Influence of water chemistry and environmental degradation on macroinvertebrate assemblages in a river basin in south-east Brazil

Benthic macroinvertebrate assemblages, water chemistry variables and environmental degradation were investigated in an Atlantic Forest region in Brazil. Seven sites of the Guapimirim river basin were studied during three sampling periods based on the rain regime: end of wet season (May 1998), dry season (August 1998), and wet season (January 1999). Four substrates were collected at each site: sand, stony substrates, litter in pool areas and litter in riffle areas. Relationships between macroinvertebrate assemblages, water chemistry variables and environmental degradation were examined using canonical correspondence analysis (CCA). According to CCA, concentrations of dissolved oxygen and chloride, and the environmental degradation, measured by the Riparian Channel Environment index, exhibited the strongest relationship to macroinvertebrate assemblages. Overall, the loss of community diversity measured by the Shannon Index along the degradation gradient was observed. Some taxa were shown to be sensitive to water pollution, especially among Plecoptera, Trichoptera, Coleoptera and some Ephemeroptera, while others such as Simuliidae, Odonata and molluscs were tolerant to moderate levels of pollutants. The Chironomidae were the only group tolerant to a high level of pollutants and degradation.     

Impact of the longitudinal and seasonal changes of the water quality on the benthic macroinvertebrate assemblages of the Andorran streams

The ecological quality of the Andorran streams was assessed in 1998-1999, based on the survey of the water chemistry and the benthic macroinvertebrate assemblages. Two types of modification of the water quality were observed in the Andorran rivers: (i) a progressive degradation along the longitudinal gradient with a chronic degradation in the lower water courses; (ii) a seasonal modification in the mid-elevation sites. Two responses of the benthic macroinvertebrate assemblages to these disturbances were observed: an extreme simplification of the composition and a change of the trophic structure of the assemblages in the more impacted sites.     

Mesohabitat-specific macroinvertebrate assemblage responses to water quality variation in mid-continent (North America) great rivers

We compared the responsiveness of macroinvertebrate assemblages to variation in water quality (ions, nutrients, dissolved metals, and suspended sediment) in two mesohabitats within the main channel of three North American great rivers, the Upper Mississippi, Missouri, and Ohio. Based on about 400 paired samples, we examined the responsiveness of benthic assemblages sampled in the littoral zone and assemblages sampled from the surface of woody snags in the main channel. The assemblages in the two mesohabitats were different in all rivers. Taxa richness was much higher in the benthos than on snags. Macroinvertebrate assemblage response to water quality variation was weak on the Mississippi River, but the reasons for this are unknown. Based on analysis of the similarity between the composition of assemblages from groups of sites with high and low concentrations of water quality variables, benthic assemblages were only slightly more sensitive to water chemistry variation than were snag assemblages. Results of two-sample comparisons between groups of sites with high and low concentrations of water quality variables were consistent with rank correlations of assemblage metrics with water quality. In general, there was little difference between habitats in response to variation in water quality on any river. Our simple method of snag sampling in great rivers is usually much easier than littoral benthic sampling because it does not require wading. Snag sampling in large rivers has some limitations (e.g., natural snags are sometimes absent, samples are semi-quantitative), but lack of sensitivity to water quality gradients compared to the benthos is not among them.     

Different roles of environmental variables and spatial factors in structuring stream benthic diatom and macroinvertebrate in Yangtze River Delta,China

Exploring the relative contribution of spatial factors and environmental variables in shaping communities is of widespread interest in biodiversity conservation and environmental management. Stream communities are hierarchically regulated by environmental variables over multiple spatial scales, and the reaction of different organisms to stressors are still equivocal. We sampled both macroinvertebrates and diatom at 80 sites and additional 10 sites for macroinvertebrates, field measured and laboratory analyzed environmental variables, from the tributaries of Qiantang River, Yangtze River Delta China in 2011. We used PCNM (principal coordinates of neighbor matrices) to generate spatial predictors. We applied redundancy analysis and variation partitioning procedures to identify key spatial and environmental factors, and to quantify their relative roles in shaping diatom and macroinvertebrate assemblages. Our results demonstrated the role of spatial and environmental variables differed in shaping benthic diatom and macroinvertebrate. Diatom assemblage variations were better explained by spatial factors, however macroinvertebrate assemblage variations were better explained by environmental variables. In terms of environmental variables, catchment scale variables (e.g., land use estimators, land use diversity) played the primary role in determining the patterns of both diatom and macroinvertebrate assemblages, whereas the influence of reach-scale variables (e.g., pH, substrates, and nutrients) appeared less. However, nutrients were the stronger factors influencing benthic diatom, whereas physical habitat (e.g., substrates) played more important role than water chemistry in structuring macroinvertebrates. Our results provided more evidence to the incorporation of spatial factors interpreting spatial patterns of stream organisms, and highlighted the useful of multiple organisms and environmental variables at different spatial scales in diagnosing mechanism of stream degradation and in building a sound stream conditions monitoring program for Yangtze River Delta.     

