Development of a multimetric index based on benthic macroinvertebrates for the assessment of natural wetlands in Southwest Ethiopia

Biotic indices are widely applied for conservation and management of aquatic resources since they allow water resources monitoring agencies to get insight in complex biological data and yield policy relevant information. Despite the worldwide popularity of biotic indices, little information on their use and applicability in Eastern Africa is available. Here, we develop a multimetric index based on macroinvertebrates to assess the ecological condition of natural wetlands in Southwest Ethiopia. Index development was based on a dataset of 222 samples collected during two consecutive years from 63 sites located at eight different wetlands. We used physico-chemical and hydro-morphological variables (land use pattern, habitat alteration, hydrological modification and chemical water quality) to classify sites as reference or degraded. We tested a total of 58 potential metrics representing various aspects of macroinvertebrate assemblages including family richness, composition, tolerance measures and presence and abundance of functional feeding groups. Metrics were selected for the development of a final index based on their sensitivity in discriminating reference from impaired sites, strength of correlation with the anthropogenic disturbance gradient, chemical measurements, and the degree of redundancy. Metrics retained for the final index were:overall family richness, family richness of Ephemeroptera, Odonata and Trichoptera (EOT), and percentage of filterer–collectors. The final index, derived from the sum of three metric scores, was divided into five water quality classes (very bad, bad, moderate, good and very good). Our final multimetric macroinvertebrate index (MMI) distinguished well between reference and impaired wetland sites and showed a significant negative response to a gradient of disturbances (R² = 0.86, p < 0.05). Moreover, it classified a validation dataset accurately with a correctly classified instances of 80% and a Cohen's Kappa value of 0.6. This MMI can be considered as a robust and sensitive tool that can be applied to evaluate the ecological condition of natural wetlands in Ethiopia, where wetland resources are under high pressure as a result of agricultural activities such as grazing and urbanization.     

Towards a multimetric index for ecological assessment of Mediterranean flatland ponds: the use of macroinvertebrates as bioindicators

Fifty-five macroinvertebrate metrics were tested for their response to pond condition in 41 ponds of northwest Spain to develop a preliminary multimetric index for ecological assessment of Mediterranean flatland ponds. Stressor specific response of individual attributes to eutrophication and habitat alteration was also investigated to identify differences in the responses of metrics to single stressors and elucidate how this might affect the performance of the final index. Several combinations were tested using discrimination efficiency (25th percentile of slightly impaired sites for metrics decreasing with perturbation and 75th percentile of slightly impaired sites for metrics increasing with perturbation) and Mann–Whitney U-test with Bonferroni adjustment (P < 0.001). The final index comprised five measures (generic richness of Chironominae, generic richness of Dytiscidae + Odonata + Tanypodinae, relative richness of Chironomidae, % Macropelopini and Shannon index) and discriminated between acceptable (good) and unacceptable (moderate) conditions with more than 86% efficiency. Moreover, all the five measures included in the final index showed unidirectional responses to eutrophication, decreasing as eutrophication increased. In contrast, the effect of habitat alteration was less clear, especially in ponds in best available conditions where a vegetation belt of shrubs and trees prevented growing of macrophitic vegetation on shores and consequently associated fauna. Interestingly, none of the functional groups (e.g. % predators and % collector–gatherers) were sensitive to degradation. Handling editor: K. Martens     

A multimetric index based on benthic macroinvertebrates for evaluation of Atlantic Forest streams at Rio de Janeiro State, Brazil

This study describes the application of a protocol for biological assessment of water quality at first to third order streams at Serra dos órg?os, an area covered by Atlantic Forest in Rio de Janeiro State, Brazil. Major impacts in the region are domestic effluents and deforestation. Our main objective is to establish biocriteria for the establishment of the Serra dos órg?os Multimetric Index (SOMI) based on benthic macroinvertebrates. We used data from previous studies, sampled by experienced biologists, from 1999 through 2002. The benthic macroinvertebrate community was sampled in 12 reference sites and seven impaired sites in three river basins: Guapimirim, Macaé and Grande, all from the same bioregion. From the 22 tested metrics, 6 were included in the SOMI (% Diptera, % Coleoptera, Family Taxa, EPT Taxa, BMWP-CETEC and % Shredders). Scores (5, 3 or 1) were developed for these metrics to allow for aggregation into the index. Seven intermediately impaired sites were used for evaluating the applicability of the multimetric index. We concluded that the SOMI is a robust easy-to-apply tool for biomonitoring programs in the Serra dos órg?os region, south-east Brazil. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorised users. Handling editor: D. Dudgeon     

