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1.
Feeding interactions among functional feeding groups (FFGs) of macroinvertebrates are robust indicators of aquatic ecosystem interactions. They provide information regarding organic matter processing, habitat condition and trophic dynamics. In tropical rivers with pronounced wet and dry seasons, macroinvertebrate based ecological monitoring tools are explicitly focused on metrics and indices, while ignoring interactions of FFGs. Therefore, the objective of this study was to investigate the functional feeding type metrics, diversity indices and feeding interactions among FFGs of macroinvertebrates along the water pollution gradient in Gilgel Gibe watershed, Ethiopia. Water quality parameters and macroinvertebrate community attributes were assessed for samples collected from upstream sites (15 sites), urban-impacted stretches (12 sites) and wetland-affected river zones (7 sites) of the watershed during the rainy (July) and dry (February) seasons. To understand the effect of pollution on the feeding interactions, stable carbon and nitrogen isotopes were analyzed. Macroinvertebrate-based diversity indices and functional feeding type metric showed deterioration of ecological integrity at the urban-impacted sites and substantial recovery in the wetland-affected downstream sites. Omnivorous feeding behavior of macroinvertebrates was noted for the upstream sites, whereas clear trophic guilds of FFGs were suggested for the wetland-affected river zones by the stable isotope results. The results of pollution gradient analysis and feeding interactions among FFGs revealed that the urban-impacted sites showed weaker interactions when compared to upstream and wetland influenced sites. This affirms the potential importance of feeding interactions among FFGs of macroinvertebrates in water quality monitoring.  相似文献   

2.
Although a large number of recent ecological studies have focused on freshwater bacterioplankton populations, knowledge of the primary factors influencing bacterial communities in urban rivers is limited. Bacterial community structure in three rivers located in Shanghai city was studied over a 1-year period using denaturing gradient gel electrophoresis (DGGE). Subsurface samples were collected every 2 months from two study sites in each river. Water was characterized when biological samples were collected by measuring temperature, pH, chloride ion, total dissolved solids (TDS), total N and total P. complex DGGE band patterns indicated high bacterial diversity in the rivers. Analysis of similarity (ANOSIM) showed that variation of the bacterial communities was higher between rivers than it was between samples from the same river. When evaluated using principal component analysis, samples collected during warmer months from any particular river tended to group together while cold-season samples generally clustered, suggesting significant seasonal impacts. Redundancy analysis was used to identify relationships between environmental factors and bacterial community composition in each individual river. Temperature, TDS, pH, TP and salt concentration were all identified as being related to bacterial community structure, with temperature being the most influential parameter in all three rivers. Our results indicated that bacterial community composition was different in the three different rivers. Even though the rivers were located in heavily disturbed urban ecosystems, temperature was the major driver of bacterial community composition, just as it is in natural systems.  相似文献   

3.
Surface water oxygen and hydrogen isotopic values are commonly used as proxies of precipitation isotopic values to track modern hydrologic processes while proxies of water isotopic values preserved in lake and river sediments are used for paleoclimate and paleoaltimetry studies. Previous work has been able to explain variability in USA river‐water and meteoric‐precipitation oxygen isotope variability with geographic variables. These studies show that in the western United States, river‐water isotopic values are depleted relative to precipitation values. In comparison, the controls on lake‐water isotopic values are not well constrained. It has been documented that western United States lake‐water input values, unlike river water, reflect the monthly weighted mean isotopic value of precipitation. To understand the differing controls on lake‐ and river‐water isotopic values in the western United States, we examine the seasonal distribution of precipitation, evaporation and snowmelt across a range of seasonality regimes. We generate new predictive equations based on easily measured factors for western United States lake‐water, which are able to explain 69–63% of the variability in lake‐water hydrogen and oxygen isotopic values. In addition to the geographic factors that can explain river and precipitation values, lake‐water isotopic values need factors related to local hydrologic and climatic characteristics to explain variability. Study results suggest that the spring snowmelt runs off the landscape via rivers and streams, depleting river and stream‐water isotopic values. By contrast, lakes receive seasonal contributions of precipitation in proportion to the seasonal fraction of total annual precipitation within their watershed. Climate change may alter the ratio of snow to rain fall, affecting water resource partitioning between rivers and lakes and by implication of groundwater. Paleolimnological studies must account for the multiple drivers of water isotopic values; likewise, studies based on the isotopic composition of fossil material need to distinguish between species that are associated with rivers versus lakes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

