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Chemical integrity plays a crucial role in maintaining the ecological integrity of aquatic ecosystems. Despite its significance, assessments of ecological integrity often prioritize biological evaluations, leading to infrequent and inadequate scrutiny of chemical integrity. Additionally, a comprehensive framework for separately assessing chemical integrity has not been established. To address this issue, we established a new index for evaluating chemical integrity, achieved through indicator screening, normalization, and weight assignment. Combined with the threshold indicator taxa analysis (TITAN) and Pearson correlation analysis, main evaluation indicators and their indicator species were identified and the corresponding response threshold was determined. These thresholds were then applied to improve the normalization method, with weights determined by indicator species proportions. This index was applied to evaluate the chemical integrity of the Huai River Basin, which is one of the largest basins in China. The results indicated that ammonia nitrogen (NH3-N), nitrate nitrogen (NO2-N), pH, and turbidity (Turb) were identified as the core parameters for evaluating chemical integrity. The conventional normalization method (max–min normalization) led to overestimation of the assessment results, whereas improved normalization method based on ecological threshold yielded better and more reasonable results. This study provided a reference for the selection of appropriate indicators and improvement of normalization method to better assess chemical integrity. And it would become a useful tool for monitoring and rehabilitating the chemical integrity in such basins.

Macroinvertebrate community structure parameters can reflect the water quality and water ecosystem health status of rivers. In this paper, using the results of macroinvertebrates in 16 urban rivers in Sichuan Province from November 2020 to March 2021, we independently evaluated the level of black odor in urban rivers based on the mathematical model. On this basis, we examined the community structure, fouling tolerance, diversity, and feeding functional groups of macrobenthos in rivers with different degrees of black odor. During the study, a total of 39 species of macroinvertebrates were collected and identified to 3 phyla, 7 classes, 16 orders, 26 families and 30 genera. Urban rivers changed from non-black and non-odorous to black and odorous: (1) the dominant species, Chironomus flaviplumus, Physa fontinalis and Barbronia weberi, changed to Chironomus flaviplumus, a fouling-tolerant species with wide adaptability; (2) According to the tolerance values (TVs), the pollution resistance categories gradually increased as the level of black odor increased, which indicated the level of black odor in water bodies; (3) The calculation of the Hilsenhoff biotic indices (HBI) indicated that 83.3% of the sampled sites were moderately to heavily polluted. In general, the severity of water quality pollution in the black and odorous type of river was significantly higher than that in the non-black and odorous type of river, and with the deepening of the degree of blackness and odor the quality of the water deteriorated; (4) The community structure had an unstable community structure and a low diversity index of macroinvertebrate species; (5) The taxa of feeding functional groups shifted from the presence of all five types of feeding functional groups to the dominance of fouling-resistant species represented by scrapers. The results summarize the characteristics and change patterns of various indicators under different black-odorous degrees, indicating that the HBI can be used as an alternative indicator for the evaluation of black odorous water, and the number of species of Chironomidae can indicate the degree of black odor in water bodies.

The loss of biodiversity in the era of fast environmental change is often revealed as biotic homogenization. In the large and nutrient-rich Lake Taihu located in eastern China, we evaluated the degree of specialization among organisms and the impact of environmental factors on macroinvertebrate assemblages. First, we measured the niche widths of macroinvertebrate species in respect to environmental conditions and utilized the Outlying Mean Index (OMI) analysis to categorize them into specialists and generalists. The effects of environmental factors on assemblages of macroinvertebrate taxa identified by varying niche widths were then investigated using the lake dataset. Within our study lake, habitats display considerable environmental gradients, resulting in habitat heterogeneity linked to several habitats, and have no barriers to species migration. Generalist macroinvertebrate taxa dominated the macroinvertebrate assemblages in our study lake, but some differences were evident among the different habitat types of the lake. The macrophyte-dominated habitat (MDH) displayed the highest species richness for both generalists (11 species) and specialists (8 species), while the algal-dominated habitat (ADH) had lower richness but higher overall abundances. Generalist species showed the largest abundances, exhibiting considerable spatial heterogeneity among the sampled sites. Our results showed that generalists shape macroinvertebrate assemblages through their abundance and richness variation in large shallow lakes. Furthermore, strong environmental gradients and a high degree of habitat connectivity within large lakes allow specialist and intermediate species to maintain high richness in resource-rich habitats, in addition to generalist species also maintaining high abundance in such lakes.

The rapid and continuous loss of biodiversity highlights the urgent need for research on functional diversity. Although the study of functional diversity has exploded in the past two decades, there is no clear guidance on how traits should be selected for index calculation, which significantly influences functional diversity results. To fill this gap, we explored how the functional diversity of freshwater macroinvertebrates has been estimated over the past 20 years and how it differs across continents and water bodies. We found that Europe is the absolute centre of research in this area and that most of the research comes from studies of European lotic waters. By fitting cumulative frequencies to the number of articles using different numbers of traits, our results showed that approximately 80% of the studies used no more than 12 traits to estimate functional diversity. Furthermore, by exploring the use frequency of numbers and types of traits in different regions and water bodies and combining them with trait grouping, we recommend the use of traits evenly from four trait groups to calculate functional diversity indices. This selection strategy can contribute to the unification of functional diversity estimations and comparative studies of different regions, thus helping to better understand and manage biodiversity loss worldwide.

Functional redundancy is an essential component of ecological insurance and indicates the properties of community assembly, maintenance of ecosystem functions, and stability under disturbance. It can be measured as alpha redundancy within a local community and beta redundancy between pairs of local communities. Although functional redundancy has been measured and discussed widely, its spatial and temporal patterns remain unclear. We hypothesized that high functional alpha redundancy accumulates within local communities under low environmental disturbance and limited interspecific competition, while high functional beta redundancy can occur under small environmental distances due to trait similarity between local communities. To test these hypotheses, we surveyed macroinvertebrates in a (sub)tropical medium river subjected to multiple anthropogenic stressors in two hydrologically different disturbance regimes: wet and dry seasons. Following the framework of Ricotta and co-workers, functional alpha (beta) redundancy was defined as the fraction of species diversity (dissimilarity) that was not expressed by functional diversity (dissimilarity). Functional alpha redundancy reduced significantly under high hydrological disturbance during the wet season. That is, the functional alpha redundancy accumulated in the dry season enhanced community resilience and provided insurance to maintain the stability of community functional diversity during the flooding period. Taxonomic and functional beta diversities decreased synchronously from the dry to wet seasons. There were no significant seasonal changes in functional beta redundancy. Our study provides a case for quantitatively measuring functional alpha and beta redundancies in macroinvertebrates and their seasonal changes in (sub) tropical disturbed rivers.

Stream ecosystems in high-mountain regions are susceptible to rapid environmental change, including warming and increased human activities. Understanding elevational patterns of stream communities and underlying drivers can facilitate the development of efficient conservation and management strategies to mitigate the impacts of these changes. Our study investigated elevational patterns of macroinvertebrate trait composition and functional diversity in six streams in the Hengduan Mountains region, Southwest China, which was recognized as one of the global biodiversity hotspots. We were particularly interested in untangling the effects of watershed human disturbance and instream physicochemical factors on elevational patterns of stream macroinvertebrates. Our results showed clear elevational patterns in both trait composition and functional diversity of macroinvertebrate communities. For trait composition, the results indicated that macroinvertebrate traits associated with mobility, habit, and feeding mode exhibited clear elevational patterns. For functional diversity, functional richness showed a positive correlation with elevation, whereas functional divergence had the opposite trend. No significant elevational pattern was detected in functional evenness and RaoQ. Further analyses found that weak human disturbance was the most important driver shaping trait composition and functional diversity of macroinvertebrates. Meanwhile, instream water temperature, primary productivity, and flow velocity also played considerable roles. Our study emphasizes the influence of watershed human disturbance on elevational patterns of macroinvertebrates in high-mountain streams. It also highlights the potential of trait composition and function diversity of macroinvertebrates as indicators for monitoring the ecological status of high-mountain streams.

