large rivers

  • 文章类型: Journal Article
    了解溶解有机物(DOM)的空间格局及其影响因素对于维持河流生态系统功能和河流健康至关重要。考虑到DOM在水质和水生生态系统中的重要作用。然而,关于DOM生物利用度的空间变化以及在大型河流系统中驱动它们的因素的知识有限。这项研究涉及长江干流沿线39个采样地点,在旱季跨越其整个长度(>5000公里)。通过测量DOC浓度和八个荧光DOM指数来评估DOM的空间模式,即荧光指数(FI-A和FI-B),Trytophan/酪氨酸,幽默A,腐殖质C,腐殖质指数(HIX-A和HIX-B),和新鲜度指数(β/α)。结果表明,长江干流中的水DOM主要来自陆源。从上盆地到下盆地观察到DOM生物利用度下降,与碳处理预测而不是河流连续体概念(RCC)保持一致。理化因素的纯效应(25.30%)大于地理因素的纯效应(9.40%)。内部转化过程决定了DOM生物利用度的显着纵向降低。虽然在大坝之前和之后的到达之间没有观察到DOM生物利用度的显着差异,发现水坝的建造可以在分段尺度上提高DOM生物利用度,并降低整个流域DOM生物利用度的空间自相关。
    Understanding the spatial patterns of dissolved organic matter (DOM) and factors that influence them is crucial for maintaining river ecosystem functions and riverine health, considering the significant role of DOM in water quality and aquatic ecosystems. Nevertheless, there is limited knowledge regarding the spatial variation of DOM bioavailability and the factors driving them in large river systems. This study involved 39 sampling locations along the main stem of the Changjiang River, spanning its entire length (>5000 km) during a dry season. Spatial patterns of DOM were assessed by measurements of DOC concentrations and eight fluorescence DOM indices, namely fluorescence index (FI-A and FI-B), Trytophan/Tyrosine, Humic A, Humic C, humification indices (HIX-A and HIX-B), and Freshness index (β/α). The results revealed that the water DOM in the main stem of the Changjiang River primarily originated from terrestrial sources. A decline in DOM bioavailability was observed from the upper to the lower basin, aligning with the carbon processing prediction rather than the river continuum concept (RCC). The pure effect of physicochemical factors (25.30%) was greater than that of geographic factors (9.40%). The internal transformation processes determined the significant longitudinal decreases of DOM bioavailability. While no significant difference in DOM bioavailability was observed between reaches before and after the dams, the construction of dams was found to improve DOM bioavailability at the subsection scale and reduce the spatial autocorrelation of DOM bioavailability across the entire basin.
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  • 文章类型: Journal Article
    随着城市人口的不断增长,城市化是对生物多样性的最大威胁之一。为了减轻负面影响,强烈建议在现代城市发展实践中纳入蓝色区域(水生栖息地),因为它们可能对当地的生物多样性保护有益。Odonata是一个旗舰群体,被广泛用于淡水保护,作为栖息地完整性和健康的生态指标。然而,我们对城市景观生态要求的理解还不完整。因此,我们分析了克罗地亚首都半自然湿地中Odonata的分类学和功能多样性。这项研究是在2020年和2023年的夏天进行的。大多数分类学和功能组合指标在两种主要栖息地类型之间具有可比性,人为干扰和天然牛弓湖泊。然而,在时间尺度上发现了显著差异,2023年大多数指标较低,表明2020年后该地区发生的极端气候事件(包括干旱)的负面影响。记录了19种,我们的结果表明,半自然城市湿地,尤其是天然牛弓湖,有很大的潜力作为Odonata的良好栖息地,甚至检测到一些物种的保护问题。在城市地区制定景观管理计划时,从水生大型植物的良好结构来看,考虑生境异质性的重要性是至关重要的(水下植物的存在,新兴和漂浮植被),这将确保当地Odonata物种的最合适的栖息地条件。
    As the human population in urban areas is continuously growing, urbanization is one of the greatest threats to biodiversity. To mitigate the negative effects, the inclusion of blue zones (aquatic habitats) in modern urban development practices is strongly recommended, as they could be beneficial for the local biodiversity conservation. Odonata are a flagship group and are widely used in freshwater conservation as ecological indicators of habitat integrity and health. However, our understanding of their ecological requirements in urban landscapes is not yet complete. Therefore, we analyzed the taxonomic and functional diversity of Odonata in a semi-natural wetland in the Croatian capital. This study was conducted in the summers of 2020 and 2023. Most taxonomic and functional assemblage metrics were comparable between the two main habitat types, anthropogenically disturbed and natural oxbow lakes. However, significant differences were found in relation to the time scale, where most metrics were lower in 2023, indicating the negative impact of extreme climate events (including droughts) that occurred in this region after 2020. With 19 species recorded, our results indicate that semi-natural urban wetlands, especially natural oxbow lakes, have great potential to function as good habitats for Odonata, where even some species of conservation concern were detected. When developing landscape management plans in urban areas, it is essential to consider the importance of habitat heterogeneity in terms of good structure of aquatic macrophytes (presence of submerged, emergent and floating vegetation), which would ensure the most suitable habitat conditions for local Odonata species.