4.
A central aspect of the Water Framework Directive 2000/60/EC addressed to Member Countries is to proceed to type-specific ecological assessment and classification by establishing typology systems. Sixty-four permanent stream sites distributed throughout mainland Greece and islands were assessed with macroinvertebrate indicators to evaluate their ecological quality. Local and catchment scale parameters were determined and recorded to obtain an integrated assessment of the main factors affecting stream integrity and macroinvertebrate communities. Twenty-three sites were classified as reference or good status in terms of biological, chemical and hydromorphological quality with the use of various metrics. Multivariate statistical techniques were performed (MDS, BIOENV, correlation analysis and PCA) to investigate the main environmental factors structuring benthic macroinvertebrate communities and to select candidate environmental variables for establishing a biotic typology for Hellenic rivers. The results revealed relatively distinct macroinvertebrate communities within defined abiotic zones of the country. Assemblages of macroinvertebrate fauna were most strongly associated to differences in geographical position, altitude, slope, catchment area, current velocity, conductivity and water temperature. In view of the lack of sufficient data at the country level on the three last variables and after considering cause-effect relationships between large scale variables and the latter, it has been demonstrated that a number of catchment scale variables could be used as robust surrogates.  相似文献   

5.
生物多样性的形成与维持(即群落构建)一直是生态学研究的重要论题。有关亚热带季风区大型河流生物多样性格局及维持机制的认识仍十分有限。以汉江上游(南水北调中线水源地)为研究区域,以大型无脊椎动物为研究对象,系统开展群落多样性时空格局及其维持机制的研究。于2015—2017年间共采集到大型无脊椎动物333个分类单元,隶属6门10纲25目110科279属,包括水生昆虫278种(83.5%),环节动物门25种(7.5%),软体动物门19种(5.7%),软甲纲7种以及其它动物4种。物种多样性在时间和空间尺度上差异显著:时间上,春季物种数最多(227种),夏季(140种)、秋季(141种)和冬季(144种)较少;空间上,自然河流金水河物种数最多(179种),而金钱河(163种)、月河(149种)、淇河(140种)和泗河(112种)等人类干扰河流相对较少。db-RDA分析表明,尽管不同季节所筛选出的关键因子有所差异,但环境因子和空间因子均显著影响着大型无脊椎动物的群落结构。变差分解分析显示,环境过滤是流域内大型无脊椎动物群落多样性维持的主导因素,而空间过程(扩散限制)则起着次要的作用。本研究对南水北调...  相似文献   

6.
大型底栖动物群落结构与水环境因子具有较强的响应关系,为了量化分析大型底栖动物群落水环境因子适宜状态以及响应关系,在太子河进行3次流域水生态调查,共获得136个站位的生态数据,通过筛选得到水环境驱动因子,并利用加权平均回归分析和临界点指示类群分析的方法,探究大型底栖动物群落物种、不同多样性水平以及功能摄食类群水环境驱动因子的最适值和阈值.结果显示,显著影响大型底栖动物群落结构的水环境因子是溶解氧、电导率、总氮.大型底栖动物敏感种的溶解氧最适值较高,耐污种较低;敏感种的电导率和总氮最适值较低,耐污种较高;大型底栖动物群落多样性水平Shannon-Wiener指数(0-1]区间的溶解氧最适值最低,(3-4]区间的溶解氧最适值最高,各Shannon-Wiener指数区间电导率和总氮最适值排序为:(0-1]区间(1-2]区间(2-3]区间(3-4]区间;在5个功能摄食类群中溶解氧最适值最高和最低分别为撕食者和直接收集者,电导率最适值最高和最低分别为直接收集者和过滤收集者,总氮最适值最高和最低分别为直接收集者和刮食者.大型底栖动物敏感种的溶解氧阈值高于耐污种类群与其他物种,而敏感种的电导率和总氮阈值低于耐污种和其他物种;大型底栖动物群落多样性水平Shannon-Wiener指数(0-1]区间与溶解氧阈值呈负响应关系,而与电导率和总氮阈值呈正响应关系,(1-2]区间、(2-3]区间、(3-4]区间与溶解氧阈值呈正响应关系,而与电导率和总氮阈值呈负响应关系;溶解氧指示的大型底栖动物功能摄食类群为撕食者,且呈正响应关系,而电导率和总氮指示的功能摄食类群都包括过滤收集者、刮食者、撕食者,且呈负响应关系,其中刮食者的电导率和总氮阈值均最高.研究表明,通过分析大型底栖动物群落水环境因子的最适值和阈值,能以数据的形式量化反映大型底栖动物群落与河流水环境因子的响应关系,对河流生态环境的保护和修复具有重要的指导意义.  相似文献   

