Ephemeroptera, Plecoptera And Trichoptera Research Articles

Impervious area percentage predicated influence of rapid urbanization on macroinvertebrate communities in a southwest China river system

Urban areas and their development depress water physicochemical properties, river habitats and aquatic biotic integrity worldwide. Benthic macroinvertebrates at 61 sites representing three types of river reach locations (upstream rural areas, intermediate and downstream of urban areas) on the Liangtan River, a rapidly urbanized river with untreated sewage discharge in southwest China, were examined to compare their community composition and diversity. Their relationships with environmental variables were also explored. The results indicate a significant reduction in sensitive EPT (Ephemeroptera, Plecoptera and Trichoptera) species, dominance by a few tolerant taxa (Oligochaeta and Chironomidae), a significant decline in biodiversity and dominance of collector-gatherers at intermediate and downstream urban sites compared with aquatic macroinvertebrates at rural sites. The community composition of urban sites were different from those of rural sites and were quite similar to those of downstream sites, but maintained a much higher Oligochaeta density. The species-environment relation was predominately explained by the percentage of impervious area (PIA) and farmland at the catchment scale. At the local scale chemical oxygen demand (COD) and pH-value explained this relationship. Six community indicators, including richness, the Shannon-Wiener index, EPT(%), collector-filterers(%), scrapers(%) and collector-gatherers(%), had exponential relationships with PIA. Density of macroinvertebrates, Oligochaeta density, Oligochaeta(%), predator(%) and shredder(%) exhibited stepped threshold response patterns with PIA. Pielou's index had an approximately negative linear relationship with PIA. For exponential pattern, a threshold value of PIA between 10.6% and 14.4% was found. For stepped threshold response pattern, the first threshold was between 11.2% and 13.8%, and the second threshold was 23.8%. Our study indicates particularly great influences of urbanization with untreated sewage on macroinvertebrates and river ecosystems. PIA also showed to be a good indicator of urbanization and an accurate predictor of urban impacts on river macroinvertebrate integrity.

Predicting the effect of land use and climate change on stream macroinvertebrates based on the linkage between structural equation modeling and bayesian network

Land use and climate change are increasingly important stressors affecting freshwater ecosystems. Although their effects on freshwater organisms have been widely studied, most studies applied traditional statistical methods, which only focus on single stressor and simple cause-effect relationships without considering the complex interactions among stressors. Therefore, we developed an integrated method by combining Structure Equation Modeling (SEM) and Bayesian Networks (BNs) to estimate the interactive effect of land use and climate change on freshwater macroinvertebrates. A field investigation was conducted in August 2009 in Taizi River Basin, Northeast China, and samples of stream macroinverterbates and water chemistry were collected from 211 sites. The SEM-BN models were developed to explore the complex relationships among land use cover (crop, forest and residential land), water quality (total phosphorus, total nitrogen and dissolved oxygen), physical factors influenced by climate change (water temperature, flow velocity), other habitat characteristics (slope and substrate composition) and macroinvertebrate EPT (Ephemeroptera, Plecoptera and Trichoptera) indices (the percentage of EPT taxa, EPT richness, EPT abundance and the Shannon-Weiner Diversity Index of EPT). Three scenarios were designed to assess the possible responses of EPT indices to land use change, climate change and their interactions. Our results showed that when the change of land use and climate were considered alone, increasing crop and urban land led to declines in EPT indices whereas moderate rise of air temperature and more rainfall had opposite effects. However, the combined effect showed that the positive effects caused by climate change could weaken some negative effects, but land use change still had stronger effect on EPT indices. Our results provided more detailed understanding on how environmental stressors affect freshwater organisms, and further catchment management should integrate the combined effect of different environmental stressors on streams.

