Macroinvertebrate Community Composition Research Articles

Mining and urbanization affect river chemical water quality and macroinvertebrate communities in the upper Selenga River basin, Mongolia (revised version)

Mongolia is a country with a quickly growing economy mainly based on the mining of gold, copper, coal, and other minerals. Mining, urbanization, and agriculture impact the water quality in the upper Selenga River basin in northern Mongolia, which is the center of the Mongolian economy. Previous measurements of pollution loads were alarming, but restricted to chemical measurements. Here, for the first time, we combine freshwater biomonitoring and laboratory water quality data across a broad gradient of water quality and land use intensity. We track the effects of different types of pollution on aquatic invertebrates and test their use as bioindicators. We collected water samples, environmental parameters, and macroinvertebrates at 36 sampling sites at the rivers of Tuul, Kharaa, and Orkhon and their tributaries Sugnugur, Boroo, Sharyn Gol, Gatsuurt, and Yeröö. PCA of catchment water quality distinguished three groups of pollutants prevalent at the sites, (1) nutrients, (2) salt ions (Cl−, Na+, Mg2+, So42−, Ca2+) and mining by-products (B, Sr, U, Mo), and (3) (heavy) metals, which often exceeded regulatory standards. We recorded a total of 59 macroinvertebrate taxa belonging to 31 families in seven insect orders plus Amphipoda and Gastropoda. Species diversity declined with higher impact. Five environmental factors structured macroinvertebrate community composition in RDA: elevation of sample location, site total nitrogen, dissolved oxygen, electrical conductivity, and water chemistry. We conclude that macroinvertebrate communities are an appropriate and inexpensive tool for monitoring water quality in Mongolia and suggest government action to establish a long-term monitoring program.

Biodiversity, Ecological Status and Ecosystem Attributes of Agricultural Ditches Based on the Analysis of Macroinvertebrate Communities

Ditches are widespread and common elements of the agricultural landscape. Although they can provide habitats for aquatic biodiversity, their ecosystem integrity and processes are generally limited or even unknown due to anthropogenic pressures and the paucity of studies on this type of aquatic ecosystem. This study aimed to enhance the knowledge on the biodiversity, ecosystem attributes and ecological status of agricultural ditches by analyzing the macroinvertebrate communities of six different ditches and those of the main river in the same area. While negligible differences in taxonomic richness were observed, macroinvertebrate community composition significantly varied among sites as a function of the heterogeneous habitat conditions. These compositional differences strongly affected the relative abundance of functional feeding groups among sites and their derived ecosystem attributes. Moreover, the ecological status assessment depicted different scenarios depending on the biomonitoring indices applied. By means of a multifaceted, but still poorly adopted, analysis of the macroinvertebrate community, ranging from the taxonomic and functional diversity to ecosystem attributes and biomonitoring indices, the results obtained in this study offer useful information on the ecology of agricultural ditches with potential insights to improving their management.

Effects of weir‐induced habitat fragmentation on the diversity and community composition of benthic macroinvertebrates in an agricultural stream

Effects of weir‐induced habitat fragmentation on the diversity and community composition of benthic macroinvertebrates in an agricultural stream

Adaption of a traditional Māori fishing method for biomonitoring: using whakaweku for sampling benthic macroinvertebrates in streams

ABSTRACT Whakaweku are bundles of bracken fern (Pteridium esculentum) traditionally placed in lakes and rivers by Māori to harvest kōura (freshwater crayfish, Paranephrops spp.) in Aotearoa, New Zealand. Previous studies show they are effective for monitoring populations of kōura and toitoi (small eleotrid fish, Gobiomorphus spp.). We wanted to determine whether whakaweku are also effective for monitoring benthic macroinvertebrate communities in streams. We placed whakaweku in a hard-bottomed and a soft-bottomed reach of a rural stream in the Waikato, and took standard ‘kick-net’ samples from the same locations. We retrieved whakaweku after two and four weeks submerged. Whakaweku gave comparable results to kick-net sampling for common macroinvertebrate metrics (MCI, SQMCI, total richness and EPT* richness). Macroinvertebrate community composition was significantly different between the two methods, but most taxa were common to both. Macroinvertebrate metrics did not change significantly between two-week and four-week colonisation periods. A wider study would show whether whakaweku can distinguish between sites over a gradient of human impact. We recommend whakaweku in Māori cultural and community stream monitoring as it is inexpensive, simple to use, captures many macroinvertebrate taxa used in biomonitoring, works in different stream types and can be used to monitor kōura, toitoi and macroinvertebrates simultaneously.

