Benthic Macroinvertebrate Community Composition Research Articles

Ecological variation in invasive brown trout (Salmo trutta) within a remote coastal river catchment in northern Patagonia complicates estimates of invasion impact.

Salmonids were first introduced into the Chilean fresh waters in the 1880s, and c. 140 years later, they are ubiquitous across Chilean rivers, especially in the southern pristine fresh waters. This study examined the brown trout (Salmo trutta) and native taxa ecology in two adjacent but contrasting rivers of Chilean Patagonia. During spring 2016 and spring-fall 2017 we examined the variation in benthic macroinvertebrate and fish community composition and characterized fish size structure, stomach contents, and stable isotopes (δ13 C and δ15 N) to understand population structure, fish diet, and trophic interactions between S. trutta and native taxa. The native Galaxias maculatus (puye) dominated the fish community (74% of abundance). S. trutta was less abundant (16% of survey catch) but dominated the fish community (over 53%) in terms of biomass. S. trutta showed distinct diets (stomach content analysis) in the two rivers, and individuals from the larger river were notably more piscivorous, consuming native fish with a relatively small body size (<100-mm total length). Native fishes were isotopically distinct from S. trutta, which showed a wider isotopic niche in the smaller river, indicating that their trophic role was more variable than in the larger river (piscivorous). This study provides data from the unstudied pristine coastal rivers in Patagonia and reveals that interactions between native and introduced species can vary at very local spatial scales.

Composition, distribution, and diversity of macrophytes and benthic macroinvertebrate communities in Eleyele Lake, southwestern Nigeria

Many human activities that have an effect on water quality and aquatic health are increasing along Eleyele Lake, which is a vital resource for domestic water supply and fishery in Ibadan, southwest Nigeria. This study provides information on the composition of macrophytes and benthic macroinvertebrates (which are bioindicators) in association with physicochemical parameters in Eleyele Lake. Water, macrophytes, and benthic macroinvertebrates were collected from four stations monthly from March to August 2021 and analysed using standard methods. The relationship between the measured physicochemical variables, macrophytes, and the abundance of benthic macroinvertebrate was explored using canonical correspondence analysis (CCA). The encountered macrophytes represented 19 species (11 emergent, six floating and two submerged) in 16 genera and 12 families. The most abundant species was Ipomea aquatica (25.83%) in station 2 and Sacciolepsis africana (19.19%) in station 1. A total of 282 benthic macroinvertebrate individuals belonging to three phyla, four classes, 11 genera, and 11 species were encountered. Pollution indicator species including Melanoides tuberculata, Biomphalaria pfeifferi and Chironomus larvae observed in all the sampling stations were the dominant species. The CCA indicated that the abundance of macrophytes correlated with depth and nutrient factors (mostly phosphate). The result of the CCA showed the abundance of Chironomus larvae being patterned by dissolved oxygen and nutrient factors (phosphate, nitrate, and sulphate). These further confirmed the polluted status of Eleyele Lake, especially by nutrient enrichment. The dominant macrophytes and benthic macroinvertebrates in Eleyele Lake are pollution-tolerant species and the lake has been impacted by nutrient enrichment.

Benthic macroinvertebrate community shifts based on Bti-induced chironomid reduction also decrease Odonata emergence

