Total Taxon Richness Research Articles

Impacts of the Koka hydropower dam on macroinvertebrate assemblages in the Awash River Basin in Ethiopia

The Koka hydropower dam is one of the oldest large dams in Ethiopia. Damming is one of the anthropogenic activities impacting the distribution of aquatic life forms. However, to date, little attention has been focused on the dam’s impacts on the river macroinvertebrate assemblages in Ethiopia. The objective of this study was, therefore, to assess the impacts of the Koka hydropower dam on macroinvertebrate assemblages in the Awash River basin in Ethiopia. In the three river reaches on the Awash River (upstream near the source of the river, midstream above the dam, and downstream below the dam), a total of 15 sites were selected for sampling. The statistical analysis tested the null hypothesis that there are no differences in macroinvertebrate assemblage patterns or a range of univariate metrics between the three river reaches. Additional analyses involved the identification of taxa responsible for significant differences in macroinvertebrate structure (e.g., percentage similarity) and an exploration of the variables that structure macroinvertebrates (e.g., canonical correspondence analysis). In the upstream, midstream, and downstream reaches of the Awash River, we recorded a total of 73 taxa belonging to 43 families and 12 orders. Trichoptera was the dominant order in the upstream river reach, whereas Diptera dominated the midstream and downstream river reaches. The diversity of macroinvertebrates decreased from upstream to midstream and downstream. The three river reaches differed significantly in Shannon and Simpson diversity indices, % EPT, EPT taxa abundance, total taxa richness, evenness index, % collectors, and % scrapers. In this study, we observed that macroinvertebrate assemblage differences and spatial patterns were significantly associated with values of river flow changes (velocity), phosphate concentration, and substrate index. The findings of this study have broad implications for the assessment of the impacts of dam construction on the rivers of the studied region in the future.

Effects of land use and soil properties on taxon richness and abundance of soil assemblages

AbstractLand‐use change and habitat degradation are among the biggest drivers of aboveground biodiversity worldwide but their effects on soil biodiversity are less well known, despite the importance of soil organisms in developing soil structure, nutrient cycling and water drainage. Combining a global compilation of biodiversity data from soil assemblages collated as part of the PREDICTS project with global data on soil characteristics, we modelled how taxon richness and total abundance of soil organisms have responded to land use. We also estimated the global Biodiversity Intactness Index (BII)—the average abundance and compositional similarity of taxa that remain in an area, compared to a minimally impacted baseline, for soil biodiversity. This is the first time the BII has been calculated for soil biodiversity. Relative to undisturbed vegetation, soil organism total abundance and taxon richness were reduced in all land uses except pasture. Soil properties mediated the response of soil biota, but not in a consistent way across land uses. The global soil BII in cropland is, on average, a third of that originally present. However, in grazed sites the decline is less severe. The BII of secondary vegetation depends on age, with sites with younger growth showing a lower BII than mature vegetation. We conclude that land‐use change has reduced local soil biodiversity worldwide, and this further supports the proposition that soil biota should be considered explicitly when using global models to estimate the state of biodiversity.

Long-term trajectory of the macroinvertebrate community in the downstream channel of a hydropower dam after the operation of a sediment bypass tunnel

A sediment bypass tunnel (SBT) is a dam facility used to mitigate reservoir sedimentation and is expected to contribute to river ecosystem restoration by delivering sediment to the degraded downstream channel. We analyzed past monitoring data of benthic invertebrates sampled downstream of the Asahi Dam in Nara Prefecture Japan to understand the long-term changes in the invertebrate community after the installation of the SBT. Before the SBT installation, the reaches upstream of the dam (one Up site) and downstream of the dam (two Down sites) showed different invertebrate communities, dominated by invertebrates that preferred clean cobble beds, sand and gravel layers, or run habitats in the former and invertebrates that preferred stable or porous beds or pool habitats in the latter. A significant increase in the Up–Down site community similarity within a few years after the SBT installation indicated a rapid recovery of the invertebrate community at the Down sites. During the 16 years of the after-SBT period, the total density and taxon richness at the Down sites increased in the early half, while they decreased in the latter half due to bed changes associated with the continuous accumulation of sediments. The change in dominant invertebrates from taxa of the large sizes to those of the small sizes and the increase in the interhabitat community similarity suggest that the bed of the Down sites became finer and flatter by sand and gravel that filled interstitial spaces of cobbles in the late stage. While the invertebrate community at the Down sites recovered dramatically by the sediment supply through the SBT, additional actions (e.g., cobble augmentation, installation of flow guiding structures) to maintain a balanced sediment size distribution and developed pool-riffle structures would be necessary to maintain the potential habitat heterogeneity and biodiversity in the long term. Our study also demonstrated that invertebrates responded to the sediment supply according to their habitat preferences, which suggests that the classifications of invertebrates by habitat-related traits (e.g., bed-residence types and pool-riffle types in this study) would help to properly understand the sediment and bed status of river reaches under channel degradation or aggradation.