In order to understand the community characteristics of macroinvertebrates in Qingyijiang River, a survey was conducted in September 2020 and July 2021. In this paper, the change of water quality was analyzed by using water environment quality and comprehensive index, and the niche of macroinvertebrates was further analyzed by using the substitution method based on the occurrence frequency of species, simulated null distribution of niche breadth and Mantel test. The results are revealed as follows: (1) There were significant changes in the number of macroinvertebrates between 2020 and 2021, but no significant changes in community composition (percentage of taxa); (2) The comprehensive evaluation results of water quality showed that the water environment of Qingyijiang River Basin in 2020 and 2021 was generally cleanest-clean. This also reflects that a series of water environmental governance measures in China have achieved remarkable results; (3) The constraints of natural and social status should also be taken into account when selecting the biological indices; (4) The results of ecological niche partitioning of macroinvertebrates show that the survival strategies of the generalists species are characterized by strong tolerance to water pollution, strong aggressive nature and mobility while the specialists species are Gastropoda with poor mobility, species that are relatively intolerant to water pollution, clingers and rare species. Mantel tests showed that only the ammonium nitrogen in 2020 had a significant effect on the specialists species; (5) When the water environment tends to be stable, clean and healthy, the specialists species can also become the generalists species.

Knowledge on the effects of habitat and flow alterations is basis for sustainable stream habitat conservation. This study explores the effects of hydrological and stream habitat alterations on the macroinvertebrates in Dinki watershed headwater streams, central highlands of Ethiopia. A total of 86 macroinvertebrate and water composite samples were collected over 25 sampling reaches in four-round sampling effort. A multivariate analysis of variance (MANOVA) was computed to assess variations in mean values of the three dependent variables (taxa abundance, richness, and diversity) across the independent variables, study sites (Dens, Gedamoch, Hagere-Selam, and Dinki). The mean differences in macroinvertebrate and environmental variables between sampling sites were computed using a one-way analysis of variance (ANOVA). Likewise, a principal component analysis (PCA) was computed to ordinate sampling sites in relation to macroinvertebrates. Furthermore, the resistance and resilience scores were calculated to quantify the invertebrates’ persistence and rate of recovery to habitat and hydrological alterations. The MANOVA indicated a significant spatial variation in taxa abundance. Both the reduced flow and spates had declined assemblage structures in all sampling sites. The PCA also showed that the stream habitat condition influenced the distribution of macroinvertebrates. In general, macroinvertebrate assemblages in both the pre-and-post disturbance events were higher in the forested Gedamoch sites, indicating the role of stream habitat conservation to buffer hydrological disturbances. As a result, management priorities aiming to protect and restore stream condition is a sound mitigation tool to maintain stream condition and its resilience to ecological disturbances.

The selection of suitable indicators is the key to the development of multi-metric bioassessment. Here, we examined how taxonomic and functional structures of macroinvertebrate communities responded to the environmental gradients in ten mountainous streams in the Weihe River and Hanjiang River basins, two subtropical biodiversity hotspots in central China. Our main objectives were: 1) to examine whether trait-based metrics performed better than taxonomic compositions in differentiating environmental gradients; 2) to test whether indicators (species and traits) were more efficient than entire communities in discriminating three site groups subjected to different levels of human disturbances. Our results showed that both taxonomic and functional trait compositions, including species- and trait-based indicators, were all sensitive to environmental disturbance. Particularly, the trait-based variables responded more sensitive to human disturbances. Indicator assemblages can be effective surrogates of entire communities in response to environmental changes. Traits- and indicators-based metrics should be considered as useful supplements in the existent bio-monitoring schemes in China. We argued that the combination of taxonomic and functional indicators should be implemented in bioassessment, as they reflect different aspects of environmental changes and anthropogenic disturbances.

Macroinvertebrate surveys are commonly used for assessing the health of freshwater systems around the world. Traditionally, surveying involves morphologically identifying the families, and sometimes genera, present in samples. Biological indices, derived from taxonomic lists, provide convenient ways to summarise community data and may be fairly insensitive to species-level changes in community compositions. In recent years, molecular techniques for identifying taxa have become increasingly popular and metabarcoding approaches that offer the ability to identify species from mixtures of whole animals (bulk-samples) or from environmental samples have gained much attention. However, generating accurate species lists from metabarcode data is challenging and can be impacted by sample type, choice of primers, community composition within samples, and the availability of reference sequences. This study compares the performance of molecular data extracted from bulk-samples against morphological data in calculating two biological indices (the Stream Invertebrate Grade Number Average Level 2 (SIGNAL2), which is calculated from family-level data, and a genus-level equivalent of this index, SIGNAL_SG) and one biological metric (taxon richness). Further, molecular indices and metrics derived from global, local or mixed reference DNA libraries and with varying degrees of filtering processes applied to them, are compared with respect to the strength of their relationships with morphological indices and metrics. Molecularly derived SIGNAL2 and SIGNAL_SG scores correlated strongly with morphologically derived scores, and were strongest when using a reference library containing a mix of local and global data. Molecularly derived richness metrics were moderately correlated with morphological taxa richness; however, the strongest correlations were observed when taxa that could not be assigned SIGNAL grades were omitted from analyses. This study highlights the utility of using molecular data as an objective and sensitive alternative to traditional freshwater biological assessment using macroinvertebrates.

Subaqueous dredging is a management activity undertaken globally to improve navigation, remove contaminants, mitigate flood risk and/or generate aggregate. Water Injection Dredging (WID) is a hydrodynamic technique involving the turbation and downstream displacement of fine sediments using vessel-mounted water jets. Despite the technique being widely applied internationally, the environmental and ecological effects of WID are poorly understood. For the first time, this study used a Before-After-Control-Impact (BACI) experimental design to assess the effects of WID on water physicochemistry, and macroinvertebrate and fish communities within a 5.7 km-long reach of tidal river. WID targeted the central channel (thalweg) to avoid disturbance of the channel margins and banks. Mean but not peak turbidity levels were substantially elevated, and dissolved oxygen levels were reduced during periods of WID, although effects were relatively short-lived (≈3 h on average). Dredging resulted in significant reductions in benthic macroinvertebrate community abundance (particularly taxa that burrow into fine sediments), taxonomic richness and diversity. In contrast, minor changes were detected in marginal macroinvertebrate communities within and downstream of the dredged reach following WID. Reductions in fish taxonomic richness and diversity were recorded downstream of the dredged reach most likely due to behavioural avoidance of the sediment plume. No visibly stressed or dead fish were sampled during dredging. Results suggest that mobile organisms and marginal communities were largely unaffected by thalweg WID and that the technique represents a more ecologically sensitive alternative to traditional channel margin mechanical dredging techniques.

Although freshwater ecosystems support a disproportionately large number of species, decision-support tools for prioritizing protected area efforts have mostly been implemented in marine and terrestrial environments. Systematic conservation planners rely on surrogate metrics to represent unsampled elements of biodiversity, yet few studies have considered the potential benefits associated with prioritizing multiple dimensions of freshwater biodiversity across multiple organism groups. In this study, we first evaluated relationships among patterns of taxonomic richness, functional diversity, functional redundancy, and biotic integrity for freshwater fish and benthic macroinvertebrate communities in the Congaree Biosphere Region, South Carolina, USA. We then used the decision-support tool Marxan to explore a potential trade-off between the number of organism groups sampled (i.e., taxonomic extent) and the multidimensional nature of biodiversity. Our central findings indicated that the processes driving patterns of taxonomic and functional diversity among organism groups were complementary, with direct implications for the evaluation of surrogate performance. Our results also suggest that within-taxa variation among measures of taxonomic and functional diversity may be more important to consider than the taxonomic representation of multiple organism groups. That is, we may be able to enhance the efficiency of conservation planning efforts by using available datasets in a more comprehensive way, as surrogate performance was largely mediated by the variation among metrics. Through the continued development of functional trait databases, we may be able to enhance the efficiency of data collection efforts and promote the timely and sustainable development of conservation strategies.

