Disturbance regimes, resilience, and recovery of animal communities and habitats in lotic ecosystems

Abstract

Disturbance regime is a critical organizing feature of stream communities and ecosystems. The position of a given reach in the river basin and the sediment type within that reach are two key determinants of the frequency and intensity of flow-induced disturbances. We distinguish between predictable and unpredictable events and suggest that predictable discharge events are not disturbances.We relate the dynamics of recovery from disturbance (i.e., resilience) to disturbance regime (i.e., the disturbance history of the site). The most frequently and predictably disturbed sites can be expected to demonstrate the highest resilience.Spatial scale is an important dimension of community structure, dynamics, and recovery from disturbance. We compare the effects on small patches (~<1 m 2) to the effects of large reaches at the river basin level. At small scales, sediment movements and scour are major factors affecting the distribution of populations of aquatic insects or algae. At larger scales, we must deal with channel formation, bank erosion, and interactions with the riparian zone that will affect all taxa and processes.Our understanding of stream ecosystem recovery rests on our grasp of the historical, spatial, and temporal background of contemporary disturbance events.

Effect of substrate stability and canopy cover on stream invertebrate communities

“…Hydrological disturbances are believed to reduce invertebrate abundance and diversity in two waysdirectly by washing away and crushing individuals (Sagar 1986;Reice et al 1990) and indirectly by reducing primary productivity or the abundance of periphyton (Robinson & Minshall 1986;Death 1996). In this study, disturbance reduced periphyton biomass but not nearly as dramatically as the artificial cover did.…”

“…One challenge is to elucidate and quantify the influence of each of these factors. Disturbance is regarded as one of the dominant forces controlling stream invertebrate communities (Resh et al 1988;Reice et al 1990;Lake 2000). Disturbance from increased discharge influences invertebrate communities by physically removing animals and by scouring epilithic layers which can be a major food source for those invertebrates (Robinson & Minshall 1986;Death 1996).…”

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

“…In addition, the impacts of RoR hydropower to salmonid populations are likely to depend on the regional context in which individual RoR hydropower projects are built (Habit et al 2007). Flow diversion by RoR hydropower in watersheds with existing impacts from forestry and other industries will likely have different, and possibly compounding, effects on salmonids in contrast with watersheds with largely intact upland and riparian forests (Reice et al 1990;Bunn and Arthington 2002). The disparity between the regional spatial scale relevant to the survival and persistence of most salmonid populations and the often reach-specific scale at which environmental impacts of individual RoR hydropower projects are typically assessed needs to be addressed.…”

“…The natural flow regime (NFR) of rivers is defined by the magnitude, frequency, duration, timing, and rate of change of flow events, each of which affects stream-dwelling aquatic organisms over short-term to evolutionary timescales (Poff et al 1997). Many anthropogenic activities can alter the flow and disturbance regimes of streams, which in turn may affect the survival and fitness of native species (Poff and Ward 1990;Reice et al 1990;Strayer and Dudgeon 2010). Impoundment of water by dams, built for either irrigation, flood control, or hydroelectricity generation, is one of the greatest anthropogenic drivers of change to NFRs.…”

Influence du compartiment trophique dans les réponses des populations de poissons aux variations artificielles de débit

“…Rather, I concentrate most of my review on the question of minimum instream flows. The disturbance frequency due to storm flows in runoff streams increases the diversity and leads to invertebrate assemblages that are in a perpétuai state of recovery (RESH et al, 1988 ;REICE et al, 1990). Natural experiments demonstrate effects of the extrême flows, either high or low on invertebrate assemblages.…”