Lotic-invertebrate Index For Flow Evaluation Research Articles

Using invertebrate functional traits to improve flow variability assessment within European rivers

Rivers are among the most threatened ecosystems worldwide and are experiencing rapid biodiversity loss. Flow alteration due to climate change, water abstraction and augmentation is a severe stressor on many aquatic communities. Macroinvertebrates are widely used for biomonitoring river ecosystems although current taxonomic approaches used to characterise ecological responses to flow have limitations in terms of generalisation across biogeographical regions. A new macroinvertebrate trait-based index, Flow-T, derived from ecological functional information (flow velocity preferences) currently available for almost 500 invertebrate taxa at the European scale is presented. The index was tested using data from rivers spanning different biogeographic and hydro-climatic regions from the UK, Cyprus and Italy. The performance of Flow-T at different spatial scales and its relationship with an established UK flow assessment tool, the Lotic-invertebrate Index for Flow Evaluation (LIFE), was assessed to determine the transferability of the approach internationally. Flow-T was strongly correlated with the LIFE index using both presence-absence and abundance weighted data from all study areas (r varying from 0.46 to 0.96). When applied at the river reach scale, Flow-T was effective in identifying communities associated with distinct mesohabitats characterised by their hydraulic characteristics (e.g., pools, riffles, glides). Flow-T can be derived using both presence/absence and abundance data and can be easily adapted to varying taxonomic resolutions. The trait-based approach facilitates research using the entire European invertebrate fauna and can potentially be applied in regions where information on taxa-specific flow velocity preferences is not currently available. The inter-regional and continental scale transferability of Flow-T may help water resource managers gauge the effects of changes in flow regime on instream communities at varying spatial scales.

Regulation of freshwater use to restore ecosystems resilience

Concern about the impacts of water regulation upon the aquatic environment has led to increasingly stringent regulatory constraints on the quantity and timing of freshwater withdrawals. For the time being these regulatory constraints tend to be articulated in terms of limits upon withdrawals, partly because of limited knowledge of the condition and resilience of the aquatic ecosystems. A more sophisticated approach to regulation would be more directly related to indicators of ecological condition. Moreover, it would consider ecosystem response to climatic events not present in the historical record. In this paper we use a combination of empirical evidence of ecosystem condition with simulation to propose and test reductions to regulatory limits on river water withdrawals and downstream minimum flow requirements. The study uses multi-level linear regression to relate the Lotic-invertebrate Index for Flow Evaluation (LIFE) to antecedent flow statistics observed in the Lee catchment, England. The selected flow statistics included extreme low (Q90) and high (Q10) flows in the summer season (April-Sept), and the median flows observed in the winter season (Oct-Mar). The derived model is used to forecast the response of the macroinvertebrate index to future flow scenarios and demand forecasts, incorporating the uncertainties in ecosystem response. Simulation is used to evaluate the sensitivity of the indices to different regulatory limits. Results indicate that macroinvertebrate health will worsen under 21st Century climate conditions, and that the existing regulation policy must be modified to maintain historically observed LIFE scores into the future. The framework demonstrates how regulations could move from precautionary limits on withdrawals to an approach based on observations, forecasting and simulation, allowing planners to refine the trade-offs between river health and reliable water supply in the face of uncertainty.

Biological indices to characterize community responses to drying in streams with contrasting flow permanence regimes

Abstract Many river networks include temporary reaches that stop flowing and may dry during unpredictable droughts (near-perennial) or more frequently (intermittent). A few biological indices have been developed to assess invertebrate community responses to hydrological variability, including the instream conditions associated with drought, but their performance in temporary streams remains poorly known. We evaluated the ability of two such indices, the Lotic-invertebrate Index for Flow Evaluation (LIFE) and the Drought Effect of Habitat Loss on Invertebrates (DEHLI), to predict responses to flow cessation and drying in temporary streams with contrasting flow permanence regimes. We used a 26-year dataset comprising spring-season invertebrate community samples and daily discharge measurements from 46 sites in a cool, wet temperate region, to examine relationships between hydrological variables and changes in index scores. We also identified taxon-specific thresholds at which occurrence changed with increasing drying and flowing durations. Both indices effectively characterized responses to increasing no-flow durations. DEHLI also reflected community changes following flow resumptions, identified differences in responses among flow permanence groups, and was particularly able to predict community responses at near-perennial sites. DEHLI scores at near-perennial sites took on average three years after a drying event to return to values typical of perennial sites, whereas responses to increasing flow duration were more erratic at intermittent sites. Lotic specialists declined whereas lentic and semi-aquatic taxa increased in occurrence with no-flow duration after summers with