7.
Algal assemblages have been widely used as an ecological indicator of aquatic ecosystem health conditions because of their specific sensitivity to a wide variety of environmental conditions. In turbid rivers, as in other aquatic systems, phytoplankton structure plays an important role in structuring aquatic food webs. Worldwide, phytoplankton is less studied in turbid, large tropical rivers compared to temperate river systems. The present study aimed to describe the phytoplankton diversity and abundance in a turbid tropical river (the Red River, northern part of Vietnam from 20°00 to 25°30 North; from 100°00 to 107°10 East) and to determine the importance of a series of environmental variables in controlling the phytoplankton community composition. Phytoplankton community was composed of 169 phytoplankton taxa from six algal groups including Bacillariophyceae, Chlorophyceae, Cryptophyceae, Euglenophyceae, Dinophyceae and Cyanobacteria. Community composition varied both spatially and with season. Sixteen measurement environmental variables were used as input variables for a three-layer backpropagation neural network that was developed to predict the phytoplankton abundance. Phytoplankton abundance was successfully predicted using the tagsig transfer function and the Levenberg-Marquardt backpropagation algorithm. The network was trained to provide a good overall linear fit to the total data set with a slope (R) and mean square error (MSE) of 0.808 and 0.0107, respectively. The sensitivity analysis and neutral interpretation diagram revealed that total phosphorus (TP), flow discharge, water temperature and P-PO43− were the significant variables. The results showed that the developed ANN model was able to simulate phytoplankton abundance in the Red River. These findings can help for gaining insight into and the relationship between phytoplankton and environmental factors in this complex, turbid, tropical river.  相似文献   

8.
The ecological condition and biodiversity values of floodplain wetlands are highly dependent on the hydrological connectivity of wetlands to adjacent rivers. This paper describes a method for quantifying connectivity between floodplain wetlands and the main rivers in a wet tropical catchment of northern Australia. We used a one‐dimensional hydrodynamic model to simulate time‐varying water depths across the stream network (i.e. rivers, streams and man‐made drains). The timing and duration of connectivity of seven wetlands (four natural and three artificial) with the two main rivers in the catchment were then calculated for different hydrological conditions. Location and areal extent of the wetlands and the stream network were identified using high‐resolution laser altimetry, and these data formed key inputs to the hydrodynamic model. The model was calibrated using measured water depths and discharges across the floodplain. An algorithm was developed to identify contiguous water bodies at daily time steps, and this gave the temporal history of connection and disconnection between wetlands and the rivers. Simulation results show that connectivity of individual wetlands to both rivers varies from 26 to 365 days during an average hydrological condition. Location, especially proximity to a main river, and wetland type (natural stream or artificial drain) were identified as key factors influencing these levels of connectivity. Some natural wetlands maintain connection with the river for most or all of the year, whereas the connectivity of some artificial wetlands varies from 26 to 36 days according to their patterns of network connection to adjacent rivers – a result that has important implications for the accessibility of these types of wetland to aquatic biota. Using readily available river gauge data, we also show how connectivity modelling can be used to identify periods when connectivity has fallen below critical thresholds for fish movement. These connectivity patterns within the floodplain network are central to the setting of river flows that will meet environmental requirements for biota that use floodplain wetlands during their life history. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