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  • 文章类型: Journal Article
    世界上最大的河流是多种多样的,地方性,受威胁的鱼类物种。然而,它们的庞大规模使大规模生物监测具有挑战性。虽然环境DNA(eDNA)元转录编码已成为较小淡水生态系统中的一种既定监测方法,其对大型河流的适用性可能会受到其横截面范围(>1公里宽和几十米深)的挑战。这里,我们从中国长江下游两个横截面的多个垂直层和水平位置采样了鱼类eDNA。仅在垂直层和水平位置的单个组合中检测到超过一半的ASV(扩增子序列变体)。在所有组合中,有7%。我们估计需要在横截面剖面上采样>100升的水,以实现ASV丰富度饱和,这相当于物种水平的60L水。没有出现一致的模式来优先考虑某些深度和水平样本,然而,我们强调同时采样和整合不同层和位置的重要性。我们的研究强调了使用eDNA方法时空间分层抽样和抽样量的重要性。具体来说,我们开发并测试了可扩展和广泛适用的策略,以促进大型河流的监测和保护。
    The world\'s largest rivers are home to diverse, endemic, and threatened fish species. However, their sheer sizes make large-scale biomonitoring challenging. While environmental DNA (eDNA) metabarcoding has become an established monitoring approach in smaller freshwater ecosystems, its suitability for large rivers may be challenged by the sheer extent of their cross sections (>1 km wide and tens of meters deep). Here, we sampled fish eDNA from multiple vertical layers and horizontal locations from two cross sections of the lower reach of the Yangtze River in China. Over half of the ASVs (amplicon sequence variants) were detected in only a single combination of the vertical layers and horizontal locations, with ∼7% across all combinations. We estimated the need to sample >100 L of water across the cross-sectional profiles to achieve ASV richness saturation, which translates to ∼60 L of water at the species level. No consistent pattern emerged for prioritizing certain depth and horizontal samples, yet we underline the importance of sampling and integrating different layers and locations simultaneously. Our study highlights the significance of spatially stratified sampling and sampling volumes when using eDNA approaches. Specifically, we developed and tested a scalable and broadly applicable strategy that advances the monitoring and conservation of large rivers.