Context specific effects of substrate composition on the taxonomic and functional diversity of macroinvertebrate communities in temperate lowland streams.

Substrate composition has been widely recognised as a primary variable shaping lotic macroinvertebrate communities at the habitat unit level. However, fundamental understanding of how communities inhabiting mineralogical habitats (i.e., gravel, sand and silt) are structured across differing rivers is lacking. Moreover, research largely focusses on gravel beds and fine sediment in general (<2 mm) and as a result detailed field observations specifically of the sand and silt fractions are lacking. Using data from five UK streams collated from published studies, we assess taxonomic and functional biodiversity (alpha and beta diversity) at the habitat unit level (as defined by substrate composition of sand, silt and gravel). We found that the composition of taxonomic communities were clearly different in all habitat units for each individual stream (and at the landscape scale), with comparable, but less strong, distinctions between substrates for functional macroinvertebrate community composition. However, alpha diversity metrics and Local Contribution to Beta Diversity (LCBD) recorded among the different habitat units varied significantly across individual rivers, and the amount of variation explained by the habitat unit for taxonomic and functional composition demonstrated considerable differences suggesting strong context dependence. The depositional fine sediment habitats of sand and silt were found to support a discrete community composition and differing levels of alpha and beta diversity within and between rivers. We advocate that care should be taken when seeking to generalise biodiversity patterns at a landscape scale as our study highlights the high degree of context dependency when considering the role of the habitat template. Moreover, our results provide evidence that discriminating between the size fractions of fine sediment habitats (sand or silt) is important to fully elucidate the wider ecological importance of these habitats and the distinct taxonomic and functional biodiversity they support.

Factors of macrozoobenthos formation in low-mountain lakes of the Russian Altai

The current state of macrozoobenthos of six low-mountain lakes of the Russian Altai was studied in different hydrological seasons (May, July, September) 2022: Aya (Aiskoe), Beloe, Kireevo, Kolyvanskoe, Koksha, and Svetloe. The aim of the article is to study the factors of formation of benthic invertebrate communities of foothill lakes of the Russian Altai. In total 156 species from 9 classes of invertebrates were identified in the zoobenthos of the studied lakes, the highest percentage of occurrence was recorded for chironomids and oligochaetes. According to the taxonomic composition of macrozoobenthos, most of the studied lakes of the Russian Altai (Aya, Beloe, Kireevo and Kolyvanskoe) were close to flatland lakes. Two lakes (Koksha and Svetloe) combined characteristics of both flatland and highland lakes. The abundance and biomass of zoobenthos in lakes Aya and Kireevo corresponded to the oligotrophic level, in lakes Beloe and Kolyvanskoe to the mesotrophic level, and in lakes Koksha and Svetloye to the eutrophic level. The structural characteristics of macroinvertebrates are indicators of the state of lake ecosystems. Therefore, in order to maintain the health of lake ecosystems, it is important to determine the limiting factors for macroinvertebrate community composition and structure. The influence of environmental factors on the composition and structure of macrozoobenthos of foothill lakes of the Russian Altai was studied. The relationship of 10 main indicators of zoobenthos structure with 30 hydro physical and hydrochemical indicators was analyzed. Using principal component analysis, multiple regression method, correlation and canonical analyses, it was revealed that the greatest influence on the development of benthic invertebrate communities in the studied lakes of the Russian Altai was exerted by nutrients, permanganate oxidability and soil character and water temperature.