9.
Matthias Brunke   《Limnologica》2004,34(4):460-478
The objective of this paper is twofold: 1) to validate the German stream typology for Schleswig-Holstein, and 2) to develop an assessment system for lake outlets. The German stream typology, based on a top-down analysis of geomorphological variables, was validated using biotic data of streams in Schleswig-Holstein, northern Germany. A null model analysis was conducted to test for differences between seven stream types (sand streams and rivers, gravel streams and rivers, partly-mineralic streams, limnic marsh streams, and lake outlets). The dataset compiled for the statistical analysis comprised 28 streams, 65 different sampling sites, 428 samples, and 296 taxa. The analysis confirmed all stream type except partly-mineralic streams, which showed faunal overlap with all types except gravel streams. Gravel streams were the most distinctive stream type. Lake outlets were shown to be a unique type, having a distinct macroinvertebrate fauna. Furthermore it was shown, that the species composition differed between lentic and lotic outlets. Canonical correspondence analysis of 19 investigated lake outlets revealed that characteristics of the lakes had only a minor effect on macroinvertebrate community structure.

The developed assessment system of lake outlets was based on the habitat association of 132 macroinvertebrate taxa. Taxa were allotted to five categories of lake outlet preferences depending on the results from ordinations, frequency tables and abundance distributions. A qualitative and a quantitative lake outlet index (LTI) were tested with independent data sets. The quantitative LTIquan proved to be more robust and only slightly affected by seasonal changes in the macroinvertebrate community composition. Assessments of lake outlets based on macroinvertebrates should be conducted in spring and autumn to reduce the risk of misclassifications, in particular, for boundary cases rated between good and moderate quality classes.  相似文献   


10.
Fast economic growth of a country contributes to the increase of activities that can also bring negative impacts on the rivers. Contamination of rivers, sedimentation, coastal erosion, decrease of aquatic life, and also flooding are some of these universal impacts. There are several rivers around the world, which are categorized as very polluted and require cleaning‐up operations. Several factors have been identified to be influencing factors in the success or otherwise of the implementation and operation of these projects. This study examined the factors related to the steps taken to clean‐up and rehabilitate these rivers and deduce by utilizing factor analysis the most critical success factors from the results obtained. A responsible river community is by far the most effective way to keep a river basin clean. Very often, however, cleaning‐up operations are necessary to revive and maintain the quality of the river so that it can be save to use as an important source of water for human consumption. It was found that community awareness was the most critical cluster of factors determining the success of the clean‐up work.  相似文献   

11.
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12.
保安湖是江汉湖群的一个典型浅水湖泊。近几十年来,随着经济的快速发展,保安湖面临多重人类压力影响,富营养化问题日趋严重。历史上曾开展过数次的保安湖底栖动物调查,但有关群落结构的长期变化及其驱动机制改变的认知仍为空白。本研究基于30余年（1986 2019）的多次调查数据,探索保安湖底栖动物的群落演变规律及其群落构建机制。研究共记录保安湖底栖动物5门10纲25目49科110属170种（历史记录154种,现场调查51种）。总物种数由1992年的107种降为2019年的51种;平均密度由1992年的433 ind．/m2增加到2019年的2177.6 ind．/m2;平均生物量由2001年的160.6 g/m2降低为2019年的26.7 g/m2。优势种在1987年有寡毛类、水生昆虫和软体动物多个类群,其后逐步演变为现阶段少数几种耐污的寡毛类和摇蚊类,如霍甫水丝蚓（Limnodrilus hoffmeisteri）、中国长足摇蚊（Tanypus chinensis）、红裸须摇蚊（Propsilocerus akamusi）等,而多年生大型软体动物衰退明显。PERMANOVA和SIMPER分析结...  相似文献   

