Physico-chemical conditions and macroinvertebrate fauna in the River Nile from Aswan to Cairo

This paper examines the distribution of benthic macroinvertebrates in relation to physico-chemical conditions along 1 035km of the River Nile from Aswan High Dam to Al Kanater Barrage, Cairo. Total Dissolved Salts and several individual chemical variables showed positive linear regression with distance from Aswan. The creation of the Aswan High Dam has reduced the ionic concentrations discharged to the Nile, but there is a gradual increase as the river flows though Egypt. Benthic macroinvertebrates show overall low taxon richness with taxa typical of a lowland riverine region. Changes in taxon richness appear to be influenced by either pollution and/or sedimentation. Sites downstream of the Kema Factory and downstream of organic discharge from Etsa Drain from Minia city show severe pollution. A Bray-Curtis Diversity Index shows these sites to be biodiversity outliers consistent with the negative impact of pollution. Examination of 95% outlying chemical values confirms gross pollution from these sites and the data as a whole suggest other sites that may also be affected by pollution. A contributor to high macroinvertebrate taxon richness appeared to be increased sedimentation, particularly in midstream samples. It is concluded that the low ionic concentrations resulting from the Aswan High Dam construction, localised pollution, and the occurrence of sediment are the main factors governing macroinvertebrate taxon richness. These factors will require careful monitoring, assessment and management if the biodiversity of the Nile is to be conserved.     

A Feasibility Study to Monitor the Macroinvertebrate Diversity of the River Nile Using Three Sampling Methods

The River Nile is one of the world’s major rivers. Its’ catchment in Egypt has a population of 75,000,000. River flow is highly regulated and there are known discharges of pollutants. 1035 km of the river downstream of the Aswan high dam was studied to test the hypothesis that representative qualitative samples can be used to estimate macroinvertebrate biodiversity. Benthic macroinvertebrates are difficult to sample in large rivers and a reliable sampling strategy is required to evaluate their ecological status. Three methods for sampling have been investigated. Ekman Grab, macrophyte sweep netting and Artificial Substrate Samplers (ASS) were used to sample 15 sites from Aswan to Cairo between September 2001 and June 2002. Organisms were identified to species level where possible. Taxon accretion curves indicated that the all taxa present at a site should be collected using either 15 grab samples, 10 macrophyte samples or 5 ASS. The best time to sample was May–June. The biodiversity of macroinvertebrates in the Nile was recorded as 50 taxa with values of 7–31 at individual bank-side sites. Mid-stream biodiversity was much lower (0–19). Lowest biodiversity occurred at sites with known pollution inputs whilst highest occurred at sites with high levels of sedimentation. A regular programme for biomonitoring is recommended which will allow current status to be confirmed and future changes detected.     

基于大型底栖无脊椎动物群落的上海市河道水质生物学评价

2011年夏秋季,在上海市全境83个河道断面开展了大型底栖无脊椎动物采样,共获取底栖动物20个分类单位(种).9个极严重污染断面未采集到活体大型底栖生物,生境基本丧失.其余74个有活体生物断面,采用三种常用生物指数:Shannon-Wiener多样性指数、Hilsenhoff耐污指数、Goodnight修正指数分别进行计算及评价.Shannon-Wiener多样性指数判别为25个严重污染和49个重污染断面;Hilsenhoff耐污指数划分38个重污染、5个中污染和31个轻污染断面;Goodnight修正指数划分33个重污染、2个中污染和39个轻污染断面.与典型河道断面的水质理化指标监测值进行对照,Shannon-Weiner多样性指数对河道水质评价的准确度较低,Hilsenhoff生物指数和Goodnight修正指数的水质评价效率及准确度均较高,断面污染等级与水质理化指标基本对应.     

