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1.
杨志  唐会元  龚云  朱迪  赵娜 《湖泊科学》2018,30(3):753-762
鱼类作为河流生物的重要组成部分,其在干支流之间的迁徙或移动不仅是常见的,而且通常与鱼类的繁殖活动相联系.金沙江下游支流作为金沙江下游河流网络的重要组成部分,分布有较为丰富的集合生境以及较高的鱼类物种多样性.研究鱼类在金沙江下游干支流的产卵迁徙对支流鱼类群聚结构变动的影响以及支流生境维持对区域鱼类种群维系的意义,对金沙江下游干支流鱼类的保护具有重要的意义.本文拟选择黑水河下游江段作为典型研究区域,通过2014年在该区域的逐月渔获物调查,采用聚类分析、基于距离的线性模型以及基于距离的冗余分析等多种多元分析方法,确定黑水河下游群聚结构的逐月变动是否严重依赖于鱼类在干支流之间的产卵迁徙以及黑水河下游自然生境的维持对区域鱼类种群的维系是否具有重要的意义.结果表明:黑水河下游鱼类群聚结构在金沙江雨季和旱季显著分离的同时,表征这种分离的8种指示种的性成熟个体丰度也在雨季和旱季间发生不同程度的变动.7种指示种鱼类性成熟个体丰度的变动能够解释黑水河下游鱼类群聚结构变动77.20%的变异,其中齐口裂腹鱼、大鳞副泥鳅和犁头鳅性成熟个体丰度的变动是影响黑水河下游鱼类群聚结构变动的3个最显著的因素,7种指示种鱼类在干支流的产卵迁徙对黑水河下游鱼类群聚结构的变动造成了明显的影响.研究表明:在金沙江干支流严重水电开发背景下,维持黑水河现有的自然生境面积对区域鱼类种群的维持具有重要意义.为实行上述目标,建议在白鹤滩水电站蓄水运行后,拆除黑水河的部分小型水坝,并采取其他河流再自然化措施以维持黑水河现有的自然生境面积.  相似文献   

2.
In order to understand the structure of fish assemblages in the modified Lima basin (Northern Portugal), two distinct datasets concerning the presence and abundance of fish species were subjected to multivariate analysis. On the River Lima two types of flow modification are present within kilometres of one another: (a) a reduced and constant flow due to hypolimnetic release; and (b) an intense and irregular flow. A comparison of their influence on fish assemblages revealed a gradient of assemblage types from tributaries to main river sites. The latter were characterised by a strong dominance of cyprinids, particularly Iberian barbel (Barbus bocagei). The former harboured two kinds of fish assemblages: those closer to the river mouth were dominated by the cyprinids Iberian chub (Squalius carolitertii) and Iberian nase (Chondrostoma polylepis), which were also frequently present in the main river; while in those further upstream the predominant species was the brown trout (Salmo trutta). Although explanatory variables such as distance from source, altitude, substrate coarseness and width were the primary correlates of fish assemblage composition, dam construction and flow regulation also had a significant effect upon assemblage structure, particularly by: i) reducing the importance of migratory species; ii) constraining the presence of trout in the regulated segments; and iii) simplifying the community, especially in the case of the constant and reduced flow regime.  相似文献   

3.
We collected quantitative macroinvertebrate samples and measured environmental and geographical parameters at 13 sites: six along the main stem and seven in tributaries close to the main channel over a 700 m gradient in altitude and 22 km longitudinal distance along the River Kokra in the Slovenian Alps. Our objectives were 1) to compare longitudinal patterns in richness and community composition between main stem and tributary sites, and 2) to determine the relative importance of the replacement and richness difference component for overall beta diversity and of environmental versus spatial distance on beta diversity among main stem and tributary sites.In total 138 taxa were identified. There were no differences between main stem and tributary sites in mean abundance or taxon richness (67 and 58, respectively). A nMDS and ANOSIM based on Bray-Curtis similarities found no separation of main stem and tributary sites, but that upper (≥880 m a.s.l) and lower sites (≤680 m a.s.l.) formed two different groups. In both main stem and tributaries taxon richness increased only slightly going downstream while the community composition (DCA1) was much better explained by altitude and distance from source.Overall, beta diversity (Sørensen and Bray-Curtis dissimilarity) was similar for the two groups, and total Sørensen dissimilarity was driven mainly by replacement in main stem (78 %) and tributary sites (77 %). Mantel tests showed that main stem dissimilarities were significantly correlated to environmental PCA distance, watercourse distance, overland distance and altitudinal differences. Tributary dissimilarities were not correlated to any of these four factors. GLMs showed that dissimilarity among main stem sites was explained only by altitude difference, while no factors were significant among tributary sites, even though nearly so for environmental PCA distance.The study illustrates the importance of measuring beta diversity along ecological gradients, such as river continua and/or altitudinal gradients, where alpha diversity may fail to detect relatively minor changes in assemblage composition. Such changes are likely to occur due to present and future climate warming.  相似文献   

