Assessment of organic pollution effect considering differences between lotic and lentic stream habitats

Based on the requirements of the Water Framework Directive, a macroinvertebrate-based assessment system to evaluate the ecological quality of streams has been developed by AQEM project consortium. In the Czech Republic the impact of organic pollution was principal pressure studied, but some morphological degradation of some sampling sites could not be avoided. A multimetric assessment system for three stream types was developed. Detrended Correspondence Analysis was used for the detection of the response of macroinvertebrate communities to the gradient of organic degradation. Significant relationships between abiotic (BOD, TOC, nutrients) and biotic (saprobic index, ASPT) indicators of organic enrichment/eutrophication were identified. Separate storage of the riffle and pool components of each multi-habitat sample allowed differences between these habitats to be compared in context of the metrics applied in the assessment system. Lotic and lentic habitats differed in taxonomic composition, ecological traits and biotic indices. The separate assessment of the riffle and pool parts of samples provides additional useful information when combined effects of organic pollution and morphological degradation are to be considered.     

Towards a multimetric index for the assessment of Dutch streams using benthic macroinvertebrates

This study describes the development of a macroinvertebrate based multimetric index for two stream types, fast and slow running streams, in the Netherlands within the AQEM project. Existing macroinvertebrate data (949 samples) were collected from these stream types from all over the Netherlands. All sites received a ecological quality (post-)classification ranging from 1 (bad status) to 4 (good status) based on biotic and abiotic variables, using a combination of multivariate analysis and expert-judgement. A number of bioassessment metrics was tested for both stream types (fast and slow running streams) to examine their power to discriminate between streams of different ecological quality within each stream type. A metric was selected for inclusion in the final multimetric index when there was no overlap of the 25th and 75th percentile between one (or more) ecological quality class(es). Out of all metrics tested, none could distinguish between all four ecological quality classes without overlap of the 25th and 75th percentile between one or more of the classes. Instead, metrics were selected that could distinguish between one (or more) ecological quality class(es) and all others. Finally, 10 metrics were selected for the assessment of slow running streams and 11 metrics for the assessment of fast running streams. Class boundaries were established, to make the assignment of scores to the individual metrics possible. The class boundaries were set at the 25th and/or 75th percentile of the individual metric values. The individual metrics were combined into a multimetric index. Calibration showed that 67% of the samples from slow running streams and 65% of the samples from fast running streams were classified in accordance to their post-classification. In total, only 8% of the samples differed more than one quality class from the post-classification. The multimetric index was validated with data collected in the Netherlands from 82 sites for the purpose of the AQEM project. Validation showed that 54% of the streams were classified correctly.     

Comparing macroinvertebrate indices to detect organic pollution across Europe: a contribution to the EC Water Framework Directive intercalibration

With the EC Water Framework Directive (WFD) the ecological status of a water body is defined by comparing the observed biological community composition present with near-natural reference conditions. The ecological status is then classified into five quality classes (high, good, moderate, poor and bad). It is of great importance that `good ecological status' has the same meaning within the European Union, since water bodies not measuring up to these standards have to be improved. Therefore, the Ecological Quality Ratios (EQR) at high-good, and good-moderate quality class boundaries will be intercalibrated. Each country has to report physical, chemical, and biological data from two sites at each of these boundaries and since most data exist for benthic macroinvertebrates, this quality element will be of great importance in the intercalibration process. The aim of this study was therefore to compare the results of different benthic macroinvertebrate metrics used to assess the impact of organic pollution (including eutrophication) (one of the major human impacts on European streams). A selection of the data sampled in the AQEM project was evaluated, where benthic macroinvertebrate- and abiotic data from four countries (Austria, the Czech Republic, Portugal and Sweden) and seven `stream types' were included. An organic pollution (including eutrophication) gradient was defined using Principal Component Analysis and the boundaries for high-good and good-moderate ecological status set by the partners from each country were used to define arbitrary class boundaries. The Average Score Per Taxon (ASPT) was well correlated with the stress gradient in most stream types, whereas the Saprobic Index worked clearly better than ASPT in those countries (Austria and the Czech Republic) where macroinvertebrates are generally identified to lower (species) as opposed to a higher (genus or family) level of identification. Defining harmonised class boundaries is difficult; this process has to consider the natural differences between stream types (e.g. in the reference values of metrics) but has to eliminate different perceptions of ecological quality.     

Assessment of temporary streams: the robustness of metric and multimetric indices under different hydrological conditions

The generalization of ecological results from temporary streams needs the study of those ecosystems across a broad scale of running waters, covering the geographical ecological constraints involved (e.g., precipitation, temperature and geology). For the particular situation of Mediterranean streams in Southern Europe, high changes in water level, with unpredicting flood events, represent an important factor determining the structure and function of Mediterranean streams. This variability, inducing accentuated changes in the macroinvertebrate community, tends to influence the assessment methodologies. A set of metrics commonly used in Europe to assess organic degradation (Shannon–Wiener index, evenness, richness, BBI, IBE, BMWP′, ASPT′, DSFI, EPT, number of Trichoptera families, percentage of Gasteropoda, Oligochaeta and Diptera) and a multimetric index (IM9) developed to assess organic degradation in southern siliceous Portuguese basins were tested to evaluate quality at two contrasting sites (one unimpaired and another impaired by an identified point source of pollution). The multimetric index (IM9) composed by: ASPT′ (average score per taxon); GOLD (one minus percentage of Gasteropoda, Oligochaeta and Diptera); and TRICF (number of Trichoptera families), was the most suitable assessment methodology. IM9 presented a quite stable temporal pattern from February in late winter until June in early summer, even under the effect of episodic floods. A stepwise regression showed that most of tested metrics were significantly related to environmental variables (soluble reactive phosphorous, dissolved inorganic nitrogen and dissolved oxygen). Only richness, IBE and BMWP′ were not significantly influenced by environmental variables. Future research must be done covering the complete gradient of organic degradation, including the extension of multimetric assessment methodologies to temporary streams located in other regions under different geological and climatic conditions.     

Macrozoobenthos communities and biocoenotic assessment of ecological status in relation to degree of human impact in small streams in southwest Germany

One of the major objectives of the VALIMAR project is to determine the ecological significance of various fish biomarker studies as indicators of chronic pollution in small streams in southwest Germany. Results of these fish biomarker investigations were compared to information from complementary studies on the meiobenthos, macrobenthos, and fish community studies to assess the ecological significance of these biomarker investigations. The main objective of this study was to provide biological assessments of the biomarker sites on the basis of the macrozoobenthos communities. Since no validated framework for the assessment of the biological integrity existed in Germany, two multimetric approaches were adapted to the whole stream system by investigating benthos and fish communities of 46 sites of varying degrees of human disturbance. Assessment of the communities was conducted in accordance with the European Community Water Framework Directive. Species distribution of benthos depended upon stream type and pollution status of streams. Biological attributes and bioindices of benthos communities, however, did not correlate with typological parameters like stream size or dominant substrate but correlated better with pollution parameters like conductivity or chloride concentration. Using a set of 18 measures, such as portion of sessile individuals, Rheoindex, oxygen availability index, and portion of pool dwellers, the benthos communities were characterized and evaluated. The composition of the fish communities was mainly determined by stream type, pollution and migration barriers. The influence of chemical parameters could be assessed by developing a“fish chemistry index”, which calculatesthe similarity of the present fish community with the potential natural community, but excludes those species strongly effected by deficits in stream channel morphology. Both fish chemistry index and benthic indices strongly correlated with pollution index parameters, clearly distinguishing between the more polluted Körsch sites and the less pollutedKrähenbach and Aich sites. Most of the single bioindices as well as overall assessment by multimetric indices indicated a gradient of decreasing quality from the reference stream Krähenbach to theslightly polluted Aich and Körsch upstream site (KE, upstream of all sewage treatment plants) and finally to the most polluted Körsch site directlybelow the most upstream sewage treatment plant (KD). According to the Water Framework Directive, the classification of ecological status of the benthos communities ranges from “high” (best of 5 classes) forthe reference stream to “bad” (5th class) for KD. Assessment of the fish community tends to score somewhat worse than the benthos due to deficits in morphological quality of the stream reaches. The benthos assessment and the newlydeveloped “fish chemistry index” correlated well with chemical water quality and hence with biomarkers, whereas ecological status of fish and overall ecological status was also influenced by river morphology. In conclusion all tested assessment methods on biocoenotic level are reliable indicators for the degree of human disturbance on small streams, whereas biomarkers are more suited for risk assessment and the investigation ofcause-effect-relationships.     

The invertebrate species index (ISI) for streams in southeast Queensland,Australia

The invertebrate species index (ISI) is a new biotic index to assess stream health in southeast Queensland, Australia, using benthic macroinvertebrates. The index aims to refine stream monitoring, in particular for eutrophication, as nutrient input is a major stressor of streams in the region. Biotic indices previously used for the region were based on sensitivity scores for macroinvertebrate families and orders, and were valid for all streams across the continent. The ISI is based on species level and tailored to the specific traits of southeast Queensland, thus yielding an increased level of detection of biological change. This will improve monitoring of environmental impact on a regional and local scale. The ISI is a site-specific index calculated as the weighted average (WA) of species’ sensitivity scores (S₁₀), with a species-specific indicator weight (W) and the abundance (A) of each species used as weights. S₁₀ scores for 203 species of benthic macroinvertebrates ranging from 10 (species most sensitive to pollution) to 1 (tolerant of excessive pollution) were derived by means of WA regression and calibration using site scores representing an environmental impact gradient. W measures the indicator strength of the species, and was derived from the weighted standard deviation of the S₁₀. The initial site scores for the WA modeling were derived using canonical correspondence analysis (CCA) to ordinate the sites along a gradient associated with 12 abiotic variables. The data on benthic macroinvertebrates are based on 212 quantitative samples collected in wadeable freshwater streams in southeast Queensland. Two major stream types, (1) small creeks, mainly of uplands and (2) larger streams and rivers of lowlands, were recognised for the region, and for both types the ISI range representing reference condition was established. These reference conditions can be used to establish ecological quality ratios by comparing observed to expected indices and to define ecological quality classes. The ISI is the first biotic index for streams in Australia that uses sensitivity scores and indicator weights for macroinvertebrate species. There is a growing trend in Australia to identify stream macroinvertebrates to species level and to study their specific traits and ecological requirements. The reasons for this are manifold; assessing and monitoring stream health is only one of them. For most regions of Australia, no common ground exists, so far, on how to use species data for stream health assessment. The new biotic index fills this gap for southeast Queensland in providing a standard for the use of species level data in stream health assessment.     

High spatial variability biases the space-for-time approach in environmental monitoring

The space-for-time approach is widely used in fundamental and applied ecology but assemblages from some habitats are highly variable. For example, streams may show marked spatio-temporal changes in the taxonomic composition of the macroinvertebrate assemblages. We exemplify the effect of the temporal component ‘season’ on some assemblage-derived stream quality assessment metrics under the assumptions of the space-for-time and the replicated samples approaches. Benthic macroinvertebrates were sampled in spring, summer, and fall from two stream types, namely streams in the Pleistocene sediments of the alpine foothills and small fine substrate dominated siliceous highland rivers in southern and central Germany. As exemplified for ASPT and the German multimetric index (MMI), the data showed no effect of season when samples were regarded as independent, whereas stream quality decreased between spring and fall in the replicated samples approach. The transformation of MMI to rank-ordered stream quality classes depicted a decrease in perceived stream quality in 29% and 54% of the sites by summer and early fall, respectively, when compared to spring samples. We thus suggest (1) to test seemingly robust metrics in a repetitive measures approach for other stream types and regions, and (2) to standardize the sampling season for ecological quality assessment. Based on this example, we assume that many subtle, but significant, environmental trends are still to be detected in highly heterogeneous habitats from various ecosystems.     

河流岸带湿地沉积物重金属分布对植被物种多样性和底栖动物群落特征的影响

河流岸带湿地栖息地完整性对河流水环境、水生态和水文的安全与健康具有重要意义,为探究河流岸带湿地表层沉积物重金属分布特征及其对植被和底栖动物的影响,对滦河干流上中下游河段表层沉积物、植物群落和底栖动物调查分析,采用生物毒性效应系数法和综合潜在生态风险指数法评价沉积物重金属污染特征,采用植被物种多样性指数和底栖动物完整性指数评价滦河植物和底栖动物群落特征,探究岸带湿地沉积物重金属空间分布与植被及底栖动物群落特征之间关系。结果表明,滦河表层沉积物总体呈清洁水平,但不同河段重金属空间分布差异较大,下游重金属生态危害系数和潜在生态风险指数高于上中游。湿地物种调查共识别维管束植物219种,大型无脊椎底栖动物105种,综合评价结果表明下游植物群落物种多样性和底栖动物群落完整性低于上中游。滦河下游岸带湿地沉积物重金属对生物群落具有生物毒性和潜在的生态风险,降低了植被物种多样性和底栖动物群落完整性。大型底栖动物完整性指数能够综合反映底栖动物群落结构特征变化,对河岸带湿地生态健康评价和监测具有重要意义。     

The use of benthic macroinvertebrate families for river quality assessment in Lithuania

The aim of this study was to evaluate the influence of environmental factors on the distribution of macroinvertebrate taxa in different sized lowland Lithuanian rivers. A secondary aim was to assess ecological river quality and to determine the most suitable biotic index. A final aim was to determine the most appropriate macroinvertebrate families for river quality assessment in Lithuania. Species composition and quantitative characteristics of benthic macroinvertebrate communities have been investigated using standard kick-sampling method by a standard hand net in 24 different river sites in spring. Physical and chemical environmental parameters were measured in the same study site as the macroinvertebrate sampling. A total of 186 taxa representing 66 families or higher taxonomic ranks of benthic macroinvertebrates have been identified. Water temperature and current velocity influenced the highest number of ivestigated families. Seven of the most tolerant and eleven of the most sensitive macroinvertebrate taxa for hydrochemical parameters related with organic pollution were determined. The DSFI method was founded to be the best index for assessment of ecological status for Lithuanian rivers until more accurate estimation method will be created.     

River channel habitat diversity (RCHD) and macroinvertebrate community

Correspondence of habitat and macroinvertebrate diversity was investigated in twenty Czech rivers. With regard to the importance of river characteristics (depth, current velocity and substratum) River Channel Habitat Diversity method was developed within this paper. The method is focused directly on the stream wetted channel and it assesses habitat diversity and richness computed as Shannon-Wiener’s index. Macroinvertebrate samples were taken by the national PERLA method at each study site, diversity index was also calculated and compared with habitat and substrate diversity. Habitat diversity was important for macroinvertebrate communities according to multivariate assessment, but contrary to the hypothesis it was not significantly correlated with macroinvertebrate diversity. Based on the results, broader rivers had lower habitat diversity than smaller streams, and were more influenced by human activities (lower habitat diversity, higher pollution). Results obtained by the RCHD and RHS methods were not significantly correlated.     

Stream invertebrate diversity reduces with invasion of river banks by non‐native plants

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Impacts of acidification on macroinvertebrate communities in streams of the western Adirondack Mountains,New York,USA

Limited stream chemistry and macroinvertebrate data indicate that acidic deposition has adversely affected benthic macroinvertebrate assemblages in numerous headwater streams of the western Adirondack Mountains of New York. No studies, however, have quantified the effects that acidic deposition and acidification may have had on resident fish and macroinvertebrate communities in streams of the region. As part of the Western Adirondack Stream Survey, water chemistry from 200 streams was sampled five times and macroinvertebrate communities were surveyed once from a subset of 36 streams in the Oswegatchie and Black River Basins during 2003–2005 and evaluated to: (a) document the effects that chronic and episodic acidification have on macroinvertebrate communities across the region, (b) define the relations between acidification and the health of affected species assemblages, and (c) assess indicators and thresholds of biological effects. Concentrations of inorganic Al in 66% of the 200 streams periodically reached concentrations toxic to acid-tolerant biota. A new acid biological assessment profile (acidBAP) index for macroinvertebrates, derived from percent mayfly richness and percent acid-tolerant taxa, was strongly correlated (R² values range from 0.58 to 0.76) with concentrations of inorganic Al, pH, ANC, and base cation surplus (BCS). The BCS and acidBAP index helped remove confounding influences of natural organic acidity and to redefine acidification-effect thresholds and biological-impact categories. AcidBAP scores indicated that macroinvertebrate communities were moderately or severely impacted by acidification in 44–56% of 36 study streams, however, additional data from randomly selected streams is needed to accurately estimate the true percentage of streams in which macroinvertebrate communities are adversely affected in this, or other, regions. As biologically relevant measures of impacts caused by acidification, both BCS and acidBAP may be useful indicators of ecosystem effects and potential recovery at the local and regional scale.     

Invasive willows drive instream community structure

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Analysis of structural and functional indicators for assessing the health state of mountain streams

Mountain streams play a key role in the conservation of aquatic biodiversity and key ecosystem services; however human activities are threatening these ecosystems as mountain areas become more and more developed and intensively used. Many of these streams are not considered in current national monitoring programs due to their small catchment area. However, assessing their status and monitoring their trends is well needed to ensure their proper management and conservation. In this study, we evaluated the use of a range of indicators related to different ecosystem structural and functional components in 2 streams affected by sewage outflows and compared with an unpolluted stream in the Picos de Europa National Park (Spain). We surveyed benthic periphyton, macroinvertebrate communities and fish assemblages and also estimated periphyton growth rates, wood decomposition rates and river metabolism. Additionally, we compared the performance of the selected indicators in different hydraulic conditions. Results revealed an effect of the organic pollution on most of the functional and structural indicators for the most polluted stream. Only the number of Ephemeroptera, Plecoptera and Trichoptera taxa, the Iberian Biomonitoring Working Party index, the invertebrate multimetric index used by the regional water agency, the fish abundance and biomass were sensitive enough to detect low levels of pollution and followed the expected response to the pollution degree. Moreover, most of the indicators behaved similarly under different hydraulic conditions, without major differences between pools and runs. However, the combination of both pool and run replicates at the reach scale resulted in a higher detection capacity of the effects of organic pollution.     

Macroinvertebrate/sediment relationships along a pesticide gradient in Danish streams

Twenty-nine Danish streams were investigated in September 1998. The streams drained catchments of varying hydrology, topography, soil type and land use. In each stream, the newly accumulated streambed sediment was sampled and subsequently analysed for pesticides. In each stream, five replicate macroinvertebrate samples were taken in the same sediments as the pesticide samples. In addition, five samples were taken in riffles to provide a complete picture of macroinvertebrate community composition. The number of detected pesticides reflected soil type and land use: in agricultural catchments on clay soils the average number of pesticides were 4.3±2.2; on sandy soils 2.6±1.0, while only 1.5±0.6 pesticides were found in streams without agricultural activities. The macroinvertebrate composition showed clear changes along this gradient of sediment pesticide concentrations. The number of the amphipod Gammarus pulex was negatively correlated with sediment pesticide concentration, while the number of Oligochaeta and Hirudinae was positively correlated. The findings indicate that pesticides have a potential to structure macroinvertebrate communities in Danish streams. However, agricultural impact is more than pesticides, and several other factors, such as channelisation, affect the macroinvertebrate community and these are not easily separated.     

A comparison of bacteria and benthic invertebrates as indicators of ecological health in streams

1. We set out to evaluate the reliability of bacterial communities as an indicator of freshwater ecological health.
2. Samples of epilithic biofilm were taken over a 1-year period from four streams, each impacted by varying degrees of human modification. The bacteria within each sample were characterised using a whole community DNA fingerprinting technique (automated ribosomal intergenic spacer analysis). Spatial and temporal differences in community structure between samples were visualised using multi-dimensional scaling and quantified using permutational multivariate anova . Macrobenthic invertebrates, which are commonly used as indicators of stream ecological health, were also sampled for comparison.
3. Multivariate analysis revealed a clear gradient in macroinvertebrate community structure between sites exposed to increased human impact. Bacterial communities, however, could only distinguish the most impacted site from the remainder.
4. Additional research is required to increase the sensitivity of bacterial community analyses before endorsing their use as an indicator of freshwater ecological health.     

Development of a biotic index using stream macroinvertebrates to assess stress from deposited fine sediment

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Characterizing macroinvertebrate communities across China: Large-scale implementation of a self-organizing map

Understanding the geographical patterns and divisions of communities is a fundamental step in achieving the sustainable management of ecosystems, especially in deteriorating global and local environments. The idea of geographical division has been applied on all continents but Antarctica, but it has never been rigorously tested for stream ecosystems in China, leaving a gap in knowledge for many basic and applied research questions regarding, for example, diversity patterns, conservation issues or climate change effects. To fill this gap, we aimed to (1) evaluate the geographical divisions of the macroinvertebrate communities in Chinese streams using the self-organizing map (SOM) method and (2) to characterize the distribution patterns in relation to different environmental variables. Macroinvertebrates were collected from 57 relatively clean stream sites covering a south-north gradient along the boundary of the geographic ladder (or altitudinal divide) in China. SOM was used to analyze large-scale biogeographical divisions of the macroinvertebrate communities. The sampling sites were divided into six clusters, distinguishing the samples from northern, central, and southern China. This pattern was also reflected by biotic metrics (abundance, biomass, taxa and sum of Ephemeroptera, Plecoptera, and Trichoptera richness, and diversity). The gradient of environmental variables, particularly water quality variables, was similar between the clusters, with the exceptions of two clusters from southwestern China when considering altitude and one cluster from northern China when considering conductivity and TN. The different clusters from the SOM were associated with indicator species, with clean-water adapted species dominating in southwestern China and pollution tolerant species in northern China. However, there were no significant correlations between environmental variables and biotic metrics. The overall combination of environmental variables and organism data suggests that spatial variation was the main predictor determining the composition of the macroinvertebrate communities on a large-scale, and the trained SOM appeared to be efficient at classifying streams on a broad geographic scale.     

A tool to assess the ecological condition of tropical high Andean streams in Ecuador and Peru: The IMEERA index

The main objective of this study was to develop a highland Andean streams ecological assessment tool for managers to determine the biological quality in this broad area of South America. Sampling was conducted during the dry season at 123 sites in eight watersheds of high Andean streams from south of Peru to North of Ecuador. The sites were at elevations above 2000 m a.s.l., and ranged in anthropogenic disturbance from none or little (reference) to highly disturbed. Using the physicochemical, hydromorphological and aquatic macroinvertebrate assemblage attributes of the reference sites, two different elevation bioregions were identified (from 2000 to 3500 m a.s.l. and those sites at altitudes higher than 3500 m a.s.l.). Differences between these two bioregions were related to the change in altitude of the most relevant environmental factors, i.e., temperature, oxygen content of the water and the extent of forested vegetation in the basin and in the riparian zone. These features were paramount to having different macroinvertebrate assemblages as demonstrated by an MDS analysis of our data. Two versions of the multi-metric index IMEERA were developed (the acronym comes from the Spanish name ‘Índice Multimétrico del Estado Ecológico para Ríos Altoandinos’) that corresponded to the two bioregions. In the lower altitude bioregion (Bosque river type, IMEERA-B index), the pressure gradient was driven by the organic pollution and the hydromorphological degradation. While in the higher elevation bioregion (Páramo and Puna river types; IMEERA-P river type), the gradient was driven by the organic pollution and the habitat heterogeneity. The IMEERA B index includes six macroinvertebrate metrics using its richness, habit characteristics and tolerance/intolerance to disturbances (EPT taxa, % clingers, % climbers, intolerant taxa, ABI and % tolerant taxa). The IMEERA P index was calculated using four metrics corresponding to macroinvertebrate richness and its tolerance/intolerance to disturbances (total taxa, intolerant taxa, ABI and % tolerant taxa). The index was validated with a set of independent data from the headwaters of Guayllabamba River in Ecuador.