TRaCK: Tropical Rivers and Coastal Knowledge

Science and knowledge that governments, communities, industries for sustainable use of Australia's tropical rivers and estuaries

Leaf litter chemistry, decomposition and assimilation by macroinvertebrates in two tropical streams

TitleLeaf litter chemistry, decomposition and assimilation by macroinvertebrates in two tropical streams
Publication TypeJournal Article
Year of Publication2012
AuthorsPettit, NE, Davies, T, Fellman, JB, Grierson, PF, Warfe, DM, Davies, PM
Start Page63
Date Published01/2012
ISSN0018-8158 (Print), 1573-5117 (Online)
KeywordsAquatic food webs, Detrital processing, Interactive effects, Mass loss, Melaleuca, Microbia community, Nauclea
Riparian vegetation typically provides substantial allochthonous material to aquatic ecosystems where micro-organisms can play an important role in organicmatter degradationwhich can support consumer biomass. We examined the effects of leaf litter quality (e.g., leaf nutrients, lignin and cellulose content), leaf species mixing, and microbial community diversity on in-stream breakdown rates of litter from dominant riparian trees (Melaleuca argentea, M. leucadendra, and Nauclea orientalis) in both a perennial and intermittent river in Australia’s wet-dry tropics. Leaf mass remaining after 82 days of in-stream incubation was negatively correlated (P\0.05) with initial leaf N and P content while initial lignin and cellulose content had no statistically significant effect. Breakdown rates of incubated leaves of both Melaleuca and Nauclea were significantly higher in mixed litter bags compared with single species litter bags. Although it was expected that leaf N content would decrease from initial levels during decomposition, we found either similar or slightly higher N content following in-stream incubation suggesting microbial colonisation increased overall N content. Stable isotopes of d13C and d15N for themajor sources and consumers in both rivers provide evidence that leaf litter was an important macroinvertebrate food source in the perennial river where heavy shading may limit algal production.However, in the intermittent river where riparian cover was low, benthic algae were the major organic carbon source for consumers. Our findings suggest that riparian tree species influence rates of in-stream organic matter processing, microbial community composition, and aquatic food web dynamics in tropical wet-dry streams.