基于底栖动物预测模型构建生物完整性指数评价河流健康

提高生物完整性指数(integrity of biotic index,IBI; 又称多参数指数multi-metric index, MMI)在时间和空间尺度的稳定性是水生态完整性评价和水环境管理实践的重要内容.本研究利用2004—2011年在浙江省多个河流采集的227个点位的底栖动物和水质理化数据,利用地理信息系统(GIS)提取样点及其对应流域的自然预测因子(如地理形态学、气候学)和土地利用数据,通过随机森林模型方法定量时间和空间尺度自然变量对生物群落的影响,构建基于预测模型控制自然因子影响方法和常规方法的MMI,并比较它们的表现力.结果表明: 基于预测模型法和基于常规方法构建的MMI的核心组成参数存在差异,随机森林模型中自然预测因子对预测模型MMI构成生物参数的解释量介于11.4%～61.2%.预测模型方法提高了MMI的精确度和准确度,但其敏感性和响应性低于常规方法的MMI.最近距离方法表明,9个评价点位和1个严重受损点位的自然属性与参照点位的自然属性存在差异性.在计算参照点位自然属性代表性范围的基础上,采用预测模型方法控制自然变量可以提高MMI的精确度和准确度,同时降低评价结果出现Ⅰ型(将健康水体误判为受损水体)或者Ⅱ型(将受损水体误判为健康水体)错误的可能性.研究结果可以为提高完整性指数评价稳定性和表现力提供方法支持.     

Development of a benthic macroinvertebrate multimetric index (MMI) for Neotropical Savanna headwater streams

Assessing the ecological impacts of anthropogenic pressures is a key task in environmental management. Multimetric indices (MMIs), based on aquatic assemblage responses to anthropogenic pressures, have been used increasingly throughout the world. The MMI approach is a low-cost, rapid field method that produces an aquatic condition index that responds precisely to anthropogenic pressures, making it useful for conservation and environmental management. We developed four candidate MMIs based on benthic macroinvertebrate assemblages sampled at 40 randomly selected sites to assess the environmental condition of streams upstream of a hydroelectric power plant in the Brazilian Neotropical Savanna biome. Those MMIs were built from landscape-adjusted and unadjusted biological metrics as well as two alternative ways of choosing metrics. The alternative MMIs performances were tested by comparing their precision to distinguish least-disturbed areas, responsiveness to discriminate least- and most-disturbed areas, and sensitivity to anthropogenic pressures at catchment and local scales. The best performing MMI had landscape-adjusted metrics and was produced through use of principal component analysis for metric selection. It included 4 metrics: Ephemeroptera richness, average tolerance score per taxon, percentage of predator individuals, and percentage of Odonata individuals adjusted by elevation. This index discriminated well the anthropogenic pressures at local- and catchment-scales, and at both scales simultaneously, as indicated by an integrated disturbance index. Our methodological development included statistical criteria for identifying least- and most-disturbed sites, calibrating for natural landscape variability, and use of non-redundant metrics. Therefore, we expect it will provide a model for environmental assessment of water resources elsewhere in Brazil and in other nations.     

Morphological alterations of lake shores in Europe: A multimetric ecological assessment approach using benthic macroinvertebrates

