Rivers as Barriers to Primate Distributions in Africa

Rivers border the geographic distributions of primate taxa, but the extent to which the rivers are effective barriers is debated. We here provide the first statistically substantiated analysis of the role of rivers as barriers to the distribution of primates in west and central Africa, as judged by the coincidence of the edge of distributions of forest-dwelling primates with rivers. We use data from the literature to analyze the distributions of 14 genera, 44 species, and 77 subspecies around 18 rivers, river groups, or stretches of rivers. Rivers bordered the distributions of more new taxa (subspecies) than of old taxa (genera), although within genera, age of origin of the taxon did not correlate with likelihood of rivers bordering distributions. Fewer taxa crossed wide rivers than crossed narrow ones. Some analyses indicated that more smaller-bodied genera were stopped by smaller rivers than were larger-bodied genera, but other analyses indicated no effect of body size. Genera with smaller geographic ranges crossed a smaller proportion of the rivers that they met than did genera with large ranges, implying a fundamental difference between small- and large-range taxa in their ability to disperse. Specialization might be the operating trait. Finally, although the aridity of the biogeographic gap in west Africa, the Dahomey Gap, is often argued to be the barrier to movement of species across the Gap, we found that for half the primate species that do not cross the Gap, the rivers that border the Gap could in fact be the effective barrier.     

THE POTENTIAL INDICATOR VALUE OF RARE TAXA RICHNESS IN DIATOM‐BASED STREAM BIOASSESSMENT1

Despite their recognized contribution to species richness, the importance of rare taxa richness in bioassessment is unclear. This study aimed to characterize the environmental factors affecting the number of rare diatom taxa in western U.S. streams and rivers, and to evaluate whether this number can be used to differentiate streams with contrasting human disturbance. Three different categories of rare taxa were used: satellite (taxa with low occurrence and low abundance), rural (taxa with high occurrence and low abundance), and urban (taxa with low occurrence and high abundance). Common taxa were included as a separate category of core taxa (taxa with high occurrence and high abundance). We analyzed 987 diatom samples collected over the period of 5 years (2000–2004) for the U.S. Environmental Protection Agency’s (EPA) Western Environmental Monitoring and Assessment Program (WEMAP). The results showed that rural taxa richness (number of rural taxa per site) increased along a longitudinal gradient from mountainous, fast‐flowing oligotrophic streams with fewer fine substrates to large, slow‐moving, nutrient‐rich rivers with abundance of fine substrates. Rural taxa richness was the only rarity metric that distinguished least disturbed (reference) sites from the most disturbed (impacted) sites, but it was significantly different only in the mountains ecoregion. Core taxa richness distinguished reference from impacted sites in the West and in each one of the three ecoregions (mountains, plains, and xeric). Our findings revealed that rural taxa richness can be used as an indicator of human disturbance in streams/rivers, especially in the mountains ecoregion, and that rarity definition is important in bioassessment.     

Keeping it simple: Benefits of targeting riffle-pool macroinvertebrate communities over multi-substratum sampling protocols in the preparation of a new European biotic index

