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The article "Preface: Secrets of shallow lakes—insights from research" published in Hydrobiologia discusses the theme of 'Secrets of Shallow Lakes' and highlights the importance of ongoing research in understanding the mysteries of aquatic ecosystems. It emphasizes the need to monitor the health of water bodies, especially in the face of environmental problems and climate change. The article also provides insights from the 11th International Conference on Shallow Lakes held in Estonia, covering topics such as lake restoration, nutrient cycling, bioindicators, and mesocosm experiments. The research presented in the article underscores the complexity of lake ecosystems and the importance of integrated management approaches to protect and maintain ecological balance. [Extracted from the article]

Leaf litter breakdown is a critical process in streams, as it plays a significant role in influencing food webs and biogeochemical cycles. Highland grasslands are often understudied landscapes, yet they are an excellent model system for evaluating how natural differences in riparian forest cover can influence litter breakdown in streams. We experimentally examined the effects of the presence and absence of riparian forest on temporal leaf litter breakdown and the associated biota in highland grassland streams. The 3-year experiment examined leaf litter breakdown in three stream reaches with riparian forest and three without. The results indicate that temperature could potentially mediate the temporal dynamics of leaf litter breakdown (mainly fine mesh) and the associated biota in highland grassland streams. No differences were found in leaf breakdown between stream reach types, but there was evidence of an increase in invertebrate density. Finally, leaf litter breakdown in the highland grasslands was more affected by annual variation than riparian forest presence, suggesting a context-dependent relationship. [ABSTRACT FROM AUTHOR]

Trout-perch (Percopsis omiscomaycus) is an abundant, small-bodied, benthic fish species often found in deeper regions of large lake ecosystems. Historical evidence suggests that Trout-perch may participate in nearshore lake food webs by migrating from deep to shallow areas at night. However, little is known about Trout-perch ecology or their potential role in nearshore food webs. We used Trout-perch abundance estimates, diet analysis, and benthic invertebrate community surveys to (1) assess Trout-perch trophic ecology in Lake Champlain, USA/CAN, and (2) determine whether deepwater prey resources existed at sufficient densities to support Trout-perch populations or whether supplemental prey resources were required. Trout-perch showed variability in size and biomass across lake regions, but diet patterns were largely consistent across the lake, with > 50% of diets consisting of emergent insect larvae and oligochaetes. Results suggest that migrations into nearshore habitats may be required to sustain Lake Champlain's Trout-perch populations, and therefore, Trout-perch could function as conduits of allochthonous energy across distinct lake habitat boundaries. This study is one of only a few that have examined the trophic ecology of Trout-perch in deep lakes and fundamentally improves our understanding of energy flow and coupling between distinct lake food web compartments in large lakes. [ABSTRACT FROM AUTHOR]

Changing nutrient concentrations and introduction of non-native species affect the energy and nutrient fluxes in aquatic ecosystems. As a response, invertebrate communities could be altered, and 'novel' trophic communities could develop. Lake Constance (Europe) experienced pronounced nutrient variation caused by cultural eutrophication (prior 1980s) and oligotrophication (post-1980) and experienced many neobiota invasions. We used archived samples to investigate the impact of oligotrophication and invasive species on carbon and nitrogen isotope signatures of littoral macroinvertebrates during spring and autumn periods from 2000 to 2015 and of littoral fish species in 2018. Isotopic signatures of invertebrate and fish species were in the same range and showed similar seasonal differences and clear patterns in respect to littoral vs pelagic food sources and trophic level. Oligotrophication did not strongly alter isotopic values and only δ15N values of invertebrates declined weakly with oligotrophication. In contrast, interannual variability of stable isotope signatures was related to abundances of the invasive Dreissena polymorpha suggesting interannual differences in the importance of benthic-pelagic coupling due to Dreissena pseudofaeces for the nutrition of littoral invertebrates. This study illustrates how stored samples can be used to detect the importance of oligotrophication and benthic-pelagic coupling on the stable isotope signatures of a benthic community. [ABSTRACT FROM AUTHOR]

As the world becomes more urbanized, multiple stressors act in complex ways, but their effects remain poorly studied in coastal island streams. Due to the small length and isolation and the limited amount of freshwater available in the islands, these ecosystems are particularly vulnerable to anthropogenic pressures. Here, we investigated the effects of urbanization on taxonomic and functional diversity of aquatic invertebrate of a subtropical coastal island. Benthic invertebrate communities were sampled using litter bags (10 mm mesh) containing mixtures of leaf litter that were colonized in the stream bottom over 30 days. We hypothesized that invertebrate communities would show alteration in taxonomic and functional composition over the urbanization gradient. Based on the invertebrate communities and their biological traits, we computed the taxonomic richness and four functional diversity indices. Significant changes in taxonomic, functional richness, evenness, and dispersion were observed. Sites with low urbanization (< 5% urbanized area) had a higher proportion of taxa with gill respiration than sites with high level of urbanization (> 15% urbanized area) had higher proportion of taxa with tegument respiration. Sites with medium (15–5% urbanized area) and high urbanization levels exhibited higher proportions of scrapers and collector–gatherers, whereas sites with low urbanization had higher proportions of shredders and collector–filters. Our results show that urbanization changed the benthic communities and their biological traits. These changes can determine variations in the ecosystem processes and compromise the ecosystem services they supply. [ABSTRACT FROM AUTHOR]

Marine habitat-forming species create structurally complex habitats that host macroinvertebrate communities characterized by remarkable abundance and species richness. These habitat-forming species also play a fundamental role in creating favourable environmental conditions that promote biodiversity. The deployment of artificial structures is becoming a common practice to help offset habitat loss although with mixed results. This study investigated the suitability of artificial flexible turfs mimicking the articulated coralline algae (mimics) as habitat providers and the effect of ocean acidification (OA) on early stage ecological communities associated to flexible mimics and with the mature community associated to Ellisolandia elongata natural turfs. The mimics proved to be a suitable habitat for early stage communities. During the OA mesocosms experiment, the two substrates have been treated and analysed separately due to the difference between the two communities. For early stage ecological communities associated with the mimics, the lack of a biologically active substrate does not exacerbate the effect of OA. In fact, no significant differences were found between treatments in crustaceans, molluscs and polychaetes diversity and abundance associated with the mimics. In mature communities associated with natural turfs, buffering capability of E. elongata is supporting different taxonomic groups, except for molluscs, greatly susceptible to OA. [ABSTRACT FROM AUTHOR]