Time series of freshwater macroinvertebrate abundances and site characteristics of European streams and rivers

Freshwater macroinvertebrates are a diverse group and play key ecological roles, including accelerating nutrient cycling, filtering water, controlling primary producers, and providing food for predators. Their differences in tolerances and short generation times manifest in rapid community responses to change. Macroinvertebrate community composition is an indicator of water quality. In Europe, efforts to improve water quality following environmental legislation, primarily starting in the 1980s, may have driven a recovery of macroinvertebrate communities. Towards understanding temporal and spatial variation of these organisms, we compiled the TREAM dataset (Time seRies of European freshwAter Macroinvertebrates), consisting of macroinvertebrate community time series from 1,816 river and stream sites (mean length of 19.2 years and 14.9 sampling years) of 22 European countries sampled between 1968 and 2020. In total, the data include >93 million sampled individuals of 2,648 taxa from 959 genera and 212 families. These data can be used to test questions ranging from identifying drivers of the population dynamics of specific taxa to assessing the success of legislative and management restoration efforts.

Influence of water quality and seasonal variations on freshwater macroinvertebrate diversity and community structure in wastewater treatment ponds, Phetchaburi Province, Thailand

Wastewater originating from the Phetchaburi municipality undergoes treatment in a series of five distinct stages at the King’s Royally Initiated Leam Phak Bia Environmental Research and Development Project (LERD) in Phetchaburi province, Thailand. These stages involve a sedimentation (pond 1), three oxidation ponds (ponds 2 to 4), and a final stabilization pond (pond 5). These ponds serve as habitats for macroinvertebrates; consequently, their diversity and composition might be influenced by fluctuations in water quality and seasonal variations. The primary aim of this research was to analyze the diversity and species composition of macroinvertebrate communities concerning varying levels of organic contamination across the five wastewater treatment ponds at LERD. This investigation spanned three seasons: cold season (December 2019), rainy season (July 2020), and hot season (April 2021). The findings revealed that the diversity and species composition of macroinvertebrate communities displayed distinct alterations across multiple environmental gradients, especially identifying the significant influence of organic loading levels observed in ponds 1 to 5. The macroinvertebrate communities exhibited two distinct groupings, with the Chironomidae and Candonidae or ostracods prevailing prominently in ponds 1 and 2 (heterogenous environments). This prevalence was attributed to the high levels of detrital food and the robust resilience of chironomid larvae and ostracods to organic pollution, thriving even in environments characterized by low dissolved oxygen levels. Conversely, the prevalence of snails from the Thiaridae family in ponds 3 to 5 (homogenous environments) indicated improved water quality conditions, notably lower organic matter levels, and a higher dissolved oxygen content. In addition, the study identified seasonal variations in macroinvertebrates, likely influenced by the differing organic loading and environmental conditions. Thus, this research provided insights into the factors shaping macroinvertebrate communities in a wastewater treatment system.

Impacts of two high‐head dams on macroinvertebrate communities in the regulated river reaches of Wujiang River, China

AbstractThe impact of two high‐head dams on macroinvertebrate communities within the regulated reaches of the Wujiang River in China was explored, using longitudinal monitoring data spanning from 2006 to 2016. In this study, we set up 10 sampling sites categorized into four areas based on different stressors and defined three stages based on the timeline of dam construction. Our findings revealed significant changes in community composition before and after dam impoundment. While certain original dominant taxa, such as Rivularia globosa and Lithoglyphopsis ovatus, remained dominant throughout the stages, mayflies and caddisflies nearly vanished in the downstream reaches of the dams. This trend was accompanied by the disappearance of taxa with low adaptability and the emergence of tolerant taxa downstream of the dams. Additionally, typical limnological taxa colonized the inundated reaches. Dam impoundment affected not only macroinvertebrate community composition but also diversity. In this study, the recovery effect of communities downstream of dams was not observed due to the limited distance, but the presence of Wujiangdu Dam upstream of the two dams for over 20 years makes us believe that in a large river system, macroinvertebrate communities downstream of high‐head dams may fully recover if the distance from the dams is long enough. The original and vulnerable species R. globosa, which demonstrated remarkable adaptability and thrived downstream of dams, should be further studied in the future.