Metacommunity ecology highlights the importance of integrating simultaneously environmental filtering and spatial processes, such as mass effects and dispersal limitation, into investigation of community assembly. However, few studies to date have tried to examine mass effects and dispersal limitation as independent ecological mechanisms along with environmental filtering in shaping biological communities in river networks. We examined the relative importance of three factor groups, i.e., environmental variables, within-river spatial factors (indicative of mass effects) and basin identity (referring to dispersal limitation) on a macroinvertebrate metacommunity and nine trait-based deconstructed sub-metacommunities from seven subtropical rivers. We applied redundancy analysis and variance partitioning to reveal the pure and shared effects of the three groups of factors on community variation. Environmental filtering, mass effects and dispersal limitation were all significant mechanisms affecting variation in macroinvertebrate communities, but their relative importance depended on biological traits. Environmental filtering explained more of the variation in the whole metacommunity, tolerant taxa and macroinvertebrate groups with weak dispersal ability (i.e., aquatic dispersal, aerial passive dispersal and large body size). In contrast, mass effects accounted for more variation in the communities of intolerant taxa and macroinvertebrate groups with strong dispersal ability (i.e., aerial active dispersal mode and medium body size). Dispersal limitation was more influential for sub-communities of moderately tolerant taxa and large-sized taxa. Our study highlights that simultaneously accounting for different spatial processes and using a trait-based approach are essential to improve our understanding of community assembly in river networks.

We used two-dimensional hydrodynamic models for the assessment of water diversion effects on benthic macroinvertebrates and associated habitat in a montane stream in Yosemite National Park, Sierra Nevada Mountains, CA, USA. We sampled the macroinvertebrate assemblage via Surber sampling, recorded detailed measurements of bed topography and flow, and coupled a two-dimensional hydrodynamic model with macroinvertebrate indicators to assess habitat across a range of low flows in 2010 and representative past years. We also made zero flow approximations to assess response of fauna to extreme conditions. The fauna of this montane reach had a higher percentage of Ephemeroptera, Plecoptera, and Trichoptera (%EPT) than might be expected given the relatively low faunal diversity of the study reach. The modeled responses of wetted area and area-weighted macroinvertebrate metrics to decreasing discharge indicated precipitous declines in metrics as flows approached zero. Changes in area-weighted metrics closely approximated patterns observed for wetted area, i.e., area-weighted invertebrate metrics contributed relatively little additional information above that yielded by wetted area alone. Loss of habitat area in this montane stream appears to be a greater threat than reductions in velocity and depth or changes in substrate, and the modeled patterns observed across years support this conclusion. Our models suggest that step function losses of wetted area may begin when discharge in the Merced falls to 0.02 m3/s; proportionally reducing diversions when this threshold is reached will likely reduce impacts in low flow years.

• Proposed a new method to assess chemical integrity in a high human-disturbed basin. • Ecological threshold was applied to improve the normalization method. • Evaluation indicators were selected since great impacts on aquatic organisms. Chemical integrity plays a crucial role in maintaining the ecological integrity of aquatic ecosystems. Despite its significance, assessments of ecological integrity often prioritize biological evaluations, leading to infrequent and inadequate scrutiny of chemical integrity. Additionally, a comprehensive framework for separately assessing chemical integrity has not been established. To address this issue, we established a new index for evaluating chemical integrity, achieved through indicator screening, normalization, and weight assignment. Combined with the threshold indicator taxa analysis (TITAN) and Pearson correlation analysis, main evaluation indicators and their indicator species were identified and the corresponding response threshold was determined. These thresholds were then applied to improve the normalization method, with weights determined by indicator species proportions. This index was applied to evaluate the chemical integrity of the Huai River Basin, which is one of the largest basins in China. The results indicated that ammonia nitrogen (NH 3 -N), nitrate nitrogen (NO 2 -N), pH, and turbidity (Turb) were identified as the core parameters for evaluating chemical integrity. The conventional normalization method (max–min normalization) led to overestimation of the assessment results, whereas improved normalization method based on ecological threshold yielded better and more reasonable results. This study provided a reference for the selection of appropriate indicators and improvement of normalization method to better assess chemical integrity. And it would become a useful tool for monitoring and rehabilitating the chemical integrity in such basins. [ABSTRACT FROM AUTHOR]

[Display omitted] • Apply a more realistic approach to independent black/odor evaluation. • Hilsenhoff biotic index is most suitable as an indicator of the degree of black odor. • The number of the genus Chironomidae is indicative of the black and odor. Macroinvertebrate community structure parameters can reflect the water quality and water ecosystem health status of rivers. In this paper, using the results of macroinvertebrates in 16 urban rivers in Sichuan Province from November 2020 to March 2021, we independently evaluated the level of black odor in urban rivers based on the mathematical model. On this basis, we examined the community structure, fouling tolerance, diversity, and feeding functional groups of macrobenthos in rivers with different degrees of black odor. During the study, a total of 39 species of macroinvertebrates were collected and identified to 3 phyla, 7 classes, 16 orders, 26 families and 30 genera. Urban rivers changed from non-black and non-odorous to black and odorous: (1) the dominant species, Chironomus flaviplumus , Physa fontinalis and Barbronia weberi , changed to Chironomus flaviplumus , a fouling-tolerant species with wide adaptability; (2) According to the tolerance values (TVs), the pollution resistance categories gradually increased as the level of black odor increased, which indicated the level of black odor in water bodies; (3) The calculation of the Hilsenhoff biotic indices (HBI) indicated that 83.3% of the sampled sites were moderately to heavily polluted. In general, the severity of water quality pollution in the black and odorous type of river was significantly higher than that in the non-black and odorous type of river, and with the deepening of the degree of blackness and odor the quality of the water deteriorated; (4) The community structure had an unstable community structure and a low diversity index of macroinvertebrate species; (5) The taxa of feeding functional groups shifted from the presence of all five types of feeding functional groups to the dominance of fouling-resistant species represented by scrapers. The results summarize the characteristics and change patterns of various indicators under different black-odorous degrees, indicating that the HBI can be used as an alternative indicator for the evaluation of black odorous water, and the number of species of Chironomidae can indicate the degree of black odor in water bodies. [ABSTRACT FROM AUTHOR]

Highlights • Macroinvertebrate community composition was altered in oil palm streams with no buffer. • Retaining riparian buffers reduced impacts on macroinvertebrate composition structure. • Macroinvertebrate abundance and richness were similar in oil palm and pristine streams. • Macroinvertebrates aggregated in leaf bags for use as habitat rather than food source. • Use of riparian buffers in tropical streams subjected to agricultural impacts is supported. Abstract Southeast Asia is undergoing extensive conversion to oil palm (Elaeis guineensis) monocultures with fast growth expected in West Africa and South America. Despite rapid conversion rates, few tropical studies evaluate land-use change impacts on stream communities, with even fewer studies examining oil palm plantations (OP). In this pioneer study we compare macroinvertebrate community assemblages and their relationships with physico-chemical properties in OP streams bordered by different riparian buffer types to streams in a lowland dipterocarp forest in Sabah, Malaysian Borneo. Our study sites were in increasing levels of riparian disturbance (reduced vegetation density, diversity and structural complexity): (i) Native reference forested sites (NF); (ii) OP streams buffered with patches of natural forest (OPF); (iii) OP streams buffered with untreated oil palm (no chemical application at buffer sites; OPOP); and (iv) OP streams without buffer (OPNB). Macroinvertebrates were collected from leaf litter bags deployed with leaves of varying quality - native Macaranga tanarius and exotic oil palm, and retrieved after 14 days. We found that although invertebrates are typically influenced by resource quality, no differences were detected in their assemblages between the leaf species. All litter bags were dominated by collector-gatherers, with few shredding invertebrates, indicating that they were using the leaves as a habitat rather than a food source. We found no significant differences in macroinvertebrate abundance, richness and sensitive taxa richness (EPT) regardless of the rate of riparian disturbance. However, PERMANOVA showed significant differences between the macroinvertebrate community composition of heavily disturbed OPNB and pristine NF streams. Retaining high quality riparian buffers in OPF streams and lower quality understory in OPOP streams posed intermediate effects on macroinvertebrate community composition. The differences between sites were explained by the increase in nutrients, particularly potassium and phosphorus, stream water temperatures and erosion levels that negatively correlated with macroinvertebrate assemblages in oil palm streams. These findings support the use of riparian buffers in oil palm plantations to mitigate land conversion impacts on macroinvertebrate communities in tropical streams. [ABSTRACT FROM AUTHOR]

