Technical note: a constant-volume artificial stream for reducing variation in aquatic process measurements.

摘要

This paper describes the construction, operation, and assessment of a constant-volume artificial stream designed to control water quality and reduce variation to improve aquatic process measurements. The system was used to investigate suspended clay influence on phosphorus acquisition (load buffering) by lotic periphyton. Spatial and temporal heterogeneity represent the greatest sources of variation in the distribution and activity of aquatic biota in natural systems. Imposing experimental treatments simultaneously addresses temporal variation. Spatial variability is managed by controlling physical and chemical variables such as temperature, light, substrate, flow, and water quality. Controlling environmental conditions leads to reduced variation in biotic state, which improves the measurement of biotic processes. This artificial stream design minimizes water volume fluctuation, which facilitates solution manipulation and measurement and reduces environmental variation. A unique reservoir and valve arrangement compensates for evaporative water loss, allowing the operating water volume of individual stream units to be maintained (<+or-1%) over long periods. In pre-experiment assessments, mean total dissolved salts were maintained to within 3% of their initial concentration over a one-week period, and suspended clay turbidity was within 4.3% after some initial settling. During experimental use, artificial stream variation in periphyton biomass and phosphorus uptake was less than that reported from several natural streams.