Invasion of non-native fishes threatens freshwater biodiversity worldwide. Yet, detailed estimates of population demography for invasive species, such as population size and body size, are rarely integrated in evaluating aquatic community responses. Our study capitalised on detailed brook trout population demographic data collected for a replicated whole lake ecosystem experiment involving experimental harvesting of exotic brook trout in nine mountain lakes. We applied environmental DNA (eDNA) metabarcoding and morphological taxonomy to examine the response of crustacean zooplankton and macroinvertebrate communities to gradients in brook trout effective density and lake elevation. Density-dependent effects of brook trout on crustacean zooplankton and macroinvertebrate communities were detected even decades after their first introductions (between 1926 & 1980). However, they were moderated by environmental factors such as elevation, lake maximum depth and dissolved organic carbon. Elevation was important in structuring crustacean zooplankton and macroinvertebrate community composition. While there were differences in explanatory variables when describing communities characterized by eDNA metabarcoding and morphological taxonomy, the principal environmental factors that structured the communities were similar. Our paper highlights persisting density-dependent impacts of exotic trout on invertebrate communities even decades after first introduction, and it considers the conservation implications for lake restoration. [ABSTRACT FROM AUTHOR]

Characterizing dispersal traits can further our ecological understanding of Neotropical stream macroinvertebrate communities, allowing us to test fundamental questions about disturbance and functional diversity responses in these systems. We combine observational and experimental approaches to measure short-term colonization of cobbles by stream invertebrates at five headwater streams arrayed along a habitat stability gradient in the Ecuadorian Andes, along with conducting drift and benthic surveys along the same gradient. Cobbles were sampled for benthic macroinvertebrate community composition and basal resource accrual at five time points over the 23-day experimental period. We found that taxonomic richness did not show clear trends across colonization time. Invertebrate community composition in the cobble colonization experiment did not approach the background benthic and drift composition over colonization time. Focal taxa showed variation in their drift and colonization propensities, with no clear relationship to habitat stability. We also found that benthic communities from less stable streams differed greatly between experimental years, highlighting the need to account for intra- and interannual differences in colonization experiments. [ABSTRACT FROM AUTHOR]

Metacommunity studies have demonstrated that local macroinvertebrate communities are structured not only by local environmental conditions but also by spatial processes. Effective bioassessment tools should account for spatial processes while doing so with the least amount of cost. In this study, we applied variance partition techniques based on redundancy analysis to assess the performance of three sets of benthic invertebrate metrics in detecting agricultural land-use effects in a SE Brazil rainforest watershed. Macroinvertebrate data were analyzed separately regarding their taxonomic, functional structure and bioindicator metrics developed for the study region. We stipulated that groups of metrics most sensitive to land-use effects should have the highest amount of variance explained by the joint effects of land use and environmental variation, independently of spatial structuring. Statistical analyses were repeated removing rare taxa in order to assess the effects of their inclusion in the responsiveness of each group of metrics. Traditional bioindicator metrics were more responsive to environmental variation associated with agriculture than taxa abundances and functional attributes. Furthermore, a few common taxa drove a high proportion of the variation observed in invertebrate communities, regardless of how invertebrate data were organized. Similar analytic approaches have the potential to be useful in curtailing sorting and identification efforts when developing macroinvertebrate-based biomonitoring protocols, especially in areas where information regarding the taxonomy of benthic communities is still poorly described. [ABSTRACT FROM AUTHOR]

Beavers and their dams, once common in small streams throughout Eurasia and North America, are returning to their original range. Beaver dams are special habitats in the aquatic-terrestrial interface, but their macroinvertebrate fauna is hardly known. This study aims to qualify and quantify the invertebrate fauna of beaver dams, taking into account the maintenance status of the dams. Nine different areas covering the top, middle and base zones of eight maintained and eight abandoned beaver dams were sampled using a specially designed suction device. The invertebrate community of beaver dams proved to be diverse and predominantly rheophilic. Community composition reflects higher flow velocities in streamside habitats; this gradient is more pronounced in maintained than in abandoned dams. Shredders are the most abundant feeding type, but they are less frequent in streamside habitats, in particular in those of maintained dams, where passive filter feeders prevail. Terrestrial/Semiaquatic taxa colonising hygropetric areas were found in streamside habitats especially of abandoned dams. Our results underline that beaver dams provide a wide variety of environmental conditions and habitat types, which enhance biodiversity in small streams and their floodplains. Beaver dams in riverine landscapes should therefore be much more valued in floodplain conservation and management. [ABSTRACT FROM AUTHOR]

In the United States, mine reclamation has been regulated under the Surface Mining Control and Reclamation Act (SMCRA) since 1977; however, there is a lack of research examining the efficacy of this legislation on restoring ecological structure and function in affected headwater streams. We compared water chemistry characteristics, rate of senescent white oak leaf litter processing, and invertebrate community composition of three first- and second-order streams draining surface mines reclaimed in accordance with SMCRA to that of streams draining three pre-SMCRA abandoned surface mines and three unmined reference watersheds within the Western Allegheny Plateau ecoregion of Ohio. Streams draining reclaimed and abandoned mines had lower pH, higher conductivity, and leaf processing rates that averaged 7 and 24 times lower, respectively, than reference streams. The invertebrate community composition of reclaimed streams differed in several respects from abandoned mine and reference streams, including a shift in proportional dominance from leaf shredding taxa to grazing and scraping taxa, such as gastropods. Although SMCRA has successfully mitigated some sources of water quality impairment, our results suggest that mine drainage remains a persistent barrier to the restoration of headwater stream ecology in mined landscapes. [ABSTRACT FROM AUTHOR]

Recent waves of illegal deforestation for cattle pasture are damaging the Indio Maíz Biological Reserve and Rama-Kriol Territory of Nicaragua, with negative consequences to aquatic ecosystems and the people they support. This study creates a framework for how deforestation from cattle ranching causes shifts in stream community structure, mediated by changes in stream habitat over time. It integrates temporally explicit land use information with stream habitat, macroinvertebrate, freshwater shrimp, and fish community data to assess impacts of cattle ranching on 15 headwater streams. The deforestation history measure (DHM), a product of deforestation amount and time since deforestation for each catchment, strongly predicted stream habitat and biotic responses. Delayed effects of land-use change such as decreased allochthonous inputs (large wood, debris) and increased bank destabilization, sedimentation, flashiness, and the scouring effect were apparent in longer deforested catchments, causing lower richness and density and higher evenness of macroinvertebrates; lower shrimp abundance; and distinct changes in fish and invertebrate community composition. Both recently and longer deforested catchments had degraded riparia and smaller sized game fish. Otherwise, recently deforested catchments were more similar to forested catchments. Nicaragua's understudied primary rainforest ecosystems should be high priority for research and conservation before they are lost. [ABSTRACT FROM AUTHOR]

To assess how the presence of an invasive plant and different-sized decomposers affect plant litter decomposition under different seasonal conditions, we allocated leaves of native Ficus virens Aiton into four different mesh sizes (0.025, 0.042, 0.5 and 5 mm) with and without invasive Alternanthera philoxeroides (Mart.) Griseb. We incubated them for 65 days in an eutrophic lake in summer and winter respectively. The average decomposition rate was significantly higher in summer than in winter, and was significantly higher in mixtures than in F. virens monocultures in both seasons. The presence of A. philoxeroides in the mixture significantly increased invertebrate density and microbial respiration rates in summer but not in winter. Furthermore, contribution of invertebrates to decomposition was higher in the early stage of decomposition and lower in the late stage in summer, yet that of microbes was relatively constant in winter. Contribution of microinvertebrates increased in summer but that of meio-, macroinvertebrates increased in winter. Our findings indicate that the presence of an invasive plant altered litter decomposition, which may depend on seasonal variations, invertebrate density and decomposition stages. [ABSTRACT FROM AUTHOR]

