Benthic Macroinvertebrate Community Composition Research Articles

Determining the Benthic Macroinvertebrate Community Composition of Freshwater Streams from Fish-Gut Analysis

Abstract The monitoring of changes in benthic macroinvertebrate communities over time facilitates the evaluation of any changes that occur in the function and structure of aquatic ecosystems. We hypothesized that it would be possible to determine, through running simulations, which trophic group of fishes' gut content can and should be used to best determine benthic macroinvertebrate community composition. Researchers could use this knowledge to estimate historic benthic macroinvertebrate communities of aquatic systems from fishes catalogued in museums. These historical data could then be compared to current data to see how macroinvertebrate communities have changed over time. In this study, we identified the fishes whose gut content most accurately reflected the benthic macroinvertebrate community of Marshalls Creek in East Stroudsburg, PA. We collected fish species and benthic macroinvertebrate samples at various sites and at different times of year to reflect seasonal variation. Enneacanthus gloriosus ...

Changes of Benthic Macroinvertebrate Community Composition Following Natural Temperature and Precipitation Increase.

To investigate the changes of dominant species of benthic macroinvertebrates according to the changes of temperature and precipitation, we surveyed twenty sites of the main Seomjin River in May and September in 2013 and 2014. The temperature, precipitation, water quality factors and substrate composition, which are important factors in benthos habitat environment, were collected and measured. The average temperature of the Seomjin River increased by 0.2℃ in 2014 compared to 2013, and the temperature increased from upstream to downstream, showing a difference of more than 3℃. Also, the annual cumulative precipitation (ACP) was increased toward low latitude. The temperature of Seomjin River increased more than twice in September (21.7~24.5℃) after rainfall compared to May (7.6~11.3℃) before rainfall, and CP (cumulative precipitation) increased about 3 times before rainfall (263 mm~287.5 mm) and after rainfall (756.3mm~882 mm). Due to washing effect by summer precipitation, total number of species and individuals for benthic macroinvertebrates were higher in May than in September. Chironomidae sp. and Choroterpes altioculus were dominated in May, Ecdyonurus levis, Macrostemum radiatum and Choroterpes altioculus were dominated in September. As a result of correlation analysis between community indices and environment factors, it was found that there is a high correlation with boulder and sand among substrate compositions. According to the results of cluster analysis based on temperature, CP and the dominant species of benthic macroinvertebrates in Seomjin River, it was divided into two groups following temperature and CP, and the dominant species and geographical position were reflected and divided into detailed groups.

Water or sediment? Partitioning the role of water column and sediment chemistry as drivers of macroinvertebrate communities in an austral South African stream

Water pollution is a critical management issue, with many rivers and streams draining urban areas being polluted by the disposal of untreated solid waste and wastewater discharge, storm water and agricultural runoff. This has implications for biodiversity, and many rivers in the developing world are now considered compromised. We investigated benthic macroinvertebrate community structure and composition in relation to physico-chemical conditions of the water column and sediments. The study was conducted in an Austral catchment subject to both urban and agricultural pollutants in two different seasons. We assessed whether sediment characteristics were more important drivers of macroinvertebrate community composition than water column characteristics. We expected clear differences in macroinvertebrate community composition and in the associated community metrics due to distinct flow conditions between the two seasons. A combination of multivariate analyses (canonical correspondence analysis (CCA)) and biological indicator analysis were used to examine these patterns. Chironomidae was the most abundant family (>60%) in the upper mainstem river and stream sites. Stream sites were positively associated with CCA axis 2, being characterised by high turbidity and lower pH, salinity, phosphate concentration, channel width and canopy cover. Canopy cover, channel width, substrate embeddedness, phosphate concentration, pH, salinity and turbidity all had a significant effect on macroinvertebrate community composition. Using CCA variation partitioning, water quality was, however, a better predictor of benthic macroinvertebrate composition than sediment chemical conditions. Furthermore, our results suggest that seasonality had little effect on structuring benthic macroinvertebrate communities in this south-eastern zone of South Africa, despite clear changes in sediment chemistry. This likely reflects the relative lack of major variability in water chemistry compared to sediment chemistry between seasons and the relatively muted variability in precipitation between seasons than the more classic Austral temperate climates.