Influence of habitat characteristics on the assemblage and distribution of Ephemeroptera, Plecoptera and Trichoptera (EPT) at selected recreational rivers in Kelantan, Malaysia

This study was carried out to identify the habitat factors that contribute to the variation of EPT at three recreational rivers in Kelantan, Malaysia. Therefore, the further implementation of EPT index as bio-indicator can be standardized and efficient. The results showed that, EPT assemblage and distribution at these rivers varies even though there is no significant difference in the water quality. Water quality of all the rivers are in the range of ‘good’ level. Therefore, regression analysis was made to confirm the main factors influencing the variation of EPT assemblage within selected recreational rivers in Kelantan, Malaysia. The substrate composition appeared as the main factor influencing the variation in distribution and composition of EPT in good water quality from the analysis. Thus, it is concluded that the substrate composition is the major factor influencing the composition and distribution of EPT in recreational river (good water quality).

Land cover disturbance homogenizes aquatic insect functional structure in neotropical savanna streams

By modifying local habitat conditions, the alteration of land cover can result in severe faunal impairment, subsequently affecting ecosystem functioning. We analyzed changes in the composition of Ephemeroptera, Plecoptera and Trichoptera (EPT) assemblages along a gradient of human disturbance intensity in 66 neotropical savanna headwater stream sites. Whereas EPT genus richness did not differ among the levels of disturbance, functional richness and diversity significantly decreased from least- to highly disturbed sites. Using a combination of RLQ and fourth-corner analyses, we found that 12 of 28 trait categories were significantly associated with changes in catchment land use and cover intensity, local physical habitat, and water quality. EPT assemblages in least-disturbed sites were characterized by higher proportions of large body size and low body flexibility with <1 reproductive cycle per year, case building, and climbing functional traits. In addition, disturbed sites demonstrated high assemblage functional homogenization compared with least disturbed sites. To our knowledge, this study is the first that examines the response of invertebrate functional structure along a gradient of human disturbance at a large spatial scale in the Neotropics. In doing so, we demonstrate the applicability of multiple trait-based approaches and the higher reliability of functional structure in comparison to taxonomic composition for assessing the effects of human disturbances in neotropical streams.

How to assess the impact of fine sediments on the macroinvertebrate communities of alpine streams? A selection of the best metrics

Excessive fine sediment accumulation (i.e., siltation) in streams and rivers originates from several human activities and globally results in heavy alterations of aquatic habitats and biological communities. In this study the correlation between fine sediment and several benthic invertebrate community metrics was tested through a manipulative approach in alpine streams, where siltation mainly results as a physical alteration (i.e., the clogging of substrate interstices) without the influence of co-occurring confounding factors. We selected 12 candidate metrics, belonging to three different categories: compositional, structural and functional. We first carried out a manipulative experiment where artificial substrates were used to provide standardized conditions of siltation. All candidate metrics were calculated for each artificial substrate and the selection of the best combination of metrics was statistically performed with an information-theoretic approach. All candidate metrics were calculated both at family level and also at a mixed level (family and genus) in order to account for the systematic resolution. Then, data from a field study on alpine streams affected by mining activities were used as independent dataset for testing the performance of the selected metrics. We found that the total taxa richness, the EPT (Ephemeroptera, Plecoptera and Trichoptera) richness and the abundance of benthic invertebrates associated to rheophilous conditions and coarse mineral substrates were the most sensitive metrics. When these metrics were aggregated into a multimetric index in the validation dataset, we observed high and significant correlations between index values and the quantity of fine sediment for both taxonomic levels, especially for the mixed level. The findings of this study provide useful tools for biomonitoring the effects of fine sediment in low order, mountainous streams and contribute to improve our diagnostic ability on stressor-specific alterations.

Landscape variables influence taxonomic and trait composition of insect assemblages in Neotropical savanna streams

