The role of invertebrates on leaf litter decomposition in streams - A review

Leaves entering low order streams are subject to physical abrasion, microbi al degradation and invertebrate fragmentation. Aquatic invertebrates feedin g on leaves are known as shredders and their densities tend to be correlate d with the spatial and temporal accumulation of organic matter in streams. Shredders discriminate among the variety of leaves normally found in the st ream; this discrimination may be related to differences in leaf toughness, plant nutrient content of leaves and the presence of secondary compounds. S hredders also consume leaves preferentially after the establishment of a we ll-developed microbial community. This preference may be the result of chan ges in leaf matrix carried out by the microbial community or the presence o f fungal hyphae with a higher nutrition value than the leaves themselves. T he immediate consequence of invertebrate feeding on leaves is the incorpora tion of plant material into secondary production and the fragmentation of l eaves. The relative importance of fungi and invertebrates in the decomposit ion process depends upon the density of shredders, which, in turn, may depe nd on litter accumulation in streams. Therefore, the type of riparian veget ation has the potential to control the diversity and abundance of shredders and changes in riparian vegetation have the potential to affect the assemb lages of aquatic invertebrates.