• We assessed the degree of organisms' specialization in a large nutrient-rich lake. • Generalist macroinvertebrate taxa dominated in Lake Taihu. • Generalists shape lake macroinvertebrate communities through high abundance and richness. • Water depth (WD) & total organic carbon (TOCs) drive macroinvertebrate assemblage shifts. The loss of biodiversity in the era of fast environmental change is often revealed as biotic homogenization. In the large and nutrient-rich Lake Taihu located in eastern China, we evaluated the degree of specialization among organisms and the impact of environmental factors on macroinvertebrate assemblages. First, we measured the niche widths of macroinvertebrate species in respect to environmental conditions and utilized the Outlying Mean Index (OMI) analysis to categorize them into specialists and generalists. The effects of environmental factors on assemblages of macroinvertebrate taxa identified by varying niche widths were then investigated using the lake dataset. Within our study lake, habitats display considerable environmental gradients, resulting in habitat heterogeneity linked to several habitats, and have no barriers to species migration. Generalist macroinvertebrate taxa dominated the macroinvertebrate assemblages in our study lake, but some differences were evident among the different habitat types of the lake. The macrophyte-dominated habitat (MDH) displayed the highest species richness for both generalists (11 species) and specialists (8 species), while the algal-dominated habitat (ADH) had lower richness but higher overall abundances. Generalist species showed the largest abundances, exhibiting considerable spatial heterogeneity among the sampled sites. Our results showed that generalists shape macroinvertebrate assemblages through their abundance and richness variation in large shallow lakes. Furthermore, strong environmental gradients and a high degree of habitat connectivity within large lakes allow specialist and intermediate species to maintain high richness in resource-rich habitats, in addition to generalist species also maintaining high abundance in such lakes. [ABSTRACT FROM AUTHOR]

• The process of selecting traits for estimating functional diversity is unclear. • Most of the estimations focused on lotic waters in Europe. • About 80% of the studies used no more than 12 traits. • Traits are suggested to be evenly distributed in four major trait groups. The rapid and continuous loss of biodiversity highlights the urgent need for research on functional diversity. Although the study of functional diversity has exploded in the past two decades, there is no clear guidance on how traits should be selected for index calculation, which significantly influences functional diversity results. To fill this gap, we explored how the functional diversity of freshwater macroinvertebrates has been estimated over the past 20 years and how it differs across continents and water bodies. We found that Europe is the absolute centre of research in this area and that most of the research comes from studies of European lotic waters. By fitting cumulative frequencies to the number of articles using different numbers of traits, our results showed that approximately 80% of the studies used no more than 12 traits to estimate functional diversity. Furthermore, by exploring the use frequency of numbers and types of traits in different regions and water bodies and combining them with trait grouping, we recommend the use of traits evenly from four trait groups to calculate functional diversity indices. This selection strategy can contribute to the unification of functional diversity estimations and comparative studies of different regions, thus helping to better understand and manage biodiversity loss worldwide. [ABSTRACT FROM AUTHOR]

The middle catchment of the Nu River is highly susceptible to debris flows. Differences in flow and substratum conditions among mainstem reaches correlate with debris flow depositions from lateral tributaries. We studied the impacts of debris flows on macroinvertebrates, especially responses in their diversity and assemblage structure to habitat modification at 22 sites in three habitats: barrier lakes and debris dams, formed by debris flow deposits barring the river, and unaffected mainstem sections. Unaffected mainstem sites supported the most diverse macroinvertebrate assemblage, with mean taxon richness, density and biomass 1.4, 1.1, and 23.6 times higher than those of debris dam sites, and 2.1, 4.2, and 7.4 times higher than those of barrier lake sites, respectively. Variance analysis revealed significant differences in diversity indices, and both taxonomic and functional feeding group composition among habitats. Although barrier lakes and debris dams had lower taxon richness, the two affected habitats contributed 17 and 16 exclusive taxa, respectively, to total taxon richness. Redundancy analysis identified habitats could be characterized by water temperature, electrical conductivity, flow velocity, and median particle size of substratum type. Significant differences in flow velocity and substratum median particle size among habitats were attributed to debris flows. Distinct assemblages within barrier lakes were associated with fine sediments. By altering habitat conditions, debris flows affect macroinvertebrate assemblages, reducing diversity locally in affected reaches, contributing to variation in diversity and assemblage structure throughout the catchment. Three genera ( Cricotopus sp., Pseudocloeon sp. and Monodiamesa sp.) are proposed as potential indicator taxa for unaffected mainstem, debris dam and barrier lake habitats, respectively. [ABSTRACT FROM AUTHOR]

Floodplains are highly diverse landscape elements within river systems and among the most endangered ecosystems worldwide. In this paper we complement indices developed to assess the ecological status of floodplain systems, compliant with the EU Water Framework Directive, to an overall “Benthic Invertebrate Floodplain Index” (BIFI). With the addition of taxa (mainly oligochaetes, chironomidae and amphipoda) to the floodplain index (FI), caddisfly (CHI), and dragon fly (OHI) indices a new extended BIFI can be calculated. We provide values for the calculation of the index derived from a comprehensive dataset of Austrian floodplain waters complemented by literature data. Values are given for those taxonomic groups which are abundant in the Austrian Danube and determinable in reasonable time. The new index was compared to published floodplain indices and tested with an independent data set at two floodplain segments along the Austrian Danube. The newly classified benthic invertebrates (NCBI) showed a good performance in comparison to the so far published indices and extend these to a better coverage of dynamic water bodies. Further the inclusion of abundant and species rich taxa improves the robustness of calculated values already with a low sampling effort. Altogether it is a promising tool for the integrated assessment of the ecological status of river-floodplain systems according to the EU Water Framework Directive. [ABSTRACT FROM AUTHOR]

Aquatic macroinvertebrates have been the basis for one of the primary indicators and a cornerstone of lotic biomonitoring for over 40 years. Despite the widespread use of lotic invertebrates in statutory biomonitoring networks, scientific research and citizen science projects, the sampling methodologies employed frequently vary between studies. Routine statutory biomonitoring has historically relied on semi-quantitative sampling methods (timed kick sampling), while much academic research has favoured fully quantitative methods (e.g. Surber sampling). There is an untested assumption that data derived using quantitative and semi-quantitative samples are not comparable for biomonitoring purposes. As a result, data derived from the same site, but using different sampling techniques, have typically not been analysed together or directly compared. Here, we test this assumption by comparing a range of biomonitoring metrics derived from data collected using timed semi-quantitative kick samples and quantitative Surber samples from the same sites simultaneously. In total, 39 pairs of samples from 7 rivers in the UK were compared for two seasons (spring and autumn). We found a strong positive correlation ( r s = +0.84) between estimates of taxa richness based on ten Surber sub-samples and a single kick sample. The majority of biomonitoring metrics were comparable between techniques, although only fully quantitative sampling allows the density of the community (individual m −2 ) to be determined. However, this advantage needs to be balanced alongside the greater total sampling time and effort associated with the fully quantitative methodology used here. Kick samples did not provide a good estimate of relative abundance of a number of species/taxa and, therefore, the quantitative method has the potential to provide important additional information which may support the interpretation of the biological metrics. [ABSTRACT FROM AUTHOR]