4.
In this study, we investigated patterns of spatial variation in macroinvertebrate assemblages in the Lower Mekong Basin (LMB) and examined their relationship with environmental factors. Cluster analysis was used to group macroinvertebrate samples and Linear Discriminant Analysis was performed to discriminate the major factors associated with the macroinvertebrate assemblages. Four clusters could be distinguished based on the dissimilarity between macroinvertebrate assemblages. The assemblages related to the tributaries and the upstream parts (cluster II) were characterized by a lower richness, abundance, diversity and a lower number of indicator taxa compared to the assemblage found downstream in the Mekong delta (cluster I). Aquatic insects and their indicator taxa (e.g. Caenodes sp., Dipseudopsis sp. and Gomphidae sp.), preferring a high-altitude environment with a high dissolved oxygen concentration and a high density of wood/shrub and evergreen forests, were the most predominant group in the assemblages occupying the tributaries and the upstream parts (cluster IIa). The assemblage found in the delta, consisting largely of molluscs and a moderate richness and abundance of worms, crustaceans and dipteran insects, was mainly represented by Corbicula leviuscula and C. moreletiana (molluscs), Namalycastis longicirris and Chaetogaster langi (worms), Corophium minutum and Grandidierella lignorum (crustaceans), and Cricotopus sp. and Clinotanypus sp. (dipteran insects). This assemblage was associated with a large watershed surface area, deep and wide rivers and a high water temperature. The intermediate assemblage (cluster IIb1) in-between could be discriminated based on land cover types including inundated, wetland and agricultural land, and was represented most by molluscs. Strikingly, the assemblage occupying the upstream parts (cluster IIa), which is related to intensified agriculture and a moderate conductivity, was characterized by a higher macroinvertebrate diversity compared to the mountainous and less impacted tributaries. This could mean that the natural stress is high in these systems for some taxa, leading to a lower overall taxonomic richness and abundance. Nevertheless, the number of taxa and the diversity of macroinvertebrates remained relatively high across the basin, especially in the delta assemblage. Therefore, the LMB deserves a particular attention for conservation.  相似文献   

5.
Fish may affect macrobenthic communities through trophic interactions and modification of habitat conditions. We compared the density, diversity and taxonomic composition of larval chironomids under low vs high fish impact, created by stocking semi-natural ponds with either young/small common carp Cyprinus carpio at low biomass densities or with high biomass densities of older/large common carp, supplemented by other cyprinids and predatory fish species.Over the study season, May–August, total chironomid abundance was considerably lower in ponds with high fish biomass than in low fish biomass ponds. In July–August larval densities declined significantly, irrespective of the fish status of the ponds. The composition of larval communities diverged between ponds with different fish status. Chironomus riparius and C. plumosus accounted for most of the observed dissimilarity. C. plumosus densities were not affected by the fish status of the pond, constituting on average >38 % of chironomid specimens in both types of ponds. C. riparius was abundant in ponds with low fish biomass (on average 30 %), but rare in ponds with high fish biomass (4 %). Other common taxa were Glyptotendipes pallens (15 % and 13 %, respectively) and Procladius sp. (14 % in ponds with low fish impact). Canonical correspondence analysis showed that fish biomass was more important in determining chironomid community composition than environmental variables indicative of pond eutrophication (total N, P, chlorophyll a and conductivity).Despite adverse effects on total abundance, chironomid diversity was higher under apparently stronger trophic pressure by fish. Fish may have relieved some chironomid species from invertebrate predation and competition with dominant Chironomus larvae. Other important drivers of chironomid assemblage and diversity patterns may include species-specific feeding modes and prey size selectivity of fish, the ability of chironomid larvae to attain size- and depth-refuge from small fish but not larger fish, and differential vulnerability of free-living and tube-dwelling larvae relative to ontogenetic niche shifts of fish.  相似文献   