Summary Stream invertebrate assemblages are structured by environmental factors acting at multiple spatial scales. Identifying the spatial scale that most influences the species–environment relationships is a major goal of community ecology. We evaluated the importance of catchment and site scales and associated environmental variables in shaping Ephemeroptera, Plecoptera and Trichoptera (EPT) assemblages in Neotropical savanna headwater streams. Sampling sites were associated with 20 catchment‐scale variables that depicted land cover and land use as well as natural geophysical variables such as altitude and climate. Site‐scale habitat was characterised by 55 variables that described habitat hydromorphology, substrate, flow, canopy, in‐stream cover and water quality. EPT traits were assessed using 28 categories of 7 biological traits, which represented the best available current knowledge for EPT in Neotropical savanna streams. We analysed the relationships between the catchment‐ and site‐scale habitat variables and the taxonomic and trait composition of insect assemblages using 1,760 samples collected in 160 stream sites. Catchment‐ and site‐scale variables both explained significant variation in EPT taxon and trait composition. Substrate, habitat hydromorphology and land use most influenced variation in taxonomic composition, whereas trait composition was mainly affected by land use. Catchment geographic position explained less assemblage variation. To our knowledge, this study is the first assessment of the impact of catchment‐ and site‐scale variables on the trait and taxon composition of stream insect assemblages in Neotropical savanna streams. It highlights the need for better regional biological knowledge of invertebrates to generate more general trait‐based approaches in freshwater ecosystem conservation.

Metal toxicity affects predatory stream invertebrates less than other functional feeding groups

Ecosystem effects of heavy metals need to be identified for a retrospective risk assessment, and potential impacts need to be predicted for a prospective risk assessment. In this study, we established a strong correlation between the toxic pressure of dissolved metals and invertebrate species. We compiled available data from a wide geographical range of Australian streams that were contaminated with heavy metals [mainly copper (Cu) and zinc (Zn)] and the corresponding invertebrate communities. Heavy metal toxicity is positively related to the proportion of predators within the invertebrate community, represented by the predatorratio, with an effect threshold range of 2.6 μg/L - 26 μg/L for Cu and 62 μg/L - 617 μg/L for Zn. These effect concentrations are in the ranges of the concentrations identified in model ecosystems and other field investigations and are just above the existing guideline limits. Heavy metals also affects the taxa richness negatively. Other community measures, such as the evenness, number of EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa, SPEcies At Risk (SPEAR)pesticides or SPEARsalinity were relatively poorly correlated with heavy metal toxicity in the streams. Therefore, we suggest applying the predatorratio within the community as a starting point for an indicator of the dissolved metal toxicity, the SPEARmetals.

Analysis and prediction of the spatial distribution of EPT (Ephemeroptera, Plecoptera, and Trichoptera) assemblages in the Han River watershed in Korea

Understanding the relationships between environmental factors and aquatic communities at the large scale is important for conserving freshwater biodiversity and sustaining ecological integrity. In this study, we evaluated the ecological status of the Han River watershed in Korea with the predictive distribution maps for EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa. From large-scale surveys, environmental and biological data for 360 sites in 189 streams and rivers in the Han River watershed in 2012 and 2013 were analyzed. Based on correlation analysis and stepwise multiple regression analysis, the factors influencing EPT richness were altitude, percent of coarse substrate, biochemical oxygen demand (BOD), and total phosphorus (TP). DPI (distribution prediction index), indicating the distribution probability of EPT assemblages, was calculated by using a frequency ratio model. This index was high in the mountainous area where altitude and percent of coarse substrate were high, but low in the urbanized area where BOD and TP were high. Verification of the model indicated high reliability of DPIs as demonstrated by the low root-mean-square-error (RMSE) values between the predicted and observed values. This study provides a basis for the sustainable management of stream ecosystems as well as paves the way for future studies such as those on environmental assessment techniques using aquatic insect communities.

Additive effects prevail: The response of biota to multiple stressors in an intensively monitored watershed

Freshwater ecosystems are impacted by a range of stressors arising from diverse human-caused land and water uses. Identifying the relative importance of single stressors and understanding how multiple stressors interact and jointly affect biology is crucial for River Basin Management.This study addressed multiple human-induced stressors and their effects on the aquatic flora and fauna based on data from standard WFD monitoring schemes. For altogether 1095 sites within a mountainous catchment, we used 12 stressor variables covering three different stressor groups: riparian land use, physical habitat quality and nutrient enrichment. Twenty-one biological metrics calculated from taxa lists of three organism groups (fish, benthic invertebrates and aquatic macrophytes) served as response variables. Stressor and response variables were subjected to Boosted Regression Tree (BRT) analysis to identify stressor hierarchy and stressor interactions and subsequently to Generalised Linear Regression Modelling (GLM) to quantify the stressors standardised effect size.Our results show that riverine habitat degradation was the dominant stressor group for the river fauna, notably the bed physical habitat structure. Overall, the explained variation in benthic invertebrate metrics was higher than it was in fish and macrophyte metrics. In particular, general integrative (aggregate) metrics such as % Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa performed better than ecological traits (e.g. % feeding types). Overall, additive stressor effects dominated, while significant and meaningful stressor interactions were generally rare and weak.We concluded that given the type of stressor and ecological response variables addressed in this study, river basin managers do not need to bother much about complex stressor interactions, but can focus on the prevailing stressors according to the hierarchy identified.

