The relation of drift to benthos density and food level in an artificial stream1

Abstract

The relationship between drift rates, benthos density, and food level for select taxa of stream invcrtebratcs was studied in an artificial stream system to dctermine if drift is independent of or dependent on population density, and if food level affects drift rates. Two taxa were introduced in a range of densities at a single level of periphyton food, and the drift from each density was measured. Four taxa were introduced in a range of densities at low and high food levels, and the drift from each density at each food level was measured.The drift of all taxa, examined by simple linear regression analysis, at each food level was judged a density independent response to increasing population density. The drift of three taxa at a given density was significantly greater at the lower food level: it is suggested that increased activity in searching for food at the lower food level resulted in increased drift.

Trophic interactions in open systems: Effects of predators and nutrients on stream food chains

“…Baetids reduced their rate of drift from nutrient-supplemented areas that were rich in algae and thus accumulated in those areas. Insect herbivores in other streams have been found to reduce their rate of departure from patches with abundant algae (Hildebrand 1974;Kohler 1984;Hinterleitner-Anderson et al 1992). Responses of other herbivore populations to nutrient enrichment may thus be influenced by their ability to redistribute themselves according to local algal abundance.…”

Effects of flow fluctuations on the daily and seasonal drift of invertebrates in a tropical river

“…Seasonal patterns in invertebrate drift can result from changes in benthic density, species life cycles and seasonal changes in water temperature and flow (Elliott, 1968;Hildebrand, 1974;Brittain and Eikeland, 1988). Diel drift periodicity is usually related to the presence of predators and the circadian rhythms of invertebrates (Waters, 1972;Flecker, 1992;Ramı´rez and Pringle, 2001).…”

An Irrigation Canal as a Lotic Mesocosm: Examining the Relationship between Macroinvertebrate Benthos and Drift

“…Alternatively, some investigators found no density-dependent relationship between benthic and drift densities (Hildebrand 1974, Humphries 2002. In these studies, drift density was directly proportional to benthic density.…”

“…This increases their risk of being swept away by the current (Allan 1978). Consequently, drift appears to be a function of the probability of dislodgement from the substrate, which would not be affected by density (Hildebrand 1974, Humphries 2002.…”

“…In most drift/benthos studies, researchers have either focused on a few species in a natural stream (i.e., Turner and Williams 2000) or studied several species isolated in artificial streams (i.e., Hildebrand 1974). Few have studied benthic community build-up and subsequent drift in newly formed streams (but see Hynes 1977, Gore 1979), yet these types of systems seem best suited for examining possible connections between the benthic community and its subsequent drift.…”