The purpose of this study was to test the performance of a new sampling strategy for bioassessment of water quality. The macroinvertebrates living in the mineral substrata of geomorphological unit riffles strategy (MMS-GUR) concentrates sampling effort on certain geomorphologically and hydrobiologically representative units within survey sites and refines the level of taxonomic sorting of pertinent macroinvertebrate communities therein. Previous data have demonstrated that the mineral substrata of geomorphological unit riffles (GURs) harbour a wide variety of macroinvertebrates and pollution-sensitive taxa [Beauger, A., Lair, N., Reyes-Marchant, P., Peiry, J.-L., 2006. The distribution of macroinvertebrate assemblages in a reach of the River Allier (France), in relation to riverbed characteristics. Hydrobiologia 571, 63–76]. These units are typical of alluvial rivers and are easily identified from the bank and easily sampled. The objectives of the present study were to specify the sampling effort required to obtain representative taxonomic data from these communities, and to compare the performance of the new protocol with that of an established multi-substratum sampling methodology (XS). Two sampling series were carried out on two rivers within the same hydro-ecoregion. Two separate data were compiled from each site, incorporating taxon lists and relevant biological, ecological and physiological trait (BEPT) information, one using conventional (XS) methodology and the other from the MMS-GUR protocol.Macroinvertebrates sampled from three GURs of the River Allier ranged from pollution-tolerant to pollution-sensitive taxa. A comparison between the two methods (MMS-GUR and XS) conducted on the Allier and the Loire confirmed the validity of GURs as representative features, showing that pollution-sensitive taxa were better represented on mineral substrata and pollution-tolerant taxa were not over-estimated. The XS method is characterised by eight samples, while preliminary studies on the Allier suggested that a maximum of 13 samples were required to obtain sufficient taxonomic richness using the MMS-GUR methodology. However in river sections where pollution-sensitive taxa were numerous, the number of MMS-GUR samples required for analysis could be reduced to 10 or 8.In the context of the EU Water Framework Directive and associated AQEM project, the MMS-GUR protocol may facilitate the comparison of different rivers by sampling macroinvertebrate communities from similar rhithron or epipotamon habitats and focussing on pollution-sensitive taxa. It has the further advantage of reducing the time and effort spent in sampling and sorting. Increasing the resolution of taxonomic information to the genus level may also improve the standard of water quality assessment.     

Development of a regional macroinvertebrate index for large river bioassessment

Large river bioassessment protocols lag far behind those of wadeable streams and often rely on fish assemblages of individual rivers. We developed a regional macroinvertebrate index and assessed relative condition of six large river tributaries to the upper Mississippi and Ohio rivers, Midwest USA. In 2004 and 2005, benthic macroinvertebrates, water chemistry, and habitat data were collected from randomly selected sites on each of the St. Croix, Wisconsin, Minnesota, Scioto, Wabash, and Illinois rivers. We first identified the human disturbance gradient using principal components analysis (PCA) of abiotic data. From the PCA, least disturbed sites showed strong separation from stressed sites along a gradient contrasting high water clarity, canopy cover, habitat scores, and plant-based substrates at one end and higher conductivity and nutrient concentrations at the other. Evaluation of 97 benthic metrics identified those with good range, responsiveness, and relative scope of impairment, as well as redundancies with other metrics. The final index was composed of Diptera taxa richness, EPT taxa richness, Coleoptera taxa richness, percent oligochaete and leech taxa, percent collector-filterer individuals, predator taxa richness, percent burrower taxa, tolerant taxa richness, and percent facultative individuals. Each of the selected metrics was scored using upper and lower thresholds based on all sites, and averaging across the nine metric scores, we obtained the Non-wadeable Macroinvertebrate Assemblage Condition Index (NMACI). The NMACI showed a strong response to disturbance using a validation data set and was highly correlated with non-metric multidimensional scaling (NMDS) ordination axes of benthic taxa. The cumulative distribution function of index scores for each river showed qualitative differences in condition among rivers. NMACI scores were highest for the federally protected St. Croix River and lowest for the Illinois River. Other rivers were intermediate and generally reflected the mixture of land use types within individual basins. Use of regional reference sites, though setting a high level of expectation, provides a valuable frame of reference for the potential of large river benthic communities that will aid management and restoration efforts.     

