三峡库区不同水文类型支流大型底栖动物对蓄水的响应

为探究三峡水库修建对库区不同水文类型支流大型底栖动物的影响,于2015年7月和2016年1月对三峡水库四条支流的大型底栖动物进行调研,分别对周期性受蓄水影响支流的非回水区与回水区和长期受蓄水影响支流的非回水区与回水区大型底栖动物群落结构进行比较研究,结果表明:⑴7月份三峡水库145米低水位时期共采集到底栖动物655头计59种(属),在受蓄水影响河段采集到底栖动物4种共40头,优势种为日本沼虾(占受蓄水影响区域的57.5%); 1月份三峡水库175米蓄水时期共采集到底栖动物1123头计69种(属),在受蓄水影响河段采集到16种238头,优势种为锯齿新米虾(占受蓄水影响区域的14.2%)。⑵周期性受蓄水影响支流的非回水区与回水区底栖动物密度、生物量和多样性指数无显著差异(P0.05);长期受蓄水影响支流的非回水区与回水区之间底栖动物密度和Pielou均匀度指数无显著差异(P0.05),但非回水区底栖动物生物量显著高于回水区(P0.05),底栖动物多样性和丰富度极显著高于回水区(P0.01)。⑶7月份影响底栖动物分布的主要环境因子共6个,分别是水深、流速、硝态氮、溶解氧、水温和电导率; 1月份影响底栖动物分布的主要环境因子共7个,分别是水温、溶解氧、总磷、流速、深度、电导率和透明度。     

Analysis of temperature variation characteristics in the three gorges reservoir area after impoundment of the three gorges dam

The construction of the Three Gorges Dam (TGD) at the end of the upper reach of the Yangtze River results in a great belt-shape of the Three Gorges Reservoir (TGR) in China. Thus the atmospheric problems related to the TGR have attracted substantial interest from most meteorologists around the world. To understand the regional temperature changes in the TGR area since the impoundment of the TGD in June 2003, temperature data from 32 meteorological stations in the TGR area during 1961—2014 period were collected, and the trends in the temperature changes in the past 20 years, including years before and after impoundment of the TGD, were analysed by the methods of cumulative anomaly analysis, moving average, and linear regression analysis. The results showed that the annual mean temperature over the TGR area showed a slight overall upward trend in the past 54 years, and the temperature rose substantially at the period between 1985 and 2014. After impoundment, a warming trend was obvious in the TGR area. The monthly mean temperature after impoundment was higher than that before impoundment.     

Preliminary investigation on the changes in trophic structure and energy flow in the Yangtze estuary and adjacent coastal ecosystem due to the Three Gorges Reservoir

Water projects in the Yangtze River basin, especially the Three Gorges Reservoir (TGR), have strongly affected the biological and ecological integrity of the Yangtze estuary and adjacent coastal ecosystems. The Ecopath with Ecosim model was applied to study trophic structure and energy flow after the impoundment of TGR based on field surveys in 2006. The model results showed that the trophic levels ranged from 1.000 to 4.058; and 44% of the energy flows originated from the detritus food chain, while 56% originated from the grazing food chain in the trophic transfer process; the transfer efficiency of the ecosystem was 10.0%, and TPP/TR (Total Primary Production/Total Respiration) was 1.899. Compared with model results in 2000 (before impoundment of TGR), the trophic structure of the ecosystem did not exhibit substantial changes; however, the mean trophic level and catch amount decreased remarkably after impoundment. The estuary and adjacent coastal ecosystems were found to be more sensitive to external perturbations after impoundment.     

