Date of Graduation

12-2013

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Evans-White, Michelle A.

Committee Member

Entrekin, Sally A.

Second Committee Member

Magoulick, Daniel D.

Third Committee Member

Sagers, Cynthia L.

Keywords

Biological sciences; Crayfish density; Landscape factors; Sedimendation

Abstract

In recent years in the United States there has been a rapid expansion in anthropogenic sources of sediment in streams including construction, agriculture, and drilling for natural gas. Potential effects land disturbance associated with activities from natural gas development on aquatic biota in surrounding streams have not yet been well documented. An increase in inorganic sediment in streams can be detrimental to organisms through a variety of mechanisms including alteration of dominant substrate type, higher turbidity resulting in lower visibility, and burial of food resources such as algae and detritus. Increasing sedimentation in stream environments through anthropogenic disturbance is a widespread problem, but few studies examine sediment effects on biological interactions and processes. I had two main objectives, which were 1) to investigate whether abundances of crayfish, an important stream organism, were correlated to natural gas well density or other natural gas related variables in stream catchments, and 2) to determine if sediment altered the grazer-periphyton interaction and if that effect was dependent upon grazer type (i.e., if sediment impacted the grazer-periphyton relationship differently between scrapers and collectors). I sampled crayfish in streams draining catchments with differing well activity to address the first research objective. A negative correlation existed between the predictor variables of the number of gas wells and the density of unpaved roads and the response variable of crayfish abundance suggesting further research examining potential natural gas activity impacts on crayfish populations may be important to avoid negative impacts of gas drilling on crayfish. Greenhouse experimental streams were employed to address the second objective and I found that increasing sediment affected the grazer-periphyton interaction differently between two grazers (crayfish and snails), where crayfish under high sediment levels provided a marginally significant net benefit to algal

biomass. In contrast, snails under high sediment conditions caused a statistically significant decline in algal biomass. This result suggests that sediment effects on grazer-periphyton interactions will depend on the grazer species and future studies could examine impacts on insect grazers that may be more sensitive to sedimentation.

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