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USGS - science for a changing world

Adam J. Copp

1. Invertebrate drift is a fundamental process in streams and rivers. Studies from laboratory experiments and small streams have identified numerous extrinsic (e.g. discharge, light intensity, water quality) and intrinsic factors (invertebrate life stage, benthic density, behaviour) that govern invertebrate drift concentrations (# m−3), but the factors that govern invertebrate drift in larger rivers remain poorly understood. For example, while large increases or decreases in discharge can lead to large increases in invertebrate drift, the role of smaller, incremental changes in discharge is poorly described. In addition, while we might expect invertebrate drift concentrations to be proportional to benthic densities...
Categories: Publication; Types: Citation; Tags: Freshwater Biology
These data were compiled from field drift collections and from a meta-analysis of published drift literature. Field data were collected in 2014 from the Colorado River downstream of Glen Canyon Dam, Arizona, from the Salt River downstream of Stewart Mountain Dam, Arizona, and from Wet Beaver Creek near the Village of Oak Creek, Arizona. These data represent flow meter measurements taken at the mouth and adjacent to a drift net, and suspended solids concentrations collected by the drift net, over varying net deployment durations.
Drift studies are central to stream and river ecological research. However, a fundamental aspect of quantifying drift — how net clogging affects the accuracy of results — has been widely ignored. Utilizing approaches from plankton and suspended sediment studies in oceanography and hydrology, we examined the rate and dynamics of net clogging across a range of conditions. We found that nets clog nonlinearly over time and that suspended solid concentrations and net mesh size exerted a strong effect on clogging rates. Critically, net clogging introduced unpredictable biases in resultant data due to the inaccuracies in water volume estimates introduced by progressive clogging. This renders the widespread approach to...
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