Chironomid larvae (Diptera: Chironomidae) often dominate aquatic macroinvertebrate communities and are a key food source for many aquatic predators, such as dragonfly and damselfly larvae (Odonata). Changes in aquatic macroinvertebrate communities may propagate through terrestrial food webs via altered insect emergence. Bacillus thuringiensis israelensis (Bti)-based larvicides are widely used in mosquito control but can also reduce the abundance of non-biting chironomid larvae. We applied the maximum field rate of Bti used in mosquito control three times to six mesocosms in a replicated floodplain pond mesocosm (FPM) system in spring for two consecutive years, while the remaining six FPMs were untreated. Three weeks after the third Bti application in the first year, we recorded on average a 41% reduction of chironomid larvae in Bti-treated FPMs compared to untreated FPMs and a shift in benthic macroinvertebrate community composition driven by the reduced number of chironomid, Libellulidae and Coenagrionidae larvae (Odonata). Additionally, the number of emerging Libellulidae (estimated by sampling of exuviae in the second year) was reduced by 54% in Bti-treated FPMs. Since Odonata larvae are not directly susceptible to Bti, our results suggest indirect effects due to reduced prey availability (i.e., chironomid larvae) or increased intraguild predation. As Libellulidae include species of conservation concern, the necessity of Bti applications to their habitats, e.g. floodplains, should be carefully evaluated.

Contribution of sediment contamination to multi-stress in lowland waters

Water bodies in densely populated lowland areas are often impacted by multiple stressors. At these multi-stressed sites, it remains challenging to quantify the contribution of contaminated sediments. This study, therefore, aimed to elucidate the contribution of sediment contamination in 16 multi-stressed drainage ditches throughout the Netherlands. To this end an adjusted TRIAD framework was applied, where 1) contaminants and other variables in the sediment and the overlying water were measured, 2) whole-sediment laboratory bioassays were performed using larvae of the non-biting midge Chironomus riparius, and 3) the in situ benthic macroinvertebrate community composition was determined. It was hypothesized that the benthic macroinvertebrate community composition would respond to all jointly present stressors in both water and sediment, whereas the whole-sediment bioassays would only respond to the stressors present in the sediment. The benthic macroinvertebrate community composition was indeed related to multiple stressors in both water and sediment. Taxa richness was positively correlated with the presence of PO4-P in the water, macrophyte cover and some pesticides. Evenness, the number of Trichoptera families and the SPEARpesticides were positively correlated to the C:P ratios in the sediment, whilst negative correlations were observed with various contaminants in both the water and sediment. The whole-sediment bioassays with C. riparius positively related to the nutrient content of the sediment, whereas no negative relations to the sediment-associated contaminants were observed, even though the lowered SPEARpesticides index indicated contaminant effects in the field. Therefore, it was concluded that sediment contamination was identified as one of the various stressors that potentially drove the benthic macroinvertebrate community composition in the multi-stressed drainage ditches, but that nutrients may have masked the adverse effects caused by low and diverse sediment contaminants on C. riparius in the bioassays.

Macroinvertebrate responses to differing riparian treatments following forest harvest in the headwaters of Trask River watershed

Although it is well-established that macroinvertebrates are an integral part of a healthy stream ecosystem, studies designed to inform forest harvest best management practices for sustainability of macroinvertebrate communities in small streams have been limited. Current riparian management practices for headwater streams generally focus on providing adequate wood supply, reducing debris flows and transport of sediment, and maintaining water quality in larger streams that contain fish. Here we studied the effects of contemporary forest harvest practices on benthic macroinvertebrate density and community composition in 12 small headwater streams as part of the Trask River Watershed Study. To account for seasonal and year-to-year variability in macroinvertebrate densities, we sampled each site at the same time of year for six years before and four years after harvest. Three watersheds were clearcut with variable riparian buffers, three were clearcut with 12 m riparian buffers, and one was thinned with 15 m buffers. Five adjacent watersheds were not treated and were studied as reference sites. All sites had approximately 50 yr old conifer and alder forests, which had revegetated following fires and harvest in prior decades.In these steep mountain streams, benthic macroinvertebrate density and community composition were generally similar across watersheds prior to harvest. Collectors were the most abundant functional feeding group, followed by shredders; scrapers were the least abundant. After harvest, in two of the three clearcut watersheds with variable buffers, the total benthic density and percentage of collectors increased, primarily due to greater numbers of Chironomidae. We also observed more abundant emergence post-harvest at these two watersheds. In the third clearcut watershed with a variable buffer and in the three clearcut watersheds with uniform 12 m riparian buffers, we did not see changes in density or functional feeding groups after harvest. We explored the spatial and temporal aspects of the data using both non-parametric and parametric statistical methods. High variability swamped the treatment effect when watersheds were grouped by riparian treatment for the repeated measure analyses, while NMDS showed a significant shift post-harvest for the watersheds with variable buffers. In the clearcut watersheds with uniform buffers, macroinvertebrates densities and community composition did not shift. At two of the clearcut watersheds with variable buffers, we observed increased density for the first two years after harvest, and chironomids comprised up to 80% of the abundance in samples. In the subsequent years, we documented mixed responses for two watersheds. It was invaluable to have multiple pre- and post-harvest sampling periods in both harvested and reference watersheds in order to better identify site specific responses to treatment and to separate background variability from responses to harvest. We show that retention of riparian vegetation on headwater streams during clearcut harvesting minimized changes in total macroinvertebrate densities and community composition. Small buffers may be key to maintenance of diverse stream invertebrate communities in headwaters.