6.
Surface sediment diatom assemblages for 86 Alpine lakes were analysed focusing on the dominant genusCyclotella and corresponding environmental data. The range of morphological variability of theCyclotella bodanica/radiosa, C. distinguenda, C. ocellata, C. comensis andC. stelligera complexes was documented. Significance tests included in the canonical correspondence analysis (CCA) indicated that total phosphorus, conductivity and surface water temperature were significantly correlated withCyclotella taxa assemblage distribution. Numerical species optima and tolerances were calculated in respect to these significant variables using weighted averaging (WA) regression and calibration. CCA and WA were able to provide information about the environmental preferences of the various morphotypes observed.  相似文献   

7.
The Qinghai Lake area is one of key regions in the Qinghai–Tibet Plateau for supporting a highly specific array of biodiversity. However, little is known about the composition and spatio-temporal patterns of benthic assemblages across this region. Herein, we examined how the community structure and community–environment relationships of macroinvertebrates varied over three consecutive years (2012–2014) across its three distinct water types of the saline main-body (MB) and sub-lakes (SSLs) and the freshwater bodies (FWBs). These waters harbored a poor benthic fauna, with identification of 30 taxa (6 in MB, 6 in SSLs and 23 in FWBs). There were distinct differences of assemblage composition among three water bodies, whereas weak (inter-year) or insignificant (seasons) differences at temporal scales. The CCA models indicated that there were highly naturally-driven environmental-assemblage relationships through time, with constant environmental factors of salinity, water depth and nutrients being the key environmental factors affecting macroinvertebrate variations. The currently overall benthic community composition and structure remains quite stable through years, indicating their suffering less from human activities. These results provide implications for projecting comprehensive benthic biomonitoring and conservation planning for those fragile and under-investigated lakes in the Qinghai–Tibet Plateau.  相似文献   

8.
Fish assemblage structure in Palair reservoir, a medium tropical reservoir along the river Paleru, a tributary of river Krishna in Southern India, was studied along the spatial gradient of the impoundment. The abundance and assemblage structure of wild fish aggregated around the fish cage units installed in the reservoir were assessed and compared with other sites. Seasonal sampling was carried out and fish community structure in terms of species composition and abundance, trophic guild, niche, tolerance, resilience and conservation status were analyzed. A total of 38 fish species were recorded wherein the family Cyprinidae dominated in the number of species (15) followed by Cichlidae and Channidae (3 each). Margalef richness index (d), Pielou’s evenness index (J’), Simpson’s index (1-λ) and Shannon index (H’) revealed significant variation across different zones. Species richness was maximum in the Site1 (d = 4.44–5.12), whereas the abundance of individuals was maximum at Site4 (H’ = 2.65–2.86) i.e. near cage in the lacustrine zone. The important species contributing to the dissimilarities among the zones were identified and percentage of their contribution was estimated using SIMPER analysis. Trophic guild of fishes indicated the dominance of omnivorous species followed by carnivores, indicating the heterotrophic phase of the reservoir. The spatial and seasonal variations in the fish assemblage structure were tested applying statistical analyses such as PERMANOVA and nMDS. The results indicated a positive impact of cage farming in supporting the wild fish fauna, influencing the large aggregations of fishes around the cages. The temporal variability in the cage-associated fish assemblage was related to recruitment periods of juveniles (e.g. E. maculates and E. suratensis in summer, and S. seenghala in monsoon seasons). The links between fish assemblages and environmental parameters were explored through DISTILM and the deterministic factors for fish abundance in the reservoir were phosphate, pH, dissolved Oxygen, total hardness and depth. The study also indicated the impacts of cage culture with record of accidental escapes of farmed fish to the reservoir system. The baseline information generated and recommendations formulated in the study are crucial for the conservation of fish diversity, fisheries enhancement and management planning of tropical peninsular reservoirs.  相似文献   

