Date of Graduation

5-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Evans-White, Michelle A.

Committee Member

Magoulick, Daniel D.

Second Committee Member

Scott, J. Thad

Third Committee Member

Willson, John D.

Keywords

Algal biomass; Flood disturbance; Gross primary production; Landscape disturbance; Natural gas development; Nutrient limitation

Abstract

Land-use change is one of the most widespread human impacts and can influence abiotic and biotic processes within surrounding streams. For example, streams in agricultural and urban watersheds receive greater light and nutrient inputs that can promote increased algal growth and primary production. Natural gas (NG) infrastructure development, a recent land use change in many regions, may also stimulate forested stream primary production, by reducing forest cover and increasing sediments and nutrient transport. I sampled streams across a NG activity gradient for algal biomass and gross primary production (GPP) to assess potential effects of this emerging land-use type. Algal biomass and GPP were positively associated with NG activity during winter, suggesting algal stimulation by nutrient enrichment of streams impacted by NG activity. To examine the nutrient limitation status of my study streams, I experimentally manipulated nitrogen (N) and phosphorus (P) in diffusing substrata and found that while P was not limiting, N-limitation was negatively related to NG activity (R2= 0.57; p= 0.03). Best management practices (BMPs) have been implemented to help reduce sediment inputs, associated with NG activity on streams, though little has been done to assess their effectiveness. I used a before-after control-impact design to test the effectiveness of implemented BMPs at reducing impacts to autotrophic processes in headwater streams and the South Fork Little Red River. There were no differences between reference and impacted sites before and after the disturbance occurred for the autotrophic processes measured. These results suggest that BMPs were effective at mitigating effects of low levels of NG activity. However, NG activity in the study watersheds was less than in surrounding areas, potentially contributing to the absence of change. In my final study, I examined how human land-use affects recovery of algal communities and metabolic processes to flood disturbances. Biomass and metabolism recovered more rapidly in urban and agricultural streams than forested streams likely due to increased nutrient availability. These findings highlight the defining role of increased nutrient availability as one main driver of effects of human land-use change on autotrophic processes in stream ecosystems.

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