Interaction between macroinvertebrates, discharge and physical habitat in upland rivers

Abstract

ABSTRACT1. 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 physical 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.5. 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.

A catchment scale evaluation of multiple stressor effects in headwater streams

“…In general, the LIFE scores were low compared to previous findings (e.g. Dunbar et al, 2010b), which is probably due to the fact that discharge was low in most of the study streams and several of the streams were characterised by low oxygen concentrations and dominated by soft substrate types, as confirmed in the multi-correlation analysis. Since the actual gradient in the hydromorphological parameters that govern the LIFE score outputs was strongly skewed (sites with poor hydromorphological properties clearly dominating), we suggest that the LIFE score results should be interpreted with care, and we therefore also suggest that the positive correlations between the LIFE scores and pesticide toxicity (from groundwater inflow), nitrogen-N concentrations and chloride concentrations are Type II errors.…”

Direct observations of the effect of fine sediment deposition on the vertical movement of Gammarus pulex (Amphipoda: Gammaridae) during substratum drying

“…Fine sediments (typically referred to as particles \ 2 mm in size; Wood & Armitage, 1997;Jones et al, 2012) can infiltrate into subsurface sediments limiting the vertical movement of instream fauna (Weigelhofer & Waringer, 2003;Mathers & Wood, 2016) through the reduction of porosity and surface-groundwater hydrological exchange (Hartwig & Borchardt, 2014). There is a widely recognised increase in the volume of fine sediment entering and being deposited in rivers as a result of agricultural practices (Lamba et al, 2015), channel management (Dunbar et al, 2010) and urbanisation (Taylor & Owens, 2009;Naden et al, 2016). Given the predicted increased frequency of stream drying events (Pyne & Poff, 2017) there is a need to examine the combined effects of sedimentation and drying on faunal populations.…”

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

“…The LIFE scores for individual families and species are based on the known associations of British benthic macroinvertebrates to flow velocity. The LIFE method and scores have been widely used in the UK to examine and assess macroinvertebrate community response to flow regime variability in a number of studies (Dunbar et al 2006, 2010a, 2010b, Monk et al 2008Dunbar and Mould 2009, Clews et al 2010, Wilby et al 2011, Vaughan and Ormerod 2012.…”