This research is divided into two main parts. Chapters 1 and 2 address the effect of thermal addition on the breakdown of Boxelder leaves (Acer negundo) in insitu and artificial stream studies. In both studies the rates for the decline in penetrance values decreased significantly in the thermally influenced treatments. Reduction in mass-loss rate coefficients was significant in the in-situ study, but not in the artificial streams. This result was due to differences in flow and macroinvertebrate colonization. Chapters 3 and 4 address the development of a methodology for testing 24-48 hr old juvenile Asiatic clams (Corbicula fluminea) to sediments in 10-day bioassays. These organisms had acceptable survivorship in the controls (>70%), excellent recovery of all exposed organisms (97.5%) and were sensitive to copper-spiked sediments. Comparitive sensitivity of this age class demonstrated them to be equally or more sensitive than other commonly used sediment test organisms including Chironomus tentans, Daphnia magna and Hyalella azteca for survival and growth endpoints in 10-day exposures. Survival and growth effects for Corbicula juveniles were seen at 25 ppb copper in the sediment. / Master of Science