Linking life history strategies and historical baseline information shows effects of altered flow regimes and impoundments on freshwater mussel assemblages

1. Human impacts on aquatic ecosystems are causing shifts in the composition and distribution of species, leading to subsequent changes in community structure. However, these changes may not be fully realised because of inadequate baseline information. In Texas, such baseline information is generally lacking for cryptic aquatic species such as unionid mussels, which will be likely to impede identification of impacted populations, potential causal factors, and the setting or achieving of management goals.
2. The Navasota River, located in central Texas, is an exception, having been comprehensively surveyed more than 40 years ago, prior to large-scale impoundment of this system. Hierarchical cluster analysis, nonmetric multidimensional scaling, and fuzzy set ordination were performed to compare assemblage structure from the 1975 survey to that of a recent survey in 2016 at similar sampling locations.
3. Comparing sites based on the presence–absence of mussel species, we found no significant differences between the number of taxa and species present; however, we did find significant filtering of mussel life history strategies. Specifically, prior to impoundment, we found that mussel assemblages were filtered based on longitudinal patterns in life history strategy from taxa that are adapted to disturbed habitats to those favoured in more stable habitats with low environmental variation.
4. However, following large-scale impoundment after 1975, we saw a shift in the hydrologic regime towards consistent, homogenised flows and a shift in assemblage structure towards equilibrium species. This shift appears to represent a discontinuity, wherein river impoundment alters physical parameters of the hydrologic regime and these changes in turn modify biotic patterns and processes.
5. Our results provide another example of how large dams can restructure mussel assemblages, highlight the importance of incorporating reference or baseline conditions wherever possible when evaluating the conservation status of aquatic biota, and provide further evidence for the use of life history theory and the serial discontinuity concept in predicting the consequences of flow alteration and river impoundment.

     

Downstream fish assemblage response to river impoundment varies with degree of hydrologic alteration

River impoundments can fundamentally restructure downstream fish assemblages by altering flow regimes. However, the degree of alteration and associated ecological change may depend on pre-existing hydrologic regimes. We used long-term datasets to compare downstream hydrological and fish assemblage responses to impoundment in two catchments classified as having intermittent and perennial-flashy natural hydrologic regimes. We observed significant shifts in fish assemblage structure at both sites after stream impoundment. The historically intermittent stream shifted to a stable perennial flow regime. Changes in fish assemblage structure covaried with changes in five different components of the flow regime; most species that increased in abundance require fluvial habitats and likely benefited from increased flows during historically low flow seasons. Shifts in fish assemblage structure were also observed in the perennial stream, despite minimal flow alteration after impoundment; however, most species shifts were associated with lentic environments, and were more likely related to proximity of reservoirs in the drainage system rather than changes in stream flow. Findings from this study confirm that downstream fish assemblage response to river impoundment can be associated with high levels of hydrologic alteration, but other factors including expansion of lentic species into lotic environments also influence shifts in assemblage structure.     

Setting Goals and Measuring Success: Linking Patterns and Processes in Stream Restoration

The influences of productivity, vegetation coverage, and benthivorous fish abundance on macroinvertebrate abundance and mean size were examined in Midwestern USA impoundments. While impoundment productivity was not strongly related to total abundance and mean size of macroinvertebrates, it was related to specific taxa. As productivity increased, Ephemeroptera and Odonata abundance decreased and Diptera abundance increased. Despite the shift in taxonomic composition, mean individual size of the macroinvertebrate community varied little with changes in impoundment productivity. Relationships between macroinvertebrates and benthivorous fish were mixed. Macroinvertebrate abundance, especially Diptera, increased with increases in bluegill Lepomis macrochirus Rafinesque abundance and decreased with increases in channel catfish Ictalurus punctatus (Rafinesque) (which are stocked annually) abundance. Fish were not related to the mean size of macroinvertebrates. Macrophyte coverage was not related to macroinvertebrate abundance or mean size. Overall, macroinvertebrate abundance was mostly related to productivity and benthivorous fish in these impoundments. Mean size of macroinvertebrates did not differ with productivity, fish abundance, or macrophyte coverage.     

