Date of Award

1-1-2014

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

First Advisor

J. Michael Trapp

Second Advisor

Susan M. Libes

Third Advisor

Erin J. Burge

Abstract

While the presence of fecal indicator bacteria such as Escherichia coli in urban stormwater has been widely documented, their occurrence and persistence in sediments are not as well understood. Traditional research into bacterial contamination of surface waters has focused on overland transport of waste material and assumes fecal bacteria such as E. coli have short lifetimes in the environment. Recent investigations suggest that E. coli can accumulate in drainage basin sediments and act as a fecal bacterial reservoir within a watershed. This thesis investigated the prevalence of E. coli populations in the sediments and overlying waters of Withers Swash (a tidal creek) under dry and wet weather conditions. Results indicated E. coli persisted in the sediment environment and were resuspened into overlying waters during times of increased flow. Rain event profile results suggested the occurrence of steady state E. coli populations in drainage basin sediments. Additionally, laboratory experiments investigated E. coli colonization of overlying waters and sediments using microcosm environments with drainage basin sediments and stormwater. These lab-based experiments also examined the importance of host sources (human and avian) to bacterial survival, expanding on the growing body of research emphasizing the importance of drainage basin sediments as they enhance the persistence and transport of the fecal indicator bacteria E. coli within a watershed. Each experiment used sediments of varying grain size and organic content to examine the influence of physical characteristics on bacterial prevalence. Results suggested host source of bacteria may be more important to initial bacterial colonization while physical characteristics of drainage basin sediments better explained extended E. coli persistence. Findings also suggested an indirect control of water column bacterial concentration by sediment type and erodibility.

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