Impact of water quality on macroinvertebrate assemblages along a tropical stream in Kenya

Prudent management of lotic systems requires information on their ecological status that can be estimated by monitoring water quality and biodiversity attributes. To understand environmental conditions in Gatharaini drainage basin in Central Kenya, a study was carried out to establish the relationship between water quality and macroinvertebrate assemblages between the months of March and September 1996. Six sampling sites, each 25 m long were selected along a 24‐km stretch of the stream, which drained land under agricultural, residential and industrial use. Water physico‐chemical data was explored using multivariate analysis of Principal Component Analysis to detect environmental trends downstream. Both macroinvertebrates and water physico‐chemical data of suggested trends were analysed for variations and correlations. Temperatures and invertebrate densities changed significantly between the dry and wet season (P < 0.01) but the fluctuations were not evident downstream. Water physico‐chemical characteristics (total dissolved solids (TDS), pH, turbidity, dissolved oxygen) and biodiversity indices (species richness, diversity, dominance, evenness) changed markedly downstream (P < 0.01). Biodiversity indices correlated inversely with TDS, pH and turbidity but positively with dissolved O₂. It was evident macroinvertebrate assemblages changed significantly downstream as opposed to functional feeding groups. Diptera was important in most sites whilst Oligochaeta dominance increased downstream corresponding to the deterioration in water quality. Collectors/browsers were the dominant functional feeding groups at most sites. This study showed that significant changes in aquatic macroinvertebrate assemblages were primarily due to water quality rather than prevailing climatic conditions.     

钱塘江中游流域不同空间尺度环境因子对底栖动物群落的影响

溪流底栖动物群落结构受不同空间尺度环境因子的共同作用。基于2010年钱塘江中游流域60个样点的大型底栖无脊椎动物和环境变量数据,寻找与研究流域底栖动物群落结构变化密切相关的关键环境变量,解析流域尺度和河段尺度的环境因子对底栖动物群落的相对影响。PCA分析表明该区域的主要环境梯度是流域内的土地利用类型及其引起的溪流物理生境退化程度和水体营养状态。CCA分析发现影响底栖动物群落的流域尺度的关键环境变量是纬度、海拔、样点所在流域大小、森林用地百分比,河段尺度是总氮、总磷、钙浓度、二氧化硅浓度和平均底质得分。偏CCA分析得到两种尺度环境因子对底栖动物变异的总解释量为26.4%,流域尺度和河段尺度变量分别为总解释量的50%和31%;方差分解结果表明研究区域大型底栖无脊椎动物受到两种尺度环境因子的综合影响,且流域尺度环境因子较河段尺度环境因子更为重要,体现了其在溪流生态系统保护、恢复、监测和评价中的重要参考价值。     

Changing ecology of Lake Victoria cichlids and their environment: evidence from C<Superscript>13</Superscript> and N<Superscript>15</Superscript> analyses

Springs are spatially restricted and insular ecotones. In the Alps, topography enhances this isolation. Springs are to a certain extent inhabited by organisms which are adapted to the relatively constant environmental conditions in springs. We examined thirty-six springs in eight different areas in the Swiss National Park (SNP) to understand if the macroinvertebrate assemblages of high-elevation springs are isolated or interconnected communities. We quantitatively and qualitatively sampled the macroinvertebrate assemblages of the springs and monitored environmental parameters. The similarity of the macroinvertebrate assemblages of the springs within and the dissimilarities between the different areas were relatively high; a clear spatial isolation was not evident. The differences of macroinvertebrate assemblages in different areas were explained by substrate parameters: springs in areas at lower altitudes were characterized by organic substrates and many water mite species. High-elevation springs were characterized by coarse inorganic substrates and Trichoptera of the genus Drusus. For spring conservation, it is important to decide on an individual basis if the loss of a single spring will have severe consequences for spring biodiversity.     

