(NEE)达到最大值, 随着模拟的降水梯度进一步增加, NEE逐渐下降; 增水处理对生态系统呼吸(ER)无显著影响; 总生态系统生产力(GEP)的变化趋势与NEE一致, 即随着增水梯度增大, GEP先增加, 并在增水20%处理达到最大值, 随后GEP开始降低。研究表明, 在高寒草甸生态系统, 水分是影响GEP和NEE的重要因素, 对ER影响较弱; 未来适度的增水(20%-40%)能促进高寒草甸生态系统对碳的吸收。     

Responses of algal communities to gradients in herbivore biomass and water quality in Marovo Lagoon, Solomon Islands

Settlement tiles were used to characterise and quantify coral reef associated algal communities along water quality and herbivory gradients from terrestrial influenced near shore sites to oceanic passage sites in Marovo Lagoon, the Solomon Islands. After 6 months, settlement tile communities from inshore reefs were dominated by high biomass algal turfs (filamentous algae and cyanobacteria) whereas tiles located on offshore reefs were characterised by a mixed low biomass community of calcareous crustose algae, fleshy crustose algae and bare tile. The exclusion of macrograzers, via caging of tiles, on the outer reef sites resulted in the development of an algal turf community similar to that observed on inshore reefs. Caging on the inshore reef tiles had a limited impact on community composition or biomass. Water quality and herbivorous fish biomass were quantified at each site to elucidate factors that might influence algal community structure across the lagoon. Herbivore biomass was the dominant driver of algal community structure. Algal biomass on the other hand was controlled by both herbivory and water quality (particularly dissolved nutrients). This study demonstrates that algal communities on settlement tiles are an indicator capable of integrating the impacts of water quality and herbivory over a small spatial scale (kilometres) and short temporal scale (months), where other environmental drivers (current, light, regional variability) are constant.     

Nodule gas exchange and water potential response to rapid imposition of water deficit

The permeability (P) of the gaseous diffusion barrier in the nodules of soybean [Glycine max (L.) Merr.] decreases when water deficits are extended over a 7 to 10 d period. The mechanism controlling P changes is unclear, but may result from the release of water to intercellular pathways, and an associated change in the nodule water potential. The purpose of these experiments was to impose water deficit treatments rapidly in order to determine the early sequence of the responses of nodule water potential and nodule gas exchange without the complications that arise from long-term water deficit treatments. A vertical, split-root system was used to separate nodule drying effects from plant water deficits by replacing humidified air that was passed over upper root nodules in well-watered plants with dry air, or by replacing the nutrient solution that surrounded lower roots with -1.0 MPa polyethylene glycol (PEG) solution, or by a combination of the dry air and PEG treatments. The PEG treatment caused large decreases in both the components of nodule water potential and nodule relative water content, but there was no indication that these factors had immediate, direct effects on either nitrogenase activity or P. After 7 h of the PEG treatment a significant decrease in nitrogenase activity was found but no decrease in P was detected. These results indicate that changes in nitrogenase activity in response to water deficits precede decreases in P. Exposure of nodules to dry air in well-watered plants had no significant effect on either nitrogenase activity or P during the 7 h treatment.     

Benthic community response to a passive fishing gear in a coastal lagoon (South Brazil)

The influence of a passive shrimp fishing gear on benthic communities was studied at Laguna Estuarine System (South Brazil), a shallow choked coastal lagoon. The gear is composed by a group of fyke nets (25 mm mesh size) set in contact to the bottom, fixed with stakes forming a cage-like structure (around 30 m²). Samplings were conducted in the two main fishery areas of the estuarine system, Mirim (sand bottoms) and Imaruí (muddy bottoms) lagoon, in May 2005. In each area, 10 fyke net enclosures and 10 nearby sites without nets (control) were sampled. Microphytobenthos biomass (chlorophyll a and phaeopigments), number of taxa/species, density, Hill’s number N ₁ and N ₂, and estimated number of species (ES₁₀₀) were used as community attributes. For the nematodes, values of the maturity index and abundance of Wieser’s feeding type were used as well. The effects of the small-scale passive shrimp fishing gear on the coastal lagoon bottoms were dependent on the benthic component analyzed and the type of sediment. Whereas macrofauna was not affected by the net enclosures, meiofauna and nematodes, particularly from the mud sites were. At the sand site, the fyke net enclosures caused a decrease in the microphytobenthos biomass and changed the relative abundances of non-selective deposit feeding and epigrowth-feeding nematodes. The results indicated that small-scale static nets, such as the studied fyke enclosures, produced low intensity levels of disturbance. However, the enclosed area by nets at Laguna had already reached around 25,000 m². Given the large proportion of the coastal population involved and the area closed by nets, management policies should consider site-specific differences within the same estuarine system.     