Impacts of wastewater treatment plants on benthic macroinvertebrate communities in summer and winter

Treated effluent from municipal wastewater treatment plants (WWTPs) is a major source of contamination that can impact population size, community structure, and biodiversity of aquatic organisms. However, because the majority of field research occurs during warmer periods of the year, the impacts of wastewater effluent on aquatic communities during winter has largely been neglected. In this study, we assessed the impacts of wastewater effluent on aquatic benthic macroinvertebrate (benthos) communities along the effluent gradients of two WWTPs discharging into Hamilton Harbour, Canada, during summer and winter using artificial substrates incubated for 8 weeks. At the larger of the two plants, benthic macroinvertebrate abundance was higher and diversity was lower at sites downstream of the outfall compared to upstream sites in both seasons. Whereas at the smaller plant, the opposite was observed, abundance increased and diversity decreased with distance from the outfall in both seasons. While the impacts of wastewater on benthic communities were largely similar between seasons, we did detect several general seasonal trends – family diversity of macroinvertebrates was lower during winter at both WWTPs and total abundance was also lower during winter, but only significantly so at the smaller WWTP. Further, benthic macroinvertebrate community composition differed significantly along the effluent gradients, with sites closest and farthest from the outfall being the most dissimilar. Our contrasting results between the WWTPs demonstrate that plants, with different treatment capabilities and effluent-receiving environments (industrial/urban versus wetland), can dictate how wastewater effluent impacts benthic macroinvertebrate communities.

Establishing the relationship between benthic macroinvertebrates and water level fluctuation in subtropical shallow wetlands.

Wetland water level fluctuations often influence benthic macroinvertebrate communities through changes in water quality, substrate, and macrophytes and, hence, affect the structure and function of aquatic ecosystems. However, there is lack of understanding on how water level fluctuations affect the structure and composition of benthic macroinvertebrates in subtropical shallow wetlands in Nepal. Here, we assessed the changes in benthic macroinvertebrate community composition in response to water level fluctuations and identified indicator taxa sensitive to such fluctuations. A study was conducted over 4 seasons covering one annual cycle of water level fluctuation in 4 wetlands of Koshi Tappu Wildlife Reserve, Nepal. The study revealed that benthic macroinvertebrate composition significantly differed across water levels. Dissimilarities in macroinvertebrate community composition were mainly attributed by families Atyidae, Dytiscidae, Baetidae, Planorbidae, Chironomidae, Bithyniidae, Sphaeriidae, and Thiaridae. Taxon specific richness, densities, and biomass varied across the water levels while no difference was documented for overall family richness, density, and biomass. Ephemeroptera and Trichoptera richness decreasedwhen water levels were low while Coleoptera and Diptera richness increased. Medium water level supported high benthic macroinvertebrate diversity. Indicator taxa analysis identified Coleoptera: Hydrophilidae and Dytiscidae, Hemiptera: Pleidae, Diptera: Muscidae and Mollusca: Sphaeriidae, Viviparidae, and Thiaridae, as indicators of low water level. Similarly, Coleoptera: Scirtidae, Hemiptera: Micronectidae and Oligochaeta: Tubificidae as indicators of medium water level, and Trichoptera: Polycentropodidae and Ephemeroptera: Caenidae as indicators of high water level. Redundancy analysis identified water level as one of the most influencing factors in benthic macroinvertebrate community variation. Considering the significant response of benthic macroinvertebrates to water level fluctuations, theyare important as ecological indicators in research aimed at developing environmental flow frameworks. Indicator speciesare likely to be a vital tool in environmental impact assessment and monitoring in relation to hydrological development. The outcomesof this research have important implications to conservation and management of wetlands to preserve the valuable ecosystem functions provided by wetlands.