Influences of low-head dams on the fish assemblages in the headwater streams of the Qingyi watershed, China

The influences of low-head dams on the fish assemblages were examined in this study, using fish data collected in six treatment and five reference sites at three low-head dams in the headwater streams of the Qingyi watershed, China. Comparing with those in the reference sites, local habitat variables were significantly altered by low-head dams in the treatment sites, involving wider channel (only in the impoundment area), deeper water and slower flow. Fish species richness varied significantly across seasons, not across site categories, suggesting that these low-head dams did not alter species richness. However, significant decreases in fish abundance and density were observed in the impoundment areas immediately upstream of dams, but not in the plunge areas downstream. Fish assemblage structures kept relative stability across seasons, and their significant difference between-site was only observed between the impoundment areas and the sites far from dams upstream. This variation in assemblage structures was due to the differing relative abundance of some co-occurring species; more lentic but less lotic fish was observed in the impoundment areas. The spatial and temporal patterns of fish assemblages were correlated with local habitat in this study area. Wetted width had negative correlation with fish species richness, abundance and density, respectively. Water temperature also positively affected species richness. In addition, wetted width, water depth, current velocity and substrate were the important habitat variables influencing assemblage structures. Our results suggested that, by modifying local habitat characteristics, low-head dams altered fish abundance and density in the impoundment areas immediately upstream of dam, not in the plunge areas immediately downstream, and thereby influenced fish assemblage structures in these stream segments.     

Patterns of Fish Use and Piscivore Abundance within a Reconnected Saltmarsh Impoundment in the Northern Indian River Lagoon, Florida

Nearly all saltmarshes in east-central, Florida were impounded for mosquito control during the 1960s. The majority of these marshes have since been reconnected to the estuary by culverts, providing an opportunity to effectively measure exchange of aquatic organisms. A multi-gear approach was used monthly to simultaneously estimate fish standing stock (cast net), fish exchange with the estuary (culvert traps), and piscivore abundance (gill nets and bird counts) to document patterns of fish use in a reconnected saltmarsh impoundment. Changes in saltmarsh fish abundance, and exchange of fish with the estuary reflected the seasonal pattern of marsh flooding in the northern Indian River Lagoon system. During a 6-month period of marsh flooding, resident fish had continuous access to the marsh surface. Large piscivorous fish regularly entered the impoundment via creeks and ditches to prey upon small resident fish, and piscivorous birds aggregated following major fish movements to the marsh surface or to deep habitats. As water levels receded in winter, saltmarsh fish concentrated into deep habitats and emigration to the estuary ensued (200% greater biomass left the impoundment than entered). Fish abundance and community structure along the estuary shoreline (although fringed with marsh vegetation) were not analogous to marsh creeks and ditches. Perimeter ditches provided deep-water habitat for large estuarine predators, and shallow creeks served as an alternative habitat for resident fish when the marsh surface was dry. Use of the impoundment as nursery by transients was limited to Mugil cephalus Linnaeus, but large juvenile and adult piscivorous fish used the impoundment for feeding. In conclusion, the saltmarsh impoundment was a feeding site for piscivorous fish and birds, and functioned as a net exporter of forage fish to adjacent estuarine waters.     

三峡水库蓄水前后水生态系统动态的初步研究

本专辑登录的论文系中国科学院知识创新工程重要方向性项目“三峡水库库区蓄水前后水生态系统变化的研究”的部分研究结果,内容包括1)蓄水前后水体理化参数变化;2)蓄水前后水生生物群落变化;3)三峡水库的富营养化问题;4)春季水华暴发过程的连续监测与动力学;5)对三峡水库生态学研究的几点思考和建议。       

Impact of a dam on benthic macroinvertebrates in a small river in a biodiversity hotspot: Cape Floristic Region, South Africa