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  • 文章类型: Journal Article
    对水电运营商来说,河流水电站蓄水中的沉淀是一个持续不断的管理问题,因为它对以下方面产生了影响:防洪和航道参数的维护。目前的泥沙管理做法往往是不可持续的,与高成本相关,并且可能对下游生物群构成风险(例如在冲洗期间)。本研究阐述了一种针对蓄水河段的新型沉积物管理策略的概念模型,该模型包括当前状态和赤字分析,以及新的沉积物管理实践的应用,这实际上是在奥地利多瑙河的研究现场实施的。这种新颖的做法包括(i)在蓄水池的位置进行砾石的局部疏浚,在防洪和航道维护方面存在问题,和(ii)通过人工放置砾石结构来重新沉积疏浚的沉积物。本研究包括通过应用通道剖面预算技术对研究地点的蓄水段进行形态分析。长期形态发展的知识是评估沉积物管理措施和阐述概念模型的基础。将蓄水中的形态动力学特征与新型沉积物管理实践的实施相结合,有助于得出在具有相似蓄水特征的大型河流中可能实施所提出的概念模型的广义陈述。我们进一步定义了几个方面,与蓄水河段的沉积物动力学有关,防洪,航道需求,和生态标准,需要考虑有效实现所提出的概念模型。
    Sedimentation in impoundments of run-of-river hydropower plants is an ongoing and progressing management issue for hydropower operators because of its consequences for e.g., the maintenance of flood protection and waterway parameters. Current practices in sediment management are often unsustainable, associated with high costs, and can pose risks for downstream biota (e.g. during flushing). The present study elaborated a conceptual model of a novel sediment management strategy for impounded river sections consisting of a current-state and deficit analysis, and the application of a novel sediment management practice, which was practically implemented at the study site at the Austrian Danube River. This novel practice consists of (i) local dredging of gravel at locations in the impoundment, which are problematic in terms of flood protection and waterway maintenance, and (ii) the re-deposition of dredged sediments by artificial placement of gravel structures. The present study included morphological analyses of the impounded section at the study site by applying the channel profile budget technique. The knowledge of the long-term morphological development served as a basis for the evaluation of the sediment management measures and for the elaboration of the conceptual model. The combination of the morphodynamic characteristics in the impoundment with the implementation of the novel sediment management practice helped to derive generalized statements for the potential implementation of the presented conceptual model in large rivers with similar impoundment characteristics. We further defined several aspects, which are related to sediment dynamics in impounded river sections, flood protection, waterway demands, and ecological criteria that require consideration for an efficient realization of the proposed conceptual model.
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  • 文章类型: Journal Article
    在大型河流中,较少研究多种环境因素对水质模式的影响。景观分析,多种统计方法,水质指数(WQI)用于检测中国最大河流的水质模式和影响因素,长江。与旱季相比,雨季总磷(TP)明显较高,化学需氧量(COD),总悬浮固体(TSS),和浊度(TUR)。WQI在雨季和旱季显示“中等”和“良好”水质,分别。与其他网站相比,三峡大坝下游的上游地区TP较低,TN,两个季节的TSS和TUR,在潮湿和干燥季节,水温越来越高,分别。水质模式主要由土地利用的异质性驱动(即,湿地,农田,和城市土地),水文学(即,水流,水位),和气候(即,降雨,空气温度)。雨季的水质主要由土地利用驱动,而旱季主要由土地利用和水文学的联合影响驱动。大型流域管理的决策者和监管者可能需要制定计划,考虑到人为和自然驱动因素对水质保护的影响。
    Influences of multiple environmental factors on water quality patterns is less studied in large rivers. Landscape analysis, multiple statistical methods, and the water quality index (WQI) were used to detect water quality patterns and influencing factors in China\'s largest river, the Yangtze River. Compared with the dry season, the wet season had significantly higher total phosphorus (TP), chemical oxygen demand (COD), total suspended solids (TSS), and turbidity (TUR). The WQI indicated \"Moderate\" and \"Good\" water quality in the wet and dry seasons, respectively. Compared with other sites, the upper reach sites that immediately downstream of the Three Gorges Dam had lower TP, TN, TSS and TUR in both seasons, and had lower and higher water temperature in the wet and dry seasons, respectively. Water quality patterns were mainly driven by heterogeneity in land use (i.e., wetland, cropland, and urban land), hydrology (i.e., water flow, water level), and climate (i.e., rainfall, air temperature). Water quality in the wet season was primarily driven by land use while the joint effect of land use and hydrology primarily drove in the dry season. Decision-makers and regulators of large river basin management may need to develop programs that consider influences from both human and natural drivers for water quality conservation.