Biomonitoring of water quality of the Osumi, Devolli, and Shkumbini rivers through benthic macroinvertebrates and chemical parameters

ABSTRACTEnvironmental monitoring of river water quality in Albania, using biological and chemical parameters, is a fast and effective way to assess the quality of water bodies.The aim of this study was to investigate Ephemeroptera, Plecoptera and Trichoptera (EPT), Biotic index-Richness using macroinvertebrates to assess the water quality, with special reference to nutrient (phosphorus and nitrogen) levels in the Devolli, Shkumbini and Osumi rivers. Our objective was to investigate the relationships between the measures of benthic macroinvertebrate communities and nutrient concentrations to assess water quality. The rivers' benthic macroinvertebrates were collected during different seasons in 2012. The biological and chemical parameters used in the current study identified them as quick indicators of water quality assessment. The total number of macroinvertebrate individuals (n = 15,006) (Osumi river: n = 5,546 organisms; Devolli river: n = 3,469 organisms; and Shkumbini river: n = 5,991 organisms), together with the EPT group (Ephemeroptera, Plecoptera, and Trichoptera), showed that the water quality at the river stations during the above-mentioned period belonged to Classes II and III (fair water quality and good water quality, respectively). The classification of the water quality was also based on the nitrogen and total phosphorus contents. The pollution tolerance levels of macroinvertebrate taxa varied from the non-tolerating forms encountered in environments with low pollution levels to the tolerating forms that are typical of environments with considerable pollution levels.

Measurement of the Ecological Integrity of Cerrado Streams Using Biological Metrics and the Index of Habitat Integrity.

Generally, aquatic communities reflect the effects of anthropogenic changes such as deforestation or organic pollution. The Cerrado stands among the most threatened ecosystems by human activities in Brazil. In order to evaluate the ecological integrity of the streams in a preserved watershed in the Northern Cerrado biome corresponding to a mosaic of ecosystems in transition to the Amazonia biome in Brazil, biological metrics related to diversity, structure, and sensitivity of aquatic macroinvertebrates were calculated. Sampling included collections along stretches of 200 m of nine streams and measurements of abiotic variables (temperature, electrical conductivity, pH, total dissolved solids, dissolved oxygen, and discharge) and the Index of Habitat Integrity (HII). The values of the abiotic variables and the HII indicated that most of the streams have good ecological integrity, due to high oxygen levels and low concentrations of dissolved solids and electric conductivity. Two streams showed altered HII scores mainly related to small dams for recreational and domestic use, use of Cerrado natural pasture for cattle raising, and spot deforestation in bathing areas. However, this finding is not reflected in the biological metrics that were used. Considering all nine streams, only two showed satisfactory ecological quality (measured by Biological Monitoring Working Party (BMWP), total richness, and EPT (Ephemeroptera, Plecoptera, and Trichoptera) richness), only one of which had a low HII score. These results indicate that punctual measures of abiotic parameters do not reveal the long-term impacts of anthropic activities in these streams, including related fire management of pasture that annually alters the vegetation matrix and may act as a disturbance for the macroinvertebrate communities. Due to this, biomonitoring of low order streams in Cerrado ecosystems of the Northern Central Brazil by different biotic metrics and also physical attributes of the riparian zone such as HII is recommended for the monitoring and control of anthropic impacts on aquatic communities.

Application of Aquatic Insects (Ephemeroptera, Plecoptera And Trichoptera) In Water Quality Assessment of Malaysian Headwater.