Top-Down Effects of Salamanders on Macroinvertebrates in Fishless Headwater Streams

Salamanders are the top predators in many fishless headwater streams, and intraguild interactions among stream salamanders are well documented. However, little is known about the top-down effects of salamanders on stream food webs or how intraguild interactions mediate these effects. To investigate the effects of salamanders on macroinvertebrate communities of headwater streams, we conducted an experiment in stream mesocosms to test for effects of two stream salamander species, namely, Eurycea bislineata and Gyrinophilus porphyriticus, alone or in combination, on benthic and emerging macroinvertebrate density, biomass, and community composition. We also assessed intraguild interactions between these salamander species by comparing Eurycea bislineata survival and G. porphyriticus growth in single-species versus two-species treatments. Gyrinophilus porphyriticus reduced benthic macroinvertebrate densities when alone but not when co-occurring with E. bislineata. There were no effects of salamanders on benthic macroinvertebrate biomass or community composition and no effects on emerging macroinvertebrate density, biomass, or community composition. Eurycea bislineata survival decreased and G. porphyriticus weight increased in two-species treatments, suggesting that intraguild predation was occurring. Overall, although some of our findings are equivocal, these results suggest that salamanders can exert top-down control on macroinvertebrate communities in fishless headwater streams, decreasing benthic macroinvertebrate density. But this effect is dependent on the salamander species present, and can be removed by intraguild interactions between salamander species.

Suggested Sampling Methodology for Lake Benthic Macroinvertebrates under the Requirements of the European Water Framework Directive

The estimation of the number of samples required for reliably monitoring lakes’ benthic macroinvertebrates is difficult due to the natural variability and cost and time constraints. To determine a statistically robust and effective sampling design, we collected benthic macroinvertebrate samples from 15 Greek natural lakes. We compared the spatial and temporal variability of the benthic macroinvertebrate community composition to identify differences among lakes, between lake zones (sublittoral and profundal) and sampling periods. Furthermore, we examined the sampling precision and determined the number of required samples to attain maximum taxa richness. The diminution of the sampling effort was estimated and the desired precision level, considering different benthic macroinvertebrate abundances, was modelled. No temporal or spatial variation between lake zones was observed in communities’ compositions. The precision of our sampling design was adequate, and rarefaction curves revealed an adequate taxa richness (&gt;70%). The developed model could be applied to assess the required sampling effort in lakes within the Mediterranean ecoregion with similar benthic macroinvertebrate abundances.

Dam cascade alters taxonomic composition of benthic macroinvertebrate community in upper Yangtze River

