Field experiments on the mobility of benthic invertebrates in a southern English stream

Abstract

1. In each of twenty‐six week‐long experiments, the colonization by macroinvertebrates of boxes of natural sediment in a stony stream was measured. The experiments took place between February and November 1992 and environmental conditions prevailing during the weeks (particularly discharge and temperature) differed widely. 2. Colonization rate also varied widely between the weekly experiments and was sensitive to discharge, temperature and background benthic density, depending on the taxa considered. 3. A ‘mobility index’ measured colonization rate independently of background benthic density. This index was most strongly and positively correlated with discharge for the abundant stonefly Leuctra nigra, the net‐spinning caddis Plectrocnemia conspersa and the Chironomidae, perhaps indicating that their mobility is physically driven by the influence of flow on drift. 4. Mobility in a second stonefly (Nemurella pictetii) was greatest in summer, when flows were low but temperature was high. Peak mobility in this species occurred during an ochreous bloom on the stream bed. It is likely the mobility of N. pictetii is more active than the other taxa. 5. There were thus differences among taxa in their mobility at baseflow and in their susceptibility to flow fluctuations. The population consequences of differences in mobility among taxa are discussed.

Modeling the influence of flow on invertebrate drift across spatial scales using a 2D hydraulic model and a 1D population model

“…Benthic invertebrates may also initiate emigration at higher rates in response to unfavorable local environmental conditions. Increased emigration may occur in areas of adverse hydrology (Fonseca and Hart, 1996;Wilcox et al, 2008;Winterbottom et al, 1997) or high predation pressure (Englund, 2005;Englund et al, 2001) that occurs in lower velocity areas (Hill and Grossman, 1993;Hughes, 1992;Malmqvist and Sackmann, 1996). The latter is especially important in the context of our simple prediction that macroinvertebrate density should be inversely proportional to flow velocity.…”

Downward, upstream or downstream? Assessment of meio- and macrofaunal colonization patterns in a gravel-bed stream using artificial substrates

“…In fact, fluvial systems are spatially heterogeneous (Pennak, 1988) and populations may survive in some habitat patches (e.g., Golladay and Hax, 1995;Palmer et al, 1995;Robertson et al, 1995). Faunal movements play an important role in regulating population densities, in facilitating reproduction and larval development, and in finding refugia from disturbances (Palmer et al, 1992;Robertson et al, 1995;Winterbottom et al, 1997). Dispersal capabilities of stream invertebrates are highly species-specific (Lancaster et al, 1996;Bilton et al, 2001;Elliott, 2003).…”

Dispersal of invasive species by drifting

“…Most of the abiotic factors tested also showed seasonal patterns. Environmental conditions during spring and summer facilitate survival and reproduction of macroinvertebrates and therefore generate an increase in biota (Winterbottom et al, 1997, Quinn et al, 1998. As seasonality incorporates multiple factors that directly affect macroinvertebrate life histories, community composition and food availability (Robinson and Burgherr, 1999), it is difficult to conclude what exactly determines seasonal fluctuations in macroinvertebrate abundances.…”