Interaction between macroinvertebrates, discharge and physical habitat in upland rivers. (Special Issue: Recent developments in classification, assessment and management strategies for freshwater habitats in Britain and Europe.)

摘要

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. 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. 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. 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. 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.