Suitable reservoirs and monitoring methods are needed to manage scarce water supplies in dry countries. We assessed here the impact on aquatic macroinvertebrates of the only dam on the Eerste River, which runs through the heart of a biodiversity hotspot, the Cape Floristic Region, South Africa. The dam and associated activities, were the only forms of disturbance in this otherwise pristine area. We sampled over 20,000 macroinvertebrate individuals and illustrated some categorical effects of the impoundment and its effects on macroinvertebrate assemblages. Macroinvertebrate species diversity below the dam was only half of that in the pristine catchment area above the dam. Furthermore, Ephemeroptera, Plecoptera and Trichoptera diversity and abundance dropped to almost zero as a result of the impoundment. In contrast, the abundance of the Diptera family Chironomidae increased substantially below the dam. These changes in macroinvertebrate diversity mirrored those recorded in biologically less diverse areas, but are of major concern in this biodiversity hotspot with its rich endemic fauna. We conclude that such an impoundment, while important for human welfare, results in a high price being paid in terms of loss of local biodiversity.     

Do rural impoundments in coastal Bay of Fundy,Canada sustain adequate habitat for wildlife?

In Canada and elsewhere in North America, impoundments are created in compensation for historic wetland loss and for habitat loss due to development projects, but these new sites are infrequently evaluated to determine how effectively they function. The Cumberland Marsh Region (CMR), located at the head of the Bay of Fundy, Canada, is of importance to migratory birds and has been subject to 300+ years of anthropogenic alteration, including impoundment creation on diked and drained tidal marsh in the last five decades. Wetland managers have noticed a pervasive decline in impoundment productivity leading to reduced waterbird usage (senescence). To understand factors that promote senescence, we analyzed abiotic and biotic proxies in sediment archives from six freshwater impoundments in two coastal watersheds to assess spatial trends across the CMR within recent decades. Our results demonstrate that impoundment productivity is driven by autochthonous nutrient sources (C/N between 7.7 and 14.4), but biogeochemical conditions can be highly variable among impoundments despite their proximity. Biogeochemical variation among top-of-core sediment samples from each impoundment was generally minimal, and thus we believe that the aging of impoundments has resulted in low productivity and organic matter accumulation due to dike stabilization and declines in nutrient loading. We conclude that these freshwater impoundments (in the CMR and likely other similar settings) are not highly productive, and may not provide abundant forage and optimal wildlife habitat which is expected of these systems; adaptive management strategies and hydrologic rehabilitation merit consideration to enhance ecological functioning. Understanding landscape attributes, hydrologic dynamics, and conditions prior to and after major human alterations should be a priority in future compensation projects.     

三峡水库175 m试验性蓄水期库区及其上游江段鱼类群落结构时空分布格局

根据2010—2012年在三峡水库及其上游江段5个江段的商业性渔获物调查结果,对该区域鱼类群落结构的时空分布格局进行了分析。调查中共收集到鱼类87种,隶属于8目18科63属。沿坝前江段溯河而上至库尾以上流水江段,鱼类种类数逐渐增加。采用聚类分析(CA)和非度量多维标度(NMDS)方法对三峡水库175 m试验性蓄水期间各江段的鱼类种类组成进行分析,发现这5个调查江段的鱼类种类组成可以分为两个类群:类群Ⅰ包括秭归、巫山、云阳3个库区的江段,其鱼类种类组成在各年间的差异程度较大;而类群Ⅱ包括库尾的涪陵江段以及上游的江津江段,其鱼类种类组成在各年间差异程度较小。采用CA和NMDS方法对鱼类群落结构时空分布格局的分析结果表明,5个调查江段的鱼类群落结构在各年间可以分为不同类群;云阳与涪陵江段的鱼类群落结构的相似性逐年增加,而与秭归、巫山江段的相似性逐年减少;涪陵江段与江津江段的鱼类群落结构相似性也呈逐年减少趋势。总体而言,175m试验性蓄水对库中和库尾江段的鱼类群落结构的影响较大,但对库首以及库尾以上流水江段的影响均较小。     

The effect of impoundment on the water chemistry of Lake Asejire, Nigeria

SUMMARY. Following the impoundment of the River Oshun to form Lake Asejire, Nigeria, in 1970, changes in the water chemistry were monitored. Chemical stratifications followed closely the pattern of thermal stratifications as the lake was chemically stratified from February to April and destratified from June to September and in January.     