The Effect of Riffle-Scale Environmental Variability on Macroinvertebrate Assemblages in a Tropical Stream

In a tropical stream (at the Soberaní;a National Park, Panama), different environmental factors were quantified in riffle habitats (water characteristics: velocity, depth, turbulence, and direction; stone characteristics: surface area, sphericity, and degree of burial; and others: substrate type, and canopy cover). Characteristics of macroinvertebrate assemblages (mean density of individuals, mean taxon richness, and cumulative taxon richness in three stones at each riffle) were related to both mean values and variability of these environmental factors at riffle scale. Macroinvertebrate density was higher in shallow, fast flowing, stony riffles, with low variability in dominant substrate type. Taxon richness was also higher in shallow riffles with loose, not buried stones, and water direction more or less parallel to the bank. Environmental variability resulted as important as mean values of environmental factors to explain variation in macroinvertebrate assemblages. This is the first study, to our knowledge, that quantifies substratum variability and demonstrates its influence on macroinvertebrate assemblages in a tropical stream.     

Land use and the ecology of benthic macroinvertebrate assemblages of high-altitude rainforest streams in Uganda

1. In sub‐Saharan Africa, tropical forests are increasingly threatened by accelerating rates of forest conversion and degradation. In East Africa, the larger tracts of intact rainforest lie largely in protected areas surrounded by converted landscape. Thus, there is critical need to understand the functional links between large‐scale land use and changes in river conditions, and the implications of park boundaries on catchment integrity. 2. The objective of this study was to use the mosaic of heavily converted land and pristine forest created by the protection of the high‐altitude rainforest in Bwindi Impenetrable National Park, Uganda to explore effects of deforestation on aquatic systems and the value of forest in buffering effects of adjacent land conversion. A set of 16 sites was selected over four drainages to include four categories of deforestation: agricultural land, deforested upstream (of the park boundary), forest edge (park boundary) and forest. We predicted that forest buffer (downstream or on the edge) would moderate effects of deforestation. To address this prediction, we quantified relationships between disturbance level and both physicochemical characters and traits of the macroinvertebrate assemblages during six sampling periods (February 2003 and June 2004). 3. Results of both principal components analysis and cluster analyses indicated differences in limnological variables among deforestation categories. PC1 described a gradient from deforested sites with poor water quality to pristine forested sites with relatively good water quality. Agricultural sites and deforested upstream sites generally had the highest turbidity, total dissolved solids (TDS), and conductivity values and low transparency values. Forest sites and boundary site groups generally exhibited low turbidity, TDS, and conductivity values and high water transparency values. Sites also clustered according to deforestation categories; forest and forested edge sites formed a cluster independent of both agricultural land and deforested‐upstream. 4. Water transparency, water temperature, and pH were the most important factors predicting benthic macroinvertebrate assemblages. Sensitive invertebrate families of Trichoptera, Ephemeroptera, Plecoptera, and Odonata dominated forested sites with high water transparency, low water temperature, and low pH while the tolerant families of Ephemeroptera, Diptera, Hemiptera, and Coleoptera were abundant in agriculturally impacted sites with low water transparency, high water temperature, and high pH. 5. This study provides support for the importance of riparian buffers in moderating effects of deforestation. Forest and forested edge sites were more similar in both limnological and macroinvertebrate assemblage structure than sites within or downstream from agricultural lands. If the protected area cannot encompass the catchment, the use of rivers as park boundaries may help to maintain the biological integrity of the rivers by buffering one side of the watercourse.     

