Understanding the Sources and Fate of Conventional and Alternative Indicator Organisms in Tropical WatersEPA Grant Number: R828829
Title: Understanding the Sources and Fate of Conventional and Alternative Indicator Organisms in Tropical Waters
Investigators: Harwood, Valerie J. , Rose, Joan B.
Institution: University of South Florida
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: September 1, 2001 through August 31, 2003
Project Amount: $388,335
RFA: Recreational Water Quality: Indicators and Interstitial Zones (2000) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water , Ecological Indicators/Assessment/Restoration
The indicator organisms used to assess water quality such as the fecal coliform group, E. coli and Enterococcus spp. may multiply or persist for long times in the warm, nutrient-rich conditions of tropical waters and soils. If so, there is a compelling need for alternative or additional indicators for water quality in states such as Florida. The specific goal of this research will be to assess the ability of the recognized indicator organisms, Escherichia coli and Enterococcus spp., to persist and multiply in Florida soils and in natural waters. The survival of potentially useful alternative indicators (Clostridium perfringens, Bacteroides fragilis bacteriophages and coliphages) under environmentally relevant conditions will also be assessed. The stability of the "fingerprints" used for two bacterial source typing (BST) methods (ribotyping and antibiotic resistance analysis) will be measured over time in the environment. BST methods are useful for defining the source of indicator organisms such as E. coli and enterococci in natural waters, and the information on fingerprint stability will be crucial to understanding the capabilities and limitations of BST in tropical waters.
Fecal coliforms, E. coli, Enterococcus spp., Clostridium perfringens, Bacteroides fragilis bacteriophage (human-specific and broad host range), and coliphage will be quantified over time by culturable counts on selective-differential media or against appropriate host bacteria. The effects of temperature, salinity, organic material, sunlight, and presence of sediments on microbial growth and survival will all be investigated. Exposure to environmental conditions will take place in contained chambers, in dialysis bags incubated in a natural pond, and in a directly seeded pond study. Environmentally exposed container studies will be used to measure survival of indicator organisms introduced directly as fecal material or soil, while in situ experiments will be conducted with indicator organisms isolated from feces and soil in the laboratory.
Persistence and growth of specific E. coli and Enterococcus strains (defined by ribotyping and antibiotic resistance analysis) will be assessed by following the raw numbers and frequency distribution over time of specific strains from different sources (cattle, dogs, wastewater, birds, soil) exposed to environmentally relevant conditions.
One of the major goals of the Clean Water Act is to ensure that U.S. waters are safe for fishing and swimming. The use of water quality indicators that accurately reflect "safety" is essential for this goal. We are now much more aware than we were in 1972, when the Clean Water Act was enacted, that the bacteria used to assess water quality have environmental sources. Indicator organisms that enter water in feces may persist for many weeks. A clear understanding of the fate (relative persistence and ability to multiply) of indicator bacteria from various sources does not exist, yet fecal material from different animal and human sources has very different implications for human health risk. Alternative indicator organisms (other than fecal coliforms, E. coli and Enterococcus) and bacterial source typing may greatly refine risk assessment, best management practices and establishment of total maximum daily loads for recreational and shell fishing waters, but without knowledge of their fate in water, their usefulness cannot be accurately assessed.