• Functional alpha redundancy was accumulated in the dry and reduced in the wet season. • Functional redundancy provided insurance for macroinvertebrates against disturbance. • Taxonomic and functional beta diversities were affected nonlinearly by environmental distance. • There was no significant seasonal change in the functional beta redundancy. Functional redundancy is an essential component of ecological insurance and indicates the properties of community assembly, maintenance of ecosystem functions, and stability under disturbance. It can be measured as alpha redundancy within a local community and beta redundancy between pairs of local communities. Although functional redundancy has been measured and discussed widely, its spatial and temporal patterns remain unclear. We hypothesized that high functional alpha redundancy accumulates within local communities under low environmental disturbance and limited interspecific competition, while high functional beta redundancy can occur under small environmental distances due to trait similarity between local communities. To test these hypotheses, we surveyed macroinvertebrates in a (sub)tropical medium river subjected to multiple anthropogenic stressors in two hydrologically different disturbance regimes: wet and dry seasons. Following the framework of Ricotta and co-workers, functional alpha (beta) redundancy was defined as the fraction of species diversity (dissimilarity) that was not expressed by functional diversity (dissimilarity). Functional alpha redundancy reduced significantly under high hydrological disturbance during the wet season. That is, the functional alpha redundancy accumulated in the dry season enhanced community resilience and provided insurance to maintain the stability of community functional diversity during the flooding period. Taxonomic and functional beta diversities decreased synchronously from the dry to wet seasons. There were no significant seasonal changes in functional beta redundancy. Our study provides a case for quantitatively measuring functional alpha and beta redundancies in macroinvertebrates and their seasonal changes in (sub) tropical disturbed rivers. [ABSTRACT FROM AUTHOR]

We examined patterns of concordance between macroinvertebrate and fish communities among adventitious and ordinate tributaries of the Monongahela River in southwestern Pennsylvania in order to determine their efficacy as mutual surrogates for the assessment of ecosystem integrity. Fish, macroinvertebrates, and 19 water quality parameters were sampled from 20 streams. Collected data were analyzed by principal components analysis, redundancy analysis, and Ward’s distance clustering matrices to determine degrees of community concordance and similarity. Fish and macroinvertebrate communities were assessed utilizing Indices of Biotic Integrity (IBI) in order to compare stream ecosystem health as expressed by each index. Adventitious and ordinate macroinvertebrate communities largely clustered in like groups with adventitious tributaries dominated by the crustacean Gammarus sp. and ordinate streams dominated by the trichopteran, Hydropsyche sp. Adventitious communities were strongly influenced by elevated total alkalinity and total suspended solids; ordinate communities by contrast to elevated total organic carbon and specific conductance. Fish communities showed no significant relationship to water quality parameters among either tributary type, but often grouped with their nearest geographic neighbor. The respective indices revealed a discord between the two communities suggesting that neither community serves as a surrogate for the other as an indicator of stream health in this basin. Both communities appeared to be driven by differences in local environmental conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Knowledge regarding elevational patterns of macroinvertebrate in high-mountain region remains limited. • Macroinvertebrate traits and functional diversity varied monotonically with elevation. • Traits related to mobility, habit, and feeding mode showed significant correlations with elevation. • Watershed human disturbance had the largest impact on trait composition and functional diversity of stream macroinvertebrates. Stream ecosystems in high-mountain regions are susceptible to rapid environmental change, including warming and increased human activities. Understanding elevational patterns of stream communities and underlying drivers can facilitate the development of efficient conservation and management strategies to mitigate the impacts of these changes. Our study investigated elevational patterns of macroinvertebrate trait composition and functional diversity in six streams in the Hengduan Mountains region, Southwest China, which was recognized as one of the global biodiversity hotspots. We were particularly interested in untangling the effects of watershed human disturbance and instream physicochemical factors on elevational patterns of stream macroinvertebrates. Our results showed clear elevational patterns in both trait composition and functional diversity of macroinvertebrate communities. For trait composition, the results indicated that macroinvertebrate traits associated with mobility, habit, and feeding mode exhibited clear elevational patterns. For functional diversity, functional richness showed a positive correlation with elevation, whereas functional divergence had the opposite trend. No significant elevational pattern was detected in functional evenness and RaoQ. Further analyses found that weak human disturbance was the most important driver shaping trait composition and functional diversity of macroinvertebrates. Meanwhile, instream water temperature, primary productivity, and flow velocity also played considerable roles. Our study emphasizes the influence of watershed human disturbance on elevational patterns of macroinvertebrates in high-mountain streams. It also highlights the potential of trait composition and function diversity of macroinvertebrates as indicators for monitoring the ecological status of high-mountain streams. [ABSTRACT FROM AUTHOR]

Many globally applied biotic indices, including the AMBI benthic index, are based on species’ sensitivity/tolerance to anthropogenic disturbances. The AMBI scoring primarily relies on the correct assignment of both taxon stressor-sensitivities and the disturbance thresholds or bands. Using an extensive, long-term monitoring dataset from New Zealand (NZ) estuaries, we describe how the AMBI has been strengthened through quantitative derivation of taxon-specific sensitivities and condition thresholds for two key estuarine stressors [mud and total organic carbon (TOC)], and the integration of taxon richness. The results support the use of the existing AMBI condition bands but improve the ability to identify cause; 2–30% mud reflected a ‘normal’ to ‘impoverished’ macrofaunal community; 30–95% mud and 1.2–3% TOC ‘unbalanced’ to ‘transitional’; and >3–4% TOC ‘transitional’ to ‘polluted’. The (refined) AMBI was also successfully validated ( R 2 values >0.5 for mud, and >0.4 for TOC) for use in shallow, intertidal dominated estuaries NZ-wide. Most biotic indices lack the ability to differentiate between anthropogenic disturbances, which in turn undermine their effectiveness for applied purposes. By integrating key quantitative information to an existing benthic index, these results enable more robust identification of coastal stressors and facilitate defensible management decisions. [ABSTRACT FROM AUTHOR]

Freshwater streams are critical resources that provide multiple benefits to humans and aquatic biota alike. As climate changes, it is projected that changes to the hydrological cycle and water temperatures will affect individual biota and aquatic ecosystems as a whole. The goal of this study was to determine the extent of climate change impacts on stream ecosystems as represented by four commonly used stream health indicators (Ephemeroptera, Plecoptera, and Trichoptera taxa (EPT), Family Index of Biotic Integrity (FIBI), Hilsenhoff Biotic Index (HBI), and fish Index of Biotic Integrity (IBI)). Seven watersheds in Michigan were selected based on stream thermal regimes. The Soil and Water Assessment Tool was used to simulate streamflow and pollutant loads. Important variables for each thermal class were selected using a Bayesian variable selection method and used as inputs to adaptive neuro-fuzzy inference systems models of EPT, FIBI, HBI, and IBI. Finally, an ensemble of climate models from the Coupled Model Intercomparison Project Phase 5 were used to determine the impacts of climate on the stream health in 2020–2040 compared to 1980–2000. The risk of declining stream health was determined using cumulative distribution functions. A stream temperature regression model was also developed to assess potential changes in stream thermal regimes, which could cause shifts in composition of aquatic communities. Several flow regime variables, including those related to flow variability, duration of extreme events, and timing were mainly affected by changing climate. At the watershed scale, most indicators were relatively insensitive to changing climate and the magnitude of stream health decline was low. However, at the reach scale, there are many instances of high risk and large magnitude of declines in the stream health indicators. At the same time, several streams experienced changes in thermal class, mostly transitioning from cold-transitional and cool streams to warm streams. This research demonstrated the applicability of the stream health modeling process in performing a climate change impacts assessment. [ABSTRACT FROM AUTHOR]