Weak Concordance between Fish and Macroinvertebrates in Mediterranean Streams

Although anthropogenic degradation of riverine systems stimulated a multi-taxon bioassessment of their ecological integrity in EU countries, specific responses of different taxonomic groups to human pressure are poorly investigated in Mediterranean rivers. Here, we assess if richness and composition of macroinvertebrate and fish assemblages show concordant variation along a gradient of anthropogenic pressure in 31 reaches across 13 wadeable streams in central Italy. Fish and invertebrate taxonomic richness was not correlated across sites. However, Mantel test showed that the two groups were significantly, albeit weakly, correlated even after statistically controlling for the effect of environmental variables and site proximity. Variance partitioning with partial Canonical Correspondence Analysis showed that the assemblages of the two groups were influenced by different set of environmental drivers: invertebrates were influenced by water organic content, channel and substratum features, while fish were related to stream temperature (mirroring elevation) and local land-use. Variance partitioning revealed the importance of biotic interactions between the two groups as a possible mechanisms determining concordance. Although significant, the congruence between the groups was weak, indicating that they should not be used as surrogate of each other for environmental assessments in these Mediterranean catchments. Indeed, both richness and patterns in nestedness (i.e. where depauperate locations host only a subset of taxa found in richer locations) appeared influenced by different environmental drivers suggesting that the observed concordance did not result from a co-loss of taxa along similar environmental gradients. As fish and macroinvertebrates appeared sensitive to different environmental factors, we argue that monitoring programmes should consider a multi-assemblage assessment, as also required by the Water Framework Directive.     

Diagnosing stream ecosystem integrity in the Ordesa‐Viñamala Biosphere Reserve,central Spanish Pyrenees

This work studied the ecological integrity of river ecosystems inside the Ordesa‐Viñamala Biosphere Reserve in the central Spanish Pyrenees. Despite its protected status, the reserve endures a considerable number of human stresses, thus the aim was to evaluate the conservation status of the two river basins inside the protected area: The Gállego River Basin, inside the transition zone of the protected area and which allows a wide range of human activities; and the Ara River Basin, inside the buffer zone where only sound ecological practices are authorised. The environmental status of river ecosystems was analysed by studying fish and macroinvertebrate communities, hydrochemical and habitat characteristics and by calculating environmental quality indices. From August to September 2011, a total of 14 sites were sampled. Fish sampling was conducted using electrofishing gear, and macroinvertebrate were sampled by applying the IBMWP and IASPT procedures. Results showed that, while the Ara River Basin maintains a solid ecological integrity, the Gállego River Basin endures important habitat alteration. Trout, the dominant and exclusive species in the Ara River, were absent and replaced by translocated native cyprinids in the Gállego River Basin. This colonisation was explained by the alteration of the stream ecosystems and their homogenisation. The study of macroinvertebrate communities and the diagnosis obtained with the environmental quality indices also enhanced the deficient ecological integrity of some sites in the Gállego River. The results suggest that the Biosphere Reserve is not providing adequate protection to streams inside its boundaries, leading to major degradation of their biological integrity.     

Seasonal shifts in the assembly dynamics of benthic macroinvertebrate and diatom communities in a subtropical river

Identifying seasonal shifts in community assembly for multiple biological groups is important to help enhance our understanding of their ecological dynamics. However, such knowledge on lotic assemblages is still limited. In this study, we used biological traits and functional diversity indices in association with null model analyses to detect seasonal shifts in the community assembly mechanisms of lotic macroinvertebrates and diatoms in an unregulated subtropical river in China. We found that functional composition and functional diversity (FRic, FEve, FDis, MNN, and SDNN) showed seasonal variation for macroinvertebrate and diatom assemblages. Null models suggested that environmental filtering, competitive exclusion, and neutral process were all important community assembly mechanisms for both biological groups. However, environmental filtering had a stronger effect on spring macroinvertebrate assemblages than autumn assemblages, but the effect on diatom assemblages was the same in both seasons. Moreover, macroinvertebrate and diatom assemblages were shaped by different environmental factors. Macroinvertebrates were filtered mainly by substrate types, velocity, and COD_Mn, while diatoms were mainly shaped by altitude, substrate types, and water quality. Therefore, our study showed (a) that different biological assemblages in a river system presented similarities and differences in community assembly mechanisms, (b) that multiple processes play important roles in maintaining benthic community structure, and (c) that these patterns and underlying mechanisms are seasonally variable. Thus, we highlight the importance of exploring the community assembly mechanisms of multiple biological groups, especially in different seasons, as this is crucial to improve the understanding of river community changes and their responses to environmental degradation.     