Besides pollution, lakes are affected by human alterations of lake-shore morphology. However, ecological effects of such alterations have rarely been studied systematically. Hence, we developed tools to assess the ecological effects of anthropogenic morphological alterations on European lake-shores based on pressure-specific response patterns of littoral macroinvertebrate community composition. Littoral invertebrates were sampled from 51 lakes in seven European countries. Sampling covered a range of natural to heavily morphologically degraded sites including natural shorelines, recreational beaches, ripraps and retaining walls. Biological data were supplemented by standardized morphological data that were collected via a Lake Habitat Survey (LHS) protocol and subsequently used to develop a morphological stressor index. Two biotic multimetric indices were developed based on habitat-specific samples (Littoral Invertebrate Multimetric based on HAbitat samples, LIMHA) and composite samples (Littoral Invertebrate Multimetric based on COmposite samples, LIMCO) through correlations with the morphological stressor index. Similarity analyses showed strong spatial differences in macroinvertebrate community composition between four main geographical regions, i.e. Western, Northern, Central and Southern Europe. The morphological stressor index as well as LIMCO and LIMHA have been developed for each geographical region specifically, thereby optimizing correlations of LIMCO and LIMHA with the respective morphological stressor index. The metric composition of LIMCO and LIMHA and their correlation coefficients with the morphological stressor index are comparable to existing national and regional methods that assess morphological lakeshore degradation via macroinvertebrate communities. Hence, LIMCO and LIMHA indices constitute a new stressor-specific assessment tool that enables comparable lake morphology assessment across Europe, as it has been developed involving a uniform methodology followed by regionalized optimization. These tools fulfil the standards of the EU Water Framework Directive and thus may complement existing assessment approaches used in lake monitoring focusing solely on lake eutrophication so far.     

Development of a macroinvertebrate multimetric index for the assessment of low-land streams in the neotropics

The water and habitat quality in Panamanian streams and rivers are being degraded by agriculture, urbanization, industrial activities, mining, and other forms of development. Thus, the need for standards, especially those examining the biological attributes of lotic systems, are urgently required. We describe the development of a multimetric index based on macroinvertebrates collected in low-land streams in the Panama Canal Watershed (PCW), which differed in their levels of human impacts. The index was developed using 12 streams and validated using a further three, all of which were sampled on four occasions, in the dry and wet seasons of 2007 and 2008. We examined 42 metrics related to macroinvertebrate community structure, composition, and function. Based on their ability to distinguish reference from moderately or severely impacted streams, and on their independence, we selected seven metrics (Margalef's index (taxa), Shannon's evenness index (taxa), number of EPT (taxa), % of Trichoptera, ratio of Chironomidae/Diptera individuals, % of scrapers, and % of shredders). These metrics were then standardized and developed into the Neotropical Low-land Stream Multimetric Index (NLSMI). Overall, the NLSMI distinguished well among the different levels of impairment (Reference, Moderate impact, and Severe impact) and showed a strong, significant correlation with principal component analysis (PCA) axis one values, with the PCA based on a set of physico-chemical variables indicative of stream quality. The wet season generally resulted in lower NLSMI values, leading us to suggest that sampling for biomonitoring be carried out in the dry season. Overall, this preliminary macroinvertebrate NLSMI shows promise for developing a biomonitoring programme to assess the ecological integrity of streams, to aid with management, restoration, and conservation, and to serve as a basis to develop a more geographically extensive multimetric index.     

A biotic index using benthic macroinvertebrates for Italian lakes

The relationship between benthic macroinvertebrates and environmental variables from 42 Italian lakes were analysed with the aim of developing a biotic index.In the investigated lakes, 570 species were found of which 373 belonged to the family of Chironomidae and 85 to the class of oligochaeta. Rare species, those present in less than 10 samples, were excluded from the analysis, leaving 57 species for data analysis.Multivariate analysis: canonical correlation analysis (CANON) and multivariate analysis of variance and covariance (MANCOVA) were carried out on a large database of 1060 sampling points, for which both environmental data (16 chemical and morphometric variables) and 57 species counts from soft bottom samples were available. In addition, a second dataset of 94 sites from small lakes sampled in 2005 in Northern Italy (Lombardy), was analysed for comparison.The data analysis (CANON) from the large database gave the following results:

• (1)the first canonical variate was related to conductivity, pH and alkalinity and accounted for 17% of the total variation;
• (2)the second canonical variate was related to total phosphorus, N-NH₄ and dissolved oxygen, and accounted for 15% of the total variation;
• (3)lake maximum depth, volume and water temperature were related to the third canonical variate, which accounted for 14% of the source of variation.