Quantification of large-spatial scale and in-stream factors affecting the structure of benthic macroinvertebrate communities in mountain streams

Habitat diversity plays a crucial role in shaping the structure and distribution of benthic macroinvertebrate communities. However, few studies have investigated the concurrent effects of such drivers operating at different spatial scales in mountain streams. Here, we assessed which environmental factors at different spatial scales, related to stream/river type and substrate, influence the diversity of benthic macroinvertebrate assemblages in mountain streams and rivers. Within the framework of the aquatic investigations of the Biodiversity Monitoring South Tyrol (BMS) – a newly-established, regional-based, long-term biodiversity monitoring program – benthic macroinvertebrates and a set of environmental factors describing water quality, stream/river hydromorphology and in-stream habitat characteristics were collected and analysed. The variation in total density, taxonomic richness, Shannon evenness and % Ephemeroptera–Plecoptera–Trichoptera taxa of stream benthic macroinvertebrates was assessed at multi-scale habitat levels, in 48 sampling sites across the mountainous region of the Autonomous Province of Bolzano/Bozen (Italy). The effects of stream/river type, substrates and different environmental factors on community composition of benthic macroinvertebrates were quantified, using a stepfoward Redundancy Analysis (RDA) and generalized additive models (GAMs). In addition, we performed an Indicator Value analysis to detect taxa that were significantly associated with a specific substrate and/or stream/river type. Overall, we observed significant differences in benthic biological metrics among both stream/river and substrate types. We also found at least one indicator taxa for each stream/river type, with environmental factors acting at reach and large-spatial scale – temperature, stream channel stability, elevation – being the key drivers in shaping macroinvertebrate distribution patterns in the analysed mountain rivers. While significant differences in macroinvertebrate community structures were found among substrates, the influence of stream/river type conditions was particularly evident. Apart from ranking environmental variables worth including in a long-term aquatic biodiversity monitoring program in mountain areas, our study provides a baseline for practical applications. For instance, depending on the desired outcome of habitat heterogeneity restoration, it can suggest the optimal scale (landscape vs. reach vs. patch) for prioritizing in-field interventions.

Effects of Acacia invasion on water quality, litterfall, aquatic decomposers, and leaf litter decomposition in streams

Abstract Small streams and their riparian vegetation are closely linked ecosystems. Thus, the invasion of native riparian forests with non‐native species can impact stream ecosystems. We assessed the effects of the invasion of broadleaf deciduous forests by evergreen, nitrogen‐fixing Acacia species on seasonal variation of relevant instream environmental variables, litterfall in the riparian area, aquatic decomposers, and leaf litter decomposition, by comparing three streams flowing through native forests (native streams) and three streams flowing through invaded forests (invaded streams) in central Portugal. Invaded streams flow through forests composed (almost) of monospecific stands of Acacia trees. Litterfall in the riparian area was sampled with fabric traps and sorted into five categories: leaf (including phyllodes), flower, fruit and seed, wood litter, and other materials. Aquatic hyphomycete conidia suspended in water were sampled to assess conidia concentration and community composition. Leaf litter of Quercus robur was enclosed in coarse‐mesh bags and incubated in streams to assess decomposition rates and associated macroinvertebrate density and community composition. Samples from each variable were collected monthly from streams over 1 year. Aquatic hyphomycete conidia concentration was higher in invaded streams in spring/summer when litter inputs, water temperature, and aquatic nutrient concentrations were higher. In contrast, conidia concentration was lower in invaded streams in autumn/winter as they received less native deciduous leaf litter in autumn than native streams. Aquatic hyphomycete community structure changed, and species richness was lower in invaded streams because aquatic nutrient concentrations were higher and leaf litter species richness was lower. Macroinvertebrate and shredder density in decomposing leaf litter did not differ between native and invaded streams, but litter bags may have artificially increased densities by providing high quality food and/or refuges in streams with poor‐quality resources. Nevertheless, macroinvertebrate community structure changed, and family richness was lower in invaded streams. Finally, decomposition rates of Q. robur leaf litter in coarse‐mesh bags were similar between stream types, despite differences in aquatic decomposer communities. Overall, Acacia invasion changed water quality, litterfall seasonality and composition, and aquatic decomposer communities (especially aquatic hyphomycetes). However, Acacia effects on macroinvertebrate density and leaf litter decomposition rates were less pronounced, suggesting that higher trophic levels may be more resilient to invasion than basal levels, or the invasion time/extent in our invaded streams was not strong enough to affect macroinvertebrates and associated processes. Instream invasion effects on aquatic hyphomycete communities were more strongly mediated by changes in litter inputs rather than increases in aquatic nutrient concentrations because they remained oligotrophic in invaded streams. Simplification of riparian and aquatic communities may render them less efficient in coping with additional environmental changes. Acacia effects might be mitigated by the maintenance of a riparian corridor composed of native vegetation. The protection of non‐invaded riparian galleries and restoration of invaded ones could protect and restore stream ecosystems.

