HCNSO Student Theses and Dissertations

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Defense Date


Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology


Oceanographic Center

First Advisor

Nwadiuto Esiobu

Second Advisor

Andrew Rogerson

Third Advisor

Donald McCorquodale


This report is part of the first study to evaluate the potential use of non-traditional and non-enteric bacteria as indicators of health risk in recreational waters and beach sand in south Florida. This study evaluated the possibility of utilizing a series of novel indicators including Staphylococcus aureus, Clostridium perfringens, Pseudomonas aeruginosa, and Vibrio species to assess beach quality. To evaluate the usefulness of these 4 novel microorganisms as potential indicators, 3 south Florida beaches were sampled for a 1 year period and during the year, the distribution across 500m of the beach (spatial analysis) and location (interstitial or attached) of the bacteria were obtained. At Hollywood Beach, Fort Lauderdale Beach, and Hobe Beach in Miami, wet sand, dry sand, and seawater samples were taken bimonthly and analyzed in a laboratory at Florida Atlantic University. In the laboratory, traditional microculture methods recommended by the USEPA were utilized to analyze the samples and bacteria.

Analysis of the yearly sampling showed that dry sand, above the high tide mark contained highly elevated and significantly more bacteria than wet sand and seawater. Furthermore, S. aureus showed promise as a reliable indicator of health risk as the highly frequented beaches of south Florida correlated with high levels of S. aureus and some non-enteric illnesses, as displayed through a beach questionnaire, were apparent with high levels of S. aureus. Elevated levels of S. aureus may be due to regrowth in the sand as shown by the fact that S. aureus were found more often attached than residing in the interstitial spaces and this suggests viable activity of the bacteria and thus, regrowth.

Positive correlations between the traditional enteric indicators and the potential indicators were displayed as well. Clostridium perfringens in the wet sand highly correlated with fecal coliforms (r = 0.98), E. coli (r = 0.87), and enterococci (r = 0.53) at Hobe beach, as did S. aureus which correlated with fecal coliforms (r = 0.81) and enterococci (r = 0.81) at Hollywood Beach.

Most of the tested bacteria in this study were found to be attached to sand grains, especially S. aureus. Attachment to substrates requires the use of flagella, polysaccharides, or capsules and thus, attachment suggests metabolic activity. The bacteria, being viably active, can then exponential grow, and this further suggests regrowth in the sand. This regrowth in the sand may then pose a significant public health risk to people at the beach, especially young children, as these organisms have been shown to cause several non-enteric illnesses such as ear infections and skin rashes.

The macrospatial analysis across the beach, up the beach, and down in the sand revealed some unevenness in the sand. The tendency for bacteria to not spread, and thus, not be even across the beach again supports the idea that the bacteria are regrowing in the sand. The sand can therefore serve as a reservoir from various sources such as runoff, beach attendees, and birds and in this reservoir, extremely high levels of potentially pathogenic bacteria can remain. The seemingly perfect environment of south Florida beaches, a tropical environment, the warm temperatures year round, high humidity, rainfall year round therefore creates an adequate niche for potentially pathogenic bacteria to reach significantly elevated levels. This study then demonstrates the need to analyze novel organisms (enteric and non-enteric) in beach sand to ensure public health safety at south Florida beaches.

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