Groundwater withdrawal has increased on multiple continents which poses risks for groundwater-dependent ecosystems. Few studies have simultaneously evaluated how multiple communities are impacted by experimental discharge reduction in streams. Our main objective was to assess how discharge reduction influenced benthic algae, invertebrates and fish in a groundwater-dependent stream. We experimentally reduced discharge by 40–60% in a third-order stream during a one-year period based on a Before-After-Control-Impact design. Discharge reduction decreased sediment grain size, mean water depth, and mean water velocity but not wetted width, wetted area or water quality. Discharge reduction caused decreases in the cell density of benthic algae but not in chlorophyll-a abundance. The total density of benthic invertebrates and of the most common taxa, as well as invertebrate taxa richness and diversity, were not impacted by discharge reduction. However, discharge reduction decreased the abundance and biomass of brown trout (Salmo trutta) and of the entire fish community. The abundance of large brown trout was disproportionately impacted by discharge reduction. Our results suggest that responses to discharge reduction in streams may be community- and taxon specific. Moderate discharge reduction can negatively impact ecosystem services provided by coldwater streams by affecting the habitat and abundance of salmonids. [ABSTRACT FROM AUTHOR]

Temporary rivers (TRs) dominate global river networks and are increasing in occurrence and spatiotemporal extent. However, few studies have investigated the communities that establish after rewetting events (i.e. the end of the dry phase), when local hydrological conditions can shape the communities through species sorting, and the spatial connectivity of sites can also influence colonisation. Here, we analysed the relative importance of both local hydrological conditions and spatial connectivity on the invertebrate communities of seven not impacted Mediterranean TRs after rewetting. We quantified the frequency and duration of drying events and the time since flow resumed. We also quantified spatial connectivity based on each site's position in the river network (i.e. network connectivity) and the presence of nearby disconnected streams. Overall, we found that both hydrological conditions and network connectivity played a significant role in structuring aquatic invertebrate communities after rewetting. Taxonomic richness, functional richness and functional redundancy decreased with the frequency and duration of drying events and increased with time since the most recent rewetting. Network connectivity showed a significant unimodal relationship with taxonomic and functional metrics. In contrast, the presence of nearby disconnected streams was negatively related to functional richness and functional dispersion. Given that flow intermittence in Mediterranean areas is expected to intensify under future global change scenarios, our results can be helpful to guide future conservation and management actions. [ABSTRACT FROM AUTHOR]

To investigate the effect of invasive Alternanthera philoxeroides mats on native leaf litter decomposition, we allocated two native leaf species of contrasting recalcitrance (Neosinocalamus affinis and Ficus virens) in litterbags with four different mesh sizes (0.025, 0.042, 0.5, and 5 mm) and the bags were either incubated under floating A. philoxeroides mats (Vegetated site) or under floating plastic foam boards without A. philoxeroides mats (Unvegetated site) for 65 days in Jianhu Lake, China, in July 2020. The average decomposition rates increased with pore size of litterbags. The interaction intensity of the site effect in leaf mass loss was negative in 0.025 mesh and positive in other meshes, while no significance existed between two native species in the same mesh sizes and sites. The contribution of microbes to decomposition was more than 50% in both sites. The contribution in the vegetation site was as follows: microbes > microinvertebrates > meioinvertebrates > macroinvertebrates, compared with microbes > macroinvertebrates > meioinvertebrates > microinvertebrates in the unvegetated site. The results suggest that A. philoxeroides mats can promote the decomposition of native leaf litter, and that the roles of micro-, meio-, and macroinvertebrates in decomposition are important but underestimated. [ABSTRACT FROM AUTHOR]

The Mediterranean region with its islands is among the top biodiversity hotspots. It houses numerous freshwater taxa with a high rate of endemism, but is heavily impacted by anthropogenic pressures and global climate change. To conserve biodiversity, reliable data on species and genetic diversity are needed especially for the scarcely known insular freshwater ecosystems. Environmental DNA (eDNA) metabarcoding provides a straight-forward opportunity to assess aquatic biodiversity. Therefore, we conducted the first eDNA metabarcoding study in one stream catchment on Sicily. Specifically, we aimed to (i) investigate spatial diversity patterns of macroinvertebrate communities, (ii) assess seasonal changes (autumn and winter), and (iii) check if dispersal barriers can be identified. Water samples were taken at 27 different sites in two seasons and eDNA metabarcoding was performed using a fragment of the mitochondrial cytochrome c oxidase subunit I gene as a marker. In total, we detected 98 macroinvertebrate species, including 28 taxa potentially new to Sicily. Exact sequence variant and species composition data showed that diversity differed between seasons with less taxa detected in winter. We also detected a dispersal barrier, which had a stronger effect in autumn. Our findings show that eDNA metabarcoding provides valuable information on Sicilian freshwater biodiversity. We therefore encourage its application for understudied regions to better understand the state and dynamics of freshwater biodiversity. [ABSTRACT FROM AUTHOR]

Fire retardants are commonly used for fighting wildfires. Retardant chemicals washed via runoff into aquatic systems may be concentrated, thus exposing aquatic species to high levels of ammonium, phosphate, and iron. These chemicals directly affect individual species, which can also cascade to the rest of the aquatic community. We investigated the effects of a prevalent fire retardant, FR CROS 134 (FR), at various concentrations (0 to 11.4 × 102 mg l−1) on larval fire salamander (Salamandra infraimmaculata) and aquatic community structure (bacteria, algae and invertebrates) using mesocosms. We show a negative effect of the presence of FR on the survivorship and time to metamorphosis of salamander larvae (94–17% and 48–64 days, respectively). Moreover, increasing FR concentrations were found to inhibit the predation rate of salamander larvae on mosquito larvae (89–14%). FR decreased the invertebrate community diversity with changes in composition and shifts in evenness and dominance (e.g., cladoceran species abundance increased, whereas calanoid copepod species declined). Finally, cyanobacteria and eukaryotic algal abundance increased, while heterotrophic bacterial abundance decreased with FR addition. The effects of fire retardants on biodiversity found here and the growing use of fire retardants worldwide call for additional evidence-based assessment of their impact, especially in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Sediment flushing from dams can help desilting reservoirs and reinstate the longitudinal sediment transfer continuity in rivers, but negative ecological impacts might arise. We monitored the ecological effects of a flushing event conducted from 27th May to 14th June 2019 in the Rienz River, in South Tyrol (NE Italy). Using a multi-habitat scheme approach, we collected macroinvertebrates 10 days before, and then 40 and 74 days after the completion of the operations. We selected seven biological traits—organism size, life cycle duration, mobility (dispersal and locomotion), feeding type, substrate and current velocity preference—to characterize and compare the invertebrate communities before and after the sediment pulse disturbance. Turbidity was recorded continuously for the entire duration of the event. Results indicate that invertebrate assemblages exhibited a general decrease in taxonomic richness and Shannon diversity 40 days after the event, but density and richness recovered over time. Shifts in species composition were observed in post flushing samples, with a reduction in density of sensitive species (Heptageniidae) and shredders. Post-flushing samples were generally characterized by sediment-tolerant taxa, able to cope with the new habitat conditions. Altered taxonomic and functional community composition following the flushing prevented the full functional recovery to pre-disturbance conditions. [ABSTRACT FROM AUTHOR]

