The three Rs of river ecosystem resilience: Resources, recruitment, and refugia

Abstract

Resilience in river ecosystems requires that organisms must persist in the face of highly dynamic hydrological and geomorphological variations. Disturbance events such as floods and droughts are postulated to shape life history traits that support resilience, but river management and conservation would benefit from greater understanding of the emergent effects in communities of river organisms. We unify current knowledge of taxonomic‐, phylogenetic‐, and trait‐based aspects of river communities that might aid the identification and quantification of resilience mechanisms. Temporal variations in river productivity, physical connectivity, and environmental heterogeneity resulting from floods and droughts are highlighted as key characteristics that promote resilience in these dynamic ecosystems. Three community‐wide mechanisms that underlie resilience are (a) partitioning (competition/facilitation) of dynamically varying resources, (b) dispersal, recolonization, and recruitment promoted by connectivity, and (c) functional redundancy in communities promoted by resource heterogeneity and refugia. Along with taxonomic and phylogenetic identity, biological traits related to feeding specialization, dispersal ability, and habitat specialization mediate organism responses to disturbance. Measures of these factors might also enable assessment of the relative contributions of different mechanisms to community resilience. Interactions between abiotic drivers and biotic aspects of resource use, dispersal, and persistence have clear implications for river conservation and management. To support these management needs, we propose a set of taxonomic, phylogenetic, and life‐history trait metrics that might be used to measure resilience mechanisms. By identifying such indicators, our proposed framework can enable targeted management strategies to adapt river ecosystems to global change.

Do We Know Enough to Save European Riverine Fish?—A Systematic Review on Autecological Requirements During Critical Life Stages of 10 Rheophilic Species at Risk

“…In conjunction with improved planning tools there is an urgent need for data about species-specific habitat requirements to streamline rehabilitation efforts. Accurate data on life history traits fostering recovery are considered most important to derive rehabilitation targets, to run realistic model scenarios, to identify possible population bottlenecks and to implement suitable mitigation methods [21]. These traits include for instance reproductive traits as well as habitat requirements of early life-stages for spawning and nursery.…”

Human influence on the morphological adjustment of river channels: The evolution of pertinent concepts in river science

“…This is included in the more general consideration of geomorphic adjustment in terms of four Rs (response, resistance, resilience, and recursion) by Phillips (). Van Looy et al () employ the three Rs of ecosystem resilience (resources, recruitment, and refugia), and the concept has been considered more broadly (Thoms, Piégay, & Parsons, ). Finally, greater attention should be given to implications of channel change because modified channels can accommodate a different frequency of flows, pertaining downstream of the urban area (Chin & Gregory, ), and reduction in channel capacity has been shown to trigger an increase in flood hazard over time on the Guadalquivir River in southern Spain (Bohorquez & Moral‐Erencia, ).…”

The role of floods and droughts on riverine ecosystems under a changing climate

“…There are two generally recognised forms of biological response to disturbance: resistance (the capacity of the biota to withstand the disturbance) and resilience (the capacity to recover from the disturbance) (Lake, ). A third type of response is opportunistic utilisation of habitats that are created by the disturbance, such as spawning or feeding habitats (Górski et al, ; Górski, Winter, De Leeuw, Minin, & Nagelkerke, ; Grift et al, ; Phelps, Tripp, Herzog, & Garvey, ; Van Looy et al, ; Welcomme, ). Resistance is observed concurrently with disturbance events, while resilience is expressed during the post‐disturbance phase.…”

“…the drag‐minimising body posture and adhesive anchoring observed in some invertebrates (Schnauder, Rudnick, Garcia, & Aberle, ) or body size‐related swimming performance (Radinger & Wolter, ; Wolter & Arlinghaus, )) and a search for areas offering refuge (Lancaster & Belyea, ; Meffe, ). Resilience is driven by the availability of refugia, connectivity and the organism's fecundity as well as flexibility of life history strategy (Arlinghaus & Wolter, ; Klemetsen et al, ; Van Looy et al, ; Wolter et al, ). Opportunism is a function of species being able to take advantage of circumstances during the disturbance.…”

“…For the ecology of a system, floods and droughts are considered physical disturbances, that is stochastic events forcing normal system environmental conditions substantially away from the mean (Death, Fuller, & Macklin, 2015;Fuller, Gilvear, Thoms, & Death, 2019;Puckridge, Sheldon, Walker, & Boulton, 1998;Stanford & Ward, 1983). Physical disturbance is a natural component of aquatic ecosystems, and aquatic biotas are adapted to deal with these disturbances (Fisher & Grimm, 1991; Lake, 2000; Lytle & Poff, 2004;Resh et al, 1988;Van Looy et al, 2019). Lake (2000) described three types of disturbance: pulse, press and ramp, which trigger three different processes that alter populations.…”