Achieving sustainable freshwater resource management and conserving biodiversity require accurate and reliable pollution impact assessment. Biomonitoring is an integrative and holistic approach to assessing impact of pollution using biological indicators. In this study, we use the assemblage structure of the freshwater macroinvertebrate family Chironomidae to assess the impact of pollution in a South African river: the Swartkops River. Based on morphological deformities in the mentum of selected genera, we developed a new index, the extended toxic score index (ETSI), to assess the extent of deviation of ecological conditions at the impacted sites from that at the control site. Four sites i.e. Sites 1–4 characterised by different degrees of pollution were selected for chironomids and physico-chemical sampling over a period of three years (August 2009–September 2012). The ETSI was developed by taking into account the severity of deformities, and genera tolerances to pollution. The index was based on the deformities in the mentum of the five most dominant genera: Chironomus , Polypedilum , Tanytarsus , Dicrotendipes and Cricotopus . The values of nutrients, electrical conductivity and turbidity were elevated, and dissolved oxygen depleted at Sites 2, 3 and 4 compared with Site 1. Metal concentrations in the water column were relatively low (<0.3 mg/l). Site 1, i.e. the control site, supported more chironomid species (30 species). Site 2, situated upstream of the Kelvin Jones wastewater effluent discharge point, but influenced by diffuse pollution sources, had more species (22 species) than Sites 3 (10 species) and 4 (18 species). The species assemblage structure clustered largely by sites than by seasons, with the assemblage at Site 1 distinct to those at Sites 2, 3 and 4. The newly developed ETSI was sensitive to pollution, distinguishing between the ecological conditions at the sampling sites. The index placed Site 2 in Category D, indicative of poor ecological condition and Sites 3 and 4 in Category E, indicative of very poor conditions. We found the ETSI to be an appropriate and useful deformity-based tool for biomonitoring, and it can easily be modified and used in other river systems, both locally and internationally. [ABSTRACT FROM AUTHOR]

Pollution of rivers is an increasing problem that affects biological diversity and structure of natural ecosystem. The present study reported the results of the preliminary analysis of diatom and macroinvertebrate communities of river Picentino (Italy, Campania) in respect of the WFD/60/2000/EC. Because of the sensitive to a variety of environmental factors the two categories of organism are used as excellent indicators of changes taking place in water ecosystems, especially eutrophication. Sampling of benthic diatoms and macroinvertebrates has been carried out in five stations along the river during April–May 2014 in order to apply the ICMi and the STAR_ICMi and assess river quality. The data showed a diversification in diatomic and macroinvertebrate communities in relation to environmental stresses and level of pollution, with the disappearance of species higher sensitive to eutrophication and organic load in the upper course of the river. River water quality was found to deteriorate from the upperstream to the downstream because of the increasing of human impact and the intensive agriculture activity along the river. We conclude that the monitoring of diatomic and macroinvertebrate communities could give detailed information about the ecological status of rivers. However it is necessary to increase the achieved data by monitoring other biological communities in order to define adequated strategies to save and preserve the rivers habitat. [ABSTRACT FROM AUTHOR]

Invasive species represent one of greatest threats to aquatic biodiversity globally and are widely acknowledged to be instrumental in modifying native community structure. Despite this, little is known about how the increasing range expansion of invasive taxa may affect routine biomonitoring tools widely employed to measure or quantify environmental quality in lotic systems. This study examined the impact of an invasive freshwater crayfish on commonly employed riverine macroinvertebrate biomonitoring tools (scores and indices) designed to respond to a range of stressors. Data from long-term monitoring sites on both ‘control’ and invaded rivers in England were examined to assess changes to biomonitoring scores following invasion by signal crayfish ( Pacifastacus leniusculus ). Results indicate that routine biomonitoring tools used to quantify potential ecological stressors which are weighted by abundance, such as the Lotic-invertebrate Index for Flow Evaluation (LIFE) score and Proportion of Sediment-sensitive Invertebrates (PSI), were subject to significant inflation following invasion. In contrast, indices based simply on the presence of taxa, such as the Average Score Per-Taxon (ASPT – a derivative of BMWP), displayed no changes compared to control rivers; or in the case of the Biological Monitoring Working Party Score (BMWP), NTAXA and EPT richness, no consistent pattern following invasion. Season had a significant effect on the interaction of crayfish and LIFE and PSI scores. Autumn samples were subject to statistical inflation following crayfish invasion whilst spring samples exhibited no significant change. The results suggest that care should be taken when interpreting routine macroinvertebrate biomonitoring data where non-native crayfish are present, or in instances where their presence is suspected. [ABSTRACT FROM AUTHOR]

Reliable and inexpensive indicators of ecosystem function are essential for accurately monitoring and describing ecosystem integrity. Currently, most state and federal assessments of aquatic ecological integrity rely on structural indicators and assume tight coupling of structure and function. We used fluorescent composition of dissolved organic matter as a metric for certain ecosystem functions and compared the resulting index of autochthonous microbial dissolved organic matter (DOM) to macroinvertebrate indicators and classifications of water quality attainment reported by the Maine Department of Environmental Protection (Maine DEP) at 142 stream sites. We observed that metrics of sensitive insect orders such as relative Plecoptera generic richness, relative Ephemeroptera abundance, and generic richness of EPT (Ephemeroptera, Plecoptera, and Trichoptera) were negatively correlated with higher values of metrics based on autochthonous microbial DOM sources. At the same time we observed an increase in the Hilsenhoff Biotic Index with increasing microbial DOM. We compared the abundance of this microbial DOM component to Maine DEP measured attainment classes and found that microbial DOM generally separated sites with high biological integrity from sites where the biotic community was highly degraded. This highlights that measures of biogeochemical ecosystem function complement measures of structure in biological assessments. [ABSTRACT FROM AUTHOR]

Freshwater organisms face numerous stressors, such as nutrient enrichment, contaminant pollution, sedimentation and alterations in stream hydrology and habitat structure. One of the most significant and widespread stressors in European freshwaters is expected to be water pollution from intensive land use. However, the information on critical threshold concentrations at which taxa decline or increase in frequency and abundance is missing for the large majority of river benthic invertebrate taxa. The main aim was to determine ecological change points for benthic invertebrate taxa at which rapid alterations in species frequency and abundance occur as a consequence of relatively small changes in the environmental gradient. These change points can be interpreted as critical threshold concentrations. A total of 468 river benthic invertebrate taxa and nine physico-chemical variables describing the daytime dissolved oxygen, chloride, nutrient concentrations and organic load were analyzed. We selected 751 river sites from a nationwide range of locations in Germany for this investigation. Depending on the physico-chemical variable, between 20.6% and 48.8% of the total number of tested taxa were assigned with a valid change point. All taxa were assigned to negative or positive response groups depending on the response direction. Except for daytime dissolved oxygen, negative responding taxa are referred to as decreasers and positive responding taxa as increasers, respectively. In total, 25.8–100% of the decreasers’ change points were below (and above in the case of daytime dissolved oxygen) the background values defined as quality criteria for German rivers by the water authorities. This indicates that stricter quality criteria may need to be set to reach the good ecological status according to the European Water Framework Directive. The calculated daytime dissolved oxygen change points were essentially in line with the species saprobic values and taxon-specific change points for physico-chemical variables fit well with the data provided in other international studies. We deliver valuable knowledge about the sensitivities and response schemes of river benthic invertebrate species. This information is especially useful for the development of efficient management and policy tools to predict the likelihood of occurrence of individual species under different levels of anthropogenic impact. [ABSTRACT FROM AUTHOR]

