Yvonne Vadeboncoeur (Advisor), David Strayer (Committee Member), Katie Hossler (Committee Member), Lynn Hartzler (Committee Member), John Stireman III (Committee Member)
Doctor of Philosophy (PhD)
Anthropogenic alterations to nitrogen, carbon, and phosphorus bioavailability have increased the flux of these resources into the biosphere and altered stream ecosystem function. Streams modify the transport of these resources to receiving ecosystems through uptake, transformation, and mineralization. Understanding how streams process carbon, nitrogen, and phosphorus can provide insight about how stream ecosystems function in landscapes where human modification is inescapable. I investigated how land use in agricultural regions affect resource availability to primary producers and consumers and the subsequent impact on stream processes. I surveyed headwater streams in three Lake Erie watersheds to determine spatiotemporal nutrient limitation of attached algae. I found that low-order streams exhibit phosphorus limitation and the severity of phosphorus limitation was greatest post-fertilizer application when the imbalance between water column nitrogen: phosphorus concentrations was greatest. These results suggest that biofilm nutrient uptake responded to landscape level influences and attached algae actively sequestered phosphorus from the water column. Agriculture alters the availability of carbon through modification of riparian vegetation. I used genomic techniques to describe longitudinal changes in microbial community composition along a stream with headwaters that lacked riparian vegetation due to row crop agriculture but the width of the forested riparian area increased downstream. The relative abundance of the most abundant microbial phyla varied along physical and chemical (light, phosphorus concentration) gradients. Land use affected physical-chemical characteristics of the river, which in turn, influenced sediment microbial community composition. The removal of riparian forested vegetation leads to increased light availability to attached algae. I investigated the effect of attached algal productivity on consumers across an experimental gradient in light intensity. Attached algal productivity and consumer production were coupled across the light gradient. I also studied how land use influenced carbon resource use by common macroinvertebrate functional feeding groups in Midwestern streams. I found that invertebrates consistently used attached algal carbon. This reliance was not affected by riparian vegetation nor the percent of the watershed dedicated to agriculture. Food web structure remained similar across the gradient in land use. This work demonstrates that attached assemblages in streams respond to landscape level processes that propagate to consumers.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
Copyright 2018, all rights reserved. My ETD will be available under the "Fair Use" terms of copyright law.