Comparison of macroinvertebrate assemblages inhabiting pristine streams in the Huron Mountains of Michigan, USA

Benthic macroinvertebrate assemblages were surveyed from similar erosional biotopes of four pristine streams in the remote Huron Mountain region of the upper peninsula of Michigan during the summers of 1992 and 1993. Semi-quantitative samples from five sites, each in a 1.5 km stretch of Mountain Stream, Pine River, Salmon-Trout River and Huron River, were the basis for structural and functional comparisons between streams. Ancillary water chemistry data reflect the relative pollution free nature of these streams. Both water chemistry and macroinvertebrate data served as the first baseline data for Huron Mountain streams. No new or rare species were found among the 194 species sampled. Temporal differences in taxonomic makeup within streams were due to differences among insect species life cycles. Taxonomic makeup between streams was generally similar, but certain differences are shown to be possibly related to factors such as lake sources, interspecific interactions, and stream size. Based on relative abundance of each functional feeding group, assemblages in all streams were functionally similar and collector-dominated. ANOVA results indicated significant differences in functional feeding group abundance and biomass between streams in every case. The functional variations reflected by specific differences in taxonomic composition between stream assemblages are discussed.     

Relationships between the Seasonal Variations of Macroinvertebrates,and Land Uses for Biomonitoring in the Xitiaoxi River Watershed,China

The impacts of differences in watershed land uses, and differences in seasonality on benthic macroinvertebrate communities, were evaluated in 12 stream sites within the Xitiaoxi River watershed, China, from April 2009 to January 2010. The composition of macroinvertebrate community differed significantly among three land use types. Forested sites were characterized by high taxa richness, diversity and the benthic‐index of biotic integrity (B‐IBI), while farmland and urban disturbed stream sites presented contrary patterns. The percentage of urban land use, conductivity, dissolved oxygen, ammonia nitrogen and total phosphorus were the major drivers for the variations. The land use related water quality stress gradients of the four sampling seasons were determined by means of four independent Principal Component Analyses. The responses of macroinvertebrate community metrics, to anthropogenic stressors, were explored using Spearman Rank Correlation analyses. All the selected metrics, including total numbers of taxa, numbers of Ephemeroptera, Plecoptera and Trichoptera taxa, percentage of non‐insect abundance, percentage of scrapers abundance, Pielou’s evenness index, Simpson diversity index, and the Benthic Index of Biotic Integrity were correlated significantly with environmental gradients (PC1) in autumn. In other seasons such correlations were less pronounced. Our results imply that autumn is the optimal time to sample macroinvertebrate communities, and to conduct water quality biomonitoring in this subtropical watershed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Links Between Anthropogenic Perturbations and Benthic Macroinvertebrate Assemblages in Afromontane Forest Streams in Uganda

Relationships between environmental variables and benthic macroinvertebrate assemblages were investigated among several sites that varied in disturbance history in Bwindi Impenetrable National Park, an Afromontane site in East Africa. Environmental variables were correlated with the level of past catchment disturbance – logging, agricultural encroachment, and present tourism activity. For example, sites in medium and high disturbance categories had higher values of specific conductance and lower water transparency than low disturbance category sites, these environmental variables may therefore act indicators of ecological quality of rivers. Environmental variables such as conductivity and water transparency were found to be good predictors of benthic macroinvertebrate assemblages, with anthropogenically stressed sites having lower diversity than the reference sites. Impacted sites were dominated by tolerant taxa such as chironomid and leeches, while ‘clean water’ taxa such as Ephemeroptera, Plecoptera and Trichoptera dominated at minimally impacted sites. Comparison of sites with different disturbance histories provided evidence for differences in benthic macroinvertebrate communities that reflect the state of forest restoration and recovery. We recommend quarterly monitoring of water quality to act as an early warning system of deterioration and tracking ecological recovery of previously impacted sites.     

Characterization of diatom assemblages in mid-altitude streams of NW Italy

Following the European Water Framework Directive, this study aims to be the first step to (i) identify diatom type assemblages in unpolluted streams in NW Italy, and (ii) find which ecological factors explain most of the variation. To achieve this, we collected physical, chemical and benthic community data from four streams in NW Italy from 2001 to 2004, for a total of 72 samples. All sampling sites were between 200 m a.s.l. and 800 m a.s.l., but differed in the dominant lithological substrate, i.e. alluvial or siliceous. Relationships between diatom communities and environmental factors were examined using canonical correspondence analysis (CCA), while Indicator Species Analysis was used to define characterizing species and accompanying species of three environmental groups identified by CCA: (1) high water quality and medium saline content, (2) high water quality and low saline content, (3) poor water quality. The diatom assemblages of the three groups of sites differed significantly, as shown by the Multi-Response Permutation Procedure. There were strong correlations between diatoms and environmental factors, especially chlorides (also highly correlated with sulphates and carbonate hardness), nitrate concentration and conductivity. The group 1 assemblage was typical of the alluvial Alpine streams with medium saline content and was characterized by mostly oligosaprobic/β-mesosaprobic taxa such as Cymbella affinis, Diatoma ehrenbergii and Staurosira pinnata. The species assemblage found in the siliceous Alpine rivers with good water quality make them suitable reference sites for a benthic diatom community. Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorised users Handling editor: K. Martens     