9.
基于2017—2022年在雅砻江甘孜以下干流及部分支流的鱼类监测数据,采用多样性指数和多元统计方法分析了该流域的鱼类群落结构。通过在雅砻江干流和6条支流21个采样点的监测及相关文献调研共获得鱼类98种,包括9种国家二级重点保护鱼类和28种长江上游特有鱼类。除干流下游Margalef丰富度指数外,其他区域多样性指数值相差不大;干流上、中、下游和6条支流间鱼类生物多样性不存在显著差异。Cluster分析和NMDS分析表明鱼类群落可以分成6组,ANOSIM检验表明6组间存在显著性差异,6组在海拔和河流等级上存在极显著和显著性差异。分别计算6个聚类组的优势种和常见种,并从栖息类型、食性和产卵类型上进行分析,结果显示6组在栖息类型和产卵类型上差异显著。二滩库区和鳡鱼河静缓流河段优势种为翘嘴鲌(Culter alburnus)、尼罗罗非鱼(Oreochromis niloticus)等,建议加强对下游流域外来物种的监测,避免发生大规模生物入侵现象。自1980s以来,雅砻江下游流域鱼类种类组成发生了明显变化,推测与梯级电站修建运行等造成生境改变有关。  相似文献   

10.
Biological assemblages are affected by both environmental and spatial processes. Spatial autocorrelation can be specially marked in discrete ecosystems patchily distributed over a large region (e.g., lakes arranged in districts). Lake typologies are exclusively based on environmental features, but we hardly know to what extent spatial patterns can hinder their implementation. We analysed the role of environmental factors and spatial autocorrelation in shaping littoral macroinvertebrate communities of 51 mountain lakes from a large Spanish region in order to test: 1) the suitability of the variables currently used to construct typologies; 2) the influence of spatial patterns on typology implementation. Biologically meaningful types of lakes were created and described by means of cluster analysis (Jaccard index) and multiple discriminant analysis. Water permanence, substrate type and vegetation were the main drivers of the assemblage composition. The cluster analysis and Mantel tests showed that spatial patterns did not generally hamper recognizing lake types. Only in the district with lakes closest to each other (Sanabria Natural Park), spatial autocorrelation was strong enough to overcome the effects of some factors (substrate type), but not others (water permanence).  相似文献   

11.
山美水库既是福建省泉州市饮用水源地,也肩负着为台湾省金门县供水的功能,但春夏季过高的pH值影响了水库水质.为此,从2020年起,调整水库鱼类放养结构和捕捞策略,并研究鱼类群落调控后山美水库浮游动物群落结构的响应及其与环境因子的关系.本研究于2020年和2021年连续两年的1月（冬季）、4月（春季）、7月（夏季）、10月（秋季）调查山美水库21个采样点的浮游动物群落结构和水环境因子.结果共鉴定出浮游动物68属102种,其中轮虫21属41种（40.20%）,原生动物32属41种（40.20%）,枝角类8属13种（12.75%）,桡足类7属7种（6.86%）.2020—2021年山美水库浮游动物平均密度为（1443.05±360.02） ind./L,平均生物量为（1.21±0.27） mg/L,2021年浮游动物密度和生物量显著高于2020年,其中,2021年枝角类和桡足类的密度分别显著高于2020年枝角类和桡足类的密度,2021年库首、库中和库尾区域枝角类生物量显著高于2020年对应区域;2021年桡足类生物量显著高于2020年.春冬季浮游动物群落的优势种主要为原生动物,夏秋季浮游动物群落的优势种主要为轮虫.根据浮游动物密度和生物量评价水体营养状态,夏季山美水库处于中营养状态,春、秋和冬季处于贫营养状态.影响浮游动物群落结构分布的主要环境因子为电导率、水温、溶解氧、硝态氮、透明度和高锰酸盐指数.研究表明调整鱼类放养和捕捞措施提高了浮游动物密度和生物量,基于此提出了通过调整鱼类群落结构改变浮游动物群落结构,进而改善水环境的建议,可为湖泊水库水环境保护和水生生物资源高效利用提供科学依据.  相似文献   