基于大型底栖动物群落的上海市河道水质生物学评价

2011年夏秋季,在上海市全境83个河道断面开展了河道底栖动物采样,共获取底栖动物20个分类单位（种）。9个极严重污染断面未采集到活体生物,生境基本丧失。其余74个有活体生物断面,采用三种常用生物指数：Shannon-Wiener多样性指数、Hilsenhoff耐污指数、Goodnight修正指数分别进行计算及评价。Shannon-Wiener多样性指数判别为25个严重污染和49个重污染断面;Hilsenhoff耐污指数划分38个重污染、5个中污染和31个轻污染断面;Goodnight修正指数划分33个重污染、2个中污染和39个轻污染断面。与典型河道断面的水质理化指标监测值进行对照,Shannon-Weiner多样性指数对河道水质评价的准确度较低,Hilsenhoff生物指数和Goodnight修正指数的水质评价效率及准确度均较高,断面污染等级与水质理化指标基本对应。     

基于底栖生物完整性指数的赣江流域河流健康评价

底栖生物完整性指数(B-IBI)是最为广泛应用的水生态系统健康评价指数之一。根据2009-2010年期间赣江流域60个采样点的底栖动物数据(15个参照点, 45个受损点), 对17个生物参数进行分布范围、判别能力和Pearson相关性分析, 确定了B-IBI指数体系由总分类单元数、甲壳和软体动物分类单元数、甲壳和软体动物%和BI指数构成。采用比值法统一各生物参数量纲, 将各个生物参数分值加和得到B-IBI指数值。根据参照点的B-IBI值的25%分位数值最终确定赣江流域河流健康评价标准。评价结果表明, 赣江流域60个采样点中19个为健康, 19个为亚健康, 14个为一般, 8个较差。综合来看, 赣江流域河流处于健康-亚健康状态: 上游各支流中绵水、贡江、上犹江和桃江为健康状态, 章水、濂水、梅江和平江为较差状态; 中游各支流健康评价结果多为健康-亚健康状态, 而乌江为较差状态; 下游各支流为健康-亚健康状态; 赣江干流上健康评价的结果均为健康。       

Critical influence of seasonal sampling on the ecological quality assessment of small headwater streams

Variability in the ecological quality assessment of reference sites was tested on small headwater streams in Ireland. Although headwater streams constitute a large portion of the river channel network, they are not routinely monitored for water quality. Various metrics were used including the Irish Q-value and the newly developed Small Streams Risk Score (SSRS), and metrics applied elsewhere in the Atlantic biogeographic region in Europe, including the Biological Monitoring Working Party score (BMWP), the Average Score per Taxon (ASPT), the Ephemeroptera, Plecoptera and Trichoptera taxa (EPT), the Belgium Biotic Index (BBI) and the Danish Stream Fauna Index (DSFI). The AQEM (version 2.5a) assessment software was used to apply some of these metrics. The spring and summer datasets are used to test the performance of biotic metrics with respect to season, and the applicability of their use to assess the ecological quality of wadeable streams. The quality status of most sites assigned by the various metrics was high using the spring invertebrate data, and an apparent considerable deviation in quality status occurred when the summer data was applied. Seasonal differences were noted using all the biotic indices and are attributed to the absence of pollution-sensitive groups in summer. Seasonal variability in the water quality status was particularly evident in acidic streams draining non-calcareous geologies with peaty soils that had relatively lower numbers of taxa. Some indices applied reflect a greater seasonal difference in the quality category assigned. The least amount of variability between seasons was obtained using the ASPT and the SSRS risk assessment system. Results suggest that reference status is reliably reflected in spring when more pollution-sensitive taxa were present, and that a new ecological quality assessment tool is required for application in summer when impacts may be most severe. This highly heterogeneous freshwater habitat seems to have too few taxa present in the summer to reliably determine the ecological quality of the stream using the available indices. Handling editor: R. Bailey     

Development of a multimetric approach to assess perturbation of benthic macrofauna in Zostera noltii beds