The effect of the impoundment of Lake Kainji, Nigeria, on the indigenous species of mormyrid fishes

SUMMARY. Changes in the numbers and species composition of mormyrid fishes since the impoundment of the Niger (Lake Kainji) are analysed. An initial decline after impoundment appears to have been reversed and these fish are now increasing. The increase is, however, restricted to a few species only; many forms common in the river are still declining or have disappeared altogether. Marked seasonal variations in abundance are described and possible explanations discussed.     

Assessing the effect of the Three Gorges reservoir impoundment on spawning habitat suitability of Chinese sturgeon (Acipenser sinensis) in Yangtze River,China

The Chinese sturgeon (Acipenser sinensis), a kind of maricolous anadromous migratory fish species, is endangered and protected in China. Historical spawning habitats were distributed in the lower reaches of Jinsha River and the upper reaches of Yangtze River. Since the establishment of the Gezhouba water conservancy pivot in 1981, the migratory route of Chinese sturgeon spawning was blocked. Therefore, the fish was forced to propagate in a new spawning ground which was mainly distributed in the 4-km-long mainstream from Gezhouba Dam to Miaozui in the middle Yangtze River. After water storage and power generation of the Three Gorges reservoir (TGR) in 2003, the propagation of Chinese sturgeon has been impacted gradually. According to field surveys, the fish used to spawn twice a year before TGR impoundment, but only once happened after that. Besides, the spawning scale is also declining with each passing year.In order to simulate and evaluate the effect of TGR impoundment on spawning habitats of Chinese sturgeon, with consideration of their reproductive characteristics, an eco-hydrodynamic model was established by coupling a two-dimensional hydrodynamic model and a fuzzy fish habitat module based on fuzzy logic inference. Flow fields at the studied site in an impoundment scenario and an assumed no impoundment scenario were simulated with the 2D hydrodynamic model. Afterwards, by linking hydrodynamic conditions to the expert knowledge base, the fuzzy habitat model used fuzzy logic inference to compute habitat suitability of the Chinese sturgeon. In addition, the approach was used to propose a suitable instream flow range during the propagation period for Chinese sturgeon. The results indicated that the suitable instream flow needed for Chinese sturgeon spawning in middle Yangtze River should be between 10,000 m³/s and 17,000 m³/s and it also showed that after TGR was put into pilot impoundment operation at the designed water level of 175 m, the habitat suitability has decreased significantly in October. Besides, the water temperature of spawning habitat increased to a higher level in propagation period due to the impoundment of the TGR. All these alterations have had imposed tremendous impacts on the propagation of Chinese sturgeon. Therefore, adjusting impoundment schedule of the TGR to recover the water flow over spawning habitat in October is a crucial way to improve the habitat suitability. Furthermore, the presented method also provides a theoretical basis for further research on the assessment of habitat suitability of aquatic species at a micro-habitat scale.     

Effects of impoundment on populations of bullhead Cottus gobio L. and minnow, Phoxinus phoxinus (L.), in the basin of Cow Green Reservoir

The distribution, growth and reproduction of bullhead, Cottus gobio , L., and minnow, Phoxinus phoxinus (L.), were studied at Cow Green Reservoir, Upper Teesdale, for 10 years following impoundment in 1970. Comparisons were made with pre-impoundment results. The length-for-age of bullheads increased after impoundment. The length-for-age of minnows decreased. In winter both species were confined mainly to deep water or to the stone facing of the earth dam. In summer they were found throughout the reservoir though bullheads were scarce in the littoral zone. Female bullheads became sexually mature at an earlier age (84% at age-group I) than before impoundment (33% at age-group I) but no change was apparent amongst males (67–62% in age-group I). The post-impoundment sex ratio did not differ from 1:1 and individual fecundity did not change after impoundment. There was a significant reduction in individual fecundity of the minnow. The mean instantaneous rate of mortality ( Z ) for bullhead of age-groups II to IV was 0.96 ± 0.34 year⁻¹, compared with 0.85 ± 0.29 year in the Tees before impoundment.     

