Experimental evidence quantifying the role of benthic invertebrates in organic matter dynamics of headwater streams

Abstract

SUMMARY. 1. The insecticide methoxychlor was applied seasonally to one of three small headwater streams in the southern Appalachian Mountains in North Carolina, U.S.A. The initial application caused massive invertebrate drift (>l,000,000 organisms/week) and resulted in a community with few shredders and reduced abundances of most insecl taxa.2. Bacterial densities and microbial respiration rates were not affected by treatment.3. Disruption of the invertebrate community resulted in significant reductions in leaf litter processing rates (50-74% reduction depending on leaf species) and in the amount of leaf litter processed annually (reduction of 25-28%).4. Reductions in leaf litter processing rates resulted in significant reductions in fine particulate organic matter (FPOM) export. Declines in both concentration and total export were detectable within 1 week of treatment. Annual FPOM export was reduced to 33% of pretreatment levels. Alteration to the invertebrate community had a much greater effect on FPOM export than a severe (50-200 year) drought.6. Course particulate organic matter (CPOM) export was not significantly influenced by treatment but was influenced by hydrologie differences among years.

Effects of riparian willow trees(Salix fragilis)on macroinvertebrate densities in two small Central Otago, New Zealand, streams

“…Cuffney et al 1990) is clearly not relevant to our study, and no increase in filterer biomass or density was observed. The filterer Austrosimulium was, however, more abundant at willow sites in Heeney Creek.…”

Abrupt biological discontinuity in a small Michigan (USA) stream due to historical riparian canopy loss

“…The precise mechanisms of this impact -such as decrease in allochthonous CPOM, increase in allochthonous FPOM, increased growth of periphyton, changes in substrate composition, increase in flooding, or competition between functional groupsstill need further study. Likewise, further study is needed on the potential impacts of headwater habitat loss on overall river systems, such as the loss of cold-water refuge habitats; the loss of fish spawning grounds; and the loss of coarse allochthonous input, processing, and export (Cuffney et al 1990). Ultimately, the biotic integrity of entire river systems is greatly dependent on the collective impacts to individual small streams such as Fairbanks Creek (Meyer et al 2007).…”

The influence of water quality and macroinvertebrate colonization on the breakdown process of native and exotic leaf types in sub-alpine stream

“…Terrestrial leaves that enter the stream generally breakdown through a sequence of processes (Webster & Benfield 1986), such as leaching (dissolution of labile organic compounds), conditioning (microbial colonization by bacteria and hyphomycetes), and consumption and fragmentation by macroinvertebrates and physical abrasion (Tank et al 2010). The rate of leaf litter breakdown is determined directly by intrinsic characteristics of the debris (LeRoy & Marks 2006;Lecerf & Chauvet 2008), water quality and geomorphological characteristics (Suberkropp & Chauvet 1995;Sponseller & Benfield 2001), and indirectly through the activity of microbial and macrobenthic organisms responsible for conditioning, fragmentation and consumption (Cuffney et al 1990;Findlay 2010). Breakdown of allochthonous leaf litter is generally measured using the leaf bag approach, because these bags are generally thought to be representative of the natural leaf accumulation on stream beds (see review in Graça et al 2005).…”