Biotic indices based on soft-bottom macrozoobenthic communities are currently used throughout Europe to assess the ecological quality of coastal and transitional water bodies according to the European Water Framework Directive. However, the performance of the currently available biotic indices still has to be tested against a variety of different impact sources. In particular, physical perturbations have received much less attention than other kind of disturbances. This study consisted in testing the capacity of currently available uni- (BOPA, AMBI and BENTIX) and multivariate (M-AMBI) Biotic Indices to assess the ecological impact of the destruction of a Zostera noltii seagrass bed in Arcachon Bay (France) following sediment deposits. Changes of habitat after this physical perturbation were hardly assessed by any of these Biotic Indices whereas analysis of the benthic community showed drastic changes of structure following the perturbation and no recovery after 15 months. This study demonstrates that these Biotic Indices must be integrated into a multimetric approach which describes better the biological integrity of the benthic community by including a complementary set of metrics. A new multimetric approach, named MISS (Macrobenthic Index of Sheltered Systems) is proposed. MISS correctly highlighted the destruction of the seagrass beds, by using 16 metrics describing the biological integrity of the macrofauna.     

A Modern Biology Syllabus at O-level

The biotic indexing of water quality and its application to A-level field work is discussed with reference to the Trent Biotic Index and Chandler Score system. These indices are related to the classification of water quality used by the Department of the Environment in the River Pollution surveys of 1970 and 1975.

The interpretation of these indices is also considered and their limitations are discussed.     

Comparative monitoring by means of diatoms,macroinvertebrates and chemical parameters of an Apennine watercourse of central Italy: The river Tenna

The WFD/60/2000/EC establishes the use of different biological indicators to assess the ecological status of rivers, in addition to chemical, physical and bacteriological parameters. At this purpose, the present study concerning the river Tenna, a central Apennine watercourse (Italy), aimed to analyse and discuss the information given by two biological indices: the Extended Biotic Index or E.B.I. that uses benthic macroinvertebrates, in the version adapted to the Italian rivers (I.B.E.), and the diatom-based Eutrophication and/or Pollution Index (EPI-D). Sampling has been carried out twice, in May (deep water conditions) and October 2006 (low water conditions), in ten stations along the hydrographic basin of the river. Chemical parameters have been determined monthly during a year because they present a higher variability than biotic indicators. The correlations between the biological and abiotic data obtained have been statistically analysed by means of the Spearman's test. The statistical data, in general, showed a direct correlation between the two biotic indices, and an inverse correlation between these and the chemical-physical and bacteriological parameters. Some of the differences of judgement emerging from the application of the two biotic indices showed a complementary response of the diatoms and macroinvertebrates to various environmental stresses. These results suggest the usefulness of an integrated multidisciplinary approach, in order to obtain a more accurate diagnosis of the health status of the watercourses.     

The Composition and Density of Epiphyton on Some Macrophyte Species in the Partly Meromictic Lake Verevi

In this paper, some important problems related to taxonomic resolution in water quality assessment by means of macroinvertebrates are discussed. Most quality indices based on macroinvertebrates only require identification up to genus or family level. Although this can be seen as a practical trade-off between taxonomic precision and time constraints and financial resources, it can result in biased assessment scores for certain stream types. An additional difficulty of identification levels other than species is caused by possible changes in taxonomy over time. A given genus may indeed have been split up into two or more genera or a species could be assigned to a different genus. These changes may alter biotic index values calculated over time, due to a change in number of taxa or replacement of one taxon by another one having a different tolerance class. An additional problem is caused by the invasion of exotic species. The genus Corbicula for instance is currently invading Belgian watercourses in increasing numbers. Since no Belgian Biotic Index (BBI) tolerance class is defined for Corbicula, this may cause inconsistencies in index calculations as well. In order to eliminate these, a semi-fixed taxa list, including a tolerance class for each taxon, for BBI calculation is proposed.     

Chironomids as water quality indicators in the River Mignone (Central Italy)

Chironomids of the River Mignone (Central Italy) were studied in order to examine their community structure and their relationship to some common biological indices (Biotic Score, Extended Biotic Index, Indice Biotique de Qualité Générale) utilizing the total macroinvertebrate fauna (chironomids generally at family level) for water quality assessment in rivers.A total of 36 taxa belonging to Tanypodinae (2 taxa), Orthocladiinae (22 taxa) and Chironominae (12 taxa) was collected at seven stations four times during a year. The results support the importance of the chironomid identification in water quality assessment studies in rivers, and demonstrate the usefulness of the factorial correspondence analysis as ordination technique based on both qualitative and quantitative chironomid data to determine environmental quality gradients.The value as bioindicator of some taxa was discussed, and chironomid assemblages were related to biological water quality of the river according to functional feeding groups.This study forms part of a larger Research project supported by MPI and CNR grants and is aimed at the biological water quality assessment of the river and at the analysis of the total macrobenthic community.     