Spatial and Annual Variation in Microbial Abundance, Community Composition, and Diversity Associated With Alpine Surface Snow.

Understanding microbial community dynamics in the alpine cryosphere is an important step toward assessing climate change impacts on these fragile ecosystems and meltwater-fed environments downstream. In this study, we analyzed microbial community composition, variation in community alpha and beta diversity, and the number of prokaryotic cells and virus-like particles (VLP) in seasonal snowpack from two consecutive years at three high altitude mountain summits along a longitudinal transect across the European Alps. Numbers of prokaryotic cells and VLP both ranged around 104 and 105 per mL of snow meltwater on average, with variation generally within one order of magnitude between sites and years. VLP-to-prokaryotic cell ratios spanned two orders of magnitude, with median values close to 1, and little variation between sites and years in the majority of cases. Estimates of microbial community alpha diversity inferred from Hill numbers revealed low contributions of common and abundant microbial taxa to the total taxon richness, and thus low community evenness. Similar to prokaryotic cell and VLP numbers, differences in alpha diversity between years and sites were generally relatively modest. In contrast, community composition displayed strong variation between sites and especially between years. Analyses of taxonomic and phylogenetic community composition showed that differences between sites within years were mainly characterized by changes in abundances of microbial taxa from similar phylogenetic clades, whereas shifts between years were due to significant phylogenetic turnover. Our findings on the spatiotemporal dynamics and magnitude of variation of microbial abundances, community diversity, and composition in surface snow may help define baseline levels to assess future impacts of climate change on the alpine cryosphere.

Monitoring of Neotropical Streams Using Macroinvertebrate Communities: Evidence from Honduras

Assessing the water quality by using biological indicators is a reliable and economically feasible way to promote environmental conservation in developing tropical countries. Here, we report one of the few examples of river biomonitoring in Honduras. In June 2005, benthic macroinvertebrates were collected from six sites in the Río Cangrejal basin. An adapted version of the Biological Monitoring Working Party index (BMWP) was used to assess the water quality because it is simple, consolidated, relatively easy to use, and needs a family-level identification. Moreover, two other community metrics were calculated, namely the total taxon richness and local contribution to beta diversity (LCBD). Differences in the biomonitoring and diversity metrics among sites and their correlations were statistically tested. Thirty-nine macroinvertebrate taxa were collected and, despite significant differences in the BMWP score, all sampling sites were classified in the high environmental quality class. A very strong and positive correlation between the BMPW and taxon richness was found, while LCBD did not vary significantly and did not correlate with the other metrics. Our results suggest that taxon richness could be used as a surrogate indicator to assess the water quality when consolidate biomonitoring methods are not available.

MICROCRUSTACEAN ASSEMBLAGES AND WATER QUALITY IN A HIGH-ALTITUDE POND IN SOUTH BRAZIL (PARANÁ)

The aim of this study was to assess the abundance and richness of microcrustacean, and water physical and chemical characteristics of a high-altitude pond in the Serra do Mar at State of Paraná. Water samples were collected quarterly between August 2015 and August 2016. Environmental conditions of pond were characterized by small pond size and depth, cold and well oxygenated water, and neutral or slightly acid pH. Mean total microcrustacean density was 945.0 ind m-3, whereas total taxon richness was 3.40. The most abundant species was Tropocyclops prasinus. The small size and the isolament of the pond, and the low temperatures were related to the low species richness and abundance. This study is unprecedented to the State of Paraná. Future studies attempt to understand the environmental conditions and distribution of microcrustaceans from high-altitude ponds.