AbstractCascade dams segment river connectivity, modify the hydrological process, and change the hydraulic properties, thus influencing the river ecosystem significantly. Ecological effects of dams have been extensively studied, but investigations on zoobenthos in a large area covering tributaries and mainstream with cascade dams are lacking. Here, we studied the features of benthic macroinvertebrate assemblages in the lower Jinshajiang River, which is the upper reach of the Yangtze River. Over 15,000 macroinvertebrate individuals were collected in the mainstream and eight tributaries. Altogether, 105 taxa belonging to 19 orders and 55 families were identified. The structure of benthic macroinvertebrate assemblages was considerably different between the natural‐flow reach and the reservoir reach in the mainstream. The diversity and abundance of Ephemeroptera, Trichoptera, and Megaloptera decreased to almost zero as a result of dam impoundment. By contrast, the abundance of Diptera, Chironomidae, and Tubificida increased significantly in the mainstream reservoir reach. The diversity of macroinvertebrate species in the mainstream reservoir reach was only half of that in the natural‐flow mainstream. The difference between macroinvertebrate assemblages in natural‐flow mainstream and tributaries was insignificant. Therefore, dam construction was considered the main cause of macroinvertebrate assemblage changes. Our results highlighted the necessity of maintaining sufficient natural river sections between cascade reservoirs to conserve the biodiversity of benthic macroinvertebrate.

Trait–environment relationships could alter the spatial and temporal characteristics of aquatic insect subsidies at the macrospatial scale

Ecological flows across ecosystem boundaries are typically studied at spatial scales that limit our understanding of broad geographical patterns in ecosystem linkages. Aquatic insects that metamorphose into terrestrial adults are important resource subsidies for terrestrial ecosystems. Traits related to their development and dispersal should determine their availability to terrestrial consumers. Here, we synthesize geospatial, aquatic biomonitoring and biological traits data to quantify the relative importance of several environmental gradients on the potential spatial and temporal characteristics of aquatic insect subsidies across the contiguous United States. We found the trait composition of benthic macroinvertebrate communities varies among hydrologic regions and could affect how aquatic insects transport subsidies as adults. Further, several trait–environment relationships were underpinned by hydrology. Large bodied taxa that could disperse further from the stream were associated with hydrologically stable conditions. Alternatively, hydrologically variable conditions were associated with multivoltine taxa that could extend the duration of subsidies with periodic emergence events throughout the year. We also found that anthropogenic impacts decrease the frequency of individuals with adult flight but potentially extend the distance subsidies travel into the terrestrial ecosystem. Collectively, these results suggest that natural and anthropogenic gradients could affect aquatic insect subsidies by changing the trait composition of benthic macroinvertebrate communities. The conceptual framework and trait–environment relationships we present shows promise for understanding broad geographical patterns in linkages between ecosystems.

Distribution patterns of benthic macroinvertebrate communities based on multispatial-scale environmental variables in the river systems of Republic of Korea

Understanding the relationship between benthic macroinvertebrates and environmental variables is the first step toward establishing sustainable freshwater ecosystems in terms of biodiversity, and this knowledge can be applied in river management. We analyzed major environmental variables that affect biotic communities on the national scale in the Republic of Korea. To achieve this goal, 2647 sampling stream sites were surveyed from 2016 to 2018 to collect benthic macroinvertebrates and measure 14 environmental variables. We identified a total of 359 taxa, belonging to 32 orders in 9 classes of 5 phyla, most of which were aquatic insects including Ephemeroptera, Odonata, Plecoptera, Coleoptera, Diptera and Trichoptera. Two-way indicator species analysis (TWINSPAN) based on biotic communities divided the sampling sites into six groups. Discriminant analysis identified gradient, streambed substrates, velocity, biological oxygen demand (BOD) and altitude as the major environmental variables that distinguished each TWINSPAN group. In addition, stream order and stream width also influenced aquatic macroinvertebrate communities, but the influence was low. The indicator taxa in each group were gradually changed from sensitive organisms preferring high altitudes, fast velocities and coarse substrates to tolerant organisms preferring low altitudes, slow velocities and fine substrates in each group from one to six. Canonical correspondence analysis confirmed that the composition of benthic macroinvertebrate communities in the Republic of Korea was dependent on stream gradient, microhabitat, organic pollution and geographical feature rather than on stream size or other water quality variables. Our study identified variables affecting the overall distribution patterns of biotic communities on a national scale and provides useful information for conservation and management of stream ecosystems in the Asian monsoon region.