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  • 文章类型: Journal Article
    大型河流的水文和泥沙过程在维持水生和沿海生态系统以及促进人类系统的文明和生产方面发挥着重要作用。因此,定量分析大型河流中水和沉积物排放的时空变化和动态,对于改善河流周边地区的流域管理和可持续发展至关重要,尤其是黄河,这是世界上沉积物含量最高的河流之一。在这项研究中,分析了1951-2020年黄河水沙排放的演变规律和空间来源,确定了不同因素对水沙排放变化的影响。结果表明:近70年来,年排水量和排沙量显著下降(p<0.05),1986年发生了突然的变化。第一个主要的排水周期大约是29年,而泥沙排放的第一个主要周期约为28年。就水和沉积物的排放源而言,影响排水量变化的主要因素是1951年至2020年的调水,而影响排沙量变化的主要因素是1951年至1985年的泥沙聚集,1986年至2020年变为支流泥沙。此外,水和泥沙排放变化也受到人为活动的影响,例如水和沉积物的转移,水坝和水库,和水土保持措施。特别是,随着时间的推移,既定的水土保持措施的水和沉积物截留能力逐渐饱和。具体来说,目前水土保持措施的最大截水和泥沙能力为122亿m3和1.9Gt,分别。总的来说,本研究的结果可以帮助将来制定水和沉积物的调节对策。
    The hydrology and sediment processes in large rivers play important roles in maintaining aquatic and coastal ecosystems and advancing civilization and production in human systems. Therefore, quantitatively analyzing the spatiotemporal variability and dynamics of water and sediment discharge in large rivers is essential for improving watershed management and sustainable development in the areas surrounding rivers, especially the Yellow River, which is one of the most sediment-laden rivers in the world. In this study, we analyzed the evolution patterns and spatial sources of water and sediment discharge in the Yellow River from 1951 to 2020 and determined the impacts of different factors on water and sediment discharge variations. The results showed that the annual water and sediment discharge significantly decreased (p < 0.05) over the past 70 years, with an abrupt change occurring in 1986. The first dominant periodicity of water discharge was approximately 29 years, while the first dominant periodicity of sediment discharge was approximately 28 years. In terms of the water and sediment discharge sources, the dominant factor affecting variations in water discharge was water diversion from 1951 to 2020, while the dominant factor affecting variations in sediment discharge was sediment aggradation from 1951 to 1985 and changed to tributary inflow sediment from 1986 to 2020. In addition, the water and sediment discharge changes were also affected by anthropogenic activities, such as water and sediment diversions, dams and reservoirs, and water and soil conservation measures. In particular, the water and sediment interception capabilities of the established soil and water conservation measures gradually became saturated over time. Specifically, the maximum water and sediment interception capabilities of the current soil and water conservation measures were 12.2 billion m3 and 1.9 Gt, respectively. Overall, the results of the present study can help tailor water and sediment regulation countermeasures in the future.
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  • 文章类型: Journal Article
    Recent studies suggest that climate change, with warmer water temperatures and lower and longer low flows, may enhance harmful planktic cyanobacterial growth in lakes and large rivers. Concomitantly, controlling nutrient loadings has proven effective in reducing phytoplankton biomass especially in North America and Western Europe. In addition, the impact of invasive benthic filter-feeder species such as Corbicula on phytoplankton has largely been overlooked in large rivers, leading to even more uncertainty in predicting future trajectories in river water quality. To investigate how nutrient control, climate change and invasion of benthic filter-feeders may affect phytoplankton biomass and composition, we assembled a large database on the entire water course of the River Loire (France) over three decades (1991-2019). We focus on cyanobacteria to provide an in-depth analysis of the 30-year trend and insights on future possible trajectories. Since 1991, total phytoplankton and cyanobacteria biomasses have decreased 10-fold despite warmer water temperature (+0.23 °C·decade-1) and lower summer flow (-0.25 L·s-1·km-2·decade-1). In the long-term, the contribution of planktic cyanobacteria to total biomass was on average 2.8%. The main factors driving total phytoplankton and cyanobacteria biomasses were total phosphorus (4-fold decrease), the abundance of Corbicula clams (from absence before 1998 to 250-1250 individuals·m-2 after 2010), the duration of summer low flows and the intensity of summer heatwaves. The River Loire constitutes an example in Europe of how nutrient control can be an efficient mitigation strategy, counteracting already visible effects of climate change on the thermal regime and flow pattern of the river. This may hold true under future conditions, but further work is needed to account for the climate trajectory, land and water use scenarios, the risk of enhanced benthic biofilm and macrophyte proliferation, together with the spread of invasive filter-feeding bivalves.
