Tiered Approach for Identification of a Human Fecal Pollution Source at a Recreational Beach:  Case Study at Avalon Bay, Catalina Island, California

Abstract

Recreational marine beaches in California are posted as unfit for swimming when the concentration of fecal indicator bacteria (FIB) exceeds any of seven concentration standards. Finding and mitigating sources of shoreline FIB is complicated by the many potential human and nonhuman sources of these organisms and the complex fate and transport processes that control their concentrations. In this study, a three-tiered approach is used to identify human and nonhuman sources of FIB in Avalon Bay, a popular resort community on Catalina Island in southern California. The first and second tiers utilize standard FIB tests to spatially isolate the FIB signal, to characterize the variability of FIB over a range of temporal scales, and to measure FIB concentrations in potential sources of these organisms. In the third tier, water samples from FIB "hot spots" and sources are tested for human-specific bacteria Bacteroides/Prevotella and enterovirus to determine whether the FIB are from human sewage or from nonhuman sources such as bird feces. FIB in Avalon Bay appear to be from multiple, primarily land-based, sources including bird droppings, contaminated subsurface water, leaking drains, and runoff from street wash-down actvities. Multiple shoreline samples and two subsurface water samples tested positive for human-specific bacteria and enterovirus, suggesting that at least a portion of the FIB contamination is from human sewage.

Rapid Detection of Enteroviruses in Small Volumes of Natural Waters by Real-Time Quantitative Reverse Transcriptase PCR

“…The results confirm the data of Katayama et al (13) and Boehm et al (1) showing that small charged filters can be used to collect enteroviruses from small volumes (ϳ1 liter) of field samples and that simple extraction of those filters and qRT-PCR can be used to detect viruses within hours. Our protocol differed from that of Katayama et al (