Accounting for spatial and temporal variation in macroinvertebrate community abundances when measuring the food supply of stream salmonids

The goal of salmonid habitat monitoring programs is to measure habitat attributes linked to salmonid productivity based on protocols that have sufficient precision to detect environmental variation at relevant spatial and temporal scales. Benthic macroinvertebrate community composition often is evaluated as part of habitat monitoring and assessment protocols, despite a lack of direct relationships between benthic composition and salmonid production. Macroinvertebrate drift provides a direct measure of the food resources available to stream salmonids, but drift is rarely evaluated as part of habitat monitoring protocols. This reluctance may stem from the complex spatial and temporal variability inherent in macroinvertebrate drift abundances and an assumed inability to obtain precise estimates of drift abundance at relevant spatial and temporal scales. We evaluated an extensive set of paired drift and benthic macroinvertebrate samples to characterize variation in the biomass and density (i.e., counts) of macroinvertebrate samples across a hierarchy of spatial and temporal scales. Results suggest that estimates of total drift biomass may offer the most precise approach for detecting differences in salmonid food availability among stream reaches and, thus, may be more appropriate than benthic sampling for incorporation into salmonid habitat monitoring programs.

Macroinvertebrate community in relation to water quality and riparian land use in a substropical mountain stream, China.

Exploring how water quality and land use shape the benthic macroinvertebrate community composition is of widespread interest in biodiversity conservation and environmental management. In this study, we investigated the structures of benthic macroinvertebrate assemblages and their environmental controls in terms of water quality and riparian land use in the Jinshui River, China. We carried out three campaigns including wet season (August 2009), dry season (November 2009), and normal season (April 2010) based on the hydrological regime in Jinshui basin. The result showed that macroinvertebrate assemblage variations were better explained by water quality factors than land use based on variance partitioning procedure. The land use of 2km upstream from the sampling sites had explained more variation than that of the whole riparian zone in upstream catchment on macroinvertebrate community, and land use of 2km upstream also had more interactions with water quality. Canonical correspondence analysis (CCA) indicated that the elements or nutrient of magnesium (Mn), selenium (Se), strontium (Sr), silicon (Si), dissolved inorganic nitrogen (DN), sulfur (S), total organic carbon (TOC), and total nitrogen (TN) in water exhibited a strong relationship with macroinvertebrate assemblages. However, the variance in water quality explained by land use was lower than that explained by water quality in rivers using redundancy analysis. Our study suggested that proximate factors (i.e., water quality) were more important to interpret the macroinvertebrate community compared to ultimate factors (i.e., land use) for macroinvertebrate assemblages in river system.

Assessing the ecological impact of banana farms on water quality using aquatic macroinvertebrate community composition

In Costa Rica, considerable effort goes to conservation and protection of biodiversity, while at the same time agricultural pesticide use is among the highest in the world. Several protected areas, some being wetlands or marine reserves, are situated downstream large-scale banana farms, with an average of 57 pesticide applications per year. The banana industry is increasingly aware of the need to reduce their negative environmental impact, but few ecological field studies have been made to evaluate the efficiency of proposed mitigation strategies. This study compared the composition of benthic macroinvertebrate communities up- and downstream effluent water from banana farms in order to assess whether benthic invertebrate community structure can be used to detect environmental impact of banana farming, and thereby usable to assess improvements in management practises. Aquatic invertebrate samples were collected at 13 sites, using kick-net sampling, both up- and downstream banana farms in fast flowing streams in the Caribbean zone of Costa Rica. In total, 2888 invertebrate specimens were collected, belonging to 15 orders and 48 families or taxa. The change in community composition was analysed using multivariate statistics. Additionally, a biodiversity index and the Biological Monitoring Working Party (BMWP) score system was applied along with a number of community composition descriptors. Multivariate analyses indicated that surface waters immediately up- and downstream large-scale banana farms have different macroinvertebrate community compositions with the most evident differences being higher dominance by a single taxa and a much higher total abundance, mostly of that same taxon. Assessment of macroinvertebrate community composition thus appears to be a viable approach to detect negative impact from chemical-intensive agriculture and could become an effective means to monitor the efficacy of changes/proposed improvements in farming practises in Costa Rica and similar systems.