13.
Lateral inflows control the spatial distribution of river discharge, and understanding their patterns is fundamental for accurately modelling instream flows and travel time distributions necessary for evaluating impacts of climate change on aquatic habitat suitability, river energy budgets, and fate of dissolved organic carbon. Yet, little is known about the spatial distribution of lateral inflows in Arctic rivers given the lack of gauging stations. With a network of stream gauging and meteorological stations within the Kuparuk River watershed in northern Alaska, we estimated precipitation and lateral inflows for nine subcatchments from 1 July to 4 August,2013, 2014, and 2015. Total precipitation, lateral inflows, runoff ratios (area-normalized lateral inflow divided by precipitation), percent contribution to total basin discharge, and lateral inflow per river kilometre were estimated for each watershed for relatively dry, moderate, or wet summers. The results show substantial variability between years and subcatchments. Total basin lateral inflow depths ranged 24-fold in response to a threefold change in rainfall between dry and wet years, whereas within-basin lateral inflows varied fivefold from the coastal plain to the foothills. General spatial trends in lateral inflows were consistent with previous studies and mean summer precipitation patterns. However, the spatially distributed nature of these estimates revealed that reaches in the vicinity of a spring-fed surficial ice feature do not follow general spatial trends and that the coastal plain, which is typically considered to produce minimal runoff, showed potential to contribute to total river discharge. These findings are used to provide a spatially distributed understanding of lateral inflows and identify watershed characteristics that influence hydrologic responses.  相似文献   

14.
The Dissolved Organic Carbon (DOC) content of rivers is the most significant part of the carbon cycle migration in the basin under consideration, and it is the basis for a comprehensive understanding of the regional carbon cycle. In this study, we periodically collected samples from four monitoring stations in the Xiying River Basin of the Qilian Mountains in the northern Qinghai-Tibet Plateau. We calculated the fluxes of organic carbon in the rivers within the study area and have discussed the influencing factors of DOC concentration in these rivers. The results showed that: (a) The DOC concentration and transport flux of the Xiying river showed significant seasonal changes. The DOC concentration during summer and autumn was higher than that in winter and spring, and the output flux in summer and autumn accounted for approximately 88.3% of the total annual output. (b) Precipitation runoff has a higher DOC concentration than meltwater runoff. Climate factors, river-water chemical characteristics, and seasonal frozen-soil changes in the river basin have significant effects on the river DOC concentration and transport flux. (c) Larger runoff causes higher DOC concentrations in rivers. Runoff is the primary means of carbon migration in the inland river basin. Carbon migration is significant from the upstream to the middle and downstream sections of the inland river basin.  相似文献   

15.
Watershed delineation is a required step when conducting any spatially distributed hydrological modelling. Automated approaches are often proposed to delineate a watershed based on a river network extracted from the digital elevation model (DEM) using the deterministic eight‐neighbour (D8) method. However, a realistic river network cannot be derived from conventional DEM processing methods for a large flat area with a complex network of rivers, lakes, reservoirs, and polders, referred to as a plain river network region (PRNR). In this study, a new approach, which uses both hydrographic features and DEM, has been developed to address the problems of watershed delineation in PRNR. It extracts the river nodes and determines the flow directions of the river network based on a vector‐based hydrographic feature data model. The river network, lakes, reservoirs, and polders are then used to modify the flow directions of grid cells determined by D8 approach. The watershed is eventually delineated into four types of catchments including lakes, reservoirs, polders, and overland catchments based on the flow direction matrix and the location of river nodes. Multiple flow directions of grid cells are represented using a multi‐direction encoding method, and multiple outflows of catchments are also reflected in the topology of catchments. The proposed approach is applied to the western Taihu watershed in China. Comparisons between the results obtained from the D8 approach, the ‘stream burning’ approach, and those from the proposed approach clearly demonstrate an improvement of the new approach over the conventional approaches. This approach will benefit the development of distributed hydrological models in PRNR for the consideration of different types and multiple inlets and outlets of catchments. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
Coral community structure is often governed by a suite of processes that are becoming increasingly influenced by land-use changes and related terrestrial discharges. We studied sites along a watershed gradient to examine both the physical environment and the associated biological communities. Transplanted corals showed no differences in growth rates and mortality along the watershed gradient. However, coral cover, coral richness, and coral colony density increased with increasing distance from the mouth of the bay. There was a negative relationship between coral cover and mean suspended solids concentration. Negative relationships were also found between terrigenous sedimentation rates and the richness of adult and juvenile corals. These results have major implications not only for Pacific islands but for all countries with reef systems downstream of rivers. Land development very often leads to increases in river runoff and suspended solids concentrations that reduce coral cover and coral diversity on adjacent reefs.  相似文献   

