Temporal effects of enhanced fine sediment loading on macroinvertebrate community structure and functional traits

Deposition of fine sediment that fills interstitial spaces in streambed substrates is widely acknowledged to have significant negative effects on macroinvertebrate communities, but the temporal consistency of clogging effects is less well known. In this study the effects of experimentally enhanced fine sediment content on aquatic invertebrates were examined over 126 days in two lowland UK streams. Taxonomic approaches indicated significant differences in macroinvertebrate community structure associated with sediment treatment (clean or sedimented substrates), although the effects were variable on some occasions. The degree of separation between clean and sedimented communities was strong within 7 of the 9 sampling periods with significant differences in community composition being evident. EPT taxa and taxon characterised as sensitive to fine sediment demonstrated strong responses to enhanced fine sediment loading. In marked contrast, faunal traits did not facilitate the detection of enhanced fine sediment loading. More widely, the study highlights the temporal dynamics of sedimentation effects upon macroinvertebrate communities and the need to consider faunal life histories when examining the effects of fine sediment loading pressures on lotic ecosystems

The fine sediment conundrum; quantifying, mitigating and managing the issues

Copyright © 2017 John Wiley & Sons, Ltd. Excess fine sediment is a global cause of lotic ecosystem degradation. Despite historic interest in identifying sediment sources and quantifying instream dynamics, tackling fine sediment problems remains a key challenge for river managers and a continued focus of international research. Accordingly, a national meeting of the British Hydrological Society brought together those working on fine sediment issues at the interface of hydrology, geomorphology, and ecology. The resulting collection of papers illustrates the range of research being undertaken in this interdisciplinary research arena, by academic researchers, environmental regulators, landowners, and consultants. More specifically, the contributions highlight key methodological advancements in the identification of fine sediment sources, discuss the complexities surrounding the accurate quantification of riverbed fine sediment content, demonstrate the potential utility of faunal traits as a biological monitoring tool, and recognize the need for improved mechanistic understanding of the functional responses of riverine organisms to excess fine sediment. Understanding and mitigating the effects of fine sediment pressures remains an important and multifaceted problem that requires interdisciplinary collaborative research to deliver novel and robust management tools and sustainable solutions

Macroinvertebrate community composition and diversity in ephemeral and perennial ponds on unregulated floodplain meadows in the UK

© 2016 Springer International Publishing SwitzerlandPonds are common and abundant landscape features in temperate environments, particularly on floodplains where lateral connectivity with riverine systems persists. Despite their widespread occurrence and importance to regional diversity, research on the ecology and hydrology of temperate ephemeral and perennial floodplain ponds lags behind that of other shallow waterbodies. This study examines the aquatic macroinvertebrate diversity of 34 ponds (20 perennial and 14 ephemeral) on two unregulated riverine floodplain meadows in Leicestershire, UK. Perennial ponds supported nearly twice the diversity of ephemeral ponds. Despite frequent inundation of floodwater and connectivity with other floodplain waterbodies, ephemeral ponds supported distinct invertebrate communities when compared to perennial ponds. When the relative importance of physical, chemical, biological and spatial characteristics was examined, physical and chemical characteristics were found to account for more variation in community composition than biological or spatial variables. The results suggest that niche characteristics rather than neutral colonisation processes dominate the structure of invertebrate communities of floodplain ponds. The maintenance of pond networks with varying hydroperiod lengths and environmental characteristics should be encouraged as part of conservation management strategies to provide heterogeneous environmental conditions to support and enhance aquatic biodiversity at a landscape scale

The effects of non-native signal crayfish (Pacifastacus leniusculus) on fine sediment and sediment-biomonitoring

© 2017 The Authors The North American signal crayfish (Pacifastacus leniusculus) has invaded freshwater ecosystems across Europe. Recent studies suggest that predation of macroinvertebrates by signal crayfish can affect the performance of freshwater biomonitoring tools used to assess causes of ecological degradation. Given the reliance on biomonitoring globally, it is crucial that the potential influence of invasive species is better understood. Crayfish are also biogeomorphic agents, and therefore, the aim of this study was to investigate whether sediment-biomonitoring tool outputs changed following signal crayfish invasions, and whether these changes reflected post-invasion changes to deposited fine sediment, or changes to macroinvertebrate community compositions unrelated to fine sediment. A quasi-experimental study design was employed, utilising interrupted time series analysis of long-term environmental monitoring data and a hierarchical modelling approach. The analysis of all sites (n = 71) displayed a small, but statistically significant increase between pre- and post-invasion index scores for the Proportion of Sediment-sensitive Invertebrates (PSI) index biomonitoring tool (4.1, p <  0.001, 95%CI: 2.1, 6.2), which can range from 0 to 100, but no statistically significant difference was observed for the empirically-weighted PSI (0.4, p = 0.742, 95%CI: − 2.1, 2.9), or fine sediment (− 2.3, p = 0.227, 95%CI: − 6.0, 1.4). Subgroup analyses demonstrated changes in biomonitoring tool scores ranging from four to 10 percentage points. Importantly, these subgroup analyses showed relatively small changes to fine sediment, two of which were statistically significant, but these did not coincide with the expected responses from biomonitoring tools. The results suggest that sediment-biomonitoring may be influenced by signal crayfish invasions, but the effects appear to be context dependent, and perhaps not the result of biogeomorphic activities of crayfish. The low magnitude changes to biomonitoring scores are unlikely to result in an incorrect diagnosis of sediment pressure, particularly as these tools should be used alongside a suite of other pressure-specific indices