Invasive bivalves increase benthic communities complexity in neotropical reservoirs

Invasive bivalves often act as ecosystem engineers, generally causing physical alterations in the ecosystems in which they establish themselves. However, the effects of these physical alterations over benthic macroinvertebrate communities’ structure are less clear. The objective of this study was to characterize the ecological effects of the invasive bivalves Corbicula fluminea and Limnoperna fortunei on the structure of benthic macroinvertebrate communities in neo-tropical reservoirs. Three hypotheses were tested: (1) invasive bivalves act as facilitator species to other benthic macroinvertebrates, resulting in communities with higher number of species, abundance and diversity; (2) invasive bivalves change the taxonomic composition of benthic macroinvertebrate communities; (3) invasive bivalves increase the complexity of benthic macroinvertebrate communities. For that it was used data from 160 sampling sites from four reservoirs. We sampled sites once in each area, during the dry season from 2009 to 2012. The first hypothesis was rejected, as the presence of invasive bivalves significantly decreased the host benthic communities’ number of species and abundance. The second hypothesis was corroborated, as the composition of other benthic macroinvertebrates was shown to be significantly different between sites with and without invasive bivalves. We observed a shift from communities dominated by common soft substrate taxa, such as Chironomidae and Oligochaeta, to communities dominated by the invasive Gastropoda Melanoides tuberculata. The biomass data corroborated that, showing significantly higher biomass of M. tuberculata in sites with invasive bivalves, but significantly lower biomass of native species. Benthic macroinvertebrate communities presenting invasive bivalves showed significantly higher eco-exergy and specific eco-exergy, which corroborate the third hypothesis. These results suggest that while the presence of invasive bivalves limits the abundance of soft bottom taxa such as Chironomidae and Oligochaeta, it enhances benthic communities’ complexity and provide new energetic pathways to benthic communities in reservoirs. This study also suggests a scenario of invasion meltdown, as M. tuberculata was facilitated by the invasive bivalves.

Composition, diversity, and environmental correlates of benthic macroinvertebrate communities in the five largest freshwater lakes of China

China’s five largest freshwater lakes (Poyang, Dongting, Taihu, Hongze, and Chaohu) are all located in lowland regions and differ greatly in lake morphology, hydrology, and water chemistry. However, basic knowledge of diversity patterns and factors driving macroinvertebrate community structure is lacking. We analyzed the composition and diversity of benthic macroinvertebrates and evaluated the roles of environmental factors and dispersal processes in determining beta diversity at both the lake and regional scales. The two Yangtze-connected lakes (i.e., Lakes Poyang and Dongting) were highest in taxonomic diversity. Differences in taxonomic composition were evident among the five lakes, with the two Yangtze-connected lakes dominated by bivalves and/or gastropods, while Lake Taihu showed great changes in taxonomic composition among sites in accordance with its high habitat heterogeneity. Lake Hongze was dominated by polychaetes, crustaceans, and bivalves. The eutrophic–hypertrophic Lake Chaohu was exclusively dominated by chironomids and oligochaetes. At the lake scale, total γ-diversity was mainly attributed to β1-diversity (among sites) ranging from 57.9 to 87.6%. The total γ-diversity at the regional scale was primarily related to higher β-diversity, with β1 and β2 (among lakes) accounting for 30.4 and 58.8% of total taxa richness, respectively. Environmental conditions appear to be important in structuring benthic macroinvertebrate communities at both the lake and regional scale. Dispersal does not appear to affect distribution of macroinvertebrates at the lake scale.

Hierarchical decomposition of trait patterns of macroinvertebrate communities in subarctic streams

Ecological research based on both species and their traits helps us understand the mechanisms structuring ecological communities. Our aim was to dismantle the effects of environmental variables measured at multiple spatial scales on the taxonomic and functional trait composition of benthic macroinvertebrate communities and to clarify the relationship between the environment and communities in high-latitude streams. Traits were combined into unique trait combinations (site-by-traits matrix), called hereafter the overall trait composition of macroinvertebrate communities, and then the matrix was decomposed into progressively smaller parts of individual traits (site-by-individual trait matrix). The effects of variables from different spatial scales on the variation in the overall trait matrix, decomposed trait matrices, and taxonomic data were analyzed using redundancy analysis and partial linear regression modeling. Our analyses indicated that: 1) the taxonomic composition of communities was more closely associated with factors measured at larger spatial scales, and the trait composition of communities was more closely associated with factors measured at smaller spatial scales, even within 1 drainage basin; 2) decomposing overall trait composition to its individual components of single traits revealed important patterns related to the potential causal factors; and 3) the abundances of organisms exhibiting different traits may be linked strongly to different environmental variables operating at different spatial scales. Our findings highlight the benefits of describing both the taxonomic and trait composition of communities when exploring the drivers of community composition. They also have direct applications in monitoring the vulnerability of high-latitude streams to future environmental changes.

