Ref ID : 7769
Florian Mermillod-Blondin, Jean-Christophe Poggiale, Caroline Tolla, Pierre Auger, Wilfried Thuiller, and Michel Creuze des Chatelliers; Using a mathematical model to simulate the influence of tubificid worms (Oligochaeta) on oxygen concentrations in hyporheic sediments. Fundamental and Applied Limnology Archiv fur Hydrobiologie 172/2:135-145, 2008
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The aim of the study was to present a model to stimulate the influence of tubificid worms (Limnodrilus sp. and Tubifex sp.) on O2 concentrations in hyporheic sediments. A mathematical model was developed to reproduce vertical distribution of O2 in experimental columns of sediment. Vertical columns were stimulated as grids with cells of 1-cm depth each. The model took into account the hydrodynamic properties, the microbial respiration and distribution, the stimulation effect of tubificids on microbial activity, and the vertical distribution of worms in the system. Parameters of the mathematical model were determined to fit experimental oxygen concentrations obtained during two experiments: one experiment testing the influence of 100 Tubifex sp. (mainly Tubifiex tubifex) and one experiment testing the effect of 100 Limnodrilus sp. (80% Limnodrilus hoffmeisteri). The spatial model gave an adequate assessment of the vertical profiles of O2 concentrations in columns with and without tubificid worms. The parameters used to fit simulations with experimental data supposed that Limnodrilus burrowed deeper and produced a higher stimulation of microbial respiration than Tubifex in our experimental system. Such results are in accordance with literature data and clearly suggest that this spatial model could be easily used to characterize the effects of animals (modification rate of the microbial respirations by animals and location of the animal effect) on biogeochemical processes in hyporheic sediments.