Assessment of freshwater ecosystem services in the Beas River Basin, Himalayas region, India

Abstract. River systems provide a diverse range of ecosystem services, examples include: flood regulation (regulating), fish (provisioning), nutrient cycling (supporting) and recreation (cultural). Developing water resources through the construction of dams (hydropower or irrigation) can enhance the delivery of provisioning ecosystem services. However, these hydrologic alterations result in reductions in less tangible regulating, cultural and supporting ecosystem services. This study seeks to understand how multiple impoundments, abstractions and transfers within the upper Beas River Basin, Western Himalayas, India, are affecting the delivery of supporting ecosystem services. Whilst approaches for assessing supporting ecosystem services are under development, the immediate aim of this paper is to set out a framework for their quantification, using the macroinvertebrate index Lotic-Invertebrate Index for Flow Evaluation (LIFE). LIFE is a weighted measure of the flow velocity preferences of the macroinvertebrate community. Flow records from multiple gauging stations within the basin were used to investigate flow variability at seasonal, inter-annual and decadal time scales. The findings show that both mean monthly and seasonal cumulative flows have decreased over time in the Beas River Basin. A positive hydroecological relationship between LIFE and flow was also identified, indicative of macroinvertebrate response to seasonal changes in the flow regime. For example, high LIFE scores (7.7–9.3) in the winter and summer seasons indicate an abundance of macroinvertebrates with a preference for high flows; this represents a high potential for instream supporting ecosystem services delivery. However, further analysis is required to understand these hydroecological interactions in the study basin and the impact on instream supporting ecosystem services delivery.

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

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.

The implications of an invasive species on the reliability of macroinvertebrate biomonitoring tools used in freshwater ecological assessments

Invasive species represent one of greatest threats to aquatic biodiversity globally and are widely acknowledged to be instrumental in modifying native community structure. Despite this, little is known about how the increasing range expansion of invasive taxa may affect routine biomonitoring tools widely employed to measure or quantify environmental quality in lotic systems. This study examined the impact of an invasive freshwater crayfish on commonly employed riverine macroinvertebrate biomonitoring tools (scores and indices) designed to respond to a range of stressors. Data from long-term monitoring sites on both ‘control’ and invaded rivers in England were examined to assess changes to biomonitoring scores following invasion by signal crayfish (Pacifastacus leniusculus). Results indicate that routine biomonitoring tools used to quantify potential ecological stressors which are weighted by abundance, such as the Lotic-invertebrate Index for Flow Evaluation (LIFE) score and Proportion of Sediment-sensitive Invertebrates (PSI), were subject to significant inflation following invasion. In contrast, indices based simply on the presence of taxa, such as the Average Score Per-Taxon (ASPT – a derivative of BMWP), displayed no changes compared to control rivers; or in the case of the Biological Monitoring Working Party Score (BMWP), NTAXA and EPT richness, no consistent pattern following invasion. Season had a significant effect on the interaction of crayfish and LIFE and PSI scores. Autumn samples were subject to statistical inflation following crayfish invasion whilst spring samples exhibited no significant change. The results suggest that care should be taken when interpreting routine macroinvertebrate biomonitoring data where non-native crayfish are present, or in instances where their presence is suspected.

Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams

Summary Elevated levels of fine sediment (suspended and deposited) are a common cause of ecological degradation in freshwater ecosystems. However, it is time‐consuming and expensive to monitor these parameters to support national and international water resource legislation. The Proportion of Sediment‐sensitive Invertebrates (PSI) index is a biomonitoring tool that is designed to identify the degree of sedimentation in rivers and streams. Despite having a sound biological basis, until now, the PSI index has only been tested against observed fine sediment data in two catchments; other published applications of the PSI index have relied on inferred fine sediment values. In this study, we report the results of a comprehensive analysis of the performance of the PSI index across a wide range of reference condition temperate stream and river ecosystems, including 835 sites with data on deposited sediment and 451 sites with data on suspended solids (>12 500 data points measured between 1978 and 2002). The effect of taxonomic level and taxonomic resolution on the performance of the PSI index was also examined, as was the performance of the PSI index against other non‐sediment‐specific indices, including Average Score Per Taxon (ASPT), Lotic‐invertebrate Index for Flow Evaluation (LIFE), Ephemeroptera, Plecoptera and Trichoptera (EPT) abundance, % EPT abundance, EPT richness and % EPT richness. The results of this study show that the PSI index was more correlated with fine sediment metrics than the other biological indices tested: rs = −0.64, (P < 0.01, n = 2502) for deposited sediment and rs = −0.50 (P < 0.01, n = 1353) for suspended solids. We highlight the optimal conditions for applying the PSI index, in its current form. Given the variability in the relationship between PSI and fine sediment metrics, we propose that the use of data from more objective, quantitative methods of measuring deposited fine sediment may help to enhance the performance of the model for future applications and advance understanding of fine sediment dynamics and the pressure–response relationship.

Effects of Impoundment on Macroinvertebrate Community Assemblages in Upland Streams

AbstractApproximately 15% of the world's river flow is regulated, but evidence for the impacts of regulation on macroinvertebrate communities remains contradictory. Sound understanding of this topic is now required to meet legislative targets (e.g. EU Water Framework Directive good ecological potential). In the UK, research has either been undertaken at large (national) or small (reach) scales, and typically, researchers have made comparisons between sites classed simply as either regulated or unregulated. We present an alternative, medium (regional) scale study and contrast three methods of defining the extent to which a site is regulated (ER): (i) regulated or unregulated (ERLOW); (ii) fully‐regulated, semi‐regulated or unregulated (ERMED); and (iii) a continuous score reflecting the relative regulated and unregulated river influence on a site (ERHIGH). The potential for highlighting the impacts of regulation of two recently developed pressure‐specific biotic indices [Lotic Invertebrate index for Flow Evaluation (LIFE) and Proportion of Sediment‐sensitive Invertebrates] is also assessed. We found that (i) regulation was associated with reduced relative abundance of Coleoptera and Ephemeroptera and enhanced relative abundance of Trichoptera, Chironomidae and Oligochaeta; (ii) Potamopyrgus antipodarum and Amphinemura sulcicollis were both positively associated with regulation; this observation is novel for the UK; (iii) ERHIGH was superior to both ERLOW and MED as a means of detecting an impact; and (iv) of all indices tested, only LIFE was significantly associated with regulation. The use of LIFE and ERHIGH should be tested further to understand the extent to which they can provide clearer insights into the effects of river regulation on macroinvertebrate communities. Copyright © 2014 John Wiley & Sons, Ltd.

The identification of hydrological indices for the characterization of macroinvertebrate community response to flow regime variability

The importance of flow regime variability for maintaining ecological functioning and integrity of river ecosystems has been firmly established in both natural and anthropogenically modified systems. River flow regimes across lowland catchments in eastern England are examined using 47 variables, including those derived using the Indicators of Hydrologic Alteration (IHA) software. A principal component analysis method was used to identify redundant hydrological variables and those that best characterized the hydrological series (1986–2005). A small number of variables (<6) characterized up to 95% of the statistical variability in the flow series. The hydrological processes and conditions that the variables represent were found to be significant in structuring the in-stream macroinvertebrate community Lotic-invertebrate Index for Flow Evaluation (LIFE) scores at both the family and species levels. However, hydrological variables only account for a relatively small proportion of the total ecological variability (typically <10%). The research indicates that a range of other factors, including channel morphology and anthropogenic modification of in-stream habitats, structure riverine macroinvertebrate communities in addition to hydrology. These factors need to be considered in future environmental flow studies to enable the characterization of baseline/reference conditions for management and restoration purposes.Editor Z.W. Kundzewicz; Guest editor M. AcremanCitation Worrall, T.P., Dunbar, M.J., Extence, C.A., Laizé, C.L.R., Monk, W.A., and Wood, P.J., 2014. The identification of hydrological indices for the characterization of macroinvertebrate community response to flow regime variability. Hydrological Sciences Journal, 59 (3–4), 645–658.