12.
太湖流域河流鱼类群落的时空分布   总被引：2，自引：1，他引：1  
确定河流鱼类群落的时空分布格局及其形成机制是开展鱼类物种多样性保护与管理的科学基础.基于2013年10月和2014年5月共2次对太湖流域57个河道样点的调查数据,初步研究太湖流域河流鱼类群落结构及其多样性的季节动态和空间分布特点.共采集鱼类5051尾,计46种,其中鲤科鱼类26种,占全部物种数的57%.10月份的鱼类多样性显著高于5月份,且2个季度的鱼类群落结构存在显著性差异.5个主要水系间的鱼类多样性差异显著,总体上,沿江水系和洮滆水系鱼类多样性较低,黄浦江水系居中,而南河水系和苕溪水系较高;鱼类群落结构也随水系而显著变化,主要表现为黄浦江水系与洮滆、苕溪和沿江水系呈显著差异.在2个一级生态分区之间,鱼类多样性无显著差异但群落结构显著不同,主要因、鲫、似鳊等优势种及宽鳍鱲、尖头鱥、中华青鳉、食蚊鱼等偶见种的空间分布差异所引起;在4个二级生态分区之间,鱼类多样性和群落结构均存在显著的空间变化.  相似文献   

13.
Andean Patagonian lakes are ultraoligotrophic and deep, have simple food webs and low fish diversity and abundance. In this work the distributional abundance data of fish was studied in two interconnected Andean Patagonian lakes with varying proportions of contrasting habitat types. Hydroacoustic data (120 kHz) were used to analyze fish abundance and habitat use during the mixis and stratification periods. Three types of habitat (near shore, surface pelagic and deep pelagic) and two groups of fish, based on size (Big Fish >12 cm total length and Fish Larvae and Small Fish <12 cm total length) were defined. The distribution of both fish groups in these lakes revealed differences in habitat use for each lake and period. Fish group abundance was related to the availability of habitat types, according to the morphology of each lake. The Big Fish group showed preference for the near shore habitat during lake stratification and always appeared as individual targets. The Fish Larvae and Small Fish group used mainly the pelagic habitat during mixis, where they formed dense sound scattering layers. However, during lake stratification many individual targets from this group were found both in pelagic and near shore habitats, which would seem to indicate a change in distributional behavior. This is possibly associated with niche changes in the Galaxiids (Galaxias spp), a key component of Northern Patagonian lake food webs. Lakes like Moreno Oeste, which are morphologically and structurally more complex, could have more diverse fish ensembles with higher abundances. In contrast, lakes of simple morphology with low development of near shore habitats and ample deep zones, like Lake Moreno Este, could present lower Big Fish abundance. The contrasting habitat availability between lakes accounts for the abundances and distribution patterns of each fish group. While in these lakes fish assemblage species composition could depends on the environmental filter, the particular structure of a fish assemblage in terms of the proportional abundances of species depends on proportional habitat type availability. We can speculate that in Andean Patagonian lakes Galaxiids mediate a habitat coupling process critical for the transfer of energy and matter in oligotrophic lakes. We may also consider that the Small Puyen in this type of lake is a keystone prey species that relieves predation pressure on other potential prey. The existence of deep pelagic habitats in numerous deep lakes in the Northern Patagonian Andean region provides not only daytime refuge for Galaxiids, which allows them to maintain their high numbers in the lakes, but could also, in the long term, act as a Galaxiid source for other water bodies.  相似文献   

14.
Cross-taxon responses to elevated nutrients in European streams and lakes   总被引：1，自引：0，他引：1  
Few studies have compared the response of different taxonomic groups to environmental stress across aquatic ecosystems. We regressed assemblage structure of fish, invertebrates, macrophytes, phytoplankton and benthic diatoms to total phosphorus concentration, after removing the effect of ecosystem size (stream order, lake surface area), using data from 66 streams and 45 lakes across Europe. In streams, the structure of benthic diatom assemblages, measured by nonmetric multidimensional scaling, showed the strongest correlation to elevated nutrient concentrations (adj. R2 = 0.495), followed by benthic invertebrates (0.376), fish (0.181) and macrophytes (0.153). For lakes, the patterns were less clear: fish (0.155), macrophytes (0.146) and phytoplankton (0.132). Cross-system comparison showed that stream assemblages were responding more strongly to nutrient concentrations than lake assemblages. Moreover, our results lend some support to the conjecture that response signatures are related to trophic level, with primary producers (benthic diatoms) responding more strongly than consumers (invertebrates, fish). Knowledge of differences in responses among taxonomic groups and between habitats to disturbance can be used to design more cost-effective monitoring programs.  相似文献   

