Grantee Research Project Results
2002 Progress Report: Prevalence and Survival of Microorganisms in Shoreline Interstitial Waters: A Search for Indicators of Health Risks
EPA Grant Number: R828830Title: Prevalence and Survival of Microorganisms in Shoreline Interstitial Waters: A Search for Indicators of Health Risks
Investigators: Rogerson, Andrew , McCorquodale, Don , Esiobu, Nwadiuto
Current Investigators: Rogerson, Andrew , McCorquodale, Don , Estiobu, Nwadiuto
Institution: Nova Southeastern University , Florida Atlantic University - Boca Raton
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 2001 through July 31, 2003
Project Period Covered by this Report: August 1, 2001 through July 31, 2002
Project Amount: $312,570
RFA: Recreational Water Quality: Indicators and Interstitial Zones (2000) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water , Ecological Indicators/Assessment/Restoration
Objective:
The objectives of this research project are to: (1) document the number of fecal organisms (E. coli, enterococci and fecal coliforms) in beach sand, and determine whether they are attached or free in interstitial water; (2) document the number of potentially novel indicator organisms (Staphylococcus aureus, Pseudomonas aeruginosa, Clostridium perfringens, Vibrio sp. coliphage (F-specific and somatic), and the occurrence of eukaryotic microbes with possible health implications; (3) compare the survival of indicator organisms in water versus sand; and (4) locate evidence of increased health risk to individuals (particularly children) exposed to beach sand rich in indicator organisms (via a beach questionnaire).
Progress Summary:
A 1-year study of fecal indicators (E. coli, enterococci and fecal coliforms) at three contrasting bathing beaches in southern Florida has shown that bacteria are concentrated in wet sand relative to the water column. Surprisingly, numbers of these bacteria are even higher in the "dry" sand above the high tide line. For example, numbers of enterococci in the water were around 10 bacteria per 100 ml, whereas in wet and dry sand, numbers averaged around 102 and 103 per 100 g sand, respectively. Micro extraction methods (using small aliquots of sand, ca. 0.1 g, rather than the bulk 100 g samples) suggest that these densities may be underestimates of the true levels of fecal bacteria in the sand. Numbers of non-traditional indicators (coliphage, Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio sp., and C. perfringens showed similar patterns with elevated levels throughout the year in sand.
Staphylococci were particularly abundant, and in dry sand, they generally ranged between 105 and 108 per 100 g sand. We conducted mesocosm experiments that investigated the behavior of "indicator" organisms. These showed that bacteria had reproduced in sand but not in seawater, suggesting that sand afforded protected micro-pockets that nurtured the bacteria. Mesocosm experiments also showed that predation might be an important regulator of "indicator" bacteria, particularly in wet sand, and that seeding from the water column (due to the filtering action of the sand) might be an important concentrating factor. Together, these interactions (regrowth, predation, and seeding) may explain the observed levels of bacteria on the beach. Additional experiments are being conducted to further understand the dynamics of indicator populations on the beach. Complementary data support the notion that these bacteria are active in sand. They are predominately attached to sand grains, and may be metabolically active. They appear to be clumped on the micro-scale, suggesting that they are concentrated in the sand as a result of growth rather than physical filtering. These observations of bacterial behavior in sand relative to water suggest that the high numbers of indicators are not true reflections of high numbers of pathogens. Rather, they suggest that environmental indicators are residing in beach sand. The beach questionnaire data support this view, because no dramatic incidences of illness associated with high indicator levels in the sand have been noted; although this conclusion is only based on 1,000 completed questionnaires (these data will be strengthened in Year 2). The only free-living eukaryotic microbe of any significance on the beach was Acanthamoeba. This opportunistic pathogen can cause severe eye infections (amoebic keratitis); it was present in about one-third of samples examined and most isolates were capable of growing between 0 and 32 ppt salt. Genotyping of the isolates (Booton and Byers, University of Ohio) showed that most were T4 strains. These are common environmental genotypes but also are the predominant type isolated from patients with keratitis. Preliminary results with an ELISA test kit showed the presence of the obligate protozoan pathogens Giardia, Entamoeba, and Cryptosporidium in sand; however, we do not know whether these are viable cysts, or merely cyst wall fragments.
Future Activities:
We will continue mesocosm experiments and palatability studies to strengthen the emerging view that regrowth, consumption, and seeding by filtering from the water column are important factors determining the survival and high abundances of fecal indicators (enterococci, E. coli, C. perfringens, and fecal coliforms) in sand as well as Staphylococcus. We will complete the identification (Biolog) of 500 beach strains of entercocci in an attempt to establish where enterococci are originating from in both the wet and dry sand. Also, we will estimate the scale of "wash out" of indicator organisms from beach sand. If this is significant, it has important implications for future monitoring of water in recreational beaches. We must conduct targeted sampling (e.g., following heavy rainfall, to try to coincide with high bacterial counts on the beach (i.e., those events producing counts significantly above the background scatter determined in Year 1). On these occasions, the high counts will be "ground-truthed" by looking for the presence of a range of pathogens (bacterial and viral) by PCR analyses using primers specific for pathogenic genes in fecal organisms. We will conduct additional micro-enumeration experiments to: (1) fine-tune spatial variation on the beach; and (2) improve the estimate of "actual" numbers of fecal indicators in sand. We will expand upon the tentative finding that pathogenic protozoa exist on the beach, by attempting to culture E. hystolitica from beach sand, document numbers of Acanthamoeba, and search for thermotolerant (42°C) amoebae. Lastly, we will continue with the beach questionnaire and conduct data analyses, and we will prepare the final report.
Journal Articles:
No journal articles submitted with this report: View all 21 publications for this projectSupplemental Keywords:
mesocosms, pathogenic protozoa, coliphage, E. coli, enterococci, fecal coliforms, Staphylococcus aureus, Clostridium perfringens, Vibrio, Pseudomonas aeruginosa., RFA, Scientific Discipline, Health, Water, Health Risk Assessment, Environmental Microbiology, Susceptibility/Sensitive Population/Genetic Susceptibility, Environmental Monitoring, Ecology and Ecosystems, genetic susceptability, Recreational Water, Biology, pathogens, recreational water monitoring, sensitive populations, bacteria, E. coli, recreational beaches, exposure, microbes, microorganisms, children, fecal coliform, water quality criteria, shoreline interstitial water, beach contamination, water quality, enterococci, indicator organisms, human health risk, sand particlesProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.