The Ephemeroptera, Plecoptera and Trichoptera (EPT) community structure and the specific sensitivity of certain EPT genera were found to be influenced by water parameters in the rivers of Gunung Jerai Forest Reserve (GJFR) in the north of peninsular Malaysia. The scores of EPT taxa richness of >10 in all rivers indicated all rivers’ habitats were non-impacted, having good water quality coinciding with Class I and Class II of Malaysian water quality index (WQI) classification of potable water. The abundance of EPT was very high in Teroi River (9,661 individuals) but diversity was lower (22 genera) than Tupah River which was highly diverse (28 genera) but lower in abundance (4,263 individuals). The lowest abundance and moderate diversity was recorded from Batu Hampar River (25 genera). Baetis spp. and Thalerosphyrus spp., Neoperla spp. and Cheumatopsyche spp. were the most common genera found. Classification for all rivers using EPT taxa Richness Index and WQI gave different category of water quality, respectively. The WQI classified Tupah and Batu Hampar rivers into Class II and Teroi River (Class I) was two classes above the classification of the EPT taxa Richness Index.

Trophic guilds of EPT (Ephemeroptera, Plecoptera, and Trichoptera) in three basins of the Brazilian Savanna

• We determined EPT trophic guilds based on gut content analysis of specimens from three Brazilian Savannah basins. • Trophic guild composition did not reflect the taxonomic distance among taxa and did not vary among basins. • Local conditions influenced EPT diet and, therefore, trophic guild composition. Insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are prominent among stream biota and are associated with many ecological processes in these environments, meaning that a proper definition of their habits is essential. We studied EPT from three watersheds in Brazil (Paraguai, Paraná, and São Francisco) in order to (i) determine the trophic guilds of EPT genera sampled; (ii) determine whether trophic guilds reflect EPT phylogenetic component (taxonomic distance); (iii) compare trophic guild composition among watersheds; and (iv) verify the effect of environmental components in trophic guild composition. Eight trophic guilds were determined based on gut content analysis: detritivores, fine-detritivores, fine-detritivores/algivores, coarse-detritivores, coarse-detritivore/algivores, periphytivores, carnivores, and omnivores. Caddisflies presented the most variable diet and many genera belonged to different trophic guilds in different basins. Overall trophic guild composition did not reflect the taxonomic distance among taxa and it did not differ among the three basins. Instead, EPT guilds were related to local environmental variables, evidencing that their diet probably varies according to local resource availability, highlighting the importance of empirical assessments of diet for ecological studies.

Temporal variation in the Ephemeroptera, Plecoptera and Trichoptera community in response to environmental drivers in a subtropical stream

Aquatic insects are important elements in the ecological dynamics of lotic systems and their distribution in these environments can be driven by several environmental factors. Based in this assumption the aim of this study was to evaluate which environmental variables act as structural driver of the Ephemeroptera, Plecoptera and Trichoptera (EPT) community. We hypothesize that community structure will display strong temporal alterations due to characteristics in subtropical regions. We evaluated the effect of water temperature, conductivity, dissolved oxygen, depth, current velocity and rainfall on the distribution of EPT community. The insects were sampled using the litter bags incubation in a third-order subtropical stream located on Santa Catarina Island, Southern Brazil. The abundance of EPT was monitored for 24 months between January 2012 and December 2013. We identified 530 EPT specimens belonging to 11 families and 20 genera. The community showed a significant variation along the monitored time, mainly attributed to Trichoptera order. In addition to the results of this work the Ecnomidae family, Austrotinodes and Neotrichia genera represent new records for Santa Catarina State. Environmental variables varied significantly during the study time and depth and rainfall were the mainly environmental drivers acting under the community structure. We also observed a negatively correlation among rainfall and EPT community, especially to Trichoptera, which showed a strong temporal variation. In this study the EPT community displays a strong temporal variation along the monitored time, mainly attributed to rainfall events, characteristic of subtropical region. We also suggest that body adaptations also have an influence in the EPT community structure, once under flood event conditions these adaptations may offer advantage or disadvantage to invertebrate establishment, as pointed in the Trichoptera order.