Guest editors: David J. Hoeinghaus, Jaquelini O. Zeni, Gabriel L. Brejão, Rafael P. Leitão & Renata G. Frederico / Neotropical Stream Fish Ecology in a Changing Landscape The Neotropical Region holds the richest diversity in the world in both terrestrial and aquatic ecosystems. Such impacts can compromise the conservation of the biodiversity and hamper the ecosystem services provided by fish (Pelicice et al., [12]), particularly in these highly biodiverse Neotropical freshwater ecosystems. Roa-Fuentes et al. ([13]) investigated agroecosystems and highlighted the importance of local drivers for maintaining stream fish biodiversity in these ecosystems. [Extracted from the article]

Intermittent stream research focuses mostly on pristine streams. The impacts of nutrient enrichment on invertebrate communities in these systems thus remains underexplored, especially in temperate climates. This study aimed to compare taxa survival during stream drying within pristine and nutrient-enriched sediment streambeds and to evaluate seedbank contribution for community recovery. Ten dry sediment subsamples were each collected from three streams of each nutrient status type. These were rehydrated for 60 days in laboratory with persisting and hatching invertebrates being recorded. Oligochaetes and molluscs were the most abundant; stoneflies and mayflies were common; caddisflies were represented by only a few specimens. The seedbank comprised of around one-third of taxa recorded during flow phases with slightly higher taxa numbers in nutrient-enriched streams. Moisture content positively affected seedbank taxa richness, while dry period duration decreased it. Taxa richness has a unimodal response to nutrient enrichment, with fine sediment proportion revealing no significant effect. Our results show a richer macroinvertebrate seedbank in drying sediments under moist conditions with mild nutrient enrichment, while raised nutrient levels limited macroinvertebrate survival. These results highlight the crucial role of seedbanks in community recovery of intermittent temperate streams, which will become more common with climate change. [ABSTRACT FROM AUTHOR]

Environmental productivity and biodiversity are two intricately linked ecological concepts. One commonly observed pattern is a unimodal curve with biodiversity peaking at intermediate levels of productivity. While unimodal relationships are by no means universal, biodiversity declines at high productivity levels (eutrophication) raise serious concerns given anthropogenic nutrient inputs into waterbodies. One habitat that may be particularly vulnerable to eutrophication are California vernal pools. These ephemeral wetlands provide habitat to numerous threatened or endangered invertebrate taxa. To investigate the impact of eutrophication on invertebrates, experimental mesocosms were setup in the California State University, Sacramento Arboretum. Thirty mesocosms were inoculated with vernal pool soil and divided into five nutrient treatments in each of six blocks. Data was collected over a 21-week hydroperiod to quantify changes over a vernal pool hydroperiod. Nutrient addition increased mesocosm turbidity, chlorophyll-a, and phosphorus levels, in addition to causing larger shifts in dissolved oxygen and pH. While nutrient enrichment increased abundances of small crustaceans, there were no effects on taxa richness, or abundances of large branchiopods or insects. While these findings improve our understanding of bottom-up effects in vernal pools, questions remain over long-term nutrient inputs and interactions with other human activities. [ABSTRACT FROM AUTHOR]

Headwater streams subjected to anthropogenic impacts are prone to environmental quality decay, which may affect stream functioning. To investigate the effects of loss of environmental quality in stream functioning, we tested the hypothesis that leaf breakdown is faster in streams with higher environmental quality, and that invertebrate community structure and microbial biomass are negatively affected by habitat simplification resulting from environmental degradation. We submerged Alchornea glandulosa leaves in litter bags in nine streams, in Southern Brazil, in an environmental gradient. We characterized breakdown rates (k), physical in-stream characteristics, abundance of invertebrate taxa, and functional groups and microbial biomass for each stream, with three mesh exclusions (fine, medium, coarse). Breakdown was faster in the most preserved stream (k = − 0.032 ± 0.005) and decreased towards the most disturbed stream (k = − 0.0034 ± 0.001). Breakdown rates were positively associated with underwater habitat complexity, equitability of macroinvertebrate taxa, and abundance of Stenochironomus sp., which together explained 51% of breakdown rate variability. Breakdown rates from the less disturbed streams (n = 7, excluding urban-influenced) were lowest in medium-mesh, intermediate in fine-mesh, and highest in coarse-mesh bags, and the only taxon that differed according to this pattern was the mining-chironomid Stenochironomus sp., which suggests that this taxon had a significant activity of leaf processing. [ABSTRACT FROM AUTHOR]

The diversity of aquatic macrophytes can offer different local conditions required to support an increased number of microhabitats, therefore resulting in diverse biotic communities. This study assessed the influence of macrophyte diversity on the ecological attributes of the associated invertebrates (diversity, richness and abundance), as well as the diet composition of a small fish, Moenkhausia forestii, that inhabits the Upper Paraná River floodplain in abundance, and present great contributions of invertebrates in its diet. The richness and diversity of invertebrates increased with increasing macrophyte diversity, while the abundance of invertebrates didn't show a significant relationship. The diet of M. forestii differed among stands and the consumption of invertebrates increased with increasing macrophyte diversity, while the consumption of aquatic plants decreased. Moreover, the trophic niche breadth of M. forestii expanded, a probable result of the increase in the ecological opportunity promoted by higher macrophyte diversity. Our study emphasizes the importance of the diversity of these plants as they structure the environment and the associated communities, and changes in the attributes of these plants could be reflected on other trophic levels and even on a local scale. [ABSTRACT FROM AUTHOR]

Many life-history events in aquatic invertebrates are triggered by seasonal changes in water temperature, but other ecological factors may be important as well. To rule out the confounding effects of changing water temperature, we studied the seasonal dynamics of an aquatic invertebrate community and their effect on a top fish predator in a thermally stable freshwater spring in South Iceland. We sampled benthic invertebrates five times over a year and conducted a mark-recapture study on the top predator in the system, small benthic Arctic charr, Salvelinus alpinus (L.). We assessed variation in diet composition and feeding preferences by calculating the electivity and individual specialisation of each fish at each sampling time. There was a clear separation of winter and summer communities for the benthic invertebrates. The variation in prey availability was also reflected in the fish diet, with higher feeding selectivity in summer than in winter for the highly abundant Chironomidae larvae. In contrast, individual specialisation as a measure of intrapopulation niche variation was higher in winter when prey availability was lower. We furthermore found that groundwater amphipods might play an important role in the winter diet of spring-dwelling Arctic charr. In conclusion, seasonal variation in the invertebrate community is an important factor to consider and has the potential to alter the phenotype (e.g. growth rates) and behaviour (e.g. feeding preferences) of higher trophic levels. [ABSTRACT FROM AUTHOR]

