Defining the natural flow regimes of boreal rivers: relationship with benthic macroinvertebrate communities

Abstract

Despite the fundamental role of river flow in determining the structure and function of lotic ecosystems, few studies have directly related features of the natural flow regime to variation in stream invertebrate assemblage composition. We classified 240 near-pristine, snowmelt-dominated Finnish streams into hydrological river types. We assessed the relationship of these types with benthic macroinvertebrate assemblage structure and examined the relative importance of hydrological variables, local-habitat variables, and geographical location in predicting variation in assemblage structure. We used a hydrological model to obtain site-specific daily discharges for a 30-y period (1981–2010) and calculated 223 flow indices based on flow index modeling tools. We used a combination of principal component and cluster analysis to classify the sites into 6 distinct hydrological types that were separated mainly by geographical location and catchment-size-related factors. Nonmetric multidimensional scaling and multire...