Physical and biological controls on fine sediment transport and storage in rivers

Excess fine sediment, comprising particles <2 mm in diameter, is a major cause of ecological degradation in rivers. The erosion of fine sediment from terrestrial or aquatic sources, its delivery to the river, and its storage and transport in the fluvial environment are controlled by a complex interplay of physical, biological and anthropogenic factors. Whilst the physical controls exerted on fine sediment dynamics are relatively well-documented, the role of biological processes and their interactions with hydraulic and physico-chemical phenomena has been largely overlooked. The activities of biota, from primary producers to predators, exert strong controls on fine sediment deposition, infiltration and resuspension. For example, extracellular polymeric substances (EPS) associated with biofilms increase deposition and decrease resuspension. In lower energy rivers, aquatic macrophyte growth and senescence are intimately linked to sediment retention and loss, whereas riparian trees are dominant ecosystem engineers in high energy systems. Fish and invertebrates also have profound effects on fine sediment dynamics through activities that drive both particle deposition and erosion depending on species composition and abiotic conditions. The functional traits of species present will determine not only these biotic effects but also the responses of river ecosystems to excess fine sediment. We discuss which traits are involved and put them into context with spatial processes that occur throughout the river network. Whilst strides towards better understanding of the impacts of excess fine sediment have been made, further progress to identify the most effective management approaches is urgently required through close communication between authorities and scientists

An index to track the ecological effects of drought development and recovery on riverine invertebrate communities

© 2017 Elsevier Ltd In rivers, the ecological effects of drought typically result in gradual adjustments of invertebrate community structure and functioning, punctuated by sudden changes as key habitats, such as wetted channel margins, become dewatered and dry. This paper outlines the development and application of a new index (Drought Effect of Habitat Loss on Invertebrates – DEHLI) to quantify the effects of drought on instream macroinvertebrate communities by assigning weights to taxa on the basis of their likely association with key stages of channel drying. Two case studies are presented, in which the DEHLI index illustrates the ecological development of drought conditions and subsequent recovery. These examples demonstrate persistent drought effects months or several years after river flows recovered. Results derived using DEHLI are compared with an established macroinvertebrate flow velocity-reactive index (Lotic-invertebrate Index for Flow Evaluation – LIFE score) and demonstrates its greater sensitivity to drought conditions. Data from a number of rivers in south east England were used to calibrate a statistical model, which was then used to examine the response of DEHLI and LIFE to a hypothetical multi-year drought. This demonstrated a difference in response between sampling seasons, with the spring model indicating a lagged response due to delayed recolonisation and the autumn model differentiating habitat loss and flow velocity-driven responses. The application of DEHLI and the principles which underlie it allow the effects of drought on instream habitats and invertebrates associated with short or long term weather patterns to be monitored, whilst also allowing the identification of specific locations where intervention via river restoration, or revision of existing abstraction licensing, may be required to increase resilience to the effect of anthropogenic activities exacerbated by climate change

Data to test RICT Model 44

This project was commissioned by the Environment Agency (EA) Ecology & Ecosystems team, part of the Agriculture Fisheries and Natural Resources department (Environment & Business Directorate, Head Office), with support from the EA Water Resources. The Ecology & Ecosystems team is in charge of EA standard invertebrate methods for assessing rivers, including river status classification, and of developing the River Invertebrate Classification Tool (RICT). RICT has at its core the River Invertebrate Prediction and Classification System (RIVPACS) model. This model has been upgraded and refined through years, with Model 44 being the latest experimental working version. Model 44 has been designed to provide more accurate predictions of invertebrate communities in rivers impacted by hydro-morphological alterations. In particular, the new input variables exclude width, depth and substrate, and are hydro-morphologically independent. In 2017, UKCEH created a UK-wide database for these new Model 44 variables (Kral et al., 2017). The aim of this project is to generate a testing dataset including a sufficient number of sites across England, and their Model 1 and Model 44 input variables so the original and new models can be compared, and should they yield different results, to assess if Model 44 is better suited for water resource assessments, and can better capture impact of flow and fine sediment pressures

Assessing the impact of errors in sorting and identifying macroinvertebrate samples

This study assesses the impact of errors in sorting and identifying macroinvertebrate samples collected and analysed using different protocols (e.g. STAR-AQEM, RIVPACS). The study is based on the auditing scheme implemented in the EU-funded project STAR and presents the first attempt at analysing the audit data. Data from 10 participating countries are analysed with regard to the impact of sorting and identification errors. These differences are measured in the form of gains and losses at each level of audit for 120 samples. Based on gains and losses to the primary results, qualitative binary taxa lists were deducted for each level of audit for a subset of 72 data sets. Between these taxa lists the taxonomic similarity and the impact of differences on selected metrics common to stream assessment were analysed. The results of our study indicate that in all methods used, a considerable amount of sorting and identification error could be detected. This total impact is reflected in most functional metrics. In some metrics indicative of taxonomic richness, the total impact of differences is not directly reflected in differences in metric scores. The results stress the importance of implementing quality control mechanisms in macroinvertebrate assessment scheme

