Role of refugia in recovery from disturbances: Modern fragmented and disconnected river systems

Abstract

/ Habitats or environmental factors that convey spatial and temporal resistance and/or resilience to biotic communities that have been impacted by biophysical disturbances may be called refugia. Most refugia in rivers are characterized by extensive coupling of the main channel with adjacent streamside forests, floodplain features, and groundwater. These habitats operate at different spatial scales, from localized particles, to channel units such as pools and riffles, to reaches and longer sections, and at the basin LeveL. A spatial hierarchy of different physical components of a drainage network is proposed to provide a context for different refugia. Examples of refugia operating at different spatial scales, such as pools, large woody debris, floodplains, below dams, and catchment basins are discussed. We hope that the geomorphic context proposed for examining refugia habitats will assist in the conservation of pristine areas and attributes of river systems and also allow a better understanding of rehabilitation needs in rivers that have been extensiveLy altered.

Hyporheic invertebrate assemblages at reach scale in a Neotropical stream in Brazil

“…This pattern copes with data from other studies, since insects are known to use HZ to seek for refuge during periods of disturbance (Sedell et al, 1990;Robertson et al, 1995;Dole-Olivier et al, 1997) or to find more stable habitats (Matthaei et al, 2000;Fowler and Death, 2001). Dole-Olivier (2011) reviewed the importance of the HZ as a protected "nursery" for eggs, early instar larvae, and quiescent stages of benthic invertebrates as Plecoptera, Ephemeroptera and Chironomidae.…”

Run-of-River hydropower and salmonids: potential effects and perspective on future research

“…However, other research conducted in reservoir-storage systems supports the idea that reduced habitat availability due to lower flows downstream of reservoir-storage dams results in short-term increases in fish densities, subsequently leading to increases in competition among and within salmonid life stages and increased susceptibility to disease (Bradford 1994;Nislow and Armstrong 2012). Geomorphically, lower flows can also reduce the frequency, diversity, and quantity of microhabitats including gravel bars, side channels, and pools that are important for salmonid spawning, overwintering, and rearing as well as for refugia during extreme flow events like floods or droughts (Sedell et al 1990;Bonneau and Scarnecchia 1998;Walters and Post 2008). In many countries and jurisdictions, mitigation measures for RoR hydropower operations, such as requiring minimum instream flows, are mandated to minimize the potential impacts of reduced flows on fish and fish habitat in RoR hydropower systems (e.g., France: Gouraud et al 2008;Portugal: Santos et al 2006;Sweden: Renöfält et al 2010) (for more information, see review by Anderson et al 2014).…”

“…RoR hydropower dams may also intercept different forms of organic matter including coarse woody debris. Coarse woody debris is a key component of fish habitat, as it promotes the formation of pools, limits erosion, and provides cover and refugia (Sedell et al 1990;Mossop and Bradford 2004). Comparisons between bypassed and upstream reaches of lowhead RoR dams found higher levels of fine sediment and significantly slower water velocity in 13 bypassed reaches as well as significant differences between upstream and bypassed reaches in 32 of 41 hydraulic variables (Baker et al 2011).…”

Nature and Functions of Cover for Riverine Fish.

“…Generally, at low flow conditions, there is a loss of the cover that is principally located near the stream margins. As a result, the deep isolated pools become essential refugia for fish in streams subjected to frequent droughts and serve as a source of fish recolonisation (SEDELL et al, 1990;FAUSCH and BRAMBLETT, 1991;ELLIOTT, 2000;LABBE and FAUSCH, 2000). Intuitively, the role of cover in providing refuge from biotic interactions must be exacerbated during low-flow periods.…”