The hyporheic zone (HZ) of streams harbors co-occurring epigean taxa and stygobionts (including HZ specialist taxa and deeper groundwater taxa) that face the same set of local environmental factors, but are derived from spatially and functionally discrete colonist pools. We investigate whether occurrences of epigean taxa and stygobionts are differentially influenced by the same set of environmental variables in HZ samples from Texas, USA. We increase the number of records for described stygobionts in the state by nearly 12%, but 26 stygobionts (35%) were undescribed species. Stygobionts had smaller average ranges (3549 km2) than epigean taxa (24,046 km2), but occurred in similar abundances. Dissolved oxygen and temperature influenced community composition in both groups, but stygobiont community composition, richness, and abundance were influenced by association with karst aquifers and surface water-groundwater exchange, whereas epigean taxa composition was only weakly influenced by the association with karst aquifers. Contrasts between epigean taxa and stygobiont occurrence patterns are primarily explained by differences in range size, dispersal ability, and the pool of potential colonizer species. This first documentation of Texas HZ communities includes 14 stygobionts previously recorded only from karst aquifers: their discovery in the HZ has important management implications. [ABSTRACT FROM AUTHOR]

Simplification of communities is a common consequence of anthropogenic modification. However, the prevalence and mechanisms of biotic homogenization among wetland systems require further examination. Biota of wetlands in the North American Prairie Pothole Region are adapted to high spatial and temporal variability in ponded-water duration and salinity. Recent climate change, however, has resulted in decreased hydrologic variability. Land-use changes have exacerbated this loss of variability. We used aquatic-macroinvertebrate data from 16 prairie-pothole wetlands sampled between 1992 and 2015 to explore homogenization of wetland communities. Macroinvertebrate communities of small wetlands that continued to cycle between wet and dry phases experienced greater turnover and supported unique taxa compared to larger wetlands that shifted towards less dynamic permanently ponded, lake-like regimes. Temporal turnover in beta-diversity was lowest in these permanently ponded wetlands. Additionally, wetlands that shifted to permanently ponded regimes also experienced a shift from palustrine to lacustrine communities. While increased pond permanence can increase species and overall beta-diversity in local areas previously lacking lake communities, homogenization of wetland communities at a larger, landscape scale can result in an overall loss of biodiversity as the diverse communities of many wetland systems become increasingly similar to those of lakes. [ABSTRACT FROM AUTHOR]

We investigated the main seasonal drivers of Phragmites australis decomposition dynamics in a freshwater karst lake subject to water level fluctuations. Physical and chemical parameters were monitored every two weeks for one year and P. australis decomposition rates were measured using the leaf bag technique during two seasons (autumn and spring). Decomposition dynamics were analyzed for the contribution of macrobenthic invertebrate colonizers and the influence of intermittent water level variations. Seasonal trends for changes in physical and chemical parameters were observed in relation to the underground origin of the water supply, which also affected the macrobenthic invertebrate communities. Decomposition rates k differed significantly between seasons (k = 0.0131 in autumn and k = 0.0115 in spring) but remained within a narrow range, reflecting the trend for changes in water temperature. Our findings show that the variability in decomposition rates was largely due to water level fluctuations (46.7% relative importance), rainfall (12.4% relative importance) and macrobenthic invertebrate communities dominated by shredders (23.9% relative importance; 40.9–93.7% of the collected samples). The influence of physical and chemical changes, particularly water temperature, was less important (relative importance 1.82%). [ABSTRACT FROM AUTHOR]

Top predator foraging strategy and prey base community composition can influence food web structure and function. To investigate the role of functional trait diversity and taxonomic richness in determining food chain length and energy flow in high elevation desert streams, we examined aquatic invertebrate community data along with carbon and nitrogen stable isotope analysis of a top predator, Abedus herberti (giant water bug). We also examined isotopic niche differences across different levels of population structure and seasons. We hypothesized that communities with higher richness would have longer food chains. We found food chain length did not vary substantially across a wide taxonomic and functional richness gradient, which contradicts theoretical mechanisms stating that more resources or higher functional diversity should lead to longer food chains. The isotopic niche of A. herberti was conserved across seasons and sites, and the majority of carbon in tissues came from allochthonous materials. Stable isotopes suggested that A. herberti occupy similar feeding niches in spring and autumn, despite seasonal changes in stream conditions, leaf litter inputs, and invertebrate community structure. Due to the strong aquatic–terrestrial linkages we identified, human activities and climate-driven alterations to the adjacent terrestrial environment may affect the dynamics and integrity of the within-stream ecosystem. [ABSTRACT FROM AUTHOR]

Didymosphenia geminata is a bloom-forming diatom that has invaded numerous temperate rivers globally. Proliferations of D. geminata can result in negative effects on invaded communities. Ecological theory suggests impacts may vary associated with trait variation in both invaded communities and the invader. Trait commonalities related to organism size are rarely considered, yet are expected to influence the outcomes of ecological (niche and neutral) processes and invader effects. We hypothesised that D. geminata would impact diversity and community composition, with effects varying between size classes, influenced by niche and spatial gradients. To examine this hypothesis, we surveyed 55 rivers along a gradient of D. geminata biomass in the South Island, New Zealand, collecting data on algal and invertebrate communities, 33 spatial predictors, and 111 physical and chemical predictors. Didymosphenia geminata biomass was associated with increased species richness in both algal and invertebrate assemblages, but blooms reduced beta-diversity resulting in more homogenous communities. Both niche and neutral processes influenced community assembly and invader effects, which varied between algae and invertebrates. However, D. geminata appeared to have a dominant influence on both communities, irrespective of organism size. These findings reinforce the substantial negative effect invasive species such as D. geminata can cause in invaded ecosystems. [ABSTRACT FROM AUTHOR]

Oxidized manganese (Mn) forms tightly bound, dark precipitates on exposed rock surfaces in rivers, which could impact benthic communities. We combined a field survey with two experiments to identify patterns in benthic invertebrate community structure and potential mechanisms creating these patterns on substrates coated with Mn oxides and on 'uncoated' substrates in a large gravel-bed river. Uncoated substrate had roughly seven times higher densities of benthic macroinvertebrates, particularly fixed retreat filter feeders such as Brachycentrus, Rheotanytarsus, and Hydropsyche, while clinger taxa had similar densities between coated and uncoated substrates. In a substrate preference experiment conducted in laboratory microcosms, nymphs of a swimming mayfly (Isonychia bicolor) were more likely to avoid Mn-coated than uncoated substrate, while nymphs of a clinger mayfly family (Heptageniidae) showed no significant substrate preference or avoidance. In a field colonization experiment, invertebrate communities established on Mn-coated substrate had significantly higher variability in taxonomic composition but similar densities to communities on uncoated rocks. Combined, these results demonstrate a large difference in biological communities and describe patterns that occur during community assembly on Mn-coated substrate. While established communities responded negatively to Mn oxides, our results indicated coated substrate might also create community heterogeneity within large river riffle habitats. [ABSTRACT FROM AUTHOR]