How does macroinvertebrate taxonomic resolution influence ecohydrological relationships in riverine ecosystems

AbstractThe taxonomic resolution of macroinvertebrate community data needs careful consideration, to ensure that research objectives in pure and applied freshwater scientific research are met. The level of taxonomy used may be driven by time and financial restrictions associated with the increasing resources and effort needed to identify organisms to a lower taxonomic resolution. This paper aims to assess the influence of taxonomic resolution on the understanding of long‐term (1985–2006) benthic macroinvertebrate community response to changes in the hydrological regime. There were marked differences in the number of taxa included in the analysis when comparing ‘species’‐ and ‘family’‐level data used to derive lotic‐invertebrate index for flow evaluation (LIFE) scores, particularly among species rich orders, such as Ephemeroptera, Plecoptera, Trichoptera and Coleoptera. The performance of the partial least squares (PLS) regression models of hydrological variables and the LIFE scores derived for different taxonomic levels were compared. Coefficients of determination were higher for species‐level LIFE data than for the same data resolved to family level. Results demonstrate that the species‐level LIFE data produced significant model components while those derived from family‐level data were not; although both models indicated the dominance of hydrological indices quantifying the duration and magnitude of the hydrological events. We conclude that there is a growing need to resolve faunal data to species level to adequately fulfil operational and legislative obligations for river management and conservation purposes. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Interaction between macroinvertebrates, discharge and physical habitat in upland rivers

1. There is a need to relate changing river flows to ecological response, particularly using methods which do not require extensive new data for water bodies without historical data. This paper describes how local-scale habitat features and changing discharge appear to influence a macroinvertebrate-based biotic index. 2. The study used 87 time-series of river biomonitoring data from upland, wadeable streams with quasi-natural flow regimes across England and Wales. Twenty-seven of the sites were matched to a nearby flow gauging station, and historical, natural flows using a generalized rainfall-runoff model were synthesized for 60 sites. All sites were matched to a River Habitat Survey (RHS) within 1 km. 3. The data were analysed using multilevel linear regression, combining sample- and site-level characteristics as predictors. Common responses were assessed across sites, using the biotic index LIFE (Lotic Invertebrate index for Flow Evaluation), an average of abundance-weighted Flow Groups which indicate the relative preference among taxa for higher velocities with gravel/cobble substrates or slow velocities with finer substrates. The aim was to understand the influence of habitat on macroinvertebrate response to antecedent high and low flow magnitude. 4. There was a positive relationship between LIFE score calculated from spring and autumn samples and antecedent high (Q10) and low flows (Q95). The relationship between summer Q10 and autumn LIFE score was steeper than the relationship between winter Q10 and spring LIFE score. Bed and bank resectioning reduced overall LIFE and increased the steepness of the response of LIFE to low (Q95) flow. 6. The models derived may be used to guide environmental flow allocations and to quantify the relative influence of flow and physical habitat change on macroinvertebrate responses. The interaction between resectioning and low flow has particular implications for the conservation of macroinvertebrate taxa with requirements for faster flowing water.

River discharge and local‐scale physical habitat influence macroinvertebrate LIFE scores

Summary1. Methods are needed to relate changing river flows to ecological response, particularly those which do not require collection of extensive new data for river segments that lack historical data. Using time‐series of river biomonitoring data from wadeable lowland streams in Denmark and the East Midlands of the U.K., we describe how local‐scale habitat features (indexed through River Habitat Survey or Danish Habitat Quality Survey) and changing river flow (discharge) influence the response of a macroinvertebrate community index. The approach has broad applicability in developing regional flow‐ecological response models.2. We analysed the data using multilevel linear regression, combining sample‐level and site‐level characteristics as predictors. We focused on the potential for common responses across sites; hence for each sample, the macroinvertebrate community was summarised into an index, Lotic Invertebrate index for Flow Evaluation (LIFE), an average of abundance‐weighted flow groups which indicate the microhabitat preferences of each taxon for higher velocities and clean gravel/cobble substrata or slow/still velocities and finer substrata.3. For the Danish fauna, the LIFE score responded to three predictors in an additive manner: high flows in the preceding 4 months (positive), substratum composition and whether the channel was meandering or straight. The East Midlands fauna responded to three predictors: high and low flows in the preceding 6 months (positive) and the degree of resectioning of the channel (negative). In both cases, LIFE responded negatively to features associated with historical channel modification. We suggest that there are several mechanisms for these relationships, including the narrower tolerances of taxa preferring high velocity habitat; these taxa are also continually recovering from extreme flow events over an inter‐annual timescale.4. At the East Midlands sites, there was an interaction between degree of resectioning and antecedent low flow. At sites with a greater extent of resectioning, the LIFE‐discharge relationship was also steeper than at less modified sites. Consideration of the underlying data suggests that there are two mechanisms for this response. Firstly, in less modified sites, refugia are present during low flows for taxa preferring higher velocities such as riffle beetles, caseless caddis, mayflies and Gammarus pulex. Secondly, high flows are associated with decreasing abundances of taxa such as molluscs, flatworms and leeches at more resectioned sites, but with stable or increasing abundances at less modified sites.5. The LIFE index responded to both antecedent flow and habitat modification in two separate data sets from lowland wadeable streams. This is the first time that the combined importance of these two factors has been demonstrated using routine invertebrate biomonitoring data. These results complement other site‐specific studies that have shown how channel structure interacts with flow to create physical habitat, and should assist future work aiming to define flow‐habitat‐biota relationships.6. The derived models may be used to help guide environmental flow allocations, for example by predicting the slope of response of LIFE score to flow for comparable new locations which lack biological data.