Assessing conservation status and trends for the world��s butterflies: the Sampled Red List Index approach

Red List Indices provide a method for assessing global trends in species?? conservation status, and for monitoring progress towards achieving conservation targets (for example, commitments under the Convention on Biological Diversity). Red List Indices are based on categorization of taxa in terms of their threat status using information on, for example, current and projected abundances, distributions, and threats. Global assessments have now been undertaken for a suite of well-known vertebrate taxa. However, highly diverse invertebrate taxa are currently very poorly represented in such assessments, and there is a danger that their threats and their utility as biodiversity indicators will be overlooked. Unlike most invertebrates, butterflies are relatively well-known globally. We describe ongoing efforts to incorporate butterflies into the Red List Index process. Because of high species richness (approximately 15,000 Papilionoidea globally) a comprehensive assessment is not feasible. Instead, we apply a ??Sampled Red List Index?? approach which draws on a subset of 1,500 focal taxa. We illustrate the process and the challenges (particularly taxonomic issues and issues of data deficiency) using a variety of case studies. The information provided should be relevant to other researchers seeking to apply the Red List Index approach to invertebrates and other diverse but poorly studied taxa.     

A comparison between diversity, similarity and biotic indices applied to the macroinvertebrate community of a small stream: the Ravella river (Como Province, Northern Italy)

This study aimed at comparing the results obtained by processing a series of data according to several diversity indices (Simpson, Berger-Parker, Margalef, Menhinick, McIntosh, Shannon) and one similarity index (Jaccard) with those obtained from two biotic indices (Trent River Biotic Index, Extended Biotic Index). In addition, Cody's index was adopted to measure the species turnover along the stream gradient. The source of the data was a study of the seasonal variations of macroinvertebrates from the Ravella stream (Como Province, Northern Italy). The conclusions are the following. There is clearly a certain connection between the organic debris in the habitat, the abundance of individuals and the decrease in the diversity value of the macroinvertebrate association. The species turnover along the stream gradient is rapid which is due, in addition to birth and death rates, to the fact that most of the insects emerge as terrestrial adults. The species abundance distribution is a very simple and powerful tool for describing and comparing the species diversity from different sampling stations. Any type of monitoring (e.g., biotic indices, diversity indices) is useful in comparing non-polluted and heavily polluted environments. Conversely, small differences between species associations are better highlighted if diversity indices with high discriminant ability (e.g., Simpson's index) or species abundance distribution are used rather than biotic indices.     

Euhydrophyte communities of the River Nile and its impoundments in Egyptian Nubia

The River Nile and its two impoundments, the Aswan Reservoir and Lake Nasser, are important habitats for submerged and floating-leaved freshwater macrophytes (euhydrophytes) in the desert region of Egyptian Nubia. Ordination and classification analysis of survey data collected during the period 1980–1986 suggested that the Aswan High Dam forms a man-made vegetational boundary, delineating two basic macrophyte community types. In Lake Nasser a community dominated by Najas spp. is present. In the Aswan Reservoir and the R. Nile downstream of the old Aswan Dam the euhydrophyte community is dominated by a Potamogeton crispus — Ceratophyllum demersum association. Differences between the two community types appear to be related to differences in physical factors (e.g. water level fluctuation and flow regime), and water chemistry, to phenological factors, and to the differing successional ages of the macrophyte communities of the Nile system upstream and downstream of the Aswan High Dam. There is some evidence for depth zonation of the submerged macrophyte community in both lake and river habitats. Strategy analysis of the euhydrophyte communities present upstream and downstream of the High Dam, over the period 1963–89, indicated that successful established-phase strategy types were similar on both sides of the dam. In the long term there seems little to prevent euhydrophyte species at present confined to below the High Dam from crossing this boundary to colonise Lake Nasser.     

