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Tracking the Primary Sources of Fecal Pollution in a Tropical Watershed in a One-Year Study
Citation:
Toledo, C., H. Ryu, J. Gonzalez, E. Huertas, G. Toranzos, AND J. Santodomingo. Tracking the Primary Sources of Fecal Pollution in a Tropical Watershed in a One-Year Study. APPLIED AND ENVIRONMENTAL MICROBIOLOGY. American Society for Microbiology, Washington, DC, 79(5):1689-1696, (2013).
Impact/Purpose:
The results from this study suggest that additional assays are needed to track human, cattle, swine, and chicken fecal pollution sources in tropical waters.
Description:
A study was conducted to determine the primary sources of fecal pollution in a subtropical watershed using host-specific assays developed in temperate regions. Water samples (n=534) from 10 different sites along the Rio Grande de Arecibo watershed were collected every two-three weeks for a period of one year. DNA was extracted from each sample and aliquots were used as the template in PCR assays targeting fecal bacteria and human-, cattle-, swine-, and chicken-fecal specific assays. Feces from 12 different animals (n=340) and wastewater treatment samples (n=16) were analyzed for assay host-specificity and host-distribution. The human-specific assay (HF183) was found to be highly specific as it did not cross-react with non-target samples. The cattle marker (CF128) cross-reacted to some extent with swine, chicken, and turkeys, and was present in 64% of the cattle samples tested. The swine assays showed poor host-specificity, while the three chicken assays showed poor host-distribution. Differences in the detection of host-specific assays were noted per site. While human and cattle assays showed moderate average detection rates throughout the watershed, areas impacted by wastewater treatment plants and cattle exhibited the highest prevalence of these markers. When conditional probability for positive signals was determined for each of the markers, the results indicated higher confidence levels for the human assay and lower levels for all the other assays. Overall, the results from this study suggest that additional assays are needed to track cattle, chicken, and swine fecal pollution sources in the RGA watershed. The results also suggest that the geographic stability of genetic markers need to be determined prior to conduct applied source tracking studies in tropical settings.