Detecting the impact of heavy metal contaminated sediment on benthic macroinvertebrate communities in tropical streams

The effects of heavy metal pollution on benthic macroinvertebrate communities in tropical streams draining ultramafic systems have not been explored, despite a pressing need for ecological risk assessment to protect and manage aquatic ecosystems in these areas. The objective of this study was to examine benthic macroinvertebrate community composition in relation to metal concentrations in stream sediments and other physico-chemical variables in the Manyame River system, which drains part of the Great Dyke of Zimbabwe. Benthic macroinvertebrate sampling and community composition analysis, sediment collection, processing and metal analysis and assessment of other variables in the water column were done once at 55 sampling sites: 12 urban, 30 communal (i.e. sparsely populated rural areas, with livelihoods centred around subsistence agriculture) and 11 Great Dyke sites. Canonical correspondence analysis and partial canonical correspondence analysis (pCCA) were used to determine the importance of sediment heavy metal concentrations in explaining benthic macroinvertebrate community composition in comparison with other factors. Water quality ranged from very poor for urban locations due to sewage pollution, to good in communal locations. Significantly high concentrations of metals (ANOVA, p<0.05) and high magnesium/calcium (Mg/Ca) ratio were recorded in sediments for the Great Dyke site locations. The Mg/Ca ratio, Ca2+, Cr3+ and K+ were found to be important metals structuring benthic macroinvertebrate communities in the study streams, with metals explaining a larger percentage (58.0%) of the total variation explained compared to other variables (35.9%). However, taxa richness, diversity, evenness, percentage of Ephemeroptera, Plecoptera Trichoptera related metrics were higher at some Great Dyke sites than at communal sites. Thus, measures of taxa richness, diversity and %EPT may provide misleading information when assessing heavy metals in moderately polluted environments as in this study. Assessment of tropical streams draining ultramafic systems that are heavy metal-contaminated should also include benthic invertebrate community structure analysis, as it is possible that common endpoints, such as %EPT, may not identify impacts to aquatic communities.

Do bio-physical attributes of steps and pools differ in high-gradient mountain streams?

The hydrologic and physical structure of streams strongly influences the biological composition of benthic macroinvertebrate communities. Research on step–pool systems in high-gradient streams has focused primarily on physical processes rather than on ecological characteristics. This study examined both the biological and physical attributes of 27 step–pool sequences in three steep mountain streams of the Smith River Basin in northern California, USA. Multivariate analysis using non-metric multidimensional scaling (NMS) found a biological separation of step and pool sites (based on benthic macroinvertebrate data) in all three study watersheds. Step habitats had greater taxa richness, diversity, %Plecoptera, %Heptageniidae, %Nemouridae, and %clingers compared to pools. Steps also differed from pools in physical characteristics such as grain size distribution, whereby steps were dominated by boulders compared to pools characterized by gravel and cobbles. Moreover, steps had higher dissolved oxygen, greater water velocity, and shallower water depths compared to pools. NMS ordinations showed a correlation between physical factors and biological communities. These results suggest the ecological importance of step–pools streams, in that the development of step sequences creates and maintains a repetitive pattern of high-quality ecological environments.

