Links between sediment structures and ecological processes in the hyporheic zone: ground-penetrating radar as a non- invasive tool to detect subsurface biologically active zones

Abstract : At the scale of geomorphological units (rif␣es, pools, and gravel bars), the contribution of the hyporheic zone to the functioning of streams and rivers depends on the hydrological exchanges between surface water and groundwater. These exchanges are largely controlled by sediment structure and texture, which are dif␣cult to assess with classical methods (shovelling and freeze coring). We aimed to evaluate the ability of a non-destructive method, ground-penetrating radar (GPR), to detect sediment structures associated with subsurface biologically active zones in a gravel-bed river. After GPR data acquisition and processing, a three-dimensional reconstruction of a gravel bar permitted the identi␣cation of two sediment facies: a cobble/gravel lithofacies denoted as ‘coarse’ and a sand/gravel lithofacies denoted as ‘␣ne’. We installed piezometers along two longitudinal pro␣les (each corresponding to a lithofacies identi␣ed by GPR) and monitored hydraulic head and temperature for 20days. Water and sediments were sampled along the two pro␣les to measure water physicochemistry, sediment characteristics, bacterial abundance and activity, and interstitial invertebrate assemblages. These measurements con␣rmed that the two pro␣les were characterized by distinct hydrological ␣ow rates and associated biological activities. Rapid water transport in the coarse pro␣le fuelled the hyporheic zone with organic matter, whereas water and organic matter supplies were lower in the ␣ne pro␣le. Consequently, the higher supply of organic matter in the coarse pro␣le was associated with higher microbial activities and invertebrate density and diversity. Therefore, GPR could be an ef␣cient tool to detect the sediment features playing a key role in hyporheic zone functioning.
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Article dans une revue
Ecohydrology, 2015, 8, pp.626-641 〈10.1002/eco.1530〉
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Soumis le : mardi 31 mai 2016 - 14:15:02
Dernière modification le : mardi 16 janvier 2018 - 16:12:47

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Florian Mermillod-Blondin, Thierry Winiarski, Arnaud Foulquier, Anne Perrissin, Pierre Marmonier. Links between sediment structures and ecological processes in the hyporheic zone: ground-penetrating radar as a non- invasive tool to detect subsurface biologically active zones. Ecohydrology, 2015, 8, pp.626-641 〈10.1002/eco.1530〉. 〈hal-01323969〉

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