Plant quantity and quality regulate the diversity of arthropod communities in a semi‐arid grassland

Abstract The quantity (e.g. biomass production) and quality (e.g. leaf nutrient content) of plants can strongly influence arthropod diversity, but few studies have tried to disentangle such effects. In this study, we examined the independent effects of plant productivity and leaf traits on the taxon richness and abundance of entire arthropod communities and multiple arthropod orders in replicated monocultures of 15 herbaceous species in the Inner Mongolian grassland. Total taxon richness of arthropod communities increased with plant productivity and an increase in a high nutrient content indicator (PC1) of plant leaf traits (e.g. high leaf nitrogen, phosphorus and water contents), but decreased with an increase in a poor nutrient content indicator (PC2) of plant leaf traits (e.g. high leaf lignin content but low SLA). Total abundance of arthropod communities increased with increasing plant productivity but decreased with increasing PC2. Many common, rather than rare arthropod orders, exhibited strong responses to the changes in plant quantity or quality. Taxon richness of Diptera, Neuroptera and Coleoptera responded positively to the increase in plant productivity and PC1, while taxon richness of Hemiptera and Coleoptera responded negatively to the increase in PC2. Abundances of Diptera and Coleoptera responded positively to the increased plant productivity, whereas abundances of Hymenoptera and Hemiptera responded negatively to the increased PC2. The order‐specific responses of arthropod richness and abundance to plant quantity or quality reflected the different food requirements and feeding behaviours of arthropods. Our findings demonstrate that plant quantity and quality can independently control richness and abundance of arthropod communities. The changes in plant productivity and nutrient content of different plant species may alter arthropod diversity and community structure, and these changes in turn may have strong cascading effects on multiple functions (e.g. prey, decomposers, pollinators and predators) in terrestrial ecosystems. A free Plain Language Summary can be found within the Supporting Information of this article.

Cladocera resting egg banks in temporary and permanent wetlands

Cladocerans are important filter-feeders transferring energy up the food web to different invertebrate and vertebrate predators. Along the flood period, cladocerans are one of the primary food sources for juvenile fish in floodplain. Resting egg banks allow cladoceran populations to overcome the environmental stress, related to several limnological changes, including complete drying of temporary wetlands. After drought, resting egg banks influence cladoceran community attributes during the cyclic and successional processes driven by episodic flood events. In this study we compared the taxonomic richness of active (from the water column) and dormant (from the sediment) Cladocera assemblages and analyzed the structure of resting egg banks, comparing the diversity, abundance and apparent viability/unviability of the eggs, between six temporary and six permanent wetlands, located along the Ovens River Floodplain, Victoria, Australia. The qualitative analysis shows higher taxonomic richness in active assemblages from temporary (24 taxa) than permanent (13 taxa) wetlands compared to dormant assemblages present in resting egg banks (9 taxa) from temporary and permanent wetlands. However, richness was influenced by taxonomic level of identification, with the majority of resting eggs only being identified to the taxonomic level of family (i.e. Chydoridae). Total taxa richness within egg banks was similar between wetland types, however, on average higher Shannon’s diversity of resting eggs was found within permanent (1.53) than temporary (0.82) wetlands. This is likely to be due to more stable wetlands not providing appropriate cues to trigger dormancy induction or breakage for specific populations, leading to higher values of evenness in permanent than temporary wetlands. Comparing permanent and temporary wetlands, higher abundance of resting eggs (more than four times) consisting of higher abundance of unviable eggs and similar viable egg abundance to permanent wetlands, was found within temporary wetlands, suggesting that the increased resting egg abundance in temporary wetlands is balanced by the losses due to factors such as predation, parasitism or other physical damage, during the terrestrial phase. Despite resistant outer shell structure, this study highlights that the damage to egg integrity is intensified in wetlands that undergo dry phases. Cladoceran resting egg banks represent the potential assemblage to recover after disturbance events such as drying, and information about these is important to ensure appropriate management and conservation of floodplain biodiversity.

