Gammarus pulex (Crustacea : Amphipoda) avoids increasing water temperature and intraspecific competition through vertical migration into the hyporheic zone: a mesocosm experiment
Gammarus pulex (crustacés: amphipodes) évite les fortes températures de l'eau et la compétition en migrant dans la zone hyporhéique: une expérience en mésocosmes
Vander Vorste, R. ; Mermillod Blondin, F. ; Hervant, F. ; Mons, R. ; Datry, T.
Type de document
Article de revue scientifique à comité de lecture
Affiliation de l'auteur
IRSTEA LYON UR MALY FRA ; LEHNA UMR CNRS 5023 UNIVERSITE LYON I FRA ; LEHNA UMR CNRS 5023 UNIVERSITE LYON I FRA ; IRSTEA LYON UR MALY FRA ; IRSTEA LYON UR MALY FRA
Résumé / Abstract
The saturated interstices below and adjacent to the riverbed (i.e., the hyporheic zone) can be a refuge for biota during low flows, flow cessation and river drying. Prior to complete drying, organisms are constrained by abiotic and biotic factors (e.g., water temperature, competition) and may respond through vertical migration into the hyporheic zone. However, it remains unclear when temperature and competition become harsh enough to trigger migration. Furthermore, potential consequences of using the hyporheic zone, which is often food-limited, on the survival, ecosystem function and physiology of organisms are unknown. We tested the hypotheses that i) Gammarus pulex, a widespread detritivore, migrates into the hyporheic zone to avoid increasing surface water temperature and intraspecific competition and ii) that these factors would reduce their survival, leaf mass consumption and energy stores. Using 36 mesocosms, three temperature (15, 20, 25°C) and species density levels (low, medium, high) were manipulated in a factorial design over 15 days. Increasing temperature to 25°C and a 3-fold increase in density both caused G. pulex to vertically migrate, and the interaction of these factors was additive, rather than antagonistic or synergistic. Importantly, survival, leaf consumption and glycogen content were reduced in high temperature and density treatments, suggesting tradeoffs between tolerating harsh surface conditions and limitations of inhabiting the hyporheic zone. Identifying that the hyporheic zone is used by invertebrates to avoid high water temperature and intraspecific competition is a key finding considering the global-scale increases in temperature and flow intermittence, yet its capacity to provide refuge is likely temporally limited.
Aquatic Sciences, vol. 79, p. 45 - 55