Persistent disconnect between flow restoration and restoration of river ecosystem functions after the removal of a large dam on the Sélune River

The removal of the two dams on the Sélune River since 2019 has led to profound changes in the aquatic ecosystem. Lentic habitats bordered by forest had shifted to new conditions (running water and sparsely vegetated riverbanks) therefore shaping organisms’ assemblies. We studied how the reestablishment of aquatic lotic habitats in interaction with riparian vegetation could mediate the restoration of important ecological functions in the new river. Six stations located along the river continuum were surveyed for 3 years after dam removal: two control stations upstream the former reservoir, three restored stations within the former reservoir, and one control station downstream. We monitored physico-chemical characteristics, phytobenthos biomass and the river’s benthic metabolism, and assessed the functional composition of macroinvertebrate communities. We compared the recorded variables among upstream, downstream and restored sampling stations. We observed a rapid recolonization by invertebrates, but a still low phytobenthic primary production in restored stations. Such a low primary productivity was also reflected in the functional composition of invertebrate communities. Three years after dam removal, there was still a significant time lag between communities recovery and expected ecosystem functioning restoration. We observed a quick colonization by aquatic running-water invertebrate communities of new lotic reaches, but a slower recovery of important ecological functions rates such as those observed in control stations.

Citizen science shows that small agricultural streams in Germany are in a poor ecological status

Agricultural pesticides, nutrients, and habitat degradation are major causes of insect declines in lowland streams. To effectively conserve and restore stream habitats, standardized stream monitoring data and societal support for freshwater protection are needed. Here, we sampled 137 small stream monitoring sites across Germany, 83 % of which were located in agricultural catchments, with >900 citizen scientists in 96 monitoring groups. Sampling was carried out according to Water Framework Directive standards as part of the citizen science freshwater monitoring program FLOW in spring and summer 2021, 2022 and 2023. The biological indicator SPEARpesticides was used to assess pesticide exposure and effects based on macroinvertebrate community composition. Overall, 58 % of the agricultural monitoring sites failed to achieve a good ecological status in terms of macroinvertebrate community composition and indicated high pesticide exposure (SPEARpesticides status class: 29 % “moderate”, 19 % “poor”, 11 % “bad”). The indicated pesticide pressure in streams was related to the proportion of arable land in the catchment areas (R2 = 0.23, p < 0.001). Also with regards to hydromorphology, monitoring results revealed that 65 % of the agricultural monitoring sites failed to reach a good status. The database produced by citizen science groups was characterized by a high degree of accuracy, as results obtained by citizen scientists and professionals were highly correlated for SPEARpesticides index (R2 = 0.79, p < 0.001) and hydromorphology index values (R2 = 0.72, p < 0.001). Such citizen-driven monitoring of the status of watercourses could play a crucial role in monitoring and implementing the objectives of the European Water Framework Directive, thus contributing to restoring and protecting freshwater ecosystems.

BENTHIC MACROINVERTEBRATE COMMUNITY IN TWO AMAZONIAN UPLAND LAKES

Studies of biological communities in Amazonian lakes are limited to floodplains of large rivers. However, the high-altitude lakes of the Serra dos Carajás differ from other lakes in the region due to the high natural concentration of iron and manganese. An important component of this biological community are the macroinvertebrates, some of which are sensitive to environmental and chemical variables. However, little is known about the influence of heavy metal concentrations on this community component in Amazonian lakes. In our study, we observed the importance of variables such as water depth and concentration of chemical elements in sediments on the macroinvertebrate community. Through a redundancy analysis, we found that the depth of the lake affects the number of species and the composition of the benthic macroinvertebrate community. We also found a relative importance of the concentration of manganese in the sediment for the community studied. Our results indicate that the macroinvertebrate community is differentiated in the marginal and central regions of the lake, since the deposition of organic matter and heavy metals in the sediment is different in these two regions of the lake. The relationship found has implications for the management and restoration of upland lakes in the Amazon, helping to preserve this unique ecosystem.

