Currently, protocols for investigating the effects of chemical pollutants on periphyton communities under natural conditions are statistically flawed and/or potentially harmful to the ecosystems in which the studies are conducted. Toxicant-releasing substrates have been proposed to allow the delivery of different levels of chemical pollutants to replicate microbial communities in situ while minimizing the amount of toxicant released into the aquatic ecosystems under investigation. The purpose of this research was to compare the copper-induced responses of laboratory periphyton communities in artificial streams to those generated using standard, laboratory toxicity testing protocols during a summer and winter experiment. Chemical-releasing substrates were successfully used to deliver copper to periphyton communities in a predictable manner, over a broad range of doses, and at fairly constant rates during one week exposure periods. / Master of Science