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Microbial dynamics associated with leaves decomposing in the mainstem and floodplain pond of a large river

Baldy, Virginie and Chauvet, Eric and Charcosset, Jean-Yves and Gessner, Mark O. Microbial dynamics associated with leaves decomposing in the mainstem and floodplain pond of a large river. (2002) Aquatic Microbial Ecology, Vol. 28 (N° 1). pp. 25-36. ISSN 0948-3055

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Official URL: http://dx.doi.org/doi:10.3354/ame028025

Abstract

Aquatic habitats of forested floodplain systems receive large inputs of allochthonous plant litter. We examined the decomposition of, and microbial productivity associated with, leaves of a common floodplain tree, Populus gr. nigra, in the mainstem and floodplain pond of a seventh order river in 2 consecutive years. Litter bags were submerged at both sites, retrieved periodically, and analyzed for litter mass loss, bacterial and fungal biomass, growth rate and production, and sporulation rates of aquatic hyphomycetes. Litter decomposition rates were similar in both sites and years (leaf breakdown coefficients k of 0.0070 to 0.0085 d–1), although microbial dynamics partly differed between sites. Species diversity of aquatic hyphomycetes was lower on leaves submerged in the pond (16 species) than in the river (21 species). Mycelial biomass was also significantly lower in the pond, with values <20 mgCg–1 of detrital C, whereas peaks of 50 and 80 mgC g–1 were reached in leaves in the mainstem. These differences contrast with the comparable fungal productivity at both sites (peak rates of 1.4 mg of mycelial C per g of detrital C per day in both years). This suggests that fungi were equally productive in both habitats but experienced greater losses in the pond. Bacterial numbers and biomass also showed the same basic pattern at both sites, although somewhat higher levels were reached in the pond (maximum of about 10^10 cells and 0.5 mg g–1 of detrital C). Bacterial- specific production rates fluctuated between 0.06 and 1.5 d–1 with lower values occurring in the floodplain pond. Although bacteria on leaves were clearly outweighed by fungi in terms of biomass, they accounted for a sizeable fraction of the total biomass (up to 11%), and up to 32% of the total microbial production. Our comparison of bacterial and fungal productivity thus points to a critical role of fungi in litter decomposition in aquatic habitats of river floodplain systems, while suggesting that bacteria must not be overlooked as important agents of litter decompositon in riverine environments.

Item Type:Article
Additional Information:Thanks to Inter-Research editor. The definitive version is available at http://www.int-res.com. The original PDF of the article can be found at Aquatic Microbial Ecology website : http://www.int-res.com/abstracts/ame/v28/n1/p25-36
HAL Id:hal-01333523
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Other partners > Swiss Federal Institute of Aquatic Science and Technology - EAWAG (SWITZERLAND)
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Deposited By: Eric Chauvet
Deposited On:29 Apr 2016 09:59

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