Selective recruitment and resurgence of tropical river phytoplankton: evidence from the Nile system of lakes,rivers, reservoirs and ponds

The recruitment of major species-components of phytoplankton is considered with reference to diverse water-bodies—rivers, headwater lakes, reservoirs and lateral waters—of the Nile system. The importance of massive ‘inocula’, carried in flowing and inter-communicating waters, is emphasised; the most direct evidence is from quantitative population dynamics in longitudinally sampled river-reservoir systems. Other indications of extraneous derivation are taken from geographical distribution and apparent invasions of newly recorded species. For five reservoirs, there are records of initial colonisation (in two) and of the annual colonisation of seasonally impounded water (in three). There was a selective recruitment of reservoir/river major species over 1 year to newly created ponds, from a massive inoculum of added river water, studied in relation to the novel and changing physical and chemical environment. Periods of predominant decomposition were there linked with the abundance of other species not observed in the original river water. Reservoir species can be carried to extend abundance far downstream, as observed in the Blue Nile where normal succession was altered by a new reservoir upstream; also in Egypt below the former Aswan Reservoir and the later High Dam Lake. The different and distinctive compositions of the phytoplankton communities in headwater lakes reflect large environmental differences that, with high downstream turbulence, probably make them insignificant for recruitment of most species typical of the downstream waters. There is evidence from hydrology and floristic similarities for recruitment from lateral standing waters along the river, especially those of one major swamp area.     

Biotic index for sediment quality assessment of watercourses in Flanders, Belgium

Today, assessment of freshwater sediments in Flanders is based on the TRIAD approach in which physical-chemical, biological and ecotoxicological data are combined. No prior experience existing in Flanders with the biological assessment of the sediment quality, several biotic indices were compared on a first set of 80 samples taken in different types of lowland watercourses. This information resulted in a first selection of suitable indices consisting of a newly created Biotic Sediment Index (BSI) and the Percentage Mentum Deformities in Chironomus (Diptera, Chironomidae larvae). The starting point of the BSI was the Belgian Biotic Index (BBI) based on a combination of the taxa diversity and the presence or absence of specific indicator groups. For the refinement of the BSI, a new set of data related to the benthic macroinvertebrate communities sampled by means of a grab in more than 400 sites was collected. Community analysis by means of multivariate techniques, combining biological information with physical-chemical and ecotoxicological data was the basis for this further refinement and the scientific foundation of the original BSI. Major amendments relate to the scores assigned to the indicator groups. This refined BSI is representative for the degree of pollution, unbiased by the type of sediment and the origin of the river basin. Like the BBI, the BSI scores can vary between 10 (excellent sediment quality) and 0 (very bad sediment quality). The index values can be converted into 4 quality classes to be represented by means of a colour code.     

广西河池地区河流基于鱼类的生物完整性指数筛选及其环境质量评估

为促进生物完整性评价法在中国的应用,加强珠江上游广西河池地区河流环境质量监测,该研究以鱼类为研究对象,初步构建了包含21个指标在内的广西河池地区河流基于鱼类的生物完整性评价的指标体系。根据鱼类调查所收集数据,结合历史资料的记录,对这些指标进行筛选和赋值,最终确立了6个指标,用于建立适合广西河池地区河流的基于鱼类的生物完整性指标体系;应用此指标体系对该地区部分河流(河段)进行了评价。评价的结果表明,小环江鱼类完整性为好;红水河、龙江和大环江为一般;刁江为极差。评价的结果与河流受人为干扰的实际情况相吻合,研究构建的评价体系可供河池周边地区使用和借鉴。生物完整性评价是水域环境质量监测的重要手段,为使生物完整性评价更加科学和客观,应加强生物完整性与环境因子之间关系的研究。     

