Spatial and Temporal Variation in Indicator Microbe Sampling is Influential in Beach Management Decisions

摘要

Fecal indicator microbes such as enterococci are often used to assess potential health risks caused by pathogens at recreational beaches. Microbe levels often vary based on collection time and sampling location. The primary goal of this study was to assess how spatial and temporal variations in sample collection which are driven by environmental parameters impact enterococci measurements and beach management decisions. A secondary goal was to assess whether enterococci levels can be predictive of the presence of Staphylococcus aureus a skin pathogen. Over a ten day period hydrometeorologic data hydrodynamic data bather densities enterococci levels and S. aureus levels including methicillin-resistant S. aureus (MRSA) were measured in both water and sand. Samples were collected hourly for both water and sediment at knee-depth and every 6 hours for water at waist-depth supratidal sand intertidal sand and waterline sand. Results showed that solar radiation tides and rainfall events were major environmental factors that impacted enterococci levels. S. aureus levels were associated with bathing load but did not correlate with enterococci levels or any other measured parameters. The results imply that frequencies of advisories depend heavily upon sample collection policies due to spatial and temporal variation of enterococci levels in response to environmental parameters. Thus sampling at different times of the day and at different depths can significantly impact beach management decisions. Additionally the lack of correlation between S. aureus and enterococci suggests that use of fecal indicators may not accurately assess risk for some pathogens.