Factors controlling leaf litter breakdown in Amazonian streams

Our objective was to assess the relative importance of leaf litter quality, and the microbial and aquatic invertebrate communities involved in leaf litter breakdown in Amazonian streams. We test the hypothesis that leaf litter quality is the driving force of leaf breakdown rates, rather than the microbial or invertebrate community, independent of stream characteristics. We incubated 3 g of Eucalyptus camaldulensis (EC), Baccharis platypoda, Symphonia globulifera, Mabea speciosa (MS), and Eperua duckeana (ED) leaves in five streams for 75, 56, 46, 26, 14, or 7 days. In all of the streams, leaf litter breakdown was higher for EC and lower in ED. This result may be related to different chemical characteristics among the five studied species. We observed higher frequency of shredders in MS and stream 4, and scrapers in streams 1 and 2. The concentration of ergosterol was higher in MS and lower in EC when adenosine triphosphate differed significantly among streams. Our data indicated that leaf litter quality (chemical and structural components) is a main factor affecting leaf breakdown in Amazonian streams.