The long-term effects of invasive signal crayfish (Pacifastacus leniusculus) on instream macroinvertebrate communities

Non-native species represent a significant threat to indigenous biodiversity and ecosystem functioning worldwide. It is widely acknowledged that invasive crayfish species may be instrumental in modifying benthic invertebrate community structure, but there is limited knowledge regarding the temporal and spatial extent of these effects within lotic ecosystems. This study investigates the long term changes to benthic macroinvertebrate community composition following the invasion of signal crayfish, Pacifastacus leniusculus, into English rivers. Data from long-term monitoring sites on 7 rivers invaded by crayfish and 7 rivers where signal crayfish were absent throughout the record (control sites) were used to examine how invertebrate community composition and populations of individual taxa changed as a result of invasion. Following the detection of non-native crayfish, significant shifts in invertebrate community composition were observed at invaded sites compared to control sites. This pattern was strongest during autumn months but was also evident during spring surveys. The observed shifts in community composition following invasion were associated with reductions in the occurrence of ubiquitous Hirudinea species (Glossiphonia complanata and Erpobdella octoculata), Gastropoda (Radix spp.), Ephemeroptera (Caenis spp.), and Trichoptera (Hydropsyche spp.); although variations in specific taxa affected were evident between regions and seasons. Changes in community structure were persistent over time with no evidence of recovery, suggesting that crayfish invasions represent significant perturbations leading to permanent changes in benthic communities. The results provide fundamental knowledge regarding non-native crayfish invasions of lotic ecosystems required for the development of future management strategies.

Environmental drivers of the benthic macroinvertebrates community in a hypersaline estuary (Northeastern Brazil)

Abstract Introduction The estuarine community of benthic macroinvertebrates spatially varies in response to changes in environmental variables in these ecosystems. Understanding this variability helps our understanding the mechanisms structuring these communities. Aim Assess the structural aspects of the benthic macroinvertebrate community in a hypersaline estuary, and to relate to environmental variables that influence the community structure along the estuary. Methods The study was conducted at Tubarão river estuary in May 2015. We sampled two estuarine areas (upper and lower), and in each zone were sampled six points composed of two replicas, one sampled in sandy bottom and the other in muddy bottom. Samples of benthic macroinvertebrates and estuarine environmental variables were collected. Environmental drivers of the benthic macroinvertebrate community were determined by Distance-based Linear Models analysis. The contribution of individual species to the dissimilarity between the areas and substrate types were determined by analysis of the percentage of similarity. Results The composition of benthic macroinvertebrate community differed between the upper and lower areas, although it was similar between the muddy and sandy bottoms. The variation in the benthic community between areas was mainly related to the influence of salinity in the upper area. In the lower area, the variation of the macroinvertebrates was related to salinity, associated with other variables in the sandy (temperature, turbidity and dissolved oxygen) and muddy (temperature, total dissolved solids and dissolved oxygen) substrates. Taxa which contributed most to the dissimilarity between the upper and lower areas were Nereididae (17.89%), Anomalocardia brasiliana (15%) and Cirratulidae (10.43%). Conclusions Salinity was the main driver of the structural aspects of the benthic macroinvertebrate community in the upper area of the estuary, although in the lower area a set of variables have structured benthic macroinvertebrates in the hypersaline estuary studied. In addition, the largest mangrove cover and less influence of the tide, may have favored the greater abundance of macroinvertebrates in the upper area.

Landscape-based cumulative effects models for predicting stream response to mountaintop mining in multistressor Appalachian watersheds

We conducted a survey of 170 streams distributed throughout the mountaintop-mining region of West Virginia (USA) and linked stream data to a temporally consistent and comprehensive land-cover data set. We then applied a generalized linear modeling framework and constructed cumulative effects models capable of predicting in-stream response to future surface-mine development within the context of other landuse activities. Predictive models provided precise estimates of specific conductance (model R2 ≤ 0.77 and cross-validated R2 ≤ 0.74), Se (0.74 and 0.70), and benthic macroinvertebrate community composition (0.72 and 0.65). Deletion tests supported the conclusion that stream degradation across the region is the result of complex, but predictable, additive and interactive effects of surface mining, underground mining, and residential development. Furthermore, we found that as stressors other than surface mining are factored out completely, the surface-mining level that results in exceedance of the 300 µS/cm conductivity benchmark increased from 4.4% in the presence of other stressors to 16.6% when only surface mining was present. Last, extrapolating model results to all unsampled stream segments in the region (n = 26,135), we predicted high levels of chemical (33%) and biological (67%) impairment to streams on the current landscape. Of this total impairment, however, <25% could be attributed to surface mining alone. These results underscore the importance of multistressor landuse models for reliable predictions of stream conditions, and the difficulty of interpreting correlations between surface mining and stream impairment without fully accounting for other landuse activities.