Subsampling that counts and identifies a random subset of individuals from field samples is widespread yet controversial. We evaluated the effects of fixed-count size on macroinvertebrate richness, site separation, and performance of modeled and null (i.e., natural variation adjusted and unadjusted, respectively) biological indices in Chinese monsoonal stream sites. To do so, we estimated the fixed-count size that was adequate to collect 95% of the estimated true regional macroinvertebrate taxa richness, and we also evaluated the effects of fixed-count size on site and group (reference vs test) separation, and the precision, sensitivity and responsiveness of modeled and null multimetric indices (MMI) and observed/expected (O/E) indices. Random subsamples of individual fixed-count sizes ranged from 50 to 500. Mean cumulative taxa richness continued to increase with increasing fixed-count size. We found that 150 and 200 individuals were needed to collect 75% of estimated true species richness 75% and 95% of the time, respectively. We estimated that at least 1500 individuals per site were required for collecting 95% of estimated true species richness. Site and group separation and classification strength also improved with increased fixed-count size. Larger fixed-count sizes improved the performance of modeled and null O/E 50 (O/E calculated using taxa with probabilities of capture ≥0.5); however, they showed no significant difference for modeled and null MMIs and O/E 0 (O/E calculated using all taxa). Overall, we found that fixed-counts affected richness and site/group separation, but not index performance. Until China develops standard sampling methods, we recommend using fixed-count sizes of 500 individuals and rarefaction of ≥200 individuals to limit the effects of sampling error for site and group separation and for precise and accurate bioassessment, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • WQI integrates biotic (R , BI , HDI) and abiotic (WQG) factors. • WQI shows that the water environment of QYJ River is generally cleanest-clean. • The results of the study reflect the success of China's water ecological civilization. • When water becomes clean, specialists species can also become generalists species. In order to understand the community characteristics of macroinvertebrates in Qingyijiang River, a survey was conducted in September 2020 and July 2021. In this paper, the change of water quality was analyzed by using water environment quality and comprehensive index, and the niche of macroinvertebrates was further analyzed by using the substitution method based on the occurrence frequency of species, simulated null distribution of niche breadth and Mantel test. The results are revealed as follows: (1) There were significant changes in the number of macroinvertebrates between 2020 and 2021, but no significant changes in community composition (percentage of taxa); (2) The comprehensive evaluation results of water quality showed that the water environment of Qingyijiang River Basin in 2020 and 2021 was generally cleanest-clean. This also reflects that a series of water environmental governance measures in China have achieved remarkable results; (3) The constraints of natural and social status should also be taken into account when selecting the biological indices; (4) The results of ecological niche partitioning of macroinvertebrates show that the survival strategies of the generalists species are characterized by strong tolerance to water pollution, strong aggressive nature and mobility while the specialists species are Gastropoda with poor mobility, species that are relatively intolerant to water pollution, clingers and rare species. Mantel tests showed that only the ammonium nitrogen in 2020 had a significant effect on the specialists species; (5) When the water environment tends to be stable, clean and healthy, the specialists species can also become the generalists species. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed a macroinvertebrate index for monitoring tropical lake water quality. [•] We first identified potential physicochemical stressors within Singapore's reservoirs. [•] Data and knowledge driven approaches were used to develop, adapt and apply indices. [•] The “BQISING” driven on the sensitivity of local taxa to stressors was most suitable. [•] Ecological assessment of tropical waters necessitates locally relevant indicators. [ABSTRACT FROM AUTHOR]

Abstract: Multimetric indices (MMI) are extremely useful indicators of anthropogenic disturbance, but that usefulness is a function of how well they have been calibrated for natural spatial and temporal variability. Nonetheless, there have been very few studies regarding the effects of such natural variability on MMI scores and metric selection, and even fewer studies on the effects of minimizing the mean of metric correlations. To do so, we calibrated and validated several adjusted and unadjusted MMI for natural gradients with different metric compositions via datasets from 161 samples collected at 83 stream sites from 2008 to 2012 across the Li River Basin, China. We used random forests to model the variation of individual metrics with natural gradients, then used their residual distributions as the adjusted response range of each metric, independent of natural environmental influence. To select core metrics for MMI, the candidate adjusted and unadjusted metrics were all screened through reproducibility, sensitivity, and redundancy tests. The adjusted MMI were more precise, less biased, and more sensitive than the unadjusted MMI. Although the unadjusted MMI were as responsive as the adjusted MMI, the unadjusted MMI increased risks of inferring type I and type II errors. Minimizing the mean of metric correlations as well as avoiding biological information redundancy improved the performance of unadjusted and adjusted MMI, but only improved precision for the adjusted MMI. Using multi-season and multi-year samples proved to be an effective and efficient assessment method to diminish natural seasonal variation in adjusted MMI, but not unadjusted MMI. We found that the adjusted MMI with the lowest mean of metric correlations using multi-season and multi-year samples performed best and reduced seasonal variability. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Data on macroinvertebrates of selected reference sites were compiled from a long-term monitoring programme carried out in the Mediterranean Catalan Basins (NE Spain) that permitted analysis for nine years, from 1996 to 2004, using a homogeneous data collection procedure. This study aims to analyse the differences in composition and structure of macroinvertebrate communities at family level in five Mediterranean river types, and the values of biological quality metrics (IBMWP and IASPT indices, taxon richness and EPT) in reference conditions. Also differences between seasons (spring vs. summer) and between dry and wet periods were analysed. The dry and wet periods were determined using the Standardised Precipitation Index (SPI). A total of 29 reference sites were selected out of 184 sampling sites analysed, and 171 reference samples were available (from 1996 to 2004), of which 88 were sampled in dry periods, whereas 83 correspond to wet periods. Differences on community composition at family level were appreciated, clustering the rivers in three different groups: (1) rivers with a continuous flow regime located in siliceous zones; (2) rivers with a continuous flow regime located in calcareous zones; and (3) temporary rivers regardless of geology. Moreover, our results explain that the characteristics of hydrological periods (dry and wet) characterize the differences between communities better than just the season. The analysis of four biological quality metrics reveals clear differences between values obtained from dry and wet periods concerning taxon richness, EPT values and IBMWP biological indices, whereas the IASPT index does not show significant differences. The median taxonomic richness in wet periods is 32 macroinvertebrate families per sample while in dry periods this value falls to 22. Reference values of IBMWP index, the total number of taxa, and EPT metric are different between dry and wet periods in spring samples, while these differences are not relevant for IASPT index except for temporary streams. Hydrological specific conditions should additionally be considered in order to better calculate biological reference conditions, and to properly apply biological quality metrics used to establish the ecological status in Mediterranean rivers, especially in temporary ones. The use of the dry–wet period classification according to the climate characteristic results is a more accurate application of the Water Framework Directive in Mediterranean rivers. Implications of future climate change should be also considered from our results. [Copyright &y& Elsevier]