广东省6座水库及其入库河流底栖动物调查与综合评价

2010年8月对广东省6座水库及其入库河流的大型底栖无脊椎动物群落进行采样调查,并分别利用Goodnight-Whitley指数和BPI指数对水库及入库河流的水质进行评估。结果表明,水库共检出底栖动物13种,优势种为霍甫水丝蚓(Limnodrilus hoffmeisteri)、苏氏尾鳃蚓(Branchiura sowerbyi)和八斑多足摇蚊(Polypedilum masudai),种类丰富度变动范围为2～5种,平均密度为277ind/m²,变动范围160～480ind/m²。入库河流的种类丰富度和密度均高于水库,共检出底栖动物28种,优势种为苏氏尾鳃蚓、霍甫水丝蚓、花翅前突摇蚊(Procladius choreus)和河蚬(Corbicula fluminea),种类丰富度变动范围为2～7种,底栖动物平均密度为382ind/m²,变动范围192～816ind/m²。水质评价结果表明,6座水库的水质状况总体良好,但入库河流均受到不同程度的污染,污染较为严重的黄岗河和黄羌河,其水库汤溪水库和公平水库也产生了污染。     

Diverse invertebrate fauna using dry sediment as a refuge in semi-arid and temperate Australian rivers

Dormant aquatic invertebrates can remain viable in riverbed sediment during dry phases, forming a source for recolonisation during wet periods. Regional differences in capacity for invertebrates to survive drying in this way are poorly understood, but may indicate regional differences in vulnerability to altered flow regimes. We compared diversity of invertebrates in dry sediment from intermittent rivers in temperate and semi-arid Australia after 4–8 weeks of drying. We predicted adaptations of semi-arid biota to severe and unpredictable drying would make dry sediment a more significant recolonisation source, with higher relative diversity when compared with temperate rivers. Emerging aquatic invertebrate assemblages were compared to those sampled in nearby pools, as a common drying refuge. Relative taxa richness in rehydrated sediments was higher in the semi-arid region (83 ± 16% of pool taxa) than the temperate (47 ± 6% of pool taxa), despite lower overall richness (24 taxa in semi-arid, 32 taxa in temperate). Semi-arid rivers had greater potential for dry riverbeds to act as a source for recolonisation, given high relative diversity and abundance in dry sediment, combined with the frequent absence of alternative refuges. However, dry riverbeds in both regions provided a significant short-term refuge for aquatic invertebrates.     

Hydromorphological degradation impact on benthic invertebrates in large rivers in Slovenia

Large rivers are amongst the most degraded ecosystems. We studied a relationship between hydromorphological degradation and benthic invertebrates in large rivers in Slovenia. Five indices of the Slovenian hydromorphological assessment methodology were used to develop a HM stressor gradient. Natural type-specific habitat diversity was considered in the hydromorphological stressor gradient building and thus two hydromorphological types of large rivers were defined. CCA ordination with five HM indices and 315 benthic invertebrate taxa revealed variations in taxa response along the HM stressor gradient. First CCA axis species values were used to develop a taxon-specific river fauna value (Rf_i), whereas tolerance values (biplot scaling) were used to determine a hydromorphological indicative weight (HW_i). Rf_i, HW_i, and log₅ abundance classes were combined using weighted average approach to construct a River fauna index for large rivers (RFI_VR). Several additional benthic invertebrate-based metrics were also tested against the HQM. A Slovenian multimetric index for assessing the hydromorphological impact on benthic invertebrates in large rivers (SMEIH_VR) was constructed from the RFI_VR and a functional metric %akal + lithal + psammal taxa (scored taxa = 100%). The strong relationship between hydromorphological stressor gradient and SMEIH_VR index provides us with an effective assessment system and river management tool.     

Do larval fishes exhibit diel drift patterns in a large,turbid river?