The analysis of the database from small lakes revealed that in the plane of the first two canonical variates dissolved oxygen was inversely correlated with the depth of sampling and that the second canonical variate showed an inverse relationship between transparency and nutrients.MANCOVA found evidence for differences between lake types and sampling years, confirmed the CANON results and allowed the quantification of the contribution of different target variables on species composition.A trophic status index was calculated ranking percentage oxygen saturation (O₂ %sat), transparency (transp) and total phosphorus (TP). The means of O₂ %sat, transp and TP weighted by the species abundances were calculated to have optimum values for each species; a benthic quality index was then obtained by multiplying the weighted means of O₂ %sat, transp and TP by species abundances and dividing the product by the total number of specimens present at each station. A significant correlation was observed between trophic status and the benthic quality index. A good agreement was also observed between the indexes calculated using the large database and the second dataset on small lakes.     

A fish-based multimetric index for Brazilian savanna streams

Multimetric indices (MMI) have been widely used to assess ecosystem conditions because they are low-cost, employ a rapid field method, and can incorporate various biological metrics at different levels of biological organization. Our objective was to create a fish-based multimetric index applicable to all streams of the Brazilian savanna biome (Cerrado), the second largest biome in Brazil and deemed a global biodiversity hotspot. We evaluated 156 sites in two river basins (Paraná and São Francisco) and selected metrics capable of distinguishing stream-sites across a gradient of anthropogenic disturbances. We employed two different MMI approaches to determine if an MMI based on natural variation-adjusted metrics performed better than one based on unadjusted metrics. In addition, we assessed the performance of the two final MMIs and their sensitivity to anthropogenic pressures at local (LDI), catchment (CDI) and both scales integrated (IDI). Finally, we employed the power of a probability sample survey design to infer headwater stream conditions across a hydrologic region of approximately 47,000 km². Our final MMI for Brazilian savanna streams included six metrics: % common species; % characiform individuals; % loricariid individuals; % trichomycterid individuals; % invertivore species, and % Poecilia reticulata individuals. MMI₁ (unadjusted metrics) performed better than MMI₂ (natural variation-adjusted metrics) in discriminating least- and most-disturbed sites, but MMI₂ distinguished intermediate from most-disturbed sites better than MMI₁. Both indices were negatively correlated with the CDI scores; however, only MMI₂ was negatively correlated with the IDI scores. We inferred that 709 km (9.35%) of streams in the studied hydrologic region were in good condition, 8115 km (82.73%) were intermediate, and 641 km (7.91%) were in poor condition. We conclude that the MMIs proposed in this study have great potential for widespread application because they integrate data from two of the most important Brazilian river basins included in a biome that represents more than 20% of the country. Furthermore, the metrics retained in the indexes are easy to access with a rapid low-cost field method. However, their feasibility in areas influenced by mining, as well as in different biomes, should be tested.     

An improved macroinvertebrate multimetric index for the assessment of wadeable streams in the neotropical savanna

Multimetric indices (MMIs) have been successfully used to assess ecological conditions in freshwater ecosystems worldwide, and provide an important management tool especially in countries where biological indicators are fostered by environmental regulations. Nonetheless, for the neotropics, the few published papers are limited to small local scales and lack standardized sampling protocols. To fill the gaps left by previous studies, we propose a stream MMI that reflects anthropogenic impacts by using macroinvertebrate assemblage metrics from a data set of 190 sites collected from four hydrologic units in the Paraná and São Francisco River Basins, southeastern Brazil. Sites were selected through use of a probabilistic survey design allowing us to infer ecological condition to the total of 9432 kilometers of wadeable streams in the target population in the four hydrologic units. We used a filtering process to determine the least- and most-disturbed sites based on their water quality, physical habitat structure, and land use. To develop the MMI, we followed a stepwise procedure to screen our initial set of biological metrics for influence of natural variation, responsiveness and discriminance to disturbances, sampling variability, and redundancy. The final MMI is the sum of 7 scaled assemblage metrics describing different aspects of macroinvertebrate assemblage characteristics: Ephemeroptera richness, % Gastropoda individuals, Shannon-Wiener diversity index, % sensitive taxa richness, % scraper individuals, temporarily attached taxa richness, and gill respiration taxa richness. The MMI clearly distinguished the least-disturbed sites from the most-disturbed sites and showed a significant negative response to anthropogenic stressors. Of the total length of wadeable streams in the study area, 38%, 35%, and 27% were classified by the MMI as being in good, fair, and poor condition, respectively. By reducing the subjectivity of site selection, rigorously selecting the set of reference sites, and following a standardized metric screening method, we developed a robust MMI to assess and monitor ecological condition in neotropical savanna streams. This improved MMI provides an effective ecological tool to guide decision makers and managers in developing and implementing improved, cost-effective environmental policies, regulations, and monitoring of those systems.     