17.
The links between flood frequency and rates of channel migration are poorly defined in the ephemeral rivers typical of arid regions. Exploring these links in desert fluvial landscapes would augment our understanding of watershed biogeochemistry and river morphogenesis on early Earth (i.e. prior to the greening of landmasses). Accordingly, we analyse the Mojave River (California), one of the largest watercourses in the Great Basin of the western United States. We integrate discharge records with channel-migration rates derived from dynamic time-warping analysis and chronologically calibrated subsidence rates, thereby constraining the river's formative conditions. Our results reveal a slight downstream decrease in bankfull discharge on the Mojave River, rather than the downstream increase typically exhibited by perennial streams. Yet, the number of days per year during which the channel experiences bankfull or higher stages is roughly maintained along the river's length. Analysis of historical peak flood records suggests that the incidence of channel-formative events responds to modulation in watershed runoff due to the precipitation in the river's headwaters over decades to centuries. Our integrated analysis finally suggests that, while maintaining hydraulic geometries that are fully comparable with many other rivers worldwide, ephemeral desert rivers akin to the Mojave are capable of generating a surprisingly wide range of depositional geometries in the stratigraphic record. © 2020 John Wiley & Sons, Ltd.  相似文献   

18.
Using quantitative geomorphic factors for regional active tectonic evolution is becoming more and more popular. Qilian Mountains-Hexi Corridor which locates in the northern edge of Qinghai-Tibet plateau is the most leading edge of the plateau's northward extension. The uplift rate of all segments and the intensity of influence from tectonic activity are the important evidences to understand the uplift and extension of the plateau. Heihe River Basin is located at the northern piedmont of the western segment of Qilian Mountains, the development of the rivers is influenced by the tectonic activity of the Qilian Mountains, and the unique river morphology is important carriers of the regional tectonic uplift. Geomorphologic indexes such as hypsometric integral, geomorphologic comentropy and river longitudinal profiles were extracted by GIS tools with free access to the Shuttle Radar Topography Mission(SRTM)DEMs, and according to the different expression of the geomorphological indexes in the Heihe River Basin, we divided the drainage basin into two parts and further compared them to each other. Recent studies reveal that obvious differences exist in the landscape factors(hypsometric integral, geomorphology entropy and river profiles)in the east and west part of the Heihe Basin. The structural intensity of the west part is stronger than that of the east, for example, in areas above the main planation surface on the western part, the average HI value is 0.337 8, and on the eastern part the HI value is 0.355. Accordingly, areas under the main planation surface are just on the contrary, indicating different structural strength on both sides. Similar phenomenon exists in the whole drainage basins. Furthermore, by comparing the fitting river profiles with the real river profiles, differential uplift is derived, which indicates a difference between west and east(with 754m on the western part and 219m on the east). Comprehensive comparison and analysis show that the lithologic factors and precipitation conditions are less influencing on the geomorphic factors of the study area, and the tectonic activities, indicated by field investigation and GPS inversion, are the most important element for geomorphic evolution and development. The variation of the geomorphologic indexes indicates different tectonic strength derived from regional structures of the Qilian Shan.  相似文献   

19.
lINTRoDUCTIONAbroadobjectiveofcooperativeresearchattheNorthwestWatershedResearchCenterandEco-HydraulicsResearchGroupistodevelopdetailedunderstandingofthetemporalandspatialvariabilityofstreamflow,sedimentandwaterquaIityconstituentsinacontinuumfromheadwatersthroughestuaries.Thispaperpresentsselectedaspectsofourongoingresearch,focusedonstreamsystemsinsemi-arid,uplandrangelandwatersheds.Publicawarenessoftheroleofriversinregionalecologicalsystems,andconcernforpreserving,enhancingandrestorin…  相似文献   

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