Previous research suggested larval fishes do not exhibit a diel drift cycle in turbid rivers (transparency <30 cm). We evaluated this hypothesis in the turbid, lower Missouri River, Missouri. We also reviewed diel patterns of larval drift over a range of transparencies in rivers worldwide. Larval fishes were collected from the Missouri River primary channel every 4 h per 24‐h period during spring‐summer 2002. Water transparency was measured during this period and summarized for previous years. Diel drift patterns were analyzed at the assemblage level and lower taxonomic levels for abundant groups. Day and night larval fish catch‐per‐unit‐effort (CPUE) was compared for the entire May through August sampling period and spring (May – June) and summer (July – August) seasons separately. There were no significant differences between day and night CPUE at the assemblage level for the entire sampling period or for the spring and summer seasons. However, Hiodon alosoides, Carpiodes/Ictiobus spp. and Macrhybopsis spp. exhibited a diel cycle of abundance within the drift. This pattern was evident although mean Secchi depth (transparency) ranged from 4 to 25 cm during the study and was <30 cm from May through August over the previous nine years. Larval diel drift studies from 48 rivers excluding the Missouri River indicated the primary drift period for larval fishes was at night in 38 rivers and during the day for five, with the remaining rivers showing no pattern. Water transparency was reported for 10 rivers with six being <30 cm or ‘low’. Two of these six turbid rivers exhibited significant diel drift patterns. The effect of water transparency on diel drift of larval fishes appears taxa‐specific and patterns of abundant taxa could mask patterns of rare taxa when analyzed only at the assemblage level.     

Global climate change in large European rivers: long‐term effects on macroinvertebrate communities and potential local confounding factors

Aquatic species living in running waters are widely acknowledged to be vulnerable to climate‐induced, thermal and hydrological fluctuations. Climate changes can interact with other environmental changes to determine structural and functional attributes of communities. Although such complex interactions are most likely to occur in a multiple‐stressor context as frequently encountered in large rivers, they have received little attention in such ecosystems. In this study, we aimed at specifically addressing the issue of relative long‐term effects of global and local changes on benthic macroinvertebrate communities in multistressed large rivers. We assessed effects of hydroclimatic vs. water quality factors on invertebrate community structure and composition over 30 years (1979–2008) in the Middle Loire River, France. As observed in other large European rivers, water warming over the three decades (+0.9 °C between 1979–1988 and 1999–2008) and to a lesser extent discharge reduction (?80 m³ s^?1) were significantly involved in the disappearance or decrease in taxa typical from fast running, cold waters (e.g. Chloroperlidae and Potamanthidae). They explained also a major part of the appearance and increase of taxa typical from slow flowing or standing waters and warmer temperatures, including invasive species (e.g. Corbicula sp. and Atyaephyra desmarestii). However, this shift towards a generalist and pollution tolerant assemblage was partially confounded by local improvement in water quality (i.e. phosphate input reduction by about two thirds and eutrophication limitation by almost one half), explaining a significant part of the settlement of new pollution‐sensitive taxa (e.g. the caddisfly Brachycentridae and Philopotamidae families) during the last years of the study period. The regain in such taxa allowed maintaining a certain level of specialization in the invertebrate community despite climate change effects.     

Polyunsaturated fatty acids in stream food webs – high dissimilarity among producers and consumers

相似文献   

The North Mediterranean Barbus lineage: phylogenetic hypotheses and taxonomic implications based on allozyme data

On the basis of distinct ecological and morphological characters, the European Barbus taxa have been clustered in two groups: a fluvio-lacustrine and a rheophilic or strictly riverine one. These two groups (or ecophenotypes) were recognized in different parts of Europe, and formed either a species assemblage ( Barbus barbus group) or a polytypic species ( Barbus meridionalis ). The hypothesis was that species of the same group belong to the same phylogenetic lineage (clade) and are the result of the same transcontinental colonization event. The analysis, using allozyme markers, of 10 taxa of the genus Barbus from France, Italy, Greece, the Czech Republic and Slovakia, showed that the taxa thought to belong to the fluvio-lacustrine and the rheophilic groups are not monophyletic. The results suggest that probably in each sub-region, the founding taxon has diverged independently to form species of two different ecophenotypes, one occupying the upstream rivers and the other the lowland rivers. Accordingly, Barbus species groups represent clusters of morphologically convergent taxa living in equivalent biotopes.     