Partitioning taxonomic diversity of aquatic insect assemblages and functional feeding groups in neotropical savanna headwater streams

Biological diversity can be divided into: alpha (α, local), beta (β, difference in assemblage composition among locals), and gamma (γ, total diversity). We assessed the partitioning of taxonomic diversity of Ephemeroptera, Plecoptera and Trichoptera (EPT) and of functional feeding groups (FFG) in neotropical savanna (southeastern Brazilian cerrado) streams. To do so, we considered three diversity components: stream site (α), among stream sites (β1), and among hydrologic units (β2). We also evaluated the association of EPT genera composition with heterogeneity in land use, instream physical habitat structure, and instream water quality variables. The percentage of EPT taxonomic α diversity (20.7%) was smaller than the β1 and β2 diversity percentages (53.1% and 26.2%, respectively). The percentage of EPT FFG collector-gatherer α diversity (26.5%) was smaller than that of β1 diversity (55.8%) and higher than the β2 (17.7%) diversity. The collector-gatherer FFG was predominant and had the greatest β diversity percentage among stream sites (β1, 55.8%). Our findings support the need for implementing regional scale conservation strategies in the cerrado biome, which has been degraded by anthropogenic activities.

Does the exclusion of meiofauna affect the estimation of biotic indices using stream invertebrates?

Biomonitoring of rivers is usually undertaken using information based on macroinvertebrate assemblages. However, exclusion of meiofauna (i.e. invertebrates less than 0.5 mm in size) when sorting benthic invertebrates can affect the estimation of densities and other biotic indices. In the present study, the effect of excluding the less than 0.5 mm fraction of invertebrates on estimation of benthic invertebrate indices was investigated in the Naro Moru River, Kenya. The Shannon–Wiener diversity index, Pielou’s evenness index, a multimetric index, Simpson’s diversity index, Margalef’s diversity index, mean invertebrate density, taxa richness, and Ephemeroptera, Plecoptera and Trichoptera (EPT) densities were determined. Only mean invertebrate and EPT densities differed significantly between the greater than 0.5 mm and total fractions. In conclusion, exclusion of meiofauna from invertebrate samples can affect the estimation of some stream invertebrate biotic indices.

Effects of small changes in riparian forest complexity on aquatic insect bioindicators in Brazilian subtropical streams

Riparian forests have positive effects on water quality and biodiversity. However, most studies have only tested the effects of distinct vegetation types or streams with and without forests, despite the fact that riparian forests differ in degrees of complexity. The aim of the present study was to test whether riparian forest complexity affected the composition and abundance of the Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa across a small environmental gradient. We also measured whether EPT genera or feeding groups responded to changes in riparian forest complexity. The study was conducted in two protection areas (i.e. Lagoa do Peri Municipal Park, PERI; and the Permanent Protection Area of Ratones, RAT) of Santa Catarina Island, Brazil. Primary production increased in streams with lower canopy percentage, and EPT assemblages differed among streams with different riparian forest complexity. In RAT, the water quality and forest variables affected EPT composition; however, in PERI, only water quality variables were important. Indicator species analysis based on genera suggested Kempnyia (Plecoptera) and Zelusia (Ephemeroptera) to be indicative of streams with greater forest complexity, whereas Farrodes (Ephemeroptera) was significant in streams of intermediate riparian forest complexity; however, no one functional group dominated. The results of the present study show that small changes in riparian forest complexity influence the composition of EPT insects in subtropical streams.

Can Rapid Assessments Predict the Biotic Condition of Restored Streams?