Variation in material transport and water chemistry along a large ephemeral river in the Namib Desert

• 1 The chemical characteristics of floodwaters in ephemeral rivers are little known, particularly with regard to their organic loads. These rivers typically exhibit a pronounced downstream hydrological decay but few studies have documented its effect on chemical characteristics and material transport. To develop a better understanding of the dynamics of floods and associated material transport in large ephemeral rivers, floods of the ephemeral Kuiseb River in south‐western Africa were tracked and repeatedly sampled at multiple points along the river's lower 220 km.
• 2 We quantified the composition and transport of solute and sediment loads in relation to longitudinal hydrological patterns associated with downstream hydrological decay. Source and sink areas for transported materials were identified, and the composition and transport dynamics of the organic matter load were compared to those described from more mesic systems.
• 3 Concentrations of sediments and solutes transported by floods in the Kuiseb River tended to increase downstream in association with pronounced hydrological decay. The contribution of particulate organic matter to total organic load is among the highest recorded, despite our observation of unusually high levels of dissolved organic matter. Hydrological decay resulted in deposition of all transported material within the lower Kuiseb River, with no discharge of water or materials to the Atlantic Ocean.
• 4 Our results suggest that longitudinal variation in surface flow and associated patterns of material transport renders the lower Kuiseb River a sink for materials transported from upstream. The downstream transport and deposition of large amounts of labile organic matter provides an important carbon supplement to heterotrophic communities within the river's lower reaches.

     

Spatial and temporal variability in epilithic biofilm bacterial communities along an upland river gradient

Riverine biofilms remain one of the least-studied habitats despite the significant increase in the examination of aquatic microbial communities in recent years. In this study, the dynamics of epilithic biofilm communities native on rocks from a low-order upland stream were examined over a period of 3 years. Spatial and temporal variations in bacterial communities were assessed using terminal restriction fragment length polymorphism, based on analysis of the 16S rRNA gene. In total, 108 epilithic biofilm samples were analysed and 170 different ribotypes were detected. A strong temporal gradient in ribotype composition was noticed, especially between samples collected in 2001 and those collected in 2002 and 2003, most likely reflecting interannual differences in weather conditions, such as temperature. A spatial gradient in ribotype composition, from upstream sites to the low-lying sites, was also evident and interpreted as an environmental variation gradient along the river course. Distinct biofilm communities consistently occurred at the first site along the river, which was significantly correlated to low pH. Temporal factors explained the highest degree of variation within the epilithic biofilms. Recurrent blooms of certain bacteria were noted within the system. Phylogenetic relationships of bacteria at one point in the river were determined using a cloning and sequencing approach, with Alphaproteobacteria dominating the community, followed by Cyanobacteria, Bacteroidetes and Betaproteobacteria.     

太湖流域河流水质状况对景观背景的响应

为探索流域水质对景观背景的响应,以太湖流域为研究对象,在0.5—24 km共9个尺度上运用冗余分析研究了土地利用、河网密度、降水量、地形等景观背景因子与河流水化学指标的关系。结果表明:2006—2010年太湖流域河流水质状况总体较差,但整体有逐渐改善的趋势,超标水质指标主要包括总磷(TP)、氨氮(AN)、生化需氧量(BOD)、化学需氧量(COD)和溶解氧(DO),上游地区主要表现为林区和平原水网区的差异,下游地区主要表现为河段上下游间的差异。河流水质受到多种景观背景因子的综合影响,并表现出尺度依赖性和区位差异性。AN、TP、DO在流域上游与聚落用地正相关,在下游则与耕地、河网密度正相关。COD、BOD在流域上游主要与自然湿地负相关,与人工湿地正相关,在下游则与坡度负相关,与河网密度正相关。总方差贡献率在上下游表现出一致的尺度依赖特征,均在较小(0.5—1 km)和较大(16 km)两个尺度上具有较高的解释能力。自然湿地和坡度,河网密度和耕地分别为上游、下游地区在较小和较大尺度上解释能力最高的景观因子。     

生态修复工程条件下污染河流水质模拟和应用

生态工程是改善河流水质的重要手段,利用数学模型可以有效模拟水环境治理和预测生态修复工程效益.本文根据实际河流资料,应用WASP水质模型进行建模和验证,模拟和评估了河流的主要化学参数,进而研究了人工湿地和曝气复氧对河流水质的生态改善作用.结果表明: WASP水质模拟结果与实测水质数据拟合良好,可以对不同生态修复情景方案进行预测分析.合理减排、人工湿地、曝气复氧均可以降低河流水体中的污染物浓度、有效改善水质.在人工湿地系统中增加曝气复氧装置,将进一步提升河流水体的生态修复效率.以吉林省伊通河曝气条件下的人工湿地工程为例,分析了其生态修复效率.结果表明: 夏季的污染物去除效果最好,可能的原因为夏季气温较高,水体中的微生物活性较强.本研究对于污染河流环境的生态修复工程设计和运行具有指导意义.