Non-wadeable river bioassessment: spatial variation of benthic diatom assemblages in Pacific Northwest rivers,USA

Current bioassessment efforts are focused on small wadeable streams, at least partly because assessing ecological conditions in non-wadeable large rivers poses many additional challenges. In this study, we sampled 20 sites in each of seven large rivers in the Pacific Northwest, USA, to characterize variation of benthic diatom assemblages among and within rivers relative to environmental conditions. Analysis of similarity (ANOSIM) indicated that diatom assemblages were significantly different among all the seven rivers draining different ecoregions. Longitudinal patterns in diatom assemblages showed river-specific features. Bray–Curtis dissimilarity index values did not increase as a function of spatial distance among the sampled reaches within any river but the Malheur. Standardized Mantel r of association between assemblage similarity and spatial distance among sites ranged from a high of 0.69 (Malheur) to a low of 0.18 (Chehalis). In the Malheur River, % monoraphids, nitrogen-tolerant taxa, and beta-mesosaprobous taxa all decreased longitudinally while % motile taxa, especially Nitzschia, showed an opposite trend, reflecting a strong in-stream water quality gradient. Similar longitudinal trends in water quality were observed in other rivers but benthic diatom assemblages showed either weak response patterns or no patterns. Our study indicated that benthic diatom assemblages can clearly reflect among-river factors. The relationships between benthic diatom assemblages and water quality within each river may depend on the strength of the water quality gradients, interactive effects of water quality and habitat conditions, and diatom sampling design.     

Macroinvertebrate‐based bioassessment of rivers in Addis Ababa,Ethiopia

Chemical‐based studies have shown pollution of rivers in Addis Ababa, Ethiopia. However, as bioassessment is not a component of the river assessment and monitoring programmes, information on the ecological status of the rivers is limited. The study assessed the ecological status of the Little and Greater Akaki Rivers using macroinvertebrates. Macroinvertebrates were collected from twelve sites twice in the dry and wet seasons. There was abundance of few tolerant, collector‐gatherer taxa with a loss of most sensitive taxa that used to be part of the river systems. Macroinvertebrate communities from upper and lower reaches showed complete differentiation on the nonmetric multidimensional scaling (NMS) ordination graph with upstream reaches composed of relatively sensitive taxa while the lower reaches dominated by tolerant taxa. Multiresponse permutation procedure (MRPP) showed significant difference between the two reaches. Macroinvertebrate communities from the dry and wet seasons did not show differentiation on the NMS ordination graph and MRPP did not show significant difference. Both rivers scored low in the South African Scoring System (SASS 5) and ETHbios, indicating ecological degradation. The results suggest that several decades of environmental degradation might have led to impoverished regional species pool, consisting mainly tolerant and generalist taxa constant throughout the year.     

Zambian Invertebrate Scoring System (ZISS): A macroinvertebrate-based biotic index for rapid bioassessment of southern tropical African river systems

An extensive survey of tropical rivers, conducted during 2009–2012 throughout Zambia, collected 151 samples of benthic macroinvertebrates, located on 95 rivers in six of the nine freshwater ecoregions. Associated data for physico-chemistry, human activities and ecosystem stressors were collected. Data were used to develop and test a new Rapid Bioassessment Protocol (the Zambian Invertebrate Scoring System: ZISS) for assessment of water quality and river condition in both wadeable and non-wadeable rivers. ZISS, which is based on the South African Scoring System (SASS), includes a total of 85 taxa, of which 79 are shared with SASS. Assignment of sensitivity weightings to new ZISS taxa was based on sensitivity weightings of closely related SASS families; known life-history modes and anatomical adaptations; and correlation of occurrence to impact ratings. The ability of the ZISS to measure impacts was assessed by determining the relationships between ZISS metrics and impacts. ZISS data for the Kafue River demonstrated the efficacy of the ZISS for detecting moderate to high impacts on water quality and river condition. ZISS represents a major step in developing a user-friendly, widely applicable, macroinvertebrate-based biotic index, which can provide easily interpretable assessments of river condition for southern tropical African rivers.     