Macroinvertebrates of Eichhornia crassipes (Pontederiaceae) roots in the alluvial floodplain of large tropical rivers (Argentina)

Introduction: Eichhornia crassipes is a dominant aquatic plant of neotropical-river floodplains and is invasive in warm waters of different continents. Plants provide food and habitat for fish, especially Prochilodus lineatus and Gymnotus omarorum, which are relevant to subsistence fishing by local indigenous communities. Objective: In this study we describe the main traits of E. crassipes floating meadows, and analyze the abundance and composition of macroinvertebrate assemblages associated with their roots in two floodplain wetlands of the Paraná River (within the Ramsar site Wetlands Chaco) and of the Pilcomayo River (within the Pilcomayo River National Park). Methods: During spring and summer, the macroinvertebrates were collected in monospecific stands of E. crassipes with a net of 962 cm2 area and 500 µm mesh size. Leaf density, the biomass of leaves and roots, the length of leaves and roots, and the water quality were measured simultaneously. Results: Temperature, oxygen concentration, and nutrient content were significantly higher and electrical conductivity was lower in the Pilcomayo than in the Paraná floodplain. E. crassipes growing in the Pilcomayo floodplain had longer leaves and less root biomass than those found in the Paraná floodplain. The number of macroinvertebrates per 1 000 g root dry weight and per m2 was significantly different between both floodplains, but the taxon richness was similar. Non Metric Multidimensional Scaling analysis differentiated the abundance of 14 selected taxa between both floodplains, and showed a high correlation between the environmental variables and macroinvertebrate abundance. The most abundant taxonomic groups in the Paraná River floodplain were oligochaetes (Naididae), ostracods mainly Cytheridella ilosvayi and larvae of non-biting midges (Chironomidae). Two families, Hydrobiidae (Heleobia parchappii) and Chironomidae accounted for 49.3 % of the total abundance in the Pilcomayo floodplain. The prawns Macrobrachium jelskii and M. amazonicum, frequent in the Pilcomayo floodplain, were not found in the Paraná floodplain. Conclusions: The different environmental conditions in both floodplains affect the abundance, composition, and the dominance of macroinvertebrate assemblages; however, the total taxa richness was similar. The area occupied by E. crassipes in the floodplains of these rivers provides the habitat that contributes most to overall biotic diversity, which must be considered in management strategies.

Effects of anthropogenic subsidy and glyphosate on macroinvertebrates in streams.

Streams and surrounding terrestrial ecosystems are closely linked by numerous resource subsidies including anthropogenic subsidies which are increasingly entering streams due to intensive human activities. Also, streams are threatened by stressors such as glyphosate-the most widely used herbicide worldwide. However, the ecological consequences of anthropogenic subsidies and glyphosate on freshwaters are not fully understood. Here, we deployed leaf litter (Cinnamomum camphora) bags containing neither, either, or both treatments of anthropogenic carrion subsidy (chicken meat) and glyphosate (coated in agar) in four streams, which had different land use (i.e., forest, village, and suburban) in Huangshan, Anhui Province, China. We aimed to investigate the individual and combined effects of anthropogenic carrion subsidy and glyphosate on macroinvertebrates in streams and whether these effects differ with land use change. Macroinvertebrate communities significantly differed among streams: biodiversity index and total taxon richness were highest in village streams and lowest in suburban stream. Overall effects of carrion subsidy and glyphosate on macroinvertebrates were not significant. However, several taxa were affected in one or more streams by the individual or combined effects of carrion subsidy and glyphosate, indicating the importance of local community structure and physical habitats in driving the response of macroinvertebrates to carrion subsidy and glyphosate. Collectively, these results imply that the effects of carrion subsidy and glyphosate on macroinvertebrates are site-specific, and future studies should cover more streams and last longer time to better understand the ecological mechanisms driving such pattern.

Agricultural Land-Use Legacy, The Invasive Alga Didymosphenia geminata and Invertebrate Communities in Upland Streams with Natural Flow Regimes.

