Artificial Stream Research

The following is adapted from a poster presentation at the 1994 North American Benthological Society Meeting.


A SIMPLE ARTIFICIAL STREAM AND PARTICLE TRACKING ANALYSIS (PTA) SYSTEM FOR RESEARCH OR CLASSROOM USE. Dave McShaffrey, Biology Department, Marietta College, Marietta, OH, USA 45750.

An artificial stream was created by nesting a 40 x 20 x 25 cm aquarium inside a 75 x 30 x 30 cm aquarium, forming channels of variable width between the aquaria. Water was driven by one or two 1000 L hr-1 water pumps. Current velocity was measured by a videomacroscopic PTA system using a Sony Video 8 Pro CCD V-220 camcorder with an 8x macro-zoom lens fitted with a +7 diopter close-up lens set. Video was recorded on 1.27 cm (1/2") VHS videotape using a Sony SLV-676UC videocassette recorder. With the camcorder lens 5.5 cm from the stream, magnification on the 69 cm (27") diagonal Sony K27TS30 monitor was 10x. Current velocity was inferred from the distance traveled by particles (bubbles produced via electrolysis) between video frames 1/30 s apart. With one pump, mean current speed at the midpoint of the inner aquarium, 4-5 cm above the channel bottom with a 5 cm wide by 10 cm deep channel was 0.25 ± 0.005 m/s (n = 100, alpha = .05); vertical displacement of the particles was approximately 4% of their horizontal displacement. With two pumps, a mean current velocity of 0.5 ± 0.007 m/s (n = 100, alpha = .05) was obtained in a 3 cm wide channel. Setting the inner aquarium at an angle produced a channel with continuously varying current velocities. Flow conditions are easily replicated while PTA allows accurate estimation of current speeds with great (< 1mm) spatial discrimination. Cost of the stream with pumps was $75 US; the video equipment cost $2500 US.


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