Response of macroinvertebrate communities to thermal regime in small Mediterranean streams (southern South America): Implications of global warming

The seasonal nature of the stream thermal regime has been recognized as an important factor for the structure of benthic macroinvertebrate communities. In this study, we show the importance of temperature and the potential implications of global warming on the composition of benthic macroinvertebrate communities in Andean watersheds. Here we show that thermal factors (mean temperature and monthly range) partially explain the seasonal variability of macroinvertebrates in Andean streams. Different thermal requirements were observed for macroinvertebrate families. Optimal monthly mean temperatures estimated for Gripopterygidae (Plecoptera), Hydrobiidae (Gastropoda) and Helicophidae (Trichoptera) were lower than 7 °C, while temperatures for Ameletopsidae, Baetidae (Ephemeroptera), Ecnomidae, Limnephilidae, Hydropsychidae, Leptoceridae (Trichoptera), Elmidae (Coleoptera) and Notonemouridae (Plecoptera) were close to 9.5 °C.According to our estimations, future global warming could cause important changes in the macroinvertebrate composition of Andean watersheds. Gripopterygidae, Austroperlidae, Diamphipnoidae (Plecoptera), Hydrobiidae and Helicophidae (Trichoptera) would be the most vulnerable families under the 2090 temperature predictions due to their preference for low temperature.

Shale gas development has limited effects on stream biology and geochemistry in a gradient-based, multiparameter study in Pennsylvania

The number of horizontally drilled shale oil and gas wells in the United States has increased from nearly 28,000 in 2007 to nearly 127,000 in 2017, and research has suggested the potential for the development of shale resources to affect nearby stream ecosystems. However, the ability to generalize current studies is limited by the small geographic scope as well as limited breadth and integration of measured chemical and biological indicators parameters. This study tested the hypothesis that a quantifiable, significant relationship exists between the density of oil and gas (OG) development, increasing stream water concentrations of known geochemical tracers of OG extraction, and the composition of benthic macroinvertebrate and microbial communities. Twenty-five headwater streams that drain lands across a gradient of shale gas development intensity were sampled. Our strategy included comprehensive measurements across multiple seasons of sampling to account for temporal variability of geochemical parameters, including known shale OG geochemical tracers, and microbial and benthic macroinvertebrate communities. No significant relationships were found between the intensity of OG development, shale OG geochemical tracers, or benthic macroinvertebrate or microbial community composition, whereas significant seasonal differences in stream chemistry were observed. These results highlight the importance of considering spatial and temporal variability in stream chemistry and biota and not only the presence of anthropogenic activities in a watershed. This comprehensive, integrated study of geochemical and biological variability of headwater streams in watersheds undergoing OG development provides a robust framework for examining the effects of energy development at a regional scale.

Assessing Spatial Distribution of Benthic Macroinvertebrate Communities Associated with Surrounding Land Cover and Water Quality

The study aims to assess the spatial distribution of benthic macroinvertebrate communities in response to the surrounding environmental factors related to land use and water quality. A total of 124 sites were surveyed at the Seomjin River basin in May and September 2017, respectively. We evaluated the abundance and composition of benthic macroinvertebrate communities based on nine subwatersheds. Subsequently, we compared the benthic information with the corresponding land use and water quality. To comprehensively explore the spatiotemporal distinction of benthic macroinvertebrate communities associated with those ambient conditions, we applied canonical correspondence analysis (CCA). The CCA results explicitly accounted for 61% of the explanatory variability; the first axis (45.5%) was related to land-use factors, and the second axis (15.5%) was related to water quality. As a result, the groups of benthic communities were distinctly characterized in relation to these two factors. It was found that land-use information is primarily an efficient proxy of ambient water quality conditions to determine benthic macroinvertebrates, such as Asellus spp., Gammarus spp., and Simulium spp. in a stream ecosystem. We also found that specific benthic families or genera within the same groups (Coleoptera, Diptera, Ephemeroptera, and Trichoptera) are also differentiated from ambient water quality changes as a secondary component. In particular, the latter pattern appeared to be closely associated with the impact of summer rainfall on the benthic community changes. Our study sheds light upon projecting benthic community structure in response to changes of land use and water quality. Finally, we conclude that easily accessible information, such as land-use data, aids in effectively characterizing the distribution of benthic macroinvertebrates, and thus enables us to rapidly assess stream health and integrity.

