Benthic bioturbator enhances CH4 fluxes among aquatic compartments and atmosphere in experimental microcosms

Authors: Figueiredo-Barros, Marcos P.; Caliman, Adriano; Leal, João J. F.; Bozelli, Reinaldo L.; Farjalla, Vinicius F.; Esteves, Francisco A.

Source: Canadian Journal of Fisheries and Aquatic Sciences, Volume 66, Number 10, October 2009 , pp. 1649-1657(9)

Publisher: NRC Research Press

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Abstract:

We utilized laboratory microcosms to evaluate the effects of a benthic sediment bioturbator (Heteromastus similis; Polychaeta; conveyor-belt deposit feeder) on vertical distributions of CH4 in sediment and net CH4 fluxes across sediment–water–air interfaces. The effect of H. similis on sediment CH4 concentration ([CH4]) varied depending on sediment depth and was strongest at higher animal densities. In comparison with defaunated controls, microcosms with the highest density of H. similis exhibited an increase in [CH4] of 3.7-fold, on average, at the sediment surface (0–2cm), but these concentrations decreased by ~2-fold in deeper sediment layers (2–8cm). However, irrespective of sediment depth, the density of H. similis resulted in an overall nonlinear reduction of bulk sediment [CH4]. Most of the observed CH4 losses from the sediment were due to CH4 oxidation, but the bioturbatory activities of H. similis also promoted significant increases in [CH4] in both the water column and the microcosm headspace. These results suggest that benthic invertebrates can mediate CH4 turnover between compartments in aquatic ecosystems, with further consequences for the coupling between benthic–pelagic food chains via the methanotrophic-mediated microbial loop, as well as increase CH4 emissions to the atmosphere.

Des microcosmes de laboratoire nous ont servi à évaluer les effets d’un perturbateur biologique des sédiments benthiques (Heteromastus similis; polychète qui se nourrit de sédiments par convoyage) sur la répartition verticale de CH4 dans le sédiment et les flux nets de CH4 à travers les interfaces sédiment–eau–air. L’effet d’H. similis sur les concentrations de CH4 ([CH4]) varie en fonction de la profondeur du sédiment et est maximal aux plus fortes densités d’animaux. En comparaison des témoins sans animaux, les microcosmes avec les densités les plus élevées d’H. similis montrent une augmentation de [CH4] de 3,7 fois en moyenne à la surface des sédiments (0–2 cm), mais ces concentration diminuent de ~2 fois dans les couches plus profondes de sédiment (2–8 cm). Cependant, quelle que soit la profondeur des sédiments, la densité d’H. similis cause une réduction générale non linéaire du [CH4] du sédiment global. La plupart des pertes de CH4 observées dans les sédiments sont dues à l’oxydation de CH4; cependant, les activités de perturbation biologique d’H. similis provoquent aussi des augmentations significatives de [CH4], tant dans la colonne d’eau que dans l’espace de tête du microcosme. Ces résultats laissent croire que les invertébrés benthiques peuvent servir d’agents dans le circulation du CH4 entre les compartiments des écosystèmes aquatiques, avec des conséquences additionnelles sur le couplage des chaînes alimentaires benthique et pélagique par l’intermédiaire de la boucle microbienne méthanotrophique, ainsi que sur l’accroissement des émissions de CH4 vers l’atmosphère.

Document Type: Research Article

Publication date: October 1, 2009

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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