Oxygen consumption in streambeds: Examining the impacts of environmental factors and hyporheic fauna

This study examines how oxygen consumption rates of streambed sediment communities vary, focusing on identifying abiotic factors that influence oxygen consumption rates, and on the importance of different invertebrate groups to these rates. I chose to measure the rate of oxygen consumption in streambed sediments because it is a measure of community activity. While studies measuring benthic (surficial streambed sediments) oxygen consumption rates have greatly aided our understanding of streams as dynamic ecosystems, few measurements of hyporheic (deeper streambed sediments) oxygen consumption exist.; The results of field and laboratory experiments that quantify the important role of an introduced species of bivalve (Corbicula fluminea) in a stream ecosystem are presented in the first chapter. Corbicula is found to likely be the single most important invertebrate species influencing carbon and food web dynamics in this stream. The results presented show both how important individual species can be to ecosystem functioning, as well as the large impact that nonnative species can have when introduced to a new habitat.; In the second chapter, I examine several environmental factors that influence the spatial and temporal variability of community oxygen consumption rates in a streambed and find that floods may have an important temporal influence on these rates. Further, I evaluate the assumptions made when measuring streambed oxygen consumption rates and find that interpretation of results requires examination of potential methodological artifacts.; In the third chapter, the importance of invertebrates to streambed oxygen consumption rates is explored through a series of comparative and experimental studies. While oxygen consumption by the microbial community may dominate streambed oxygen consumption, the invertebrate community is also found to have an important role in determining sediment oxygen consumption rates and thus invertebrates influence stream ecosystem metabolism.; This research represents an important contribution to three areas of ecology: (1) quantifying the impact of exotic species on ecosystem dynamics; (2) furthering our understanding of hyporheic oxygen consumption rates and factors that influence those rates; and (3) quantifying for the first time the role of invertebrates to streambed oxygen consumption rates.