A closed artificial stream for conducting experiments requiring a controlled species pool

Abstract

Experimental testing of ecological theory in the field is often difficult because of the number of factors influencing the test system. Adequate control of relevant variables may require the use of laboratory microcosms for the performance of proper experimental tests. Our efforts to study the effects of species invasion sequence on community structure and ecosystem properties of the developing system, requires that the experimental systems be closed. To meet our demanding experimental requirements, we have designed a closed artificial stream that permits careful control over algal species introductions while minimizing the risks of contamination by unwanted species. In assessing the performance of these streams, we examined the variability among experimental replicates in water chemistry parameters and biomass accumulation. Those water chemistry parameters that were not greatly influenced by biological processes in the streams (Ca, Mg, bicarbonate, and sulfate) had average coefficients of variation less than 10%. Those parameters that were clearly influenced by biological processes (P, N, Fe, and Si) had average coefficients of variation ranging from l3.5%-40.4%. Ash free dry mass had an average coefficient of variation of 23.3%, but chlorophyll a was much more variable at 183%. This pattern of variation indicates that the artificial streams performed well in terms of replicability, but some experimental goals may require carefully conceived designs that adequately partition sources of variation in biologically mediated variables to obtain satisfactory results.

Effects of Water Velocity and Specific Surface Area on Filamentous Periphyton Biomass in an Artificial Stream Mesocosm

“…For example, high levels of periphyton growth and accumulation have impaired the use of rivers and streams for drinking water [9], damaged aquatic habitat [10], and degraded the aesthetic and recreational uses of rivers and streams [11]. Because many factors (i.e., water velocity, nutrient concentration, light intensity, substratum availability, and water temperature) have been reported to affect the growth and accumulation of periphyton, numerous established criteria and thresholds have been suggested to prevent the excessive growth and accumulation of periphyton in various environments [12,13].…”