Detritus Processing by Macroinvertebrates in Stream Ecosystems

The detritus pathway is that in which plant or animal material dies and is then attacked by microorganisms. More of the energy fixed by autotrophic organisms is probably transferred through this route than through the grazing pathway (98). Detritus cannot be precisely defined in terms of its chemical composition or associated microorganisms. As an operational definition, Boling et al (16) defined it as all particulate (>0.45-μm particle diameter) organic matter (reduced carbon compounds) together with associated microbiota—fungi, bacteria, protozoa, and other microinvertebrates. Microbes are included as part of the detritus because the relationship between them and the organic substrate is so intimate that independence is never observed in nature; also, efficient separation techniques applicable to field-collected detritus are nonexistent. The role of detritus in aquatic ecosystems was discussed in two recent symposia (1, 109). Studies of biological decomposition are interdisciplinary in nature and were a theme of the International Biological Programs in freshwater, marine, and terrestrial projects (1). Thus, with the upsurge of interest in this topic, it is timely to review contributions, especiajly on the