Artificial substrata for reducing periphytic variability on replicated samples

Abstract

Periphyton accrual (chlorophyll a) was evaluated utilizing two different geometrically shaped artificial glass substrata. The first consisted of small coverslips attached to a glass slide (Dilks & Meier 1981), while the other method employed both horizontally and vertically oriented small culture tubes. Sufficient numbers of each type were placed in Fleming Creek (Ann Arbor, Michigan), a second order temperate stream, to permit four collections of three replicates for each type at 5-day intervals. With the exclusion of the first collection (after 5 days), the variability among the replicates was less than 8 percent. Analysis of the chlorophyll a data by ANOVA and simple linear regression showed least amount of variation in horizontally positioned test tubes, followed by those of vertical orientation, and then by the coverslips. The highest concentration of periphyton biomass measured in chlorophyll a was, however, observed in the vertically placed test tubes. The coverslips and horizontally incubated tubes collected comparable concentrations of chlorophyll a over the exposure period.