In temperate headwater streams, intra-annual variation in energy input is critical in influencing aquatic food webs. We used stable isotope analysis to explore how seasonal variation in energy sources likely influenced invertebrate composition together with isotopic niche patterns of a cyprinid minnow, the chubbyhead barb Enteromius anoplus within a southern temperate headwater stream. Basal food sources had lower carbon and nitrogen stable isotope values in winter and spring compared to summer and autumn. Seasonal variations in the aquatic invertebrate communities were depicted by differences in the composition of gatherer and predator groups together with occurrence of scrapers in summer. Temporal changes in the isotopic values of these invertebrate groups appeared to coincide with that of basal food resources. The chubbyhead barb exhibited seasonal variation that was characterised by larger isotopic niches in winter compared to summer. Tissue-specific comparisons revealed larger isotope niche size based on fin tissue than muscle tissue during the cold period but comparable isotope niche sizes in the warm period. Contrasting inter-tissue isotopic niche patterns, the cold period suggested the likelihood of tissue physiological differences. Comparable isotopic niche patterns in summer and autumn suggested the possibility of synchronised physiological processes for both tissues. This suggested the potential for fin tissue as non-lethal alternative when inferring food web dynamics for this species. [ABSTRACT FROM AUTHOR]

We evaluated the influence of mesohabitats and catchments on the structural and functional composition of invertebrate communities associated with leaf patches in Atlantic Forest streams. We hypothesized that invertebrate communities would be more influenced by inter-habitat than inter-catchment variation, i.e., invertebrate taxonomic and trophic composition would differ more between pools and riffles than among catchments. Invertebrate richness differed among catchments only, while values of total abundance and biomass were higher in pools. The influence of mesohabitats on the structure of invertebrate communities was high, and most taxa had specificities with one mesohabitat. Among insect shredders, Grypopterigidae (Plecoptera) and Blattodea occurred more in riffles; Phylloicus, Nectopsyche, and Triplectides (Trichoptera) occurred more in pools. The biomass of omnivorous macroconsumers ( Trichodactylus fluviatilis and Macrobrachium potiuna) was higher in pools and also differed among catchments. Except gathering-collectors, the taxonomic composition of functional feeding groups differed between pools and riffles. The obtained results corroborated the hypothesis that the structural and functional composition of invertebrate communities is more influenced by inter-habitat than by inter-catchment variation, and reinforced the importance of maintaining the biological and geomorphological characteristics of streams to allow the accumulation of leaves in different mesohabitats and preserve the aquatic biodiversity. [ABSTRACT FROM AUTHOR]

Species inhabiting intermittent streams must survive flow cessation and drying in situ (resistance) or recolonize temporary habitats when flow returns (resilience). Some studies have found that species are resistant to seasonal drying and can persist in small remnant pools after flow ceases, while others observed rapid declines in species richness when flow ceases. However, relatively few studies have demonstrated both resistance across dry seasons and resilience across multiple wet and dry cycles. Here, we quantify seasonal and interannual changes in aquatic invertebrate community structure from 2009 to 2012 in a coastal California intermittent stream. We predicted that temporary pools and riffles would have lower richness and distinct assemblages when compared to perennial pools, and that richness would decline across the dry season. Temporary riffles exhibited lower richness values than pools, but we found no richness differences, and small compositional differences, between perennial and temporary pools. Furthermore, invertebrate richness, density, and composition changed significantly in temporary pools only immediately before drying, when depths declined >80%. These results suggest that invertebrate communities at John West Fork were not only resilient (exhibiting recovery in <6 months) to flow cessation, but also were resistant to declining water levels across the dry season. [ABSTRACT FROM AUTHOR]

Deforestation of riparian forests can directly influence stream macroinvertebrate communities, through changes in resource availability, habitat quality, and hydrological alterations. Here we evaluated whether mean discharge and discharge coefficient of variation (CV), estimated over a 15-month study, influenced forested and deforested stream macroinvertebrate communities. Higher diversity and mean discharge were recorded in deforested streams, and community composition was strongly related to mean discharge. Streams formed a gradient of both mean discharges and discharge CV, which both influenced patterns of diversity. Discharge CV negatively influenced diversity in a nonlinear model, whereas both mean discharge and discharge CV influenced differentiation of macroinvertebrate communities among five sampling occasions. Similarity among sampling times within each stream estimated by the Morisita-Horn index decreased with increasing mean discharge, whereas response to CV was quadratic, with higher similarity at intermediate values and lower similarity at more extreme values. These results suggest that stability of stream macroinvertebrate communities display different responses to mean discharge and discharge CV, and that hydrological alterations can interact with land use changes to determine community dynamics at local scales. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Bryophytes are known to provide habitat and refugia for stream invertebrates, but there are few reports documenting use of bryophytes in tropical streams. We investigated invertebrate assemblages in moss in pools, runs and riffles from wet to dry seasons in tropical Australian streams. We investigated assemblage dynamics, responses to disturbance, the importance of flow, and use of moss for establishment and habitat. Invertebrates had higher diversity in moss than other habitats (in riffles, 23 vs. 11-19 families in 3 other habitats; in pools, 24 vs. 15-20 families), and greater abundance, especially of small individuals (riffles: ~59,000 vs. ~9000-23,000 m; pools: ~52,000 vs. ~10,000-36,000 m). Densities increased as flow and moss availability declined. Artificial disturbance (heavy abrasion) removed ~70% of individuals and 40% of taxa, but responses of different taxa varied between pools and riffles. In a colonisation experiment, natural densities were achieved in 8 weeks. Transplanting of artificial moss between pools and riffles demonstrated high invertebrate fidelity to the moss habitat, except for loss or gain of a few flow-dependent taxa in riffle-pool and pool-riffle transplants, respectively. Thus, moss has a substantial role in providing habitat, refugia and nursery sites for many invertebrate taxa in tropical streams. [ABSTRACT FROM AUTHOR]

The Santa Cruz River is the last free-flowing river in Argentinean Patagonia. Two dams are projected, and no comprehensive pre-impoundment study has been undertaken. The present study investigated macroinvertebrate communities along three different hydrological periods and at three river sections located upstream and downstream of future dams. Fifty-three macroinvertebrate taxa were identified, with the most abundant orders being Ephemeroptera, Plecoptera, Coleoptera, and Crustacea (particularly amphipods). Ordination methods (CCA) and generalized linear models (GLM) were applied. According to the CCA, the main environmental variables related to macroinvertebrate density were temperature, suspended solids, depth, and substrate size. For the GLM, the main factors associated with macroinvertebrate abundance were location and hydrological period, and variables with the highest influences were temperature, substrate size, current speed, and depth. We anticipate that dam construction will modify in-stream habitat conditions, leading to changes in (i) macroinvertebrate community structure and (ii) local fish abundance due to loss of key prey taxa. [ABSTRACT FROM AUTHOR]