Detection of organic pollution of streams in southern Sweden using benthic macroinvertebrates

A ²¹⁰Pb-dated sediment core from a small bay in the southern basin of Lake Petén Itzá, Guatemala documents recent cultural eutrophication. Increased sediment accumulation beginning ～1930 A.D. coincided with catchment population growth and was a consequence of watershed deforestation and increased surface run-off. At the same time, geochemical records from the Lake Petén Itzá sediment core indicate increased phosphorus loading and organic matter accumulation. High nutrient concentrations after 1965 A.D. coincided with lower sediment C/N ratios, suggesting an increase in the relative contribution of phytoplankton to the organic matter pool. This inference is confirmed by the dominance of eutrophic and hypereutrophic diatom species. Organic matter δ¹³C values decreased after 1965 A.D., seemingly contradicting other indicators of recent eutrophication in the southern basin of Lake Petén Itzá. Relatively depleted δ¹³C values in recent sediments, however, may reflect a contribution from ¹³C-depleted sewage effluent. Increased δ¹⁵N of organic matter after 1965 A.D. indicates changes in the dissolved inorganic nitrogen delivered to the lake. The relatively small increase in δ¹⁵N (～0.6‰ ) is less than might be expected with nitrate loading from sewage and soils, and might be offset by the presence of nitrogen-fixing cyanobacteria with low δ¹⁵N values.     

Assessing acid stress in Swedish boreal and alpine streams using benthic macroinvertebrates

Sixty streams in northern Sweden were sampled for benthic macroinvertebrates in spring and autumn of 2000 as part of the European Union project AQEM (the Development and Testing of an Integrated Assessment System for the Ecological Quality of Streams and Rivers throughout Europe using Benthic Macroinvertebrates). Samples were taken using a harmonised multi-habitat sampling procedure and a large number of parameters describing the streams and their catchments were recorded for all sampling sites. From the stream water chemistry characteristics unbiased measures of acid stress were derived, based on the Swedish Ecological Quality Criteria (EQC) for acidity status. These criteria do not, however, assess the degree of human influence to a stream. Therefore, in the following analysis of classification, the Swedish EQC status criteria are applied as if they were a measure of human influence. Three new multimetric acid indices using benthic macroinvertebrates were developed for the AQEM project. These, together with a large number of other benthic macroinvertebrate indices including a number of indices aimed at detecting acid stress, were evaluated for their ability to detect acid stress, using both spring/early summer and autumn sampling. Surprisingly, the acid index that is in general use in northern Sweden worked well in spring/early summer, but because of a (probable) re-colonisation of more acid sensitive taxa, the index values changed from classifying streams as affected in spring/early summer to classify streams as non-affected by acid stress in autumn. Another Swedish acid index (included in the Swedish Environmental Quality Criteria developed by the Swedish EPA) and developed for southern Sweden was strongly correlated between spring/early summer and autumn and could thus be sampled in the autumn and indicate acid stress from spring flood declines in pH. This is of great importance since the local County boards of northern Sweden generally argue that sampling has to be done in the spring to see the effects of acid stress, when sampling is difficult for logistic reasons. Whether or not the three indices developed for the AQEM project (and extensively based on the south Swedish acid index) were truly better than the south-Swedish acid index to assess acid stress in northern Sweden could not be clearly determined in the present study.     

Refining a kick sampling strategy for the bioassessment of benthic macroinvertebrates in headwater streams