Climate-influenced catchment hydrology overrides forest management effects on stream benthic macroinvertebrates in a northern hardwood forest

Our present understanding of the effects of natural and anthropogenic disturbances on aquatic systems in forested landscapes is based on a long history of studies relating physical, chemical and biological variables to biotic responses. The explanatory relationships resulting from this work have proven informative for ensuring environmentally-sound forest management, but such evaluations have not been applied to all forest types and management conditions and rarely in the context of aquatic ecosystem services. In this study, we applied a combination of field measurements and modelling to derive a comprehensive suite of physical, chemical, and biological variables (n = 80) to develop explanatory relationships between these variables and benthic macroinvertebrate community composition of headwater streams in managed forests. The work was conducted in a northern hardwood forest catchment that contains a gradient of disturbance, ranging from undisturbed to actively managed over the past 25 years, and a history of research that has generated an extensive relevant dataset. From among the initial suite of 80 variables, we found that those related to hydrological patterns and processes (i.e. flow variability; conductivity) were most strongly associated with benthic macroinvertebrate community structure. We also found that selection-based forest harvesting had no measurable adverse effects on benthic macroinvertebrate communities. By better defining the relationships between physical, chemical and biological indicators of aquatic ecosystem function, our work provides information required to make effective monitoring and management decisions aimed at ensuring sustainability of forest-based aquatic ecosystem services, particularly in the face of a changing climate.

Evaluation of aquatic macro-invertebrate populations: a model for emergent bio-monitoring guide for quantifying uncleanness of some Rivers in Northern Central Nigeria

The objectives of this study are to examine the composition, abundance and distribution of benthic macroinvertebrate communities, assess the health status and evaluate the spatial relationships of some selected Rivers. A total of 1251 individuals of macroinvertebrate taxa was recorded in this study. The percentage composition of the taxonomic groups obtained from the Twenty-two (22) stations were: Chironomidae (Diptera) (40.85%), Ephemeroptera (14.95%), Oligochaeta (9.83%), Amphibian (7.99%), Ceratopogonidae (Diptera) (7.11%), Mollusca (4.00%), Hemiptera (3.44%), Coleoptera (2.56%), Ostracoda (2.24%), Zygoptera (1.44%), Nematoda (1.12%), Decapoda (0.80%), Trichoptera (0.56%), Anisoptera (Odonata) (0.48%), Polychaeta (0.32%), Lipdoptera (0.08%) and Hydrachnidae (0.08%). The findings of this study indicated that Omeme, Kpansi Afara and Etsu rivers were classified as very poor category; exceeding the set benchmark. Etsu 11 and Afara Rivers were within the fair category. The Bray-Curtis indices revealed that there was similarity in all the stations Sustainable anthropogenic activities are recommended to avoid displacement of benthic communities.Keywords: Neighboring clusters; Ecozones; North central; Pollution index; Benthic macroinvertebrates; Derive savannah

Dam Removal Effects on Benthic Macroinvertebrate Dynamics: A New England Stream Case Study (Connecticut, USA)

