Microbial pollution at the land-sea interface : fate and transport of fecal indicators and human pathogens in beach sands and sediments
- This research investigates the role of beach sands and sediments as reservoirs of fecal indicator bacteria and human pathogens using both laboratory microcosms and field experiments. Fecal indicator bacteria (FIB) are used to predict the presence of pathogens and to minimize the potential health risks associated with pathogens in recreational waters. This research reveals that FIB are nearly ubiquitous in California beach sands. In a field study...Ninety-one percent of the beaches sampled had detectable Enterococcus spp. (ENT) while 62% had detectable E. coli (EC) in their sands. A field study was used to investigate the role of waves and tides as a physical connection through which fecal indicators can be transported from beach sands to the coastal ocean. The process of "over-beach" transport is documented at Lovers Point Beach, California, suggesting that resuspension of ENT from beach sands can instigate beach advisories. It is also shown that naturally occurring ENT can replicate (0.20 - 0.63 per day) in Lovers Point beach sands under environmentally relevant conditions. A follow up survey of beaches along the CA coast documents the presence of the human-specific fecal marker in Bacteriodales spp. and human pathogens in beach sands. At least one human pathogen was detected at 27% of the beaches surveyed along the California coast, suggesting that contact with beach sands may lead to increased human health risks. Follow-up persistence studies were conducted for pathogens and indicators and revealed that that many of the pathogens and indicators we tested for in the field study can persist upward of 10 - 15 d in sands. Finally, we extended our knowledge of FIB in beach sands to sediments and investigated the potential for river sediments and soils to act as sources of microbial contaminants to the Hanalei River (Kauai, HI). A mass balance model that accounted for losses due to deposition of FIB-laden sediments, sources due to resuspension of FIB-laden sediment, and losses due to bacterial inactivation was used to explore the cause of the observed sources and sinks along the river. The model indicated that the resuspension or deposition of FIB-laden river sediments accounted for less than 1% of the observed EC and ENT loadings along the river. The research presented in this dissertation ties together multiple microbiological methods and engineering principles to shed light on the fate and transport of FIB and human pathogens in natural environmental systems.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Yamahara, Kevan Masato
|Stanford University, Civil & Environmental Engineering Department
|Statement of responsibility
|Kevan M. Yamahara.
|Submitted to the Department of Civil and Environmental Engineering.
|Thesis (Ph.D.)--Stanford University, 2011.
- © 2011 by Kevan Masato Yamahara
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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