Beach Sands along the California Coast Are Diffuse Sources of Fecal Bacteria to Coastal Waters
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- 作者：Kevan M. Yamahara ; Blythe A. Layton ; Alyson E. Santoro ; Alexandria B. Boehm
- 刊名：Environmental Science & Technology
- 出版年：2007
- 出版时间：July 1, 2007
- 年：2007
- 卷：41
- 期：13
- 页码：4515 - 4521
- 全文大小：233K
- 年卷期：v.41,no.13(July 1, 2007)
- ISSN：1520-5851
文摘
Fecal indicator bacteria (FIB) are nearly ubiquitous inCalifornia (CA) beach sands. Sands were collected from55 beaches along the CA coast. Ninety-one percent of thebeaches had detectable enterococci (ENT) while 62%had detectable E. coli (EC) in their sands. The presenceof a putative bacterial source (such as a river), the degreeof wave shelter, and surrounding land use explained asignificant (p < 0.05) fraction of the variation in both ENTand EC densities between beaches. Sand characteristicsincluding moisture content, organic carbon, and percent fines,significantly (p < 0.05) influenced only EC densities inbeach sand. We assayed 34 of 163 sand samples forsalmonellae, but did not detect this bacterial pathogen.The potential for FIB to be transported from the sand to seawas investigated at a single wave-sheltered beach withhigh densities of ENT in beach sand: Lovers Point, CA (LP).We collected samples of exposed and submerged sandsas well as water over a 24 h period in order to compare thedisappearance or appearance of ENT in sand and thewater column. Exposed sands had significantly higherdensities of ENT than submerged sands with the highestdensities located near the high tide line. Water column ENTdensities began low, increased sharply during the firstflood tide and slowly decreased over the remainder of thestudy. During the first flood tide, the number of ENT thatentered the water column was nearly equivalent to the numberof ENT lost from exposed sands when they were submergedby seawater. The decrease in nearshore ENT concentrations after the initial influx can be explained by ENT die-off and dilution with clean ocean water. While some ENT inthe water and sand at LP might be of human originbecause they were positive for the esp gene, others lackedthe esp gene and were therefore equivocal with respectto their origin. Follow-up sampling at LP revealed the presenceof the human specific Bacteroides marker in water andsand.