Effects of invertebrates in lotic ecosystem processes.

Abstract

This chapter focuses on various processes that are influenced by invertebrate activities rather than on individual functional groups themselves. Invertebrates influence lotic ecosystem processes by several mechanisms. First, invertebrates alter resource quantity, size and shape. Second, invertebrates enchance downstream movement of carbon and associated nutrients. Third, their activity can also enchance retention of carbon and nutrients. Fourth, predators, through their influence on standing crop of prey, may affect all processes. This chapter also addresses how large-scale physical changes along stream gradients affect invertebrate assemblages and their primary roles in stream ecosystems.

Forest canopy cover determines invertebrate diversity and ecosystem process rates in depositional zones of headwater streams

“…Depositional zones contribute to stream biodiversity by hosting specialised invertebrate taxa such as burrowers and shredders (Wagner, 1991;Lloyd & Ormerod, 1992;Dangles, 2002b) and by offering refuges to rheophilic animals during spates (Lancaster & Hildrew, 1993). Stream invertebrates drive many key ecosystem-level processes (Covich, Palmer & Crowl, 1999;Wallace & Hutchens, 2000). Studies on leaf litter breakdown have shed light on the major contribution of shredders to the conversion of leaf litter into finer particles and biomass (Cuffney, Wallace & Lugthart, 1990).…”

The influence of geomorphic unit spatial distribution on nitrogen retention and removal in a large river

“…Studies in small streams observed the impacts of macroinvertebrates on nutrient cycling when their biomass was high (Newbold et al, 1982;Merritt et al, 1984;Wallace and Hutchens, 2000). For example, Small et al (2009) found that the macroinvertebrates increased the downstream velocity of the nonlimiting nutrient and delayed the downstream transport of the limiting nutrient.…”

Terrestrial and Longitudinal Linkages of Headwater Streams

“…In small headwater streams, where the physical environment stores organic particles, invertebrate assemblages are dominated by shredders, gatherers, and invertebrate predators (Wallace and Hutchens 2000). Their feeding actions tend to decrease the particle size of the organic resources and favor the downstream export of FPOM, which is more easily transported than the larger CPOM.…”

“…The dissimilarities in production and community structure between up-and down-stream sites of the Little Tennessee River resulted from unequal distribution of resources along the river gradient (Wallace and Hutchens 2000). Hall et al (2000) and Rosi-Marshall and Wallace (2002) used the trophic basis of production method (Benke and Wallace 1980) to estimate the annual food consumption by invertebrates at up-and down-stream sites.…”