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University of Melbourne (2018)

Novel approaches to investigate the complex interactions of bioturbation and clogging in the hyporheic zone

Lakhanpal, Garima

Titre : Novel approaches to investigate the complex interactions of bioturbation and clogging in the hyporheic zone

Auteur : Lakhanpal, Garima

Université de soutenance : University of Melbourne

Grade : Masters Research thesis 2018

Résumé
Bioturbation activity by macroinvertebrates in freshwaters may influence the hyporheic exchange processes in river systems. In this study, I focus on understanding the complex interaction of bioturbation by upward conveyor macroinvertebrates Lumbriculus variegatus and clogging processes in the hyporheic zone through novel methodological approaches. Upward conveyors are bottom feeders which align themselves vertically (heads buried in the sediment with their posterior ends at the surface water interface) and ingest and egest in a way that sediments move vertically upwards. The study aims at investigating (i) the effects of bioturbation on hyporheic flowpath patterns in clogged and unclogged sandy bedforms and (ii) the vertical spatial distribution of bioturbators in clogged sandy bedforms using an experimental setup. There is a paucity of agreed methodology to study the effects of bioturbation on hyporheic exchange processes in flowing waters. Therefore, this study is focused on developing the methods to understand these interactions in the laboratory flume. The above-mentioned objectives were addressed by running a series of dye tracing experiments in a recirculating perspex flume of dimensions 2.5m (L) X 0.2m (W) X 0.3m (H) filled with triple washed sand of 0.2mm mean particle size. The sand bed was later clogged with clay particles of 0.002mm to compare the flowpaths in clogged and unclogged bed conditions. Using image analysis of the injected dye flowpaths and X-ray technology for understanding the galleried structures created by the bioturbators we are able to better understand the role of these organisms in clogged river beds and their importance in the hyporheic exchange processes. Galleries were imaged using the micro-CT scans by taking core samples along the flume and scanning the top 5 cm of the core. This study can help us understand the need and importance to protect the bioturbator communities for maintaining ecosystem services and healthy functioning of the hyporheic zone.

Mots clés : bioturbation ; hyporheic zone ; clogging ; hyporheic exchange ; Lumbriculus variegatus

Présentation

This item is embargoed and will be available on 2021-04-18.

Page publiée le 10 novembre 2019