Previous | Next | Table of Contents
Chapter 3: Sand Contamination Studies
Study 1: Bacteria in Freshwater Sands
Study by: Elizabeth Wheeler Alm, Janice Burke and Anne Spain[i]
Title: Fecal indicator bacteria are abundant in wet sand at freshwater beaches[ii]
Period: 2001 - 2002
Location: Six public bathing beaches along Lake Huron in St. Clair County, Michigan
Purpose of Study: The purpose of this study was to evaluate the potential of wet, freshwater sand to be a reservoir of intestinal bacteria. This was one of the first studies to address the survival and persistence of fecal bacteria in freshwater sands.
What is Known:
- Fecal contamination at bathing beaches can be hazardous to humans, because feces may contain bacteria, viruses, and protozoa that can be ingested and cause intestinal disease.
- With no additional input, levels of fecal indicators decline, in water. Several factors have been proposed to explain this decline including inactivation due to UV radiation,[iii] and sunlight inactivation.[iv] Additionally, fecal bacteria are also less able to obtain nutrients in water unlike those associated with the sediment particles.[v]
- Enteric bacteria have been known to exhibit longer survival times in sediment than in overlaying water.[vi]
What the Study Confirmed:
- At each of the six beaches, fecal indicator bacteria were more abundant in sand than in water.
- Compared to water, enterococci counts in sand were 4–38 times higher and E. coli counts were 3–17 times higher.
- Enterococci counts were consistently low in water, but they were dramatically higher in the sand.
- The results of this study were consistent with work on freshwater beaches in England, where fecal indicator counts were an order of magnitude greater in sand than in the overlying water.
- The presence of fecal indicator bacteria in beach sand suggests that pathogenic bacteria of intestinal origin may also be present in the sand.
Results of the Study
Printed in: Alm, E.W., J.M. Burke, E.L. Francis, and A.J. Matthews. 2002. Fecal Indicator Abundance Higher in Freshwater Bathing Beach Sand Than in Water Column. Great Lakes Beach Conference 2002. [on-line http://www.great-lakes.net/glba/pdf/Alm.pdf. Accessed 6/30/2005]
Study 2: Bacteria in Marine Sands
Study by: Tomoyuki Shibata*, Helena M. Solo-Gabriele*[vii], Lora E. Fleming[viii], Samir Elmir[ix]
Title: Monitoring Marine Recreational Water Quality Using Multiple Microbial Indicators in an Urban Tropical Environment[x]
Period: March 2001 – August 2001
Location: Two Beaches in Miami-Dade County, Florida
Purpose of Study: This study does not look at the presence of indicator bacteria in sand specifically. Rather, the primary objective of the authors was to evaluate and compare multiple indicator microbes for two beach sites located in Miami, Florida. In the course of their study, they also describe the presence of these indicator bacteria in marine sands.
What is Known:
- The beach sand survey, conducted at Beach A, focused on collecting samples from the ‘‘swash’’ zone of the beach. The swash zone is the depth zone in which sediments are disturbed by wave action near the shoreline[xi].
- Studies have shown that fecal coliform, E. coli, and enterococci are found in the environment in the absence of a known sewage source of contamination and have been shown to multiply within warm tropical environments.
What the Study Confirmed:
- Results showed that concentrations of indicator microbes were highest during high tide with ‘‘hot spots’’ at various points along the shoreline. None of the offshore sampling points had detectable levels of indicator microbes. The waters around the Miami Seaquarium generally had low levels of microbes. These results suggest that the shoreline is the primary source of indicator microbes and this source is most pronounced during high tide when the water level reaches its highest point along the shore.
- The results suggest that there may be an additional source(s) of indicator microbes other than sewage.
- Data collected indicated that the source of indicator microbes comes from the shoreline, as evidenced by the higher indicator microbe concentrations as the shore was approached. The authors agree that one possible source of the microbes may be the sand itself.
- In the results from the sand survey, indicator microbes were observed in all sand samples collected from the shoreline at Beach A.
- The authors recommend that the role of sand be further evaluated on the survival and the multiplication of the indicator microbes at this particular site.
Previous | Next | Table of Contents
[i] Department of Biology, Central Michigan University
[ii] Alm et. al. 2003. Fecal Indicator Bacteria Are Abundant in Wet Sand at Freshwater Beaches; Water Res 37:3978-3982.
[iii] Y. Y. Chan & E. G. Killick; “The effect of salinity, light and temperature in a disposal environment on the recovery of E.coli following exposure to ultraviolet radiation” 1995; 29(5) 1373-77
[iv] Davies-Colley RJ et. Al." Inactivation of faecal indicator microorganisms in waste stabilisation ponds: interactions of environmental factors with sunlight,” Water Res 1999;33(5):1220– 30.
[v] Davies CM, Long JAH, Donald M, Ashbolt NJ. “Survival of fecal microorganisms in marine and freshwater sediments;” Appl Environ Microbiol 1995;61(5):1888–96.
[vi]Gerba, C. P., & J. S. McLeod. 1976. “Effect of sediments on the survival of Escherichia coli in marine waters.” Appl. Environ. Microbiol. 32:114–120.
[vii]Department of Civil, Architectural, & Environmental Engineering, University of Miami
[viii]Rosensteil School of Marine and Atmospheric Science, University of Miami
[ix]Miami-Dade County Health Department
[x] Shibata T., Solo-Gabriele H., Fleming L.E., Elmir S., 2004, Monitoring Marine Recreational Water Quality Using Multiple Microbial Indicators in an Urban Tropical Environment, 2004, Water Research, 38;3119-3131
[xi]Marine Biology Web, “Glossary of Marine Biology” <http://life.bio.sunysb.edu/marinebio/glossary.tuvwxyz.html> (Accessed February, 2005)