The integrity of freshwater ecosystems worldwide is under threat from agriculture and invasive species. Past agricultural activity can have persistent effects on aquatic diversity even decades after restoration, and the spread of invasive species is increasingly difficult to prevent due to globalisation. In the South Island of New Zealand, the invasive diatom Didymosphenia geminata (Didymo) causes nuisance blooms in streams. The impact of Didymo on stream invertebrate communities in upland streams with natural flow regimes remains poorly understood. We investigated the relationships between legacy effects of agriculture, Didymo and benthic invertebrate communities at 55 stream sites in Mahu Whenua, a 530 km2 conservation area comprising four former New Zealand high-country farms. The farms were destocked of sheep 4-9 years before stream sampling started. Kick-netting was used to collect macroinvertebrates from 7-23 streams within each farm to provide a land-use legacy gradient. Moreover, samples from 16 sites with clearly visible Didymo mats covering most of the stream bed (indicating high biomass and a dominant role in the biofilm) were compared with 39 sites without such Didymo mats. Total invertebrate taxon richness and EPT richness (taxon richness of larval mayflies, stoneflies and caddisflies) were lower in the stream catchments destocked most recently. When Didymo was present, relative EPT abundance was lower than when Didymo was absent, and Deleatidium mayflies decreased whereas midges and oligochaetes increased. These results highlight the need to look at past land-use practices when restoring high-country streams after agricultural impacts. They also show that Didymo can have negative effects on invertebrate communities in upland streams with natural flow regimes, a stream type previously overlooked in studies on this invasive diatom.

Efficiency of Surber net under different substrate and flow conditions: insights for macroinvertebrates sampling and river biomonitoring

In biomonitoring great attention has been paid on the selection of the best indices and metrics, often neglecting a simple but fundamental aspect: how reliable are the sampling methodologies? We tested the efficiency of the Surber net in collecting stream macroinvertebrates by comparing two samples collected consecutively on the same plot. We found that substrate particle size and water depth and velocity significantly affected sampling efficiency, especially regarding the total taxa richness, EPT (Ephemeroptera, Plecoptera and Trichoptera) richness and density. This study therefore provides useful insights to collect stream macroinvertebrates using the Surber net under different near-bed conditions.

How altitudinal gradient affects the diversity and composition of benthic insects in arid areas streams of northern East Algeria?

This study was carried out to evaluate the variation of diversity and composition of benthic insects in streams, along an altitudinal gradient in an arid area of Belezma National Park, Northern East of Algeria. Benthic entomofauna was sampled in the spring season of 2015, 2017 and 2018 at 28 sampling sites distributed along 4 streams unaffected by human pressure. The altitudinal gradient varies between 1045 m and 1500 m. At each site, we measured 5 physicochemical parameters of water and other physical factors describing each site (velocity, depth and width). All of these environmental factors vary significantly with altitude. A total of 78 taxa belonging to 55 families and 8 orders of benthic insects were identified. Both diversity and abundance of studied entomofauna vary with altitudinal gradient. The highest values of diversity were found in the fourth altitudinal zone (AZ4: up to 1400 m, total taxa richness = 52) and AZ3 (1300 to 1400 m, Shannon index = 3.16). The average number of individuals in AZ1 is higher than in all the other altitudinal zones (mean individuals number = 102.75). The General Linear Model analysis shows that the altitudinal gradient is in favour of high diversity but in disfavour of population abundance. The hierarchical clustering analysis revealed three cluster groups of benthic insects, which are altitudinal indicators. Diptera and Ephemeroptera in downstream stations are mainly replaced by Coleoptera in upstream ones.

Seasonal patterns of stream macroinvertebrate communities in response to anthropogenic stressors in monsoonal Taiwan

Freshwater ecosystems are affected by a variety of anthropogenic stressors. Temporal variability of biotic communities in these ecosystems makes it difficult to accurately assess the impacts of specific stressors, which has seldom been considered in understudied regions of Asia. We studied the seasonal effects of anthropogenic stressors on stream macroinvertebrates based on sampling every three months over two years at five stream sites in central Taiwan. Several macroinvertebrate metrics (taxon richness, Shannon diversity index, and relative abundance of Trichoptera) were lower during the wet season than the dry season. The presence of dams caused changes in the structure of macroinvertebrate communities, decreased the seasonal variability in relative abundances of Trichoptera, as well as resulted in lower dissolved inorganic nitrogen concentrations and larger substrate size. The presence of urban areas had less or no influence on environmental factors and structural changes. However, significantly lower total abundance, taxon richness, and relative abundance of Trichoptera occurred in the presence of either dams and/or urban areas. One key management implication from the present study is that bioassessment utilizing macroinvertebrates should be facilitated by awareness of the potential role of temporal factors on the effects of anthropogenic stressors, especially in monsoonal Asia.