15.
During summer, wind driven coastal upwelling dominates in the Central Cantabrian Sea (southern Bay of Biscay). Nevertheless, atmospheric forcing is highly variable and wind pulses may cause noticeable and fast hydrographic responses in the shelf region. In this paper, the composition and vertical distribution of the summer ichthyoplankton assemblage during the daytime at a fixed station, located on the Central Cantabrian Sea shelf, are documented. Also, the impact of a short-time scale hydrographic event on the abundance and structure of the larval fish assemblage is examined. Significant small-scale temporal hydrographic variability was observed. Currents showed changes in speed and direction and significant changes in thermocline depth were also observed. A total of 34 taxa of fish larvae were identified. Engraulis encrasicolus eggs and larvae of the shelf-dwelling species Trachurus trachurus, Capros aper and E. encrasicolus dominated the ichthyoplankton assemblage. The distribution of E. encrasicolus eggs and fish larvae was vertically structured. E. encrasicolus egg concentration increased exponentially towards the surface. Fish larvae showed a subsurface peak of concentration and their vertical distribution was not conditioned by thermocline depths. The short term hydrographic event did not affect the vertical distribution of fish larvae but it accounted for significant temporal changes in larval fish assemblage structure and abundance. Results suggest that temperature and light intensity are important factors in the vertical distribution of fish larvae. They also indicate that the temporal monitoring of the larval fish assemblage in this region requires multiple sampling sites.  相似文献   

16.
Ichthyoplankton and mesozooplankton were sampled and fluorescence and physical environmental variables were measured off the NW and N Iberian Peninsula coasts, during April 2005. A total of 51 species of fish larvae, belonging to 26 families, were recorded. Sardina pilchardus, with 43.8% and 58.7% of the total fish egg and larval catches, respectively, dominated the ichthyoplankton assemblage. The study area was divided by a cross-shelf frontal structure into two hydrographic regions that coincided with the Atlantic and Cantabrian geographic regions. Ichthyoplankton abundance was higher in the Cantabrian region while larval diversity was higher in the Atlantic region. This was the main alongshore variability in the structure of the larval fish assemblage. Nevertheless, the stronger variability, related with the presence of a shelf-slope front, was found in the central-eastern Cantabrian region where two major larval fish assemblages, an “outer” and a “coastal”, were distinguished. The Atlantic region, where the shelf-slope front was not found, was inhabited by a single larval fish assemblage. Canonical correspondence analysis revealed that, off the NW and N Iberian Peninsula coasts, the horizontal distribution of larval fish species in early spring may be explained by a limited number of environmental variables. Of these, the most important were the physical variables depth and sea surface temperature.  相似文献   

17.
We investigated the effect of contrasting trophic conditions on the distribution and dominance patterns of Oligochaeta species assemblages in lake sediments and their relation to the environmental variables depth, season, and substrate. The study was performed on the highly eutrophic Lake Haussee and the oligotrophic Lake Stechlin, both hardwater lakes in the Baltic Lake District of Northern Germany. Quantitative monthly and seasonal sampling took place over one year at 14 representative sites, covering littoral and profundal sediments of both lakes. Between-lake differences in the profundal were clearcut with an absence of any zoobenthos in Lake Haussee and a peculiar meiobenthic species assemblage in Lake Stechlin (Collado et al. 1999). Between-lake differences in the littoral, however, were small and mainly attributable to a small number of species exclusive to Lake Stechlin and an overall higher abundance of oligochaetes, especially naidids, in Lake Haussee. Species-richest family in both lakes were Naididae; Tubificidae were dominant in Lake Stechlin; in Lake Haussee Tubificidae and Naididae were equally abundant. Most striking were diversity of habitat types and species distribution patterns in the littoral. Multivariate analysis (CA, CCA) showed that the distribution patterns of oligochaete species assemblages are significantly correlated with depth, season and substrate. Depth is the major factor when the whole water body is considered. When confining to the littoral, species abundance and distribution are strongly related to seasonality and substrate type. Naididae show, in general, maximal abundances in autumn and summer and a preference for plants, plant debris and soft sediments; Tubificidae are more abundant in spring and prefer mineral substrate. The relation between seasonality, substrate and food availability is discussed.  相似文献   