Environmental drivers of leaf breakdown in an urban watershed

Leaf-litter breakdown is an important ecosystem process in urban streams, but urbanization may have complicated effects on breakdown rates. Low abundance of macroinvertebrate shredders may slow breakdown, but rates may increase if high nutrient concentrations stimulate microbial decomposers or if flooding enhances leaf fragmentation. We measured the relative importance of multiple environmental drivers on breakdown of eastern cottonwood (Populus deltoides) leaves at 5 sites in the urbanized North Branch of the Chicago River watershed. Few specialized macroinvertebrate shredders were present, but generalist macroinvertebrates, including isopods (Asellus aquaticus) and amphipods (Gammarus sp.) were abundant at all sites. We tested macroinvertebrate effects on breakdown rate in large- and small-mesh bags. We measured discharge, nutrient concentrations, benthic macroinvertebrate community composition, and subwatershed land use at each site. Leaf breakdown differed significantly among sites and between mesh types. Discharge and isopod abundance were positively related to breakdown rates, whereas nutrient concentrations were unrelated to breakdown rates. Abundances of isopods and amphipods were significantly higher in litter bags than in benthic samples. We conducted follow-up experiments in artificial streams to measure the separate effects of water velocity and isopods on leaf breakdown based on conditions from field sites. Increasing water velocity from 0.02 (control) to 0.07 m/s (high velocity) increased leaf breakdown by 33%, and adding isopods (density = 1034 individuals/m2) increased leaf breakdown by 40%. Measuring environmental controls on leaf breakdown throughout urban watersheds is critical to the use of breakdown rates as an assessment tool for urban stream ecosystems. Our study provides input data for models of stream ecosystem function at urban sites and informs management approaches for urban streams at the watershed scale.

Effects of human activities on benthic macroinvertebrate community composition and water quality in the upper catchment of the Mara River Basin, Kenya

AbstractLand‐use changes in the upper reaches of the Mara River Basin have modified their biophysical and hydrological processes, resulting in water quality degradation in streams. This study was conducted to investigate the effects of human activities on water quality and macroinvertebrates along the Nyangores River, one of the main tributaries of the Mara River, Kenya. Seven sampling sites were chosen to correspond to the loss of riparian cover, livestock watering and human activities (e.g. laundry washing, bathing, cultivation, wastewater inputs, dumping of solid wastes from urban areas and settlements along the river). Physical–chemical variables and water samples for nutrient analyses were collected monthly from February to July 2012. Benthic macroinvertebrates also were collected at the same sites as for the water quality samples. Two‐way analysis of variance tested the significant differences for each variable among the sites. Similarity percentages (SIMPER) analysis was used to identify the key taxa contributing to differences between minimally disturbed and most disturbed conditions in the study area. The results indicated increased nutrient concentrations in agricultural and settlement areas. Significant (P &lt; 0.05) spatial–temporal variations in water quality variables were observed. A total of 42 macroinvertebrate genera were encountered, with Ephemeroptera, Plecoptera and Trichoptera orders dominating the minimally disturbed areas, and Diptera dominating the disturbed areas receiving point and no‐point solid and liquid wastes, including nutrients, from urban areas and settlements. Canonical correspondence analysis (CCA) revealed significant relationships between macroinvertebrate communities and measured physicochemical variables. The results of this study indicate the need for protection of riparian zones and treatment of sewerage wastes before their release into waterways. The dumping of solid wastes near streams and rivers also is discouraged, to maintain the quality of surface waters and aquatic organisms.

Nutrient- and sediment-induced macroinvertebrate drift in Honduran cloud forest streams

Montane cloud forests are hydrologically unique, critically endangered ecosystems and frequently major sources of potable water, which have come under increasing pressure from human activities. It is therefore of vital importance that our understanding of the effects of anthropogenic stressors on the aquatic biota in these ecosystems is improved. To this end, a series of flow channel-based field experiments was performed to quantify the effects of nutrient enrichment and deposited fine sediment (two stressors commonly observed in tropical regions) on river macroinvertebrate assemblages in a cloud forest park in Honduras. Macroinvertebrate communities responded to the addition of nutrients (released from struvite) through an increased percentage abundance drifting and to elevated sediment levels with an increased percentage abundance and richness drifting in the first 24 h following treatment. A shift in community structure was also observed in response to elevated nutrients with lower abundances of some taxa and an overall decrease in richness. Our results indicate that increased nutrient loading and sedimentation can alter benthic macroinvertebrate community composition in high-altitude neotropical streams. Macroinvertebrate communities may be impacted via direct toxicity of nutrients and clogging of interstitial spaces and/or reductions in refugia due to sedimentation.