Influence of debris flows on macroinvertebrate diversity and assemblage structure

The middle catchment of the Nu River is highly susceptible to debris flows. Differences in flow and substratum conditions among mainstem reaches correlate with debris flow depositions from lateral tributaries. We studied the impacts of debris flows on macroinvertebrates, especially responses in their diversity and assemblage structure to habitat modification at 22 sites in three habitats: barrier lakes and debris dams, formed by debris flow deposits barring the river, and unaffected mainstem sections. Unaffected mainstem sites supported the most diverse macroinvertebrate assemblage, with mean taxon richness, density and biomass 1.4, 1.1, and 23.6 times higher than those of debris dam sites, and 2.1, 4.2, and 7.4 times higher than those of barrier lake sites, respectively. Variance analysis revealed significant differences in diversity indices, and both taxonomic and functional feeding group composition among habitats. Although barrier lakes and debris dams had lower taxon richness, the two affected habitats contributed 17 and 16 exclusive taxa, respectively, to total taxon richness. Redundancy analysis identified habitats could be characterized by water temperature, electrical conductivity, flow velocity, and median particle size of substratum type. Significant differences in flow velocity and substratum median particle size among habitats were attributed to debris flows. Distinct assemblages within barrier lakes were associated with fine sediments. By altering habitat conditions, debris flows affect macroinvertebrate assemblages, reducing diversity locally in affected reaches, contributing to variation in diversity and assemblage structure throughout the catchment. Three genera (Cricotopus sp., Pseudocloeon sp. and Monodiamesa sp.) are proposed as potential indicator taxa for unaffected mainstem, debris dam and barrier lake habitats, respectively.

Macroinvertebrate Community in Subsurface-Flow Constructed Wetlands for Wastewater Treatment under High and Low Pollutant Stress in China

Constructed wetlands (CWs) for wastewater treatment had drawn much attention for their additional function of conserving freshwater ecosystems. The purpose of this study was to evaluate the macroinvertebrate biodiversity of two subsurface-flow and surface-flow hybrid CW systems (Qimei CW system (QCWS) and Kejiyuan CW system (KCWS)) under high and low pollutant stress in China. Nonmetric multidimensional scaling (NMDS) and canonical correspondence analysis (CCA) were used to analyze the water quality and aquatic macroinvertebrates community data. The results indicated that the subsurface-flow CW could conserve significant macroinvertebrate biodiversity (total taxon richness 17). The community structure was influenced by habitat types (i.e., subsurface-flow vs. surface-flow CWs) under low pollutant stress, and this influence was somehow masked by influence of water quality under high pollutant stress. Good pollutant removal rates were obtained in decreasing the concentrations of total nitrogen (66.37% and 27.28%), total phosphorus (58.93% and 37.55%), and loadings of biochemical oxygen demand (28.38% and 73.71%) in QCWS and KCWS, respectively. This study implied that subsurface-flow CWs could achieved good performance in both water purification and biodiversity conservation, which could provide a more solid basis for the application of subsurface-flow CWs.