Macroinvertebrate community composition and river health assessment in plateau rivers of Guizhou Province, China

Plateau rivers are considered regional water resource depots, hydropower energy bases, cradles of aquatic dispersal, and barriers to invasive alien species. In this study, 20 major plateau rivers from Guizhou Province, China, were studied to (1) investigate the composition, functional feeding group distribution, and diversity of macroinvertebrates; and (2) assess the ecosystem health of the rivers using the macroinvertebrate Family Biotic Index. Among the macroinvertebrate species, the dammed river sections primarily contained Corbicula fluminea and C. nitens from the Lamellibranchia, the urban river sections harbored Bellamya aeruginosa and Semisulcospira cancellata from the Gastropoda, and the reference river sections contained sensitive taxa including mayfly Ecdyonurus yoshidae and caddisfly Stenopsyche tlenmushanensis. Among the major plateau rivers in Guizhou, urban river sections exhibited the highest density of macrobenthic organisms. The Shannon-Wiener index was lowest in dammed sections, followed by urban sections, while reference sections exhibited the highest diversity. As for functional feeding groups, the density of filter feeders was significantly higher than that of other groups. In contrast, the density of gatherer-collectors and the shredders was relatively low. Assessment of the aquatic ecosystem health in Guizhou Plateau rivers showed that dammed sections were primarily in an unhealthy state, urban sections mainly fell into the sub-healthy category, and reference sections had a relatively good health status. The results from this study provide baseline data that is useful for water resources management, hydropower energy utilization, and ecological and environmental protection of the plateau rivers.

Preliminary data on the structure of macroinvertebrate communities and the physicochemical conditions of the Toumanguié and Bosso rivers under the influence of agricultural activities in the Aboisso department (south-east, Côte d'Ivoire)

The Toumanguié agricultural zone in the Sud-Comoé region of south-eastern Côte d'Ivoire contains several agricultural plantations and a dense and varied hydrographic system including the Bosso and Toumanguié rivers. However, knowledge of the ecological status of these two rivers is almost unavailable to the scientific community to assess the impact of agricultural activities. The purpose of this one-off study, carried out in March 2023, was to provide initial data on the physicochemical state and composition of macroinvertebrate communities in these two rivers. Four (4) sampling points were defined on these rivers. Measurements of the water physicochemical parameters (temperature, dissolved oxygen transparency, conductivity and pH) were taken in situ between 06:00 and 08:00 in the morning using a multiparameter, and some water samples were taken for the determination of nutrients. Macroinvertebrates were collected using a Van Veen bucket and a dip net. Analysis of the physicochemical parameters showed that the water in the Toumanguié agricultural zone was of relatively good quality and conducive to the survival of aquatic macroinvertebrates. However, the nutrient values indicated that the water was slightly polluted as a result of the degradation of organic matter. 34 taxa belonging to 26 families and 11 orders were identified, with a predominance of insects. Diptera were predominant. The taxa commonly collected in these rivers were: Cricotopus kisantuensis, Polypedilum fuscipenne, Chironominae and Diplonychus sp. The macroinvertebrate communities in these two rivers were not very diversified but were relatively balanced in terms of diversity index values.

Consistent but Delayed Timing of Precipitation Affects Community Composition of Prairie Pothole Birds and Aquatic Macroinvertebrates, but not Wetland Plants

Consistent but Delayed Timing of Precipitation Affects Community Composition of Prairie Pothole Birds and Aquatic Macroinvertebrates, but not Wetland Plants

Macroinvertebrate community responses to salinity around non-saline–saline confluences in the Draa River basin, Morocco