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  • 文章类型: Journal Article
    Reduced body size is among the universal ecological responses to global warming. Our knowledge on how altered body size affects ecosystem functioning in ectothermic aquatic organisms is still limited. We analysed trends in the cell size structure of phytoplankton in the middle Danube River over a 34-year period at multiple levels: (1) average cell size of assemblages (ACS), (2) within the centric diatom community and (3) in the dominant centric diatom taxon: Stephanodiscus. We asked whether global warming and human impacts affected the average cell size of phytoplankton. Also, whether the altered size structure affected how chlorophyll-a, as an ecosystem functioning measure, relates to the ACS of phytoplankton. The cell size of phytoplankton decreased significantly at all organisation levels, and the assemblages became more dispersed in cell size over time. Environmental variables related to global warming and human impacts affected the ACS of phytoplankton significantly. The relationship between chlorophyll-a and the ACS of phytoplankton shifted from negative linear to broad and then narrow hump shape over time. Longer water residence time, warming and decline in nutrients and suspended solids decrease the ACS of phytoplankton in the middle Danube and expectedly in other large rivers. Our results suggest that cell size decrease in phytoplankton, especially of centric diatoms, constrains planktic algal biomass production in large rivers, independently of algal density. Such cell size decrease may also affect higher trophic levels and enhance the more frequent occurrence of \"clear-water\" plankton in large, human-impacted rivers under global change.
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  • 文章类型: Journal Article
    目的:2019年7月和8月在印第安纳州的WabashRiver和WhiteRiver,目的是确认历史物种种群的持续存在,并发现以前没有记录的种群。
    方法:Ephoron专辑(Say)(多翅目)的值得注意的新数据,伊顿(Eaton)(Heptageniidae),锥藻(沃尔什)(Palingeniidae),据报道,Tortopsisprimus(McDunnough)(Polymitarcyidae)。
    OBJECTIVE: Mayflies (Insecta: Ephemeroptera) were collected from the Ohio River, Wabash River and White River in Indiana during July and August 2019, with the goals of confirming the continued existence of historic populations of species and discovering previously undocumented populations.
    METHODS: Notable new data for Ephoron album (Say) (Polymitarcyidae), Heptagenia elegantula (Eaton) (Heptageniidae), Pentagenia vittigera (Walsh) (Palingeniidae), and Tortopsis primus (McDunnough) (Polymitarcyidae) are reported.
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  • 文章类型: Journal Article
    Large floodplain rivers (LFRs) are among the most threatened ecosystems on Earth and their utilization is expected to grow. Therefore, the need to develop more effective spatial prioritization tools to maintain their multifunctionality becomes increasingly important. We present a novel approach to land use design and conservation planning of LFRs and demonstrate its applicability using a case study for the Danube River, Central-Europe. Specifically, we use indicators of habitat naturalness and complexity to define four main land use functions for LFRs: (1) relatively intact areas with high habitat complexity, which are of high priority for conservation (C), (2) degraded and simplified areas, which are not suited for conservation, but for human utilization (HU), (3) relatively natural areas with low habitat complexity, which are suited both for conservation and for sustainable use of goods and services (LS), (4) degraded areas with relatively high habitat complexity potential, which should be used for rehabilitation (R). While C and HU spare land primarily for conservation and for human utilization, respectively, categories LS and R share land both for biodiversity conservation and for human use and well-being. Results of the case study show that the different land use functions did not clearly separate spatially along the evaluated segment, but distributed relatively equally. Area weighted indices highlighted the importance of large floodplains, while non-weighted indices indicated the importance of many smaller segments with narrow floodplain riparian zone, which can still be important for conservation or rehabilitation purposes. Our multiscale analysis revealed how land use categorizations depend on index use, index weightings and spatial resolution of land use function maps, which should be considered by management. The suggested methodology provides a transparent framework to any stakeholder groups on how to plan out management actions in the context of land conservation and ecosystem services delivery of LFRs.
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