Biological invasions in rivers and associated ecosystems: New insights, challenges, and methodological advancements

The spread and successful establishment of invasive non-native species (INNS) is a key driver of lotic ecosystem degradation globally within the Anthropocene era. Despite historic interest in biological invasions, tackling INNS remains a key challenge for managers of freshwater systems and a continued focus of international research. Spanning nine countries, four continents and four biogeographic regions this special issue illustrates the range of research being undertaken in this interdisciplinary field. The contributions highlight key advances in the identification of abiotic and biotic factors which may facilitate / enable the spread of INNS, alongside novel methodological developments in monitoring and managing INNS. New insights into the potential implications of INNS establishment for the receiving ecosystem and future challenges are also presented. Despite the wealth of research focused on riverine and associated ecosystem invasions, INNS remain an ongoing threat to global ecosystem health, with future invasions and geographical ranges continuing to evolve through anthropogenic modification of habitats and climatic change.</p

Riverine fine sediment content and hyporheic physicochemistry and macroinvertebrate data associated with an artificial flood in Switzerland

Data provided is primary data collected in Swiss National Park to investigate the effects of an artificial flood pulse on fine sediment content and hyporheic physicochemical and hyporheic macroinvertebrate communities. The following explains the data. Sediment - this relates to fine sediment content of the river bed collected using the resuspension stilling well method collected before and after the artificial flood. Columns as follows:Site - Site ID - 1-4Sediment - fine sediment content (g/m2)Type - 1 is surface content and 2 is total fine sediment content with the shallow interstitial pore space included (Time - 1 is before the artificial flood, 2 is immediately after artificial flood and 3 is 10 months after artificial floodSample provides a unique sample ID Replicate - 5 replicate samples per site per type per timeHyp_physicochemical - this relates to hyporheic physicohemical data collected by the bou rouche method before and after the artificial flood and corresponds to the hyporheic macroinvertebrate data provided. Columns as follows:Less 2mm- total dry weight of particles 500μm2-1mm - dry weight of particles in the fraction 1000μmless 1mm- dry weight of particles in the fraction 500μmpH - pH of the 5L of water extractedppm - total dissolved solids (TDS, ppm)Conductivity - conductivity (μS cm-1) of the 5 L of water extractedTemperature - water temperature (°c) of the 5 L of water extractedOxygen - dissolved oxygen content (mg l-1) of the 5 L of water extracteddelta - difference between water level of stream and water level in bou rouche. If delta is positive = upwelling, if negative = downwelling.VHG - vertical hydraulic gradientDepth - sampled at 0.25 or 0.50 m below river bedSample provides a unique sample ID Hyp_invert - this relates to hyporheic macroinvertebrate data collected by the bou rouche method before and after the artificial flood. Samples were identified to lowest taxonomic resolution, mainly species or genus. Columns as follows:Site - Site ID 1-4Depth - sampled at 0.25 or 0.50 m below river bedTime - 1 is before the artificial flood, 2 is 1 day after artificial flood and 3 is 7 days after artificial flood. Sample provides a unique sample ID </div

Artificial flood reduces fine sediment clogging enhancing hyporheic zone physicochemistry and accessibility for macroinvertebrates

River regulation globally has reduced the riverine connectivity (longitudinal, lateral and vertically) with significant consequences for their abiotic and biotic components. To restore the ecological integrity of regulated rivers, artificial floods are increasingly being employed in large-scale flow restoration efforts. Despite considerable recognition regarding the ecological and geomorphological effects of artificial floods on benthic habitats, understanding the implications for the hyporheic zone is essentially absent. This void in our management knowledge base is considerable given that one of the most widely associated consequences of flow regulation is excessive deposition of fine sediment (sedimentation; particles In this study, we examined the effects of an artificial flood on the hyporheic zone of the River Spöl in Switzerland. Fine sediment content of shallow benthic substrates (ca. 10 cm) was significantly reduced following the flood. The flushing of fine sediment was also apparent in hyporheic substrates (depths of 0.25 and 0.50 m), resulting in a reconnection of previously clogged interstitial pathways. The opening of interstitial pore space enhanced physicochemical conditions in the hyporheic zone, such as improved dissolved oxygen concentrations, and supported greater taxa richness.Alterations in the composition of shallower hyporheic assemblages (0.25 m) were evident following the flood. These results indicated that benthic pore space became more connected to surface waters following the flood, thereby enhancing accessibility for interstitial organisms.Our results suggest that artificial floods can be an effective management tool to restore spatial heterogeneity in sediment composition and pore space and improve vertical connectivity for macroinvertebrates. We anticipate that artificial floods would be required on a regular basis given the re-accumulation of fine sediment 10 months later in our study system. We encourage river managers and scientists to consider flow disturbance and restoration in a holistic manner that encompasses the multiple spatial dimensions of connectivity, including the hyporheic ecotone.</div