Immediate impacts of the second impoundment on fish communities in the Three Gorges Reservoir

Long and short term investigations have revealed dramatic changes in fish communities after impoundments by reservoirs. However, the process of these changes during impoundment remains poorly studied. In 2005 and 2006, before and during the second stage of impoundment of the Three Gorges Reservoir (TGR), in the upper reaches of the Yangtze, China, we investigated fish catches to assess the impacts of reservoir filling on fish community structure. We conducted sampling at 2 sites, Wanzhou reach, which had been inundated by the first water filling in 2003, and Fuling reach, which still remained a riverine site before this water filling. The results revealed an evident and immediate shift of fish communities from lotic to lentic components. In the Wanzhou reach, during the filling, the abundance percentage of lentic fish increased to 94% compared to 69% before the filling. In the Fuling reach, after the filling, lotic fish declined in abundance from 99% to 85%, while lentic fish increased from less than 1% to 12% in abundance. Based on our investigation and the regulation scheme of the TGR, we predicted that after the completion of the Three Gorges Dam (TGD), there would be typical lacustrine, transitional and riverine zones in TGR, with their corresponding fish assemblages. We suggest that long term monitoring should be conducted to evaluate the future ecological effects, and different strategies implemented in these three zones for conservation purposes.     

Evaluation of eutrophication control in Lake Chivero,Zimbabwe, by multivariate analysis of zooplankton

Zooplankton was a useful tool in evaluation of eutrophication control in Lake Chivero, a tropical man made impoundment. Principal component analysis revealed both spatial and temporal changes in zooplankton community structure which were related to nutrient inflows as well as changes in nutrient content of the lake. Studies on filtration rates of different algae by Bosmina longirostris and Daphnia lumholtzi demonstrated that the response of zooplankton to eutrophication was related to their inability to utilize colonial algal species that develop in a nutrient rich-environment.     

三峡库区支流生境因子对库区蓄水的响应

三峡水库的运行调度,使库区支流形成了截然不同的3种河段类型:完全受水库蓄水影响的145m回水段(完全河段),既受蓄水影响又受自然洪汛影响的145—175m回水段(双重河段)以及不受蓄水影响的大于175m的自然河流段(自然河段)。为明确库区蓄水对河流不同河段生境因子的影响程度及差异,对三峡库区36条重要支流的254个河段进行河流生境调查,进行不同河段下生境指标的因子分析,并进一步分析水文情势自然性与不同河段各生境因子的相关关系。结果表明,植被状况对3种不同河段来说均为重要生境因子,但受三峡水库蓄水影响,完全河段植被结构不完整;受库区蓄水影响,完全河段与双重河段及自然河段相比,流速流态状况、表层覆盖物状况、河岸带宽度、湿润率等生境因子有明显改变;水文情势自然性对不同河段生境因子的影响不同。     

Morphological responses of a stream fish to water impoundment

Water impoundment imposes fundamental changes on natural landscapes by transforming rivers into reservoirs. The dramatic shift in physical conditions accompanying the loss of flow creates novel ecological and evolutionary challenges for native species. In this study, we compared the body shape of Cyprinella venusta collected from eight pairs of river and reservoir sites across the Mobile River Basin (USA). Geometric morphometric analysis of the body shape showed that river populations differ from reservoir populations. Individuals inhabiting reservoirs are deep-bodied and have a smaller head, a more anterior dorsal fin, a shorter dorsal fin base and a more ventral position of the eye than C. venusta in streams. The direction of shape divergence within reservoir–river pairs was consistent among pairs of sites, and the shape of C. venusta in reservoirs is strongly correlated with reservoir size. These findings show that physical characteristics of reservoirs drive changes in the morphological attributes of native fish populations, indicating that water impoundment may be an important, yet largely unrecognized, evolutionary driver acting on aquatic biodiversity.