Impacts of Indian waterfern (Ceratopteris thalictroides (L.) Brongn.) infestation and removal on macroinvertebrate biodiversity and conservation in spring‐fed streams in the Australian arid zone

Abstract Removal of invasive macrophytes is a priority for river managers. However, the ecological effects of macrophyte removal on macroinvertebrate diversity are rarely examined but may be of particular significance in conservation reserves and when threatened species are present. This study investigated the macroinvertebrate fauna inhabiting invasive and native macrophytes in spring‐fed channels in the Millstream‐Chichester National Park, Australia. The effects of waterfern management (periodic hand‐weeding) were examined by comparing assemblages at weeded and unweeded reaches on three occasions. Ceratopteris thalictroides harboured a diverse, insect‐dominated macroinvertebrate assemblage, including the endangered damselfly Nososticta pilbara. Total taxon richness was similar between waterfern and native macrophytes, but macroinvertebrate assemblages differed in the dry season. Damselflies (including N. pilbara) were associated with waterfern‐dominated reaches, whereas dragonfly nymphs were more common among native macrophytes. Weeding altered macroinvertebrate assemblage composition. Some weeded reaches developed assemblages indistinguishable from those in native‐dominated reaches, but others did not. Weeded reaches often supported taxa that were rare or absent from waterfern‐dominated reaches, including suspension feeders, found also in native‐dominated reaches. Odonata are particularly diverse at Millstream, with 18 species recorded. Odonate species richness was significantly lower at weeded reaches than unweeded reaches. Nososticta pilbara and other short‐range endemic species were absent from weeded reaches. As most odonates are univoltine, these adverse effects on local population size may affect species persistence. Invasive macrophyte species may support a high diversity of native invertebrates, including endangered and short‐range endemic species. Furthermore, although hand‐weeding appeared to enable a greater diversity of species to co‐exist, the removal of a large biomass of macrophytes appeared to remove whole cohorts of insect populations from stream reaches, including endangered species. Removal of invasive macrophytes should not be implemented without understanding their effects on invertebrate assemblage composition and life‐cycles.

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

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

The effect of channelization on the biological quality of lowland streams using macroinvertebrates as proxies

We studied whether and how channelization affects macroinvertebrate communities and biological quality in lowland streams of Estonia (Northern Europe). Two datasets of semi-quantitative samples (collected during 2001–2010) were used: (1) pairwise data (natural sites located upstream of the channelized sites; 22 streams, 24 pairs), and (2) background data (73 natural sites from 62 streams, 73 channelized sites from 62 streams). The mean stream order in both datasets was 3. Channelization had no significant effects on physicochemical parameters or on macroinvertebrates in the pairwise dataset where channelization was done decades earlier. However, it had several negative effects on macroinvertebrates in the background dataset where several areas had probably been maintained more recently. Richness of sensitive data, Shannon diversity, mean sensitivity, organic pollution index, and multimetric quality were significantly lower for the modified sites than for the natural sites. Only total taxon richness and score of hydromorphology were not significantly affected by channelization. Thus, several macroinvertebrate metrics that indicate water pollution, proved to be sensitive to channelization as well. The recovery conditions (such as stream type, channelization season, recovering duration, etc.) have been poorly studied and would deserve further attention.

Spatial variability of the surf zone fish and macroinvertebrate community within dissipative sandy beaches in Oregon, USA

AbstractHabitat heterogeneity can influence biological communities by providing a diversity of areas that can be occupied by different species. Sandy beach surf zones are often considered homogenous environments; however, sand bars moved by currents and waves can produce trench‐like shapes or troughs that provide heterogeneity. The influence of habitat heterogeneity produced by sand movement is unclear despite the fact that surf zones are an important habitat for larval and juvenile fish and macrocrustaceans. To determine if, and how, the fish and macroinvertebrate communities present in trough and non‐trough or flat areas of Oregon surf zones differ, we compared species assemblages in both areas at three beaches adjacent to estuary mouths over 2 years. Troughs had different communities compared with flat areas, with higher total catch (mean ± SD = 123.2 ± 122.1 versus 43.6 ± 44.5 individuals × 100 m−2) and taxon richness (6.7 ± 2.7 versus 4.0 ± 2.3 taxa); these differences were potentially due to water movement, prey availability and sediment size. The fish and macroinvertebrate communities did not vary between years but there were significant differences among beaches, with the most distinct community present at the only beach adjacent to an estuary without a jetty at its mouth, which was possibly due to higher species movement between the surf zones and estuary. Fish and macrocrustacean surf zone communities varied spatially within and among beaches in relation to habitat heterogeneity provided by sand movement and, potentially, the influence of adjacent habitats.