Mediterranean rivers are hotspots for biodiversity, and riverine species are adapted to regular physical perturbations that affect channel morphology during flashy rainfall-runoff events. Dams alter flow regimes, changing flood magnitude and frequency; they also interrupt the continuity of sediment transport. Changes in both flood and sediment transport regimes affect downstream channel dynamics and the ecological functioning of fluvial systems. This paper examines the effects of flow regulation on bed disturbance, invertebrate assemblages and their biological traits in a Mediterranean river (the Siurana, NE Iberian Peninsula). Results are put in the broader context of the whole Ebro river catchment. The Siurana Reservoir causes a complete inversion of the seasonal flow regime and reduces flood magnitude notably. Upstream from the reservoir, torrential floods mobilize surface and subsurface bed materials, regularly disturbing the physical habitat; downstream, geomorphological activity in the channel is almost nonexistent. Altogether, damming causes significant differences in taxonomic composition of the benthic invertebrate communities; density and biomass increase notably below the dam although diversity decreases. At the broader scale taxa with active aerial dispersal traits dominate unregulated reaches in areas with marked Mediterranean hydro-climatic regimes, whereas reaches with more stable regimes are characterized by fully aquatic detritivore species. [ABSTRACT FROM AUTHOR]

The distribution of macroinvertebrates in the heads and tails of riffles were examined in an in situ field experiment under stable baseflow conditions. Paired colonisation cylinders were used to examine the influence of vertical hydraulic exchange (upwelling and downwelling) and horizontal interstitial flow on the patterns of sedimentation and invertebrate colonisation. Sedimentation rates were greatest in cylinders permitting vertical and horizontal flow (VHE cylinders), and were significantly lower (29%) in cylinders where only vertical flow and ingress of fine sediment were possible (VE cylinders). The results demonstrate that horizontal interstitial flows represent an important pathway for fine sediment transport. Differences in fine sediment accumulation were also observed between riffle heads and tails. Significantly higher sedimentation rates were recorded in riffle tails, with the macroinvertebrate communities characterised by larger proportions of fine sediment tolerant taxa. In contrast, riffle head communities were characterised by greater proportions of sediment sensitive taxa, and in the case of VHE cylinders, shredders and EPT taxa. The results demonstrate that spatial differences in fine sediment deposition are evident at the riffle scale as a function of vertical and horizontal subsurface flows and that these factors play a key role in the distribution of macroinvertebrate fauna. [ABSTRACT FROM AUTHOR]

Seamounts in the Ross Sea were surveyed during the New Zealand IPY-CAML research voyage in 2008. Admiralty seamount, and seamounts of the Scott Island Seamount chain (Scott Island, Scott A, Scott B, Scott South) were sampled to examine variability in benthic faunal communities of seamounts. Multivariate analysis of video and still image data showed that benthic community composition was highly variable both within and between seamounts. The distribution patterns of benthic communities varied considerably, with very high densities of certain taxa in some places, sparse fauna in many others, and highly patchy distributions for others. Dissimilarities between seamounts were influenced by differences in population densities of taxa, the proportions of transects in which taxa were present, and by taxa being restricted to only one seamount or group of seamounts. Scott Island seamount was less similar to the others, despite the greater distances between Admiralty and Scott A and B seamounts. The observed variability in community composition was mainly associated with differences in depth, chlorophyll concentration, and seabed rugosity. Results support an earlier hypothesis that the location of seamounts relative to the Ross Sea gyre could be an important factor determining the composition and abundance of benthic invertebrate communities. [ABSTRACT FROM AUTHOR]

Many tropical regions lack models predicting the biological and environmental conditions expected in any given area, thus precluding the implementation of reference condition-based water policies. We focused on streams of French Guiana, and tested two predictions: geomorphology determines ecological sub-regions that have typical invertebrate communities, and diversity declines as anthropogenic pressure increases. Sixty-five stream sites were sampled for benthic invertebrates and physical-chemical variables across various watersheds. We used the Self-Organizing Map algorithm (neural network) to model relationships between invertebrate communities and environmental variables. Sites characterized by invertebrate communities clustered into two major subsets matching French Guiana's hydro-ecoregions: the coastal alluvial plain characterized by recent sediment and low elevations, and the Guiana Shield characterized by an eroded rocky substrate and dense rainforests. Changes in community composition, and to a lesser extent taxonomic richness within each sub-region revealed ecological impacts of gold mining and logging, further clustering hydro-ecoregions into subsets of reference and impaired sites. Further analyses would, however, be needed to identify tipping points between natural and disturbed states, especially in remote headwater streams where gold mining had the harsher impact upon freshwater diversity, making upstream communities resembling the most downstream impacted ones. [ABSTRACT FROM AUTHOR]

Non-native trout species have been associated with many negative effects in receiving ecosystems. The first aim of this study was to determine the impact of non-native rainbow trout Oncorhynchus mykiss on distribution and abundance of native mountain catfish Amphilius uranoscopus within Afro-montane streams in Nyanga Mountains, eastern Zimbabwe. The second aim was to compare macro-invertebrate community responses to the presence of the trout and the catfish. We examined trout impact on catfish's habitat associations, whereas macro-invertebrate composition was compared using open fish and fish exclosure experiments in habitats with and without trout. Trout influenced both the distribution and abundance of the catfish that occupied shallow reaches possibly to avoid predation from trout that occurred in the deeper habitats. Within trout invaded reaches, most macro-invertebrate taxa were more abundant in exclosure than open treatments. By contrast, within trout-free reaches, most macro-invertebrates either did not differ between treatments or were generally more abundant in open than exclosure treatments. This suggests that the macro-invertebrate communities responded differently within invaded and non-invaded reaches. By influencing distribution and abundance of native biota, non-native rainbow trout may have wider ecological effects, such as influencing trophic interrelationships within invaded habitats. [ABSTRACT FROM AUTHOR]

Streams and rivers in mediterranean-climate regions (med-rivers) are subjected to sequential, yet contrasting hydrologic disturbances of drying and flooding. Although seasonally predictable, these disturbances can vary in intensity and duration within and among mediterranean-climate regions (med-regions). Consequently, med-rivers differ in the permanence of their aquatic habitats. To persist, species have acquired matched resistance and resilience adaptations. They gain resistance either by enduring the stress or avoiding it. Community recovery (or resilience) is achieved with cessation of hydrologic stress that permits maximization of re-colonization and reproduction. Endurance strategies are usually disturbance-specific, but avoidance enables organisms to cope with both drying and flooding, and is the prevalent resistance strategy. Correspondingly, community persistence depends to a large extent on the integrity of refuges, an aspect that has so far been little explored. Existing information suggests that seasonal community succession becomes more pronounced with increasing aridity and declining water permanence. The invertebrate community in semi-arid med-rivers can therefore undergo succession through three to four identifiable assemblages, whereas in perennial streams the difference between wet and dry period assemblages is smaller. Community turnover is influenced by the intensity of the hydrologic disturbances and varies between wet and drought years. [ABSTRACT FROM AUTHOR]