Small headwater streams constitute a large proportion of the river channel network in many parts of the world. In this study, two multihabitat kick sampling methods (60-second and 20-second) were compared across 10 small headwater streams in the southwest and east of Ireland in spring and summer 2009 to determine the influence of sampling on various benthic macroinvertebrates in headwater streams. The performance of each method, over time and replication, was examined using a range of benthic macroinvertebrate metrics, as well as the community composition and structure recorded by both methods. The ability to recruit taxa, as well as the field sampling and laboratory processing effort required for each method, was also assessed. Results indicated that both kick sampling methods generally recorded similar metric scores with the exception of taxonomic richness (t = 180 s and n = 9 replicates test) where the 20-second kicks consistently out preformed those calculated for the 60-second kicks. All other metrics compared generally performed equally as well regardless of the method used. Multivariate analysis of macroinvertebrate community assemblage, using SIMPROF, RELATE and CS-SMC analyses, further highlighted the high similarity in the macroinvertebrate assemblage recorded between both methods. Finally, the 20-second kicks recruited taxa as efficiently as 60-second kicks samples so long as replication was equal but required less sampling effort (NSE) and processing time. Therefore, the shorter 20-second kicks can be used to assess the ecological health of headwater streams, provided that adequate replication is adopted, resulting in significant effort, cost and time savings.     

Development and application of benthic macroinvertebrate-based multimetric indices for the assessment of streams and rivers in the Taihu Basin,China

The development of biological indicators for assessing ecological conditions in streams and rivers is urgently needed in China, particularly in heavily impacted regions. The aim of this study was to develop and apply benthic macroinvertebrate-based multimetric indices (MMIs) for the assessment of streams and rivers in the western hill and eastern plain aquatic ecoregions of the Taihu Basin. MMIs were based on samples collected from October 16 to November 8 2012 at 120 sites in streams and rivers. Least disturbed sites defined the reference conditions. Chemical water quality, physical habitat, and land use were used as criteria to identify reference sites in the basin. Metrics related to benthic macroinvertebrate richness, composition, diversity and evenness, pollution tolerance, and functional feeding groups were screened by range, sensitivity, responsiveness, and redundancy tests. Total number of taxa; percentage of Ephemeroptera, Trichoptera and Odonata (% ETO); Berger–Parker’s index (BP); Biotic index (BI); and percentage of filterers–collectors (% FC) were used to construct the MMI for the western hill aquatic ecoregion (MMI_W). Total number of taxa, percentage of Crustacea and Odonata (% CO), BP, BI, and % FC were used to construct the MMI for the eastern plain aquatic ecoregion (MMI_E). The MMI scores were obtained by combining the rating categories (excellent, good, fair, poor, and very poor). The MMIs were tested using a separate subset of the data, and the results indicated that the newly developed MMIs were robust in terms of percentage of sites correctly classified, coefficient of variation, box-separation ratios, and separation powers. The ecological status was then evaluated based on the MMI scores. The results indicated that the general ecological status of streams and rivers in the Taihu Basin was rated lower than “good”, the western hill aquatic ecoregion was rated “fair” and the eastern plain aquatic ecoregion was rated “poor”. Moreover, the MMIs showed a significant negative response to an increasing gradient of disturbance. Therefore, these preliminary MMIs can be used as assessment tools in ecological biomonitoring and management of the Taihu Basin.     

Modelling the hydraulic preferences of benthic macroinvertebrates in small European streams

1. Relating processes occurring at a local scale to the natural variability of ecosystems at a larger scale requires the design of predictive models both to orientate stream management and to predict the effects of larger scale disturbances such as climate changes. Our study contributes to this effort by providing detailed models of the hydraulic preferences of 151 invertebrate taxa, mostly identified at the species level. We used an extensive data set comprising 580 invertebrate samples collected using a Surber net from nine sites of second and third order streams during one, two or three surveys at each site. We used nested non‐linear mixed models to relate taxon local densities to bed shear stresses estimated from FliesswasserStammTisch hemisphere numbers. 2. An average model by taxon, i.e. independent from surveys, globally explained 25% of the density variations of taxa within surveys. A quadratic relationship existed between the average preferences and the niche breadth of taxa, indicating that taxa preferring extreme hemisphere numbers had a reduced hydraulic niche breadth. A more complete model, where taxa preferences vary across surveys, globally explained 38% of the variation of taxa densities within surveys. Variations in preferences across surveys were weak for taxa preferring extreme hemisphere numbers. 3. There was a significant taxonomic effect on preferences computed from the complete model. By contrast, season, site, average hemisphere number within a survey and average density of taxa within a survey used as covariates did not consistently explain shifts in taxon hydraulic preferences across surveys. 4. The average hydraulic preferences of taxa obtained from the extensive data set were well correlated to those obtained from two additional independent data sets collected in other regions. The consistency of taxon preferences across regions supports the use of regional preference curves for estimating the impact of river management on invertebrate communities. By contrast, the hydraulic niche breadths of taxa computed from the different data sets were not related.     