Reconstructing riverine paleo-flow regimes using subfossil insects (Coleoptera and Trichoptera): the application of the LIFE methodology to paleochannel sediments

Sub-fossil insect remains have the potential to characterise changing environmental conditions in both lentic and lotic water systems, however, relatively few studies have been undertaken in riverine environments. This paper uses sub-fossil caddisfly larvae (Trichoptera) and aquatic beetles (Coleoptera) to reconstruct river flow conditions for a large paleochannel (from multiple monoliths) using the Lotic invertebrate Index for Flow Evaluation (LIFE). Examination of the larval Trichoptera and Coleoptera remains indicated a marked change in the community and flow environment, as suggested by paleoLIFE scores within the profile of three of the monoliths examined. At the base of the channel the community was characterised by taxa indicative of high energy lotic habitats with predominantly mineral substrates (e.g. Trichoptera: Hydropsyche contubernalis and Brachycentrus subnubilis, Coleoptera: Elmis aenea and Esolus parallelepipedus). Within three of the monoliths there was a change in community composition to one indicative of a low energy backwater/lentic environment with abundant submerged and emergent vegetation (e.g. Trichoptera: Phryganea bipunctata and Limnephilus flavicornis, Coleoptera: Colymbetes fuscus and Hydrobius fuscipes). Detrended Correspondence Analysis (DCA) and loss of mass on ignition (LOI) indicated the presence of a strong environmental gradient within the data, associated with river flow. The utilisation of two aquatic insect orders provides clear evidence of temporal changes within the instream community and when combined with knowledge of ecological and habitat associations, allows differences between the two groups to be interpreted more clearly.

River flow indexing using British benthic macroinvertebrates: a framework for setting hydroecological objectives

A method linking qualitative and semi-quantitative change in riverine benthic macroinvertebrate communities to prevailing flow regimes is proposed. The Lotic-invertebrate Index for Flow Evaluation (LIFE) technique is based on data derived from established survey methods, that incorporate sampling strategies considered highly appropriate for assessing the impact of variable flows on benthic populations. Hydroecological links have been investigated in a number of English rivers, after correlating LIFE scores obtained over a number of years with several hundred different flow variables. This process identifies the most significant relationships between flow and LIFE which, in turn, enables those features of flow that are of critical importance in influencing community structure in different rivers to be defined. Summer flow variables are thus highlighted as being most influential in predicting community structure in most chalk and limestone streams, whereas invertebrate communities colonizing rivers draining impermeable catchments are much more influenced by short-term hydrological events. Biota present in rivers with regulated or augmented flows tend to be most strongly affected by non-seasonal, interannual flow variation. These responses provide opportunities for analysing and elucidating hydroecological relationships in some detail, and it should ultimately be possible to use these data to set highly relevant, cost-effective hydroecological objectives. An example is presented to show how this might be accomplished. Key areas of further work include the need to provide robust procedures for setting hydroecological objectives, investigation of habitat quality and LIFE score relationships in natural and degraded river reaches and evaluation of potential links with other biological modelling methods such as RIVPACS. Copyright © 1999 John Wiley & Sons, Ltd.