The duration of channel drying affects survival of Gammarus pulex (Amphipoda: Gammaridae) within subsurface sediments: an experimental flume study

Rachel Stubbington,Jonathan Millett,Paul J Wood,Atish N Vadher

doi:10.1007/s10750-018-3652-6

Rachel Stubbington, Jonathan Millett + Show 2 more

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https://doi.org/10.1007/s10750-018-3652-6

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Abstract

Field studies have demonstrated that benthic fauna use hyporheic sediments during drying events in temporary rivers, but the factors influencing the survival of fauna in subsurface sediments remain poorly quantified. Laboratory mesocosm experiments were conducted to determine how the length of drying events (1, 7, 14 and 21 days) influenced the survivorship of Gammarus pulex (L.) (Amphipoda: Gammaridae). The water level was reduced to 5 cm below the substrate surface during drying experiments and held at 5 cm above the sediment surface during control experiments. The results demonstrate that G. pulex survivorship was reduced with increasing length of the experiment, particularly in the drying treatment compared to the control treatment. We show that G. pulex can persist in subsurface sediments for up to 21 days during surface drying. In view of interacting climatic drivers and water resource pressures that are increasing the spatial and temporal occurrence of streambed drying, our results have important implications for stream management. Our results also highlight the utility of mesocosm-based studies for elucidating the abiotic controls of macroinvertebrate survival during stream drying events.

Highlights

Temporary streams experience periods of reduced hydrological connectivity as surface water levels decline, often resulting in sections of the streambed becoming dry (Boulton, 2003; Larned et al, 2010)
Gammarus pulex survivorship decreased with increasing duration for both experiment conditions, but was reduced to a greater extent during the drying experiments
Survivorship was lower for drying experiments compared to experiments in which surface water persisted

Summary

Introduction

Temporary streams experience periods of reduced hydrological connectivity as surface water levels decline, often resulting in sections of the streambed becoming dry (Boulton, 2003; Larned et al, 2010). Flow cessation and surface drying events typically result in a reduction in the abundance of rheophilic taxa (Chessman, 2009; Verdonschot et al, 2015), an increased dominance of generalist taxa able to persist in isolated pools (Robson et al, 2011) and the persistence of a limited number of desiccationtolerant taxa in drying sediments (Stubbington et al., 2009; Datry, 2012). Adaptations of temporary stream fauna that enhance resistance and resilience to surface drying include behavioural responses, for example movement into saturated subsurface sediments (Vander Vorste et al, 2016a; Vadher et al, 2017), life history adaptations, for example aestivation and diapause (Strachan et al, 2015) and physiological adaptations including desiccation tolerance of egg, juvenile or adult life stages (Stubbington et al, 2016)

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