Biotic element analysis in biogeography

Biotic element analysis is an alternative to the areas-of-endemism approach for recognizing the presence or absence of vicariance events in a given region. If an ancestral biota was fragmented by vicariance events, biotic elements or clusters of distribution areas should emerge. We propose a statistical test for clustering of distribution areas based on a Monte Carlo simulation with a null model that considers the spatial autocorrelation in the data. The hypothesis tested is that the observed degree of clustering of ranges can be explained by the range size distribution, the varying number of taxa per cell, and the spatial autocorrelation of the occurrences of a taxon alone. A method for the delimitation of biotic elements which uses model-based Gaussian clustering is introduced. We demonstrate our methods and show the importance of grid size by means of a case study, an analysis of the distribution patterns of southern African species of the weevil genus Scobius. The example highlights the difficulties in delimiting areas of endemism if dispersal has occurred and illustrates the advantages of the biotic element approach.     

Replacement of a native freshwater macroinvertebrate species by an invader: implications for biological water quality monitoring

The rate of freshwater invasions may be increasing, and macroinvertebrate invaders can have significant impacts on native macroinvertebrate assemblage structure through biotic interactions. More pollution-tolerant invaders can often replace native species. We examined implications of a species replacement for accurate biological monitoring of river systems using biotic indices. Our study uses Northern Ireland and the Isle of Man as examples of countries that possess river networks with many riverine macroinvertebrate assemblages subject to invasion. The introduced amphipod crustacean Gammarus pulex has replaced the native species G. duebeni celticus in many rivers in N. Ireland and the Isle of Man. Extensive seasonal data sets (119 sites) from three river networks, Lough Neagh and the Lagan in N. Ireland, and island-wide in the Isle of Man, were used to investigate the assumed equivalence of the native and invader in biotic indices concerned with the water quality monitoring system. Based on the derivation of the Biological Monitoring Working Party (BMWP) score, the Average Score Per Taxon (ASPT), as an example of a commonly used biotic index of water quality, we found index scores were lower in G. pulex sites compared to G. d. celticus-only sites. This indicated that assemblages were dominated by taxa more tolerant of organic pollution in the invader sites and more sensitive in the native sites. Inclusion of the invader in generation of the ASPT index, overinflated the ASPT values obtained compared to those with the native’s inclusion. This questions the accuracy of the ASPT and similar indices in rivers where the invader had replaced the native. We argue that with invasion pressures increasing, the validity of water quality indices such as the BMWP/ASPT needs to be re-examined in catchments where invaders have replaced natives. Indices such as the BMWP/ASPT are based on family level taxa and are inevitably coarse in their resolution given the wide range of water qualities tolerated by different genera within families. We argue that this resolution is even more compromised by the presence of very pollution-tolerant invaders, who may have replaced natives in disturbed or degraded river systems. The whole structure of water quality indices such as the BMWP/ASPT may need revising to take into account the presence of invasive species within monitored assemblages.     

Use of Macrophytes in Assessing the Ecological Status of Small River (by the Example of the Okhta River,St. Petersburg)

Hydrochemical and hydrobiological characteristics have been studied at 13 sites in the Okhta River within the precincts of St. Petersburg in 2010. The Water Pollution Index (WPI), calculated according to hydrochemical parameters, characterizes the river water quality as “very polluted” to “extremely polluted.” According to the Pantle–Buck–Sláde?ek Saprobity Index, obtained on the basis of macrozoobenthos characteristics, polysaprobic and α-mesosaprobic zones can be distinguished in the watercourse. The species richness of river macrophytes is low (18 species). The Macrophyte Water Quality Index makes it possible to assess water quality in the range from “polluted” to “very polluted” water. Macrophyte trophic indexes MTR, IBMR and TIM indicate a high trophy level in the watercourse sites. Based on the analysis of hydrochemical materials and the data on macrozoobenthos and macrophytes, the general tendency is similar: deterioration of water quality downstream. Macrophyte characteristics reflect changes in hydrochemical parameters downstream the river course. А strong correlation (r =–0.76) is found between the Macrophyte Water Quality Index and WPI. The possibility of using the data on macrophytes in small rivers for assessing water quality is demonstrated.