Freshwater salinization increasingly threatens river ecosystems in arid regions. In situ studies on effects of salinity on freshwater communities are still scarce, especially in largely understudied areas of Africa. To compare macroinvertebrate communities in differing salinity levels, we conducted a confluence-based study in the Draa River basin in Morocco by focusing on two tributaries and their joint downstream sections, in the immediate vicinity of three confluences. Our study revealed that α-diversity differed only minimal. Although only around five taxa comprised over 90% of specimens per section, the more saline sections exhibited proportionally more salt-tolerant generalist species. There was lower β-diversity between the downstream section and each tributary compared to between tributaries, indicating a mixed community after the confluence. The trait profile of the saline El Mellah displayed more resistance and resilience traits to disturbances than the less saline Iriri. Furthermore, low water flow reduced the abundance of sensitive taxa. Overall, we observed minimal differences in macroinvertebrate community composition, due to low γ-diversity in the basin. However, the confluence-based study design remains valuable for investigating effects of specific stressors on ecosystems by excluding large-scale geographic patterns, as compared sites are close and therefore share the same climate, geology, and altitude.

Ecological importance of low-order streams to macroinvertebrate community composition in Afromontane headwater streams

Low-order streams contribute to the abiotic and biotic character of large rivers and are renowned for harboring unique forms of aquatic flora and fauna. However, most studies on headwater streams mainly focus on the mainstems and overlook the contribution of the tributary systems. Moreover, low-order streams are generally overlooked in legislation and bioassessment programs, and consequently not protected in many countries. To contribute to the recognition of the ecological importance of low-orders streams, this study focused on determining whether river network characteristics and associated physico-chemical parameters can be used to effectively predict the variabilities in macroinvertebrate assemblage characteristics between first-order and second-order streams in the headwaters of the Nzoia River Basin, Kenya. The study quantified the structural and functional community composition, diversity, similarity, and richness of macroinvertebrate communities between the two river systems. Dissolved oxygen, coarse particulate organic matter, conductivity, stream width, depth, discharge and flow velocity were the main predictors of the diversity and distribution of macroinvertebrates in the first order and second-order streams. The first order streams recorded higher abundance of macroinvertebrates than the second-order streams. Taxa from families Ephydridae, Elmidae, Gomphidae, and genera Euthraulus, Neoperla, Orthothrichia and Prosopistoma were limited to the second-order stream sites while families Ceratopogonidae, Pisuliidae, Dytiscidae and genus Trichosetodes occurred exclusively in the first-order stream sites. Collector-filterers and collector-gatherers were the most abundant functional feeding groups (FFGs) in the two river systems. Scrapers were abundant in the second-order stream while shredders were abundant in the first order streams. The distinctness in the structural and functional composition of macroinvertebrates between the two river systems suggests that linkages among streams in a network as exemplified in the Nzoia River Basin, support and foster biodiversity.

A method for evaluating sediment-induced macroinvertebrate community composition changes in Idaho streams.

Human activities can increase sediment delivery to streams, changing the composition, distribution, and abundance of stream aquatic life. Few U.S. states have numeric water quality standards for streambed sediment under the Clean Water Act, so managers often need to develop local application-specific benchmarks. This study developed stream surface fine sediment <2 mm (sand and fines, SF) and macroinvertebrate fine sediment biotic index (FSBI) benchmarks and an application framework to test for sediment-induced macroinvertebrate community composition changes in 1st-4th order Idaho streams. FSBI reference benchmarks were calculated as the 25th percentile FSBI value among reference sites within three ecoregion-based site classes. Two approaches were used to develop SF benchmarks. Quantile regression was used to define reach-specific SF benchmarks representing an upper bound value expected under reference conditions. In addition, logistic regression was used to predict SF values with 50% and 75% probability that FSBI is worse than reference within each stream order and site class. The strength of association between SF benchmarks and macroinvertebrate community condition was evaluated by calculating relative risk using multiple datasets and examining responses of multiple macroinvertebrate indicators to SF benchmark status. SF reference benchmarks generally had stronger associations with poor macroinvertebrate condition than SF stressor-response benchmarks. Across datasets and macroinvertebrate indicators, poor macroinvertebrate condition was 1.8-3 times more likely when SF reference benchmarks were exceeded than when achieved. We propose rating the strength of evidence for a surface fine sediment-induced macroinvertebrate community composition change at the sample event scale as 'unlikely' if both SF and FSBI reference benchmarks are achieved, having 'mixed evidence' if only one reference benchmark is achieved, and 'likely' if both reference benchmarks are not achieved. We recommend combining ratings with other relevant data in a weight-of-evidence approach to assess if sediment impairs aquatic life.