Dam removal is an increasingly common stream restoration tool. Yet, removing dams from small streams also represents a major disturbance to rivers that can have varied impacts on environmental conditions and aquatic biota. We examined the effects of dam removal on the structure, function, and composition of benthic macroinvertebrate (BMI) communities in a temperate New England stream. We examined the effects of dam removal over the dam removal time-series using linear mixed effects models, autoregressive models, non-metric multidimensional scaling, and indicator and similarity analyses. The results indicated that the dam removal stimulated major shifts in BMI community structure and composition above and below the dam, and that the BMI communities are becoming more similar over time. The mixed model analysis revealed that BMI functional groups and diversity were significantly influenced by sample site and several BMI groups also experienced significant interactions between site and dam stage (P &lt; 0.05), while the multivariate analyses revealed that community structure continues to differ among sites, even three years after dam removal. Our findings indicate that stream restoration through dam removal can have site-specific influences on BMI communities, that interactions among BMI taxa are important determinants of the post-dam removal community, and that the post-dam-removal BMI community continues to be in a state of reorganization.

Changes in benthic invertebrate communities of central Appalachian streams attributed to hemlock woody adelgid invasion

Eastern hemlock trees (Tsuga canadensis [L.] Carr.) often dominate riparian vegetation of central Appalachian headwater streams, and the invasive hemlock woolly adelgid (Adelges tsugae Annand; HWA) has decimated hemlock stands in this region. Although research concerning HWA impacts on soil, hydrology, and forest structure is emerging, associated changes in stream structure and function are not as well documented. We quantified HWA-invasion effects on benthic macroinvertebrate communities in 21 headwater streams across Ohio, West Virginia, and Virginia (USA) representing unimpacted, moderate invasion, and severe invasion, respectively. We observed differences in benthic macroinvertebrate community composition; severely invaded sites exhibited the highest diversity, whereas moderate sites had the lowest diversity. The composition of macroinvertebrate functional feeding groups exhibited shifts as well. For example, the relative abundance of herbivorous invertebrates increased from 4% (± 3%) at unimpacted sites to 23% (± 14%) at severely impacted sites. Changes in macroinvertebrate density, diversity, and functional-group composition were associated with sediment grainsize distribution (proportion bedrock and D84), large-wood characteristics (volume and density), and nutrient concentrations (PO4 and NH4). Our results suggest that in-stream physical and chemical alterations associated with HWA-invasion and subsequent hemlock decline are associated with changes in stream invertebrate diversity and trophic relationships. We demonstrate how a pervasive terrestrial invader can influence in-stream biotic communities.

Response to basal resources by stream macroinvertebrates is shaped by watershed urbanization, riparian canopy cover, and season.

Riparian reforestation is a common restoration action in urban streams, but relatively little is known about the influence of local riparian vegetation in the face of watershed-scale urban land cover. Allochthonous organic matter and benthic algae are important basal energy resources in streams, but the roles of watershed urbanization vs near-stream vegetation in the availability of these resources are not well understood. Our goal was to understand how the interaction of land cover at 2 spatial scales (watershed vs reach) and seasonal dynamics shape basal resources and their effects on macroinvertebrate communities. We assessed relationships between seasonal patterns in standing stocks of particulate organic matter (POM) and benthic periphyton and macroinvertebrate community composition in openand closed-canopy reaches of 4 urban and 4 reference streams in northern Kentucky, USA. POM standing stocks were not strongly influenced by watershed or riparian condition. Benthic algal biomass was greater in urban than in reference streams in all seasons and in open than in closed riparian canopies in summer when light levels are most affected by a deciduous canopy. Relationships between macroinvertebrate functional feeding group (FFG) biomass and their primary food resources were influenced by watershed land use and season, but riparian canopy effects were minor. The proportion of collectors varied by season, whereas the proportion of shredders was higher in reference than urban streams. Scraper biomass was influenced by benthic algal biomass and varied seasonally, whereas predator biomass was driven by prey-insect biomass. Periphyton density was affected by the interaction of watershedand reach-scale land cover and was the only basal resource strongly related to consumer taxa. Watershed land use influences the stream ecosystem, but local riparian canopy may be important in limiting benthic algal accumulation.