Five rapid visual stream assessment methods were applied to 65 restored streams in North Carolina, and the results were correlated with measured macroinvertebrate community metrics to evaluate predictive ability. The USEPA Rapid Bioassessment Protocol (RBP), USDA Stream Visual Assessment Protocol (SVAP), Peterson’s Riparian Channel and Environmental Inventory (RCE), NCSU Eco-Geomorphological Assessment (EGA), and NCSU Stream Performance Assessment (SPA) were applied by teams with expertise in hydrology, fluvial geomorphology, and aquatic ecology. Predictions of most macroinvertebrate metrics were improved by re-weighting assessment variables using principal component analysis (PCA) and including watershed factors (e.g., size, slope, land use). The correlations of EGA, RCE, SPA and SVAP assessment results to macroinvertebrate metrics were most improved by variable re-weighting using PCA, while the correlations of RBP were most improved by adding watershed parameters. Akaike’s Information Criterion (AIC) indicates that PCA re-weighting including watershed parameters improves the predictor model for the total number of dominant EPT taxa more than using the sum total raw points for all five assessment methods. To demonstrate the application of the study results, a single-value index was generated for the RBP method using principal component regression (PCR) based on the EPT (Ephemeroptera, Plecoptera and Trichoptera) taxa metric.

Multiple‐stressor effects on stream invertebrates: a mesocosm experiment manipulating nutrients, fine sediment and flow velocity

Summary Land‐use changes have degraded ecosystems worldwide. A particular concern for freshwater biodiversity and ecosystem function are stressors introduced by intensified agriculture. Typically several stressors affect freshwater ecosystems simultaneously. However, the combined effects of these multiple stressors on streams and rivers are still poorly understood, yet of critical importance to improve freshwater management. We investigated responses of benthic macroinvertebrates to three globally important agricultural stressors affecting streams (nutrient enrichment, fine sediment deposition and reduced current velocity), using 64 stream mesocosms (full‐factorial 2 × 2 × 2 design, eight replicates of each treatment combination) established on the banks of the Breitenbach Stream (Hesse, Germany). The experiment ran for 1 month (16 days of colonisation, 14 days of manipulations), and all invertebrates in the mesocosms were collected at the end of this period. Fourteen of the 17 studied invertebrate response variables were affected by one or more stressors each. Negative effects on richness or abundance of pollution‐sensitive Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa were particularly common. Overall, both sediment addition and stream flow velocity reduction had pervasive and strong effects. Responses to sediment addition were mostly negative, whereas decreased current velocity reduced several EPT metrics but increased the abundances of some of the other common taxa. Nutrient enrichment had few effects, but these were consistently negative. Combined stressor effects were mainly additive, with only two interactions found in total, both between reduced velocity and nutrients (on the crustacean Gammarus spp. and ceratopogonid midges). This finding implies that multiple‐stressor responses may be predicted from knowledge of single‐stressor effects in this stream community (unlike the often synergistic or antagonistic responses observed elsewhere). However, further taxon‐specific responses and interactions among stressors may have been obscured by limited taxonomic resolution, especially for the numerically dominant Chironomidae. Genetic approaches are required to address this limitation in the future.

Macroinvertebrate community responses to duration, intensity and timing of annual dry events in intermittent forested and pasture streams

Intermittent streams comprise the majority of stream length in many parts of the world, particularly dry regions. Many dry regions are expected to experience longer and more intense dry periods as the global climate changes. The response of benthic macroinvertebrate communities in intermittent streams to current variability in dry-period duration and intensity may predict their future response to climate change, but such responses require quantification in different stream types and climate zones. I compared the macroinvertebrate community among drier and wetter years from 2008 to 2012 in intermittent forested and pasture streams in a relatively warm, dry region of New Zealand. I predicted that macroinvertebrate communities would decline in density and taxonomic richness with increasing dryness, and that drought-sensitive Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa would show a stronger response than Diptera and non-insects. EPT richness and density did decline with increasing dry period duration, whereas total macroinvertebrate density and richness, and Diptera richness, showed weak and/or non-significant relationships. I predicted that loss of remnant pools (a potential dry-season refuge) would cause a decline in macroinvertebrate richness and density, but found no significant difference between years with and without pools. I predicted that years when flow resumed late in the autumn (when temperatures are too cool for insect flight) would have lower EPT richness and density than years when flow resumed early, and results confirmed this. Intermittent pasture stream communities showed a weaker response to dry period duration than communities in intermittent forested streams, as taxa relatively tolerant of agricultural stressors are also relatively tolerant of drying. Results suggest that global climate change will cause a loss of drought-sensitive species from intermittent streams in this region.