18.
Variation in habitat structure provided by macrophytes is regarded as one of the determinants of macroinvertebrate species composition in lentic ecosystems, but mechanisms underlying this relationship appear to be confounded with site-specific factors, such as physicochemical factors, epiphyton and composition of the vegetation. To better understand the relationship between structural complexity of a macrophyte stand and its macroinvertebrate assemblage composition, it is essential to determine the ecological role of different components of habitat structure for the phytomacrofauna. Using artificial structures as macrophyte mimics, representing three growth forms (stems, broad-leaved, finely dissected) and three structure surface areas (0.1, 0.2, 0.3 m2), a full factorial field experiment was conducted in a series of drainage ditches. We investigated if macroinvertebrate assemblages colonizing the structures were affected by an increase in macrophyte structure surface area, structural complexity, or by a combination of both, and if the observed patterns were consistent among sites differing in physicochemical and habitat characteristics. Assemblages were characterized both in terms of taxonomic and functional composition, because we expected that non-taxonomic aggregation of species into functional categories would give a different insight in habitat complexity-macroinvertebrate relationships in comparison to approaches based on the taxonomic assemblage composition. Ditch intrinsic factors, in part reflected in the periphyton on the structures, explained the major proportion of the variance in both the taxonomical macroinvertebrate assemblages and functional groups among structures. Contrary to our expectation, patterns in the taxon-based and functional dataset resembled each other. Only a minor contribution of growth form to the explained variance was observed in the taxonomical dataset, whilst differences in functional composition were unrelated to habitat structure. In conclusion, processes operating on larger spatial scales overrode the micro-scale effects of habitat structural complexity and surface area on macroinvertebrates.  相似文献   

19.
Submerged aquatic vegetation (SAV) constitutes a major component of fish habitat, providing support for epiphytes and invertebrates as well as shelter from predators. The effects of wetland epuration from a mesotrophic to a nearly oligotrophic state were examined over a 15?km long reach of the St. Lawrence River under the direct influence of major farmland tributaries. We hypothesized that the nutrient-enriched zone would support a higher biomass of SAV, epiphytes, macroinvertebrates and fish than the nitrogen-deficient epurated zone located downstream of the wetland. Predictions included that the enriched habitat would support a richer fish assemblage, with higher biomass and growth of juvenile yellow perch than found in the epurated zone. Results supported these hypotheses, demonstrating the chain of effects of nutrient reduction on the biomass of SAV (fourfold drop), invertebrate prey (ninefold), small (threefold) and large (1.5-fold) fish between the two zones. In addition to the reduction in SAV biomass, the replacement of filamentous chlorophytes by benthic mats of filamentous cyanobacteria in the epurated zone resulted in a less complex 3-D habitat structure and a low invertebrate availability for fish. Oligotrophication by wetland epuration exerted negative effects on fish habitat quality, food quantity and availability, with an impairment of juvenile perch growth and recruitment. A generalized model of the changes in habitat carrying capacity occurring with epuration (oligotrophication) or eutrophication is presented, with examples of other aquatic systems in which strong linkages between trophic status, SAV, invertebrates and fish productivity were also demonstrated.  相似文献   

20.
随着人类活动对自然生态系统的负面影响不断加剧,无创性生物多样性评估变得越来越重要。本研究旨在利用环境DNA宏条形码技术研究赣江下游南昌段鱼类多样性,并从不同季节（春、夏、秋、冬）、不同水层（上层、中层和下层）和不同取样位置（近岸和离岸）比较鱼类环境DNA信息的物种组成和多样性。结果表明：利用环境DNA宏条形码技术在赣江下游南昌段检测到鱼类114种,其中83种为历史记录种。不同季节的鱼类环境DNA信息的多样性和组成显示出极显著差异。上层水检测到的鱼类物种数分别显著多于中层水和下层水,且中层水和下层水检测到的鱼类在上层水中绝大多数都被检测到。上层水、中层水和下层水的鱼类环境DNA信息的多样性和组成不具有显著性差异。近岸检测到鱼类物种数多于离岸的,鱼类多样性指数无显著性差异,但群落结构具有显著性差异。RDA分析表明,赣江下游鱼类环境DNA受温度和pH的影响较大。本研究能够为基于环境DNA宏条形码的赣江鱼类资源的调查提供基线数据,并对后续赣江鱼类资源环境DNA宏条形码监测实施不同目的的采样策略提供依据;可为使用环境DNA宏条形码技术研究流水系统鱼类多样性提供技术参考,为环境DNA宏条形码技术应...  相似文献   

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