Spatial structure in lotic macroinvertebrate communities in England and Wales: relationship with physicochemical and anthropogenic stress variables

We describe the relationship between macroinvertebrate community composition, the physicochemical environment and anthropogenic impacts, in running water sites across a range of water qualities in England and Wales. We have also investigated the degree of spatial structure present in both the macroinvertebrate community and the measured environment. Selected explanatory variables could account for 26% of the variation in lotic macroinvertebrate assemblage composition across England and Wales. The explanatory power of the CCA model was based predominantly on a combination of local scale variables (substrate, alkalinity, urban run-off) and regional scale variables (discharge category, northing). The physicochemical gradient associated with changes in stream type from headwaters to estuary dominated assemblage composition. The influence of pollution and habitat modification were of secondary importance. There was a substantial level of spatial structure to both the physicochemical (47% of its explanatory power spatially structured) and anthropogenic stress data (63% of its explanatory power spatially structured), which resulted in a high level of predictable spatial structuring in macroinvertebrate assemblages. Almost 40% of the variation in assemblage composition accounted for by the explanatory model exhibited spatial structure. Positive spatial autocorrelation in macroinvertebrate community composition extended to sites up to 150 km apart. As a consequence, community composition could be described from northing and easting with 75% of the explanatory power of the eight physicochemical variables. Our study has confirmed the importance of the longitudinal gradient within catchments, as well as the geographical position of the catchment to macroinvertebrate communities. We have also demonstrated how quantifying the spatial structure in the dataset can improve our understanding of the factors influencing macroinvertebrate community structure

Bringing European river quality into line: an exercise to intercalibrate macro-invertebrate classification methods

Intercalibration requires the value of the boundary between high and good status classes, and that between good and moderate status as defined by national biological assessment systems, to be consistent with definitions outlined in the Water Framework Directive and comparable between Member States. This intercalibration, the first attempted at such a wide European scale, was performed on the response of river macro-invertebrates to multiple stressors using national data from fifteen Member States belonging to the Central Baltic Geographical Intercalibration Group (CBGIG). Member State based their boundaries on samples that are not directly comparable because of differences in sampling methods and defined their boundaries using different biotic indices. In order to facilitate a comparison of boundaries, values of national classification systems were expressed as ecological quality ratios (EQRs: ratio between the measured status of the biological quality element and the expected value of the biological status at reference state) and translated to a common metric. Mean ecological boundary values were calculated from national boundary values that were agreed for adoption by the Member State, provided the boundary values and assessments systems on which they were based complied with a stringent list of criteria. A range representing an acceptable degree of uncertainty around the mean high/good and good/moderate boundary values, known as the ¿harmonisation band¿ (mean boundary value ± 0.05 EQR units) was defined to account for variation between national methods. In order to ensure comparability of ecological status, Member States with boundary values below this band were required to adjust their boundary value to fall within the harmonisation band.JRC.H.1-Water Resource

The STAR project: context, objectives and approaches

STAR is a European Commission Framework V project (EVK1-CT-2001-00089). The project aim is to provide practical advice and solutions with regard to many of the issues associated with the Water Framework Directive. This paper provides a context for the STAR research programme through a review of the requirements of the directive and the Common Implementation Strategy responsible for guiding its implementation. The scientific and strategic objectives of STAR are set out in the form of a series of research questions and the reader is referred to the papers in this volume that address those objectives, which include: (a) Which methods or biological quality elements are best able to indicate certain stressors? (b) Which method can be used on which scale? (c) Which method is suited for early and late warnings? (d) How are different assessment methods affected by errors and uncertainty? (e) How can data from different assessment methods be intercalibrated? (f) How can the cost-effectiveness of field and laboratory protocols be optimised? (g) How can boundaries of the five classes of Ecological Status be best set? (h) What contribution can STAR make to the development of European standards? The methodological approaches adopted to meet these objectives are described. These include the selection of the 22 stream-types and 263 sites sampled in 11 countries, the sampling protocols used to sample and survey phytobenthos, macrophytes, macroinvertebrates, fish and hydromorphology, the quality control and uncertainty analyses that were applied, including training, replicate sampling and audit of performance, the development of bespoke software and the project outputs. This paper provides the detailed background information to be referred to in conjunction with most of the other papers in this volume. These papers are divided into seven sections: (1) typology, (2) organism groups, (3) macrophytes and diatoms, (4) hydromorphology, (5) tools for assessing European streams with macroinvertebrates, (6) intercalibration and comparison and (7) errors and uncertainty. The principal findings of the papers in each section and their relevance to the Water Framework Directive are synthesised in short summary papers at the beginning of each section. Additional outputs, including all sampling and laboratory protocols and project deliverables, together with a range of freely downloadable software are available from the project website at www.eu_star.a