New methods for the investigation of leaf litter breakdown in river sediments

Simon Navel (1) , Christophe Piscart (1) , Florian Mermillod-Blondin (1) , Pierre Marmonier (1)

1 E3S - Équipe 3 - Écologie, Évolution, Écosystemes Souterrains

The breakdown rate of leaf litter buried inside river sediments (i.e., in the hyporheic zone) remains poorly known. The burial of large bags (15 9 15 cm) used in the benthic layer generates disturbances of the vertical connectivity with surface water, and thus affects the breakdown rate. We performed field and laboratory experiments to test the suitability of two leaf litter containers: small litter bags (5 9 4 cm) and perforated stainless steel cylin- ders (6 cm long, 1.6 cm in diameter), both introduced inside sediments using mobile mini-piezometers (1 m long, 1.7 cm or 3 cm in diameter). We compared the two containers for (i) the hydrological exchanges toward leaf litter, (ii) the impact of a benthic shredder on leaf breakdown, and (iii) the response of leaf litter breakdown to changes in sediment characteristics. The two methods give similar patterns of breakdown rates with stream sediment characteristics, but the use of perforated stainless steel cylinders provides an artifi- cial empty volume in which invertebrates can over degrade leaf litter. Small plastic bags do not alter physico-chemical conditions around leaf litter and give lower values of breakdown rates in the hyporheic zone.

Mots clés: Organic matter recycling; Hyporheic zone; Sediment characteristics; Field and laboratory experiments

Domaines: Biodiversité et Ecologie

Simon Navel, Christophe Piscart, Florian Mermillod-Blondin, Pierre Marmonier. New methods for the investigation of leaf litter breakdown in river sediments. Hydrobiologia, 2013, 700, pp.301-312. ⟨10.1007/s10750-012-1239-1⟩. ⟨halsde-00784639⟩