A method to estimate the population size of benthic macroinvertebrates in streams

Summary A method is described by which samples of stream macroinvertebrates can be linked to the roughness of the substratum, the water depth, the velocity, and to a combination of these factors, i.e., Froude number and thickness of the laminar sublayer, at the exact point of sampling. The abundance of Odagmia ornata (Diptera: Simuliidae), the species considered in this study, was not related to roughness, but depended with increasing significance on depth, velocity, Froude number, and laminar sublayer. Therefore, it is suggested that the population size of stream macroinvertebrates can be estimated using the relationships between abundance and the most suitable hydrodynamic factor. For this purpose it is necessary only to measure the physical factors and then to calculate the abundance, using both these measurements and the abundance-hydrodynamic factor relationships formerly established.A longer section of a stream with a relatively wide range of habitats was sampled for 1 week, during which the new method yielded results that reached the level of accuracy per sampling effort obtained to date only when a narrower range of habitats was sampled, usually only one stream riffle. Under the latter conditions, the new method is suggested to yield results of increased accuracy, particularly if samples are taken within a short period.     

Design and implementation of rapid assessment approaches for water resource monitoring using benthic macroinvertebrates

Abstract Benthic macroinvertebrates are the group of organisms most widely used for assessment of water resources. Rapid assessment approaches are intended to be efficient and cost effective; savings are found in reduced sampling and more efficient data analysis. Rapid bioassessment programmes have been quickly accepted and now cover most of the United States (US) and equivalent programmes cover all of the United Kingdom (UK). Rapid bioassessment programmes are designed to screen large regions, pinpointing trouble spots worthy of more detailed attention. Fundamental to all rapid bioassessment methods is the classification of streams so that comparisons can be made between reference areas and areas of concern, or test sites with similar characteristics. Both the UK and US approaches assess habitat characteristics. These characteristics are used to predict the fauna expected at a test site in the UK approach; in the US they are used as an aid to classification and interpretation of aquatic faunal data. Habitat assessments in the US are also used to determine whether poor water quality or degraded habitat are stressing the invertebrate communities. This is a major development in approaches to water resource assessment. In the UK, a model developed using multivariate statistics uses a few environmental variables thought to be unaffected by human activities to predict the fauna expected at a test site. The US approaches analyse data using several indices (or metrics) presumed to represent ecological features of interest. These indices have a range of sensitivities to different kinds of stress and must be calibrated for the area of interest. The two approaches have been developed in isolation but may have much to offer each other. Developing programmes are advised to consider both. Future needs include: development of procedures that can be applied to large rivers and to lakes; further refinement of ecological principles underlying metric choice; the inclusion of chemical criteria and toxicity tests to establish thresholds that indicate impairment; and development of criteria indicating the necessity for implementation of quantitative assessment studies.     

Responses of benthic macroinvertebrates in small intermittent streams to silvicultural practices

We examined macroinvertebrate communities in small(0.1-1.0 m²) pools of intermittent streams (alwayscontainingsome water but without perennial flow) with small watersheds(2-6 ha) subjected to five types of forest harvest to assesspotential impacts of the different harvest methods. Bufferstrips10 m wide were left on each side of the streams. Each harvesttreatment was coupled with a similar unharvested referencestand.An incomplete block design included three 0.05 m² vacuumsamples from each treatment paired with three from theadjacentreferences. There was a high degree of similarity amongreferencesfor parameters other than taxonomic composition (e.g.macroinvertebrate density, number of species, Shannondiversity,functional groups, etc.). Statistically significantdifferenceswere found between references and treatments and among harvestmethods but the responses varied among response variables(density,Shannon-Weiner diversity, species composition), differentspeciesassemblages (all invertebrates, chironomids,Ephemeroptera-Plecoptera-Trichoptera [EPT], isopods), andfunctional group categories (shredders, collector-gatherers).Wecollected 56 taxa, 7–16 per site, with low communitysimilarity(mean Jaccards=0.18, mean Bray-Curtis percentdissimilarity=81). The most severe harvest treatmentsresultedin the highest diversities of total invertebrates in thesesmallspring pool communities.