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Interactions between fauna and sediment control the breakdown of plant matter in river sediments

Navel, Simon and Mermillod-Blondin, Florian and Montuelle, Bernard and Chauvet, Eric and Simon, Laurent and Piscart, Christophe and Marmonier, Pierre Interactions between fauna and sediment control the breakdown of plant matter in river sediments. (2010) Freshwater Biology, 55 (4). 753-766. ISSN 0046-5070

(Document in English)

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Official URL: http://dx.doi.org/10.1111/j.1365-2427.2009.02315.x


1. A substantial portion of particulate organic matter (POM) is stored in the sediment of rivers and streams. Leaf litter breakdown as an ecosystem process mediated by microorganisms and invertebrates is well documented in surface waters. In contrast, this process and especially the implication for invertebrates in subsurface environments remain poorly studied. 2. In the hyporheic zone, sediment grain size distribution exerts a strong influence on hydrodynamics and habitability for invertebrates. We expected that the influence of shredders on organic matter breakdown in river sediments would be influenced strongly by the physical structure of the interstitial habitat. 3. To test this hypothesis, the influence of gammarids (shredders commonly encountered in the hyporheos) on degradation of buried leaf litter was measured in experimental systems (slow filtration columns). We manipulated the structure of the sedimentary habitat by addition of sand to a gravel-based sediment column to reproduce three conditions of accessible pore volume. Ten gammarids were introduced in columns together with litter bags containing alder leaves at a depth of 8 cm in sediment. Leaves were collected after 28 days to determine leaf mass loss and associated microbial activity (fungal biomass, bacterial abundance and glucosidase, xylosidase and aminopeptidase activities). 4. As predicted, the consumption of buried leaf litter by shredders was strongly influenced by the sediment structure. Effective porosity of 35% and 25% allowed the access to buried leaf litter for gammarids, whereas a lower porosity (12%) did not. As a consequence, leaf litter breakdown rates in columns with 35% and 25% effective porosity were twice as high as in the 12% condition. Microbial activity was poorly stimulated by gammarids, suggesting a low microbial contribution to leaf mass loss and a direct effect of gammarids through feeding activity. 5. Our results show that breakdown of POM in subsurface waters depends on the accessibility of food patches to shredders.

Item Type:Article
Additional Information:Thanks to Wiley editor. The original PDF of the article can be found at Thermochimica Acta website : http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2427.2009.02315.x/abstract
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Université Claude Bernard-Lyon I - UCBL (FRANCE)
French research institutions > Institut national de recherche en sciences et technologies pour l’environnement et l’agriculture - CEMAGREF (FRANCE)
Laboratory name:
Deposited On:19 Mar 2014 11:02

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