Detecting the magnitude of human-induced disturbance events, such as forest harvest, on biological communities is often confounded by other environmental gradients and scales at which these effects are examined. In this study, benthic invertebrates were collected from 43 streams across four basins and two geographic regions to (1) determine whether invertebrate abundance and community structure are best explained by historic forest harvest, landscape variables or a combination of both, and (2) evaluate associations among harvest, landscape variables, in-stream physical habitat, and invertebrates. Nonmetric multidimensional scaling showed that invertebrate community structure was primarily explained by watershed area and elevation, and basin and region but not by measures of forest harvest. Model selection using an information-theoretic approach and Akaike's information criterion indicated that watershed area was the most important variable explaining clinger and long-lived taxa richness, while basin was the most important variable explaining total abundance, and total, Ephemeroptera, Plecoptera, and Trichoptera taxa richness. Forest harvest ranked lower than landscape variables in relative importance in all models. These results suggest that landscape characteristics were relatively more important in predicting invertebrate community structure than forest harvest, and should therefore be considered when assessing the impacts of both reach and watershed scale forest harvest on benthic communities. Perhaps, the levels of forest harvest examined in this study had only marginal effects on benthic invertebrates because these ecosystems are naturally resilient as a result of frequent disturbance from forest fires. [ABSTRACT FROM AUTHOR]

Reduction of flow constitutes one of the most severe human alterations to rivers, as it affects the key abiotic feature of these ecosystems. While there has been considerable progress in understanding the effects of reduced flow on benthic macroinvertebrates, cascading effects of flow reduction on dissolved oxygen concentrations (DO) have not yet received much attention. We compared the macroinvertebrate composition between reference conditions and a situation after several years of discharge reduction in the Spree River (Brandenburg, Germany). Community composition shifted from rheophilic species to species indifferent to flow conditions. Filter feeders were partially replaced by collector/gatherers, which likely reduces the retention of organic matter, and thus the self-purification capacity of the river section. These shifts were associated with low discharge during summer, cascading into daily DO concentration minima of less than 5 mg l which prevailed 74% of the days in summer. This depletion of DO after flow reduction presumably caused the observed species turnover. Hence, flow reduction in lowland rivers may not only directly impair the ecological functions provided by benthic macroinvertebrates but may also act indirectly by depleting DO concentrations. [ABSTRACT FROM AUTHOR]

Detailed studies of the macroinvertebrate benthos and zooplankton communities in Loch Leven, the largest shallow lowland lake in Scotland, UK, were carried out from 1966 to 1973 as part of the International Biological Programme (IBP). The results revealed a reduction in species diversity that was attributed to increasing eutrophication. This work provides a baseline against which the response of the invertebrate communities to subsequent changes in management can be assessed. This article compares macroinvertebrate benthos and zooplankton data from the IBP study with the post-IBP era during which changes at Loch Leven included a 60% reduction in the phosphorus input from external sources and variations in fish stocking rates. Only in recent years has there been evidence of ecological recovery by the invertebrate communities: the number of macroinvertebrate and zooplankton taxa has increased (including taxa considered to be sensitive to nutrient enrichment) and invertebrate abundances have declined. These changes appear to reflect the improvements in water quality and habitat conditions at Loch Leven that have occurred as a result of the recent reduction in nutrient loads, albeit with a substantial delay before any ecological response could be detected. This time lag in recovery has important implications for assessing improvements in the ecological status of other lake systems, as is required by the EU Water Framework Directive. [ABSTRACT FROM AUTHOR]

The East River (Dong Jiang), a major tributary of the Pearl River (Zhu Jiang, the second largest river in China by discharge), is situated in southern China, which has the highest rates of urbanization and development on Earth. The East River also provides 80% of Hong Kong’s water supply. However, there have been no ecological studies to examine the combined impacts of changes in land use and water quality degradation on this river ecosystem. We tested the hypothesis that land-use disturbance and water quality degradation would significantly reduce benthic biodiversity in the East River by investigating macroinvertebrate community composition and relating it to data on water quality and catchment condition. The percentage of total impervious area within each catchment (%TIA—an indicator of land-use disturbance) was negatively related to a composite water quality index—the ERWQI—we developed for the East River. Modeling by partial least squares projection to latent structures (PLS) showed that family richness and relative abundance index (RAI) of macroinvertebrates were strongly influenced by both %TIA and ERWQI. Multi-response permutation procedure (MRPP) tests showed highly significant differences in family richness composition and RAI of macroinvertebrates among sites in the upper, middle, and lower course of the East River. MRPP also revealed differences in the family richness composition of nighttime drift samples between upper and middle site groups. Abundance (individuals m−3) and total family richness of drifting macroinvertebrates at each site were positively related to %TIA (range: 1.0–8.5%), while drift biomass was negatively related to dissolved oxygen and positively related to total suspended solids. Thus, human disturbances associated with land-use changes (increasing %TIA) and nutrient inputs severely degraded ecosystem integrity and the water quality of the East River and thereby reduced aquatic biodiversity. [ABSTRACT FROM AUTHOR]

Macroinvertebrates are one of the key components of lake ecosystems and are required to be monitored alongside other biological groups to define ecological status according to European Union legislation. Macroinvertebrate communities are highly variable and complex and respond to a diverse series of environmental conditions. The purpose of this study was to examine the relative importance of environmental variables in explaining macroinvertebrate abundance. A total of 45 sub-alpine lakes were sampled for macroinvertebrates in the shallow sublittoral. Environmental variables were grouped into four types: (1) aquatic physical and chemical parameters, (2) littoral and riparian habitat, (3) lake morphometric parameters and (4) sediment chemical characteristics. Nonparametric multiplicative regression (NPMR) was used to model the abundance of individual macroinvertebrate taxa. Significant models were produced for nine out of the 24 taxa examined. Sediment characteristics were the group most frequently included in models and also the factors to which taxa abundance was the most sensitive. Aquatic physical and chemical variables were the next group most frequently included in models although chlorophyll a was not included in any of the models and total phosphorus in only one. This indicates that many taxa may not show a direct easily interpretable response to eutrophication pressure. Lake morphometric factors were included in several of the models although the sensitivity of macroinvertebrate abundance tended to be lower than for sediment and aquatic physical and chemical factors. Habitat factors were only included in three models although riparian vegetation was found to have a significant influence on the abundance of Ephemera danica indicating that ecotone integrity is likely to play a role in its ecology. Overall, the models tended to be specific for species with limited commonality across taxa. Models produced by NPMR indicate that the response of macroinvertebrates to environmental variables can be successfully described but further research is required focussing in more detail on the response of key taxa to relevant environmental parameters and anthropogenic pressures. [ABSTRACT FROM AUTHOR]