Choosing the best method for stream bioassessment using macrophyte communities: Indices and predictive models

The bioassessment and monitoring of the ecological status of rivers using macrophytes has gained new momentum since macrophytes were recognised as biological quality elements for the implementation of the European Water Framework Directive (WFD; EU/2000/60).Our objectives were to test the suitability of two predictive modelling approaches to macrophyte communities as a tool for water quality assessment, and to compare their performance with other more common approaches—the use of macrophytes as indicators of the trophic status of rivers and multimetric indices. We used floristic and environmental data that were collected in the spring of 2004 and 2005 from around 400 sites on rivers across mainland Portugal, western Iberia.We build two predictive models: MACPACS (MACrophyte Prediction And Classification System) and MAC (Macrophyte Assessment and Classification) based on RIVPACS and the BEAST methods, respectively. Whereas MACPACS is derived from taxa occurrence data, MAC uses a quantitative measure of taxa abundance. Both models showed good performance in predicting reference sites to the correct group and low rate of misclassification errors. However, they performed differently. MAC depicts a reliable response to the overall human-mediated degradation of fluvial systems, as does the multimetric index (RVI, Riparian Vegetation Index), but MACPACS presented only a poor correlation with the Global Human Disturbance Index and with the nutrients input. The incorporation of abundance data in vegetation predictive models appears to be particularly important to the detection of high levels of degradation. The values for correlations with physical–chemical pressure variables were lower than expected for MTR (Mean Trophic Rank) due to an insufficient number of scoring species found in Portuguese fluvial systems. Our results suggest that the most effective methods for bioassessment in Mediterranean-type rivers are either the RVI or the MAC predictive model.     

Community structure of benthic invertebrates in interior Alaskan (USA) streams and rivers

Taxonomic composition of benthic invertebrates in interior Alaskan streams and rivers is summarized from published and unpublished data. Diptera dominate the Alaskan stream fauna and constitute a larger proportion of the benthos in Alaskan streams than in streams of temperate North America. Plecoptera and Ephemeroptera are the next most abundant in Alaskan streams with Trichoptera generally very scarce. Several orders that occur regularly in streams of temperate North America are absent (or in very low abundance) in interior Alaskan streams: Hemiptera, Odonata, Megaloptera, Coleoptera. Net-spinning caddisflies, burrowing mayflies, and several families of stoneflies (Pteronarcyidae, Peltoperlidae and Perlidae) are conspicuous by their absence or extreme scarcity. Taxonomic composition varies significantly among hydrologic regions (major watersheds) and among stream types (springs, headwater streams, small rivers, and large rivers). Only two taxa (Chironomidae and Nemouridae) significantly increase in proportional contribution from south to north while many taxa decrease.     

Using Phytoplankton to Assess the Trophic Status of German Rivers

We introduce the German multi‐metric assessment method PhytoFluss for large rivers, based on phytoplankton, which can be used to implement the European Water Framework Directive (WFD). First, we examined the response of chlorophyll a concentration to total phosphorus (TP) at 220 German river sites. Rivers could be assigned to one of four groups, based on the response curves: a) streams with high specific run‐off (Rhine, Danube) had the lowest yield of chlorophyll a per unit of TP, followed by b) low yield in small lowland rivers (Trave, Stepenitz), c) medium‐sized lowland rivers (Spree) and large central mountain rivers (Main) had intermediate yields of chlorophyll a, and d) streams with low specific run‐off (Elbe, Weser) and Baltic tributaries (Penne, Warnow) had the highest yield of chlorophyll a per unit of TP. To define the five trophic status classes of phytoplankton biomass according the WFD, the chlorophyll a boundaries were derived from these response curves at the 75% percentile level. All selected sites were pre‐classified with the combined trophic boundaries for TP and chlorophyll a to create the new four taxa composition metrics: The proportions of Chlorophytes, Cyanobacteria, or Pennales and of indicator taxa were selected as indicative parameters. When applying the final PhytoFluss method to 418 years of investigation from 150 German river sites, the percentages in each status according to the bio‐ component phytoplankton were: high 3%, good 19%, moderate 42%, poor 30%, and bad 5%. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ecological variation in invasive brown trout (Salmo trutta) within a remote coastal river catchment in northern Patagonia complicates estimates of invasion impact