Community Composition of Lake Zooplankton, Benthic Macroinvertebrates and Forage Fish Across a pH Gradient in Kejimkujik National Park, Nova Scotia, Canada

The composition of zooplankton, benthic macroinvertebrate (BMI) and forage fish communities of 20 lakes in and near Kejimkujik National Park and National Historic Site were evaluated as part of Environment Canada’s Acid Rain Biomonitoring Program. The pH of study lakes ranged from 4.3 to 6.6. Lake pH was positively correlated with alkalinity, calcium and magnesium concentrations and negatively correlated with colour, aluminium, total organic carbon and nitrogen. Gradients in overall BMI community composition and total BMI richness were strongly related to the gradient in pH, but the composition of zooplankton and forage fish communities were more strongly related to other environmental parameters such as elevation. Potential indicator species for future acid rain monitoring included Daphnia catawba, the amphipod Hyalella azteca, pill/pea clams Pisidium casertanum and Pisidium ferrugineum and larval water scavenger beetle Berosus. These chemical and biological data provide a baseline for future evaluation of the continued effects of anthropogenic deposition to this acid-sensitive region of Atlantic Canada.

Factors affecting spatiotemporal benthic macroinvertebrate diversity and secondary production in a semi-arid watershed

Spatial and temporal changes of the benthic macroinvertebrate (BMI) community composition and secondary production provide valuable information about the current ‘health’ of aquatic systems. We analyzed seasonal and inter-annual changes in BMI communities at five sites along an elevation and land use gradient in the Walker River, NV, USA. In addition, bimonthly collections of Baetis mayflies were made at two sites to assess the effect of nutrient enrichment on Baetis secondary production. BMI community composition changed spatially and temporally in response to the physicochemical environment. BMI diversity was positively correlated to substrate size and stream width but negatively correlated with stream temperature and organic pollutants. Cluster analysis based on BMI community composition revealed a similar community structure along the river, except at one site which was located below the outflow of a eutrophic reservoir. The BMI community in the river was dominated by collector–gatherers while shredders were absent through most of the downstream and impaired sites. Secondary production of Baetis was almost twice as high at the nutrient-enriched site (1.3 g dry mass m−2 yr−1) than at the undisturbed site (0.7 g m−2 yr−1), most likely the consequence of warmer water temperatures and superior food quality. Results from this study imply that a variety of anthropogenic activities have altered disparate reaches of the Walker River and that BMI community composition would change towards natural conditions with an increase in discharge and reduced water temperature and nutrients. This work also underscores the importance of considering biotic indices and secondary production to effectively assess stream ecosystem health and to design successful restoration strategies.

Invasive species as driving factors for the structure of benthic communities in Lake Constance, Germany

The composition of benthic macroinvertebrate communities is influenced by a variety of factors, including the introduction of invasive species. However, only few analyses of factors influencing benthic community structure exist, especially those including invasive species. Our aim was to examine the importance of biotic factors on spatial and temporal variations in the benthic community within one system (Lake Constance, Germany). We examined the dependence of benthic community structure on invasive species by non-metric multidimensional scaling and distance-based redundancy analysis based on Bray–Curtis similarities. The three significant biotic factors explained 40% of the community variability. The mayfly Centroptilum luteolum and the snail Potamopyrgus antipodarum were positively associated with the amount of Chara, whereas some caddisfly taxa and Chironomidae were positively associated with the density of Dreissena polymorpha, which is a pattern most likely caused by their different habitat preferences. Several benthic taxa especially indigenous gammarids and Asellus aquaticus tended to decline with increased densities of the invasive amphipod Dikerogammarus villosus. Furthermore, density of D. villosus explained 26% of the benthic variability, demonstrating the strong impact of this species. Overall, our study demonstrates the large impact of invasive species on the composition of benthic macroinvertebrates.