The influence of substrate type on macroinvertebrate assemblages within agricultural drainage ditches

Artificial drainage ditches are common features in lowland agricultural catchments that support a wide range of ecosystem services at the landscape scale. Current paradigms in river management suggest activities that increase habitat heterogeneity and complexity resulting in more diverse floral and faunal assemblages; however, it is not known if the same principles apply to artificial drainage ditch systems. We examined the effects of four artificial substrates, representing increasing habitat complexity and heterogeneity (bricks, gravel, netting and vegetation), on macroinvertebrate community structure within artificial drainage ditches. Each substrate type supported a distinct macroinvertebrate community highlighting the importance of habitat heterogeneity in maintaining macroinvertebrate assemblages. Each substrate type also displayed differing degrees of community heterogeneity, with gravel communities being most variable and artificial vegetation being the least. In addition, several macroinvertebrate diversity metrics increased along the gradient of artificial substrate complexity, although these differences were not statistically significant. We conclude that habitat management practices that increase habitat complexity are likely to enhance macroinvertebrate community heterogeneity within artificial drainage channels regardless of previous management activities.

     

Comparative Environmental Assessment in the Studies of Benthic Diatom,Macroinvertebrate, and Fish Communities

Community response to environmental gradients operating at hierarchical scales was assessed in studies of benthic diatoms, macroinvertebrates and fish from 44 stream sites in the New York City watershed. Hierarchical cluster analysis (TWINSPAN) of diatoms and fish partitioned the study sites into four groups, i.e., acid streams, reservoir outlets and wetland streams, large eutrophic streams, and small eutrophic streams; macroinvertebrate TWINSPAN distinguished an additional group of silty eutrophic streams. The correspondence among the three assemblage TWINSPAN groupings was moderate, ranging from 51 to 57%. The similarity across the four major group types was the highest among large eutrophic stream and acid stream assemblages, and the lowest among small eutrophic stream assemblages. Stepwise discriminant function analysis revealed that environmental factors discriminated most effectively the diatom grouping and least effectively the fish grouping. The best environmental predictors for diatom and macroinvertebrate grouping were conductance and percent surface water, while population density was most powerful in separating the fish groups. Carbaryl was the only pesticide that correlated with macroinvertebrate grouping. Partial redundancy analyses suggested a differential dependence of freshwater communities on the scale of the environmental factors to which they respond. The role of small‐scale habitat and habitatland cover/land use interaction steadily increased across the diatom, macroinvertebrate, and fish assemblages, whereas the effect of large‐scale land cover/land use declined.     

Macroinvertebrate assemblage patterns as indicators of water quality in the Xindian watershed,Taiwan

In the present study, we assessed the water quality along a stretch of the watershed with considerable economic importance at the Xindian in Taiwan, using macroinvertebrate assemblages, along with environmental variables. The research was carried out at the seven sampling sites (abbreviated as XD1–XD7) where human impacts varied in intensity from upstream tributaries to the downstream of the Xindian watershed from December 2010 to December 2011. All variables except for the hardness, pH, dissolved oxygen, conductivity, turbidity, phosphate, ammonia, and alkalinity were significantly different (P < 0.05) between the sampling sites. A total of seventy seven taxa belonging to forty five families within eight insect orders, along with three non-insect invertebrate taxa were recorded, with most representative orders being Ephemeroptera and Diptera. Mean values of the density, abundance of macroinvertebrates, Shannon index, Simpson index, and Pielou's evenness were much higher in the reference sites, XD2, XD3, and XD4 compared with impacted sites, XD5, XD6, and XD7. Most of the benthic metrics were greatest in the reference site compared to the impacted site. Only the composition measures, percentages of Chironomidae and Oligochaeta which are more tolerant to pollution were dominant in the impacted site, XD7. As the results of assessment by different benthic metrics, water quality of Xindian watershed became gradually worse from upstream to downstream. Generally, our results suggest that macroinvertebrate assemblages can be used for assessment of water quality.     

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.