Salmonids were first introduced into the Chilean fresh waters in the 1880s, and c. 140 years later, they are ubiquitous across Chilean rivers, especially in the southern pristine fresh waters. This study examined the brown trout (Salmo trutta) and native taxa ecology in two adjacent but contrasting rivers of Chilean Patagonia. During spring 2016 and spring–fall 2017 we examined the variation in benthic macroinvertebrate and fish community composition and characterized fish size structure, stomach contents, and stable isotopes (δ¹³C and δ¹⁵N) to understand population structure, fish diet, and trophic interactions between S. trutta and native taxa. The native Galaxias maculatus (puye) dominated the fish community (74% of abundance). S. trutta was less abundant (16% of survey catch) but dominated the fish community (over 53%) in terms of biomass. S. trutta showed distinct diets (stomach content analysis) in the two rivers, and individuals from the larger river were notably more piscivorous, consuming native fish with a relatively small body size (<100-mm total length). Native fishes were isotopically distinct from S. trutta, which showed a wider isotopic niche in the smaller river, indicating that their trophic role was more variable than in the larger river (piscivorous). This study provides data from the unstudied pristine coastal rivers in Patagonia and reveals that interactions between native and introduced species can vary at very local spatial scales.     

雅鲁藏布江流域底栖动物多样性及生态评价

雅鲁藏布江起源于喜马拉雅山,是世界上海拔最高的河流之一,是流经我国西藏境内重要的国际河流,其河流生态系统具有特殊地貌及生态条件。研究该流域底栖动物多样性分布特征及其影响因子,是科学评价该区域河流生态系统健康状况,实现资源可持续开发利用的基础。2009年10月—2010年6月期间,以底栖动物作为指示物种,对雅江流域干支流及堰塞湖的14个采样断面进行河流生态评价。采用Alpha及Beta生物多样性指数分别指示局部采样河段及全区域的底栖动物多样性。对采样断面底栖动物组成分析发现:14个采样断面共采集到底栖动物110种,隶属57科102属。雅江干流底栖动物种类数最高为29,平均为19。支流年楚河种类数为17。支流拉萨河,尼洋河,帕龙藏布的最高种类数分别为25,33,36;平均种类数分别为21,21,22,生物多样性普遍高于干流。整个流域中底栖动物平均种类数相差不大,但种类组成和密度相差较大。调查区域的Beta多样性指数β高于低海拔地区的相似的山区河流,说明雅江流域内底栖动物群落差异性高于正常海拔地区。对14个采样断面的物种组成进行除趋势对应分析表明:影响雅江流域底栖动物多样性的主要因素为河型,河床阻力结构,堤岸结构,水流流速。保持稳定的阶梯-深潭结构和自然堤岸结构,以及适宜的流速有利于保护雅江河流生态。     

Effects of larvicide treatment on invertebrate communities of Guinean rivers,West Africa

Biological and hydrological data collected from 1984 to 1998 in three Guinean rivers were analysed to evaluate adverse effects of biological and chemical larvicides applied for the control of blackfly Simulium damnosum, vector of the parasitic digenean worm Onchocerca volvulus. Although most of the variation in invertebrate populations were flow-related, larvicide applications affect community structure reducing the abundance of the most sensible taxa. In spite of these results, in the long term the rarefaction of some invertebrate taxa (i.e. Tricorythidae) does not cause a significant reduction of total invertebrate densities because of the corresponding increase of other taxa (i.e. Hydropsychidae and Philopotamidae). The functional structure of the communities is also not affected.