Supplementary Information files for: Patchiness in flow refugia use by macroinvertebrates following an artificial flood pulse

Supplementary Information files for: Patchiness in flow refugia use by macroinvertebrates following an artificial flood pulseFlow refugia, locations that maintain substrate stability and low hydraulic stress during periods of high flow, can ensure riverine resilience in the face of increasing hydrological unpredictability. Despite their known importance, they have been overlooked in recent years with work on drought refugia currently seeing greater attention. Moreover, research on the role of flow refugia during artificial flood pulses in regulated rivers, where flood disturbances are no longer part of the hydrograph, is essentially absent. Here, we compared flow refugia for benthic macroinvertebrates among six habitats (main channel, side channel, riffle, margin, lentic including a floodplain pond, and inundated floodplain) within four different sites in response to an artificial flood pulse. We found that the grain-size distribution and macroinvertebrate community composition changed at each site following the flood. Macroinvertebrate assemblages became longitudinally homogeneous, but within-site beta diversity and taxa richness remained temporally stable following the flood pulse, suggesting the presence of flow refugia. In this respect, margin, inundated floodplain and lentic (a floodplain pond) habitats provided important flow refugia locations, particularly for the mobile mayfly Rhithrogena sp. In contrast, low substrate stability in riffle and side channels resulted in limited refugia potential for most taxa. Refuge use was however patchy with high levels of intra-habitat variability being evident for Rhithrogena sp. and the amphipod Gammarus fossarum in margin and side channel habitats. Further work is required to advance our knowledge of flow refugia in rivers with differing flow regimes to enable their integration into management and restoration schemes.<br

Taxonomic and functional macroinvertebrate diversity of high‐altitude ponds in the Macun Cirque, Switzerland

Global environmental change is threatening freshwater biodiversity with ecological impacts predicted to be particularly severe in high-altitude regions. Despite this, an ecological understanding of high-altitude pond networks remains patchy, with only limited knowledge of the environmental and spatial predictors of taxonomic and functional diversity. Moreover, previous studies of pond ecosystems have focused primarily on taxonomic richness and largely overlooked functional diversity.This study examined the influence of local environmental and spatial factors on taxonomic and functional α and β diversity (including the turnover and nestedness-resultant components) of 17 high-altitude (~2,500 m above sea level) pond macroinvertebrate communities, in the Macun Cirque, Switzerland.Spatial processes (pond connectivity) were important drivers for taxonomic α diversity, while local environmental variables (pond permanence and surface area) were important determinants of functional α diversity. Species turnover was the most important component of β diversity for taxonomic composition, and functional composition demonstrated a nested spatial pattern.Variation in taxonomic and functional composition (and the turnover and nestedness components of β diversity) were determined by local environmental variables despite the limited environmental gradients within the pond network. No significant effects of spatial variables on community composition were recorded for either facet of diversity, indicating that compositional variation was determined at a local scale. Water temperature, depth and pond permanence were consistently the most important measured drivers of diversity.Given the importance of both spatial and environmental variables in structuring taxonomic and functional diversity, landscape-scale conservation and management activities that aim to improve or protect high-altitude freshwater biodiversity should focus on maintaining connectivity among ponds and environmental heterogeneity, particularly pond surface area, water depth, and hydroperiod. Understanding the mechanisms driving taxonomic and functional diversity will be critically important for the management and conservation of macroinvertebrate communities in high-altitude pond networks in the face of climatic warming.</div

Patchiness in flow refugia use by macroinvertebrates following an artificial flood pulse

Flow refugia, locations that maintain substrate stability and low hydraulic stress during periods of high flow, can ensure riverine resilience in the face of increasing hydrological unpredictability. Despite their known importance, they have been overlooked in recent years with work on drought refugia currently seeing greater attention. Moreover, research on the role of flow refugia during artificial flood pulses in regulated rivers, where flood disturbances are no longer part of the hydrograph, is essentially absent. Here, we compared flow refugia for benthic macroinvertebrates among six habitats (main channel, side channel, riffle, margin, lentic including a floodplain pond, and inundated floodplain) within four different sites in response to an artificial flood pulse. We found that the grain-size distribution and macroinvertebrate community composition changed at each site following the flood. Macroinvertebrate assemblages became longitudinally homogeneous, but within-site beta diversity and taxa richness remained temporally stable following the flood pulse, suggesting the presence of flow refugia. In this respect, margin, inundated floodplain and lentic (a floodplain pond) habitats provided important flow refugia locations, particularly for the mobile mayfly Rhithrogena sp. In contrast, low substrate stability in riffle and side channels resulted in limited refugia potential for most taxa. Refuge use was however patchy with high levels of intra-habitat variability being evident for Rhithrogena sp. and the amphipod Gammarus fossarum in margin and side channel habitats. Further work is required to advance our knowledge of flow refugia in rivers with differing flow regimes to enable their integration into management and restoration schemes.</div