Drying duration and stream characteristics influence macroinvertebrate survivorship within the sediments of a temporary channel and exposed gravel bars of a connected perennial stream

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

doi:10.1007/s10750-018-3544-9

Atish N Vadher, Jonathan Millett + Show 2 more

Open Access

https://doi.org/10.1007/s10750-018-3544-9

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Abstract

Intermittent rivers, which experience periods of flow cessation and streambed drying, occur globally. Given that the frequency and duration of stream drying events is likely to increase as a result of anthropogenic pressures and global climate change, riverbed sediments may become increasingly important as refuge habitat for benthic macroinvertebrates. Our study examined the effect of surface water loss and increasing drying duration on the survivorship of the most abundant benthic invertebrate, Gammarus pulex (L.) (Amphipoda: Gammaridae), inhabiting the wet subsurface sediments of exposed gravel bars within a perennial stream and a connected temporarily flowing side channel. G. pulex survivorship declined more over time during drying conditions compared to control conditions (flowing water present). Survivorship was greater in the temporary channel and may reflect the greater water retention capacity of fine sediments in the subsurface and abiotic stability compared to the free-draining exposed gravel bars on the main channel. Our results illustrate that saturated subsurface sediments may facilitate G. pulex persistence during surface drying events and highlight the need for effective refuge management and conservation for instream fauna during drying events.

Highlights

Intermittent rivers experience periods of surface flow cessation and typically the drying of some or all of the river bed (Bogan et al, 2015; Datry et al, 2016)
The frequency and duration of ‘no-flow’ and streambed drying events may increase in some global regions based on future climate change predictions (Bonada et al, 2007a; Verdonschot et al, 2010; Ledger & Milner, 2015; Pyne & Poff, 2017), a greater understanding of the response of lotic ecosystems to drying duration would help guide future management options
We examined the effect of increasing duration of surface water loss on the survivorship of G. pulex using mesocosms within the bed of two adjacent 100 m long channels of a temperate zone stream comprising i) a temporary flowing channel, and ii) exposed gravel bars of a perennially flowing channel

Summary

Introduction

Intermittent rivers experience periods of surface flow cessation and typically the drying of some or all of the river bed (Bogan et al, 2015; Datry et al, 2016). These streams comprise a large proportion of the total channel length across the globe, occurring throughout climatic zones from the poles to the equator (Leigh et al, 2016a), making a significant contribution to regional biodiversity (Stubbington et al, 2017), but have typically been overlooked and excluded from national and international legislation protecting streams from anthropogenic degradation (Acuna et al, 2014, 2017). There is a need to quantify the effects of stream drying on population structure and functioning in lotic ecosystems (Dewson et al, 2007)

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