Abstract: Biotic indices for algae, macroinvertebrates, and fish assemblages can be effective for monitoring stream enrichment, but little is known regarding the value of the three assemblages for detecting perturbance as a consequence of low-level nutrient enrichment. In the summer of 2006, we collected nutrient and biotic samples from 30 wadeable Ozark streams that spanned a nutrient-concentration gradient from reference to moderately enriched conditions. Seventy-three algal metrics, 62 macroinvertebrate metrics, and 60 fish metrics were evaluated for each of the three biotic indices. After a group of candidate metrics had been identified with multivariate analysis, correlation procedures and scatter plots were used to identify the four metrics having strongest relations to a nutrient index calculated from log transformed and normalized total nitrogen and total phosphorus concentrations. The four metrics selected for each of the three biotic indices were: algae—the relative abundance of most tolerant diatoms, the combined relative abundance of three species of Cymbella, mesosaprobic algae percent taxa richness, and the relative abundance of diatoms that are obligate nitrogen heterotrophs; macroinvertebrate—the relative abundance of intolerant organisms, Baetidae relative abundance, moderately tolerant taxa richness, and insect biomass; fish—herbivore and detritivore taxa richness, pool species relative abundance, fish catch per unit effort, and black bass (Micropterus spp.) relative abundance. All three biotic indices were negatively correlated to nutrient concentrations but the algal index had a higher correlation (rho=−0.89) than did the macroinvertebrate and fish indices (rho=−0.63 and −0.58, respectively). Biotic index scores were lowest and nutrient concentrations were highest for streams with basins having the highest poultry and cattle production. Because of the availability of litter for fertilizer and associated increases in grass and hay production, cattle feeding capacity increases with poultry production. Studies are needed that address the synergistic effect of poultry and cattle production on Ozark streams in high production areas before ecological risks can be adequately addressed. [Copyright &y& Elsevier]

• Stream conditions are critical filters to stream macroinvertebrate assemblages. • Spate has more drastic effect on macroinvertebrates than flow reduction. • Streams with stable refugee contribute to mitigate ecological disturbances. • Conservation of stream habitats is plausible to buffer hydrological disturbances. Knowledge on the effects of habitat and flow alterations is basis for sustainable stream habitat conservation. This study explores the effects of hydrological and stream habitat alterations on the macroinvertebrates in Dinki watershed headwater streams, central highlands of Ethiopia. A total of 86 macroinvertebrate and water composite samples were collected over 25 sampling reaches in four-round sampling effort. A multivariate analysis of variance (MANOVA) was computed to assess variations in mean values of the three dependent variables (taxa abundance, richness, and diversity) across the independent variables, study sites (Dens, Gedamoch, Hagere-Selam, and Dinki). The mean differences in macroinvertebrate and environmental variables between sampling sites were computed using a one-way analysis of variance (ANOVA). Likewise, a principal component analysis (PCA) was computed to ordinate sampling sites in relation to macroinvertebrates. Furthermore, the resistance and resilience scores were calculated to quantify the invertebrates' persistence and rate of recovery to habitat and hydrological alterations. The MANOVA indicated a significant spatial variation in taxa abundance. Both the reduced flow and spates had declined assemblage structures in all sampling sites. The PCA also showed that the stream habitat condition influenced the distribution of macroinvertebrates. In general, macroinvertebrate assemblages in both the pre-and-post disturbance events were higher in the forested Gedamoch sites, indicating the role of stream habitat conservation to buffer hydrological disturbances. As a result, management priorities aiming to protect and restore stream condition is a sound mitigation tool to maintain stream condition and its resilience to ecological disturbances. [ABSTRACT FROM AUTHOR]

Abstract: Rapid biological assessment (RBA) methods involving non-quantitative sampling of aquatic macroinvertebrates, sub-sampling of only a proportion of the organisms collected, and identification only to genus-level were used to assess responses over up to 7 years following the cessation of discharges from five sewage treatment plants into small streams in the Blue Mountains, Australia, and an increased volume of discharge into another stream. Multivariate analysis (ordination and analysis of similarities) did not always show an obvious recovery after discharge cessation: assemblages sampled upstream and downstream of discharge points were not always clearly closer in ordination space after cessation than before and statistically significant differences between upstream and downstream assemblages generally remained after cessation, apparently because of natural medium-scale spatial variability. However, the tolerance-based SIGNAL-SG biotic index demonstrated some recovery in all cases of discharge cessation, and a lag in recovery of about a year. A lesser recovery in the more urbanised catchments was attributed to persistent pollution from sources other than treatment plant discharges. The biotic index also revealed subtle biological change that was not predictable from monitoring data on nutrient concentrations. The SIGNAL-SG biotic index derived from RBA sampling provides an easily communicated measure of the effectiveness of investment in abatement of sewage impacts on stream macroinvertebrates in the Blue Mountains. [Copyright &y& Elsevier]

The impacts of co-occurring stressors (river regulation by a dam and mine drainage) on hyporheic macroinvertebrate assemblages and environmental variables were investigated in a mountainous area of central Colorado at seven sampling sites in Lake Fork during two different seasons. Specific aquatic macroinvertebrate assemblages were associated with river regulation and trace element impacts. Paraleuctra was primarily associated with mining impacted sites, while Polycelis, Hydra, and Simulium were most abundant at sites nearest the dam. There were sometimes large differences in toxicity between hyporheic and surface water samples. Occasionally toxicity was present in the surface water, but absent in hyporheic water from the same site, while on one date, toxicity was detected in the hyporheic but undetected in surface water. The distinct taxa found in the hyporheic, and differences between hyporheic and surface water quality suggest that understanding the hyporheic zone is important in the study of impacted aquatic systems. [Copyright &y& Elsevier]

• Macroinvertebrate communities were investigated in ten mountainous streams. • Indicators were proved to be efficient in discriminating environmental gradients. • Trait-based metrics responded more readily to human disturbances. The selection of suitable indicators is the key to the development of multi-metric bioassessment. Here, we examined how taxonomic and functional structures of macroinvertebrate communities responded to the environmental gradients in ten mountainous streams in the Weihe River and Hanjiang River basins, two subtropical biodiversity hotspots in central China. Our main objectives were: 1) to examine whether trait-based metrics performed better than taxonomic compositions in differentiating environmental gradients; 2) to test whether indicators (species and traits) were more efficient than entire communities in discriminating three site groups subjected to different levels of human disturbances. Our results showed that both taxonomic and functional trait compositions, including species- and trait-based indicators, were all sensitive to environmental disturbance. Particularly, the trait-based variables responded more sensitive to human disturbances. Indicator assemblages can be effective surrogates of entire communities in response to environmental changes. Traits- and indicators-based metrics should be considered as useful supplements in the existent bio-monitoring schemes in China. We argued that the combination of taxonomic and functional indicators should be implemented in bioassessment, as they reflect different aspects of environmental changes and anthropogenic disturbances. [ABSTRACT FROM AUTHOR]

• DNA from bulk insect samples can be used to derive river health indices. • DNA derived indices correlate strongly with morphologically derived indices. • Reference libraries should contain a mix of local and global references. Macroinvertebrate surveys are commonly used for assessing the health of freshwater systems around the world. Traditionally, surveying involves morphologically identifying the families, and sometimes genera, present in samples. Biological indices, derived from taxonomic lists, provide convenient ways to summarise community data and may be fairly insensitive to species-level changes in community compositions. In recent years, molecular techniques for identifying taxa have become increasingly popular and metabarcoding approaches that offer the ability to identify species from mixtures of whole animals (bulk-samples) or from environmental samples have gained much attention. However, generating accurate species lists from metabarcode data is challenging and can be impacted by sample type, choice of primers, community composition within samples, and the availability of reference sequences. This study compares the performance of molecular data extracted from bulk-samples against morphological data in calculating two biological indices (the Stream Invertebrate Grade Number Average Level 2 (SIGNAL2), which is calculated from family-level data, and a genus-level equivalent of this index, SIGNAL_SG) and one biological metric (taxon richness). Further, molecular indices and metrics derived from global, local or mixed reference DNA libraries and with varying degrees of filtering processes applied to them, are compared with respect to the strength of their relationships with morphological indices and metrics. Molecularly derived SIGNAL2 and SIGNAL_SG scores correlated strongly with morphologically derived scores, and were strongest when using a reference library containing a mix of local and global data. Molecularly derived richness metrics were moderately correlated with morphological taxa richness; however, the strongest correlations were observed when taxa that could not be assigned SIGNAL grades were omitted from analyses. This study highlights the utility of using molecular data as an objective and sensitive alternative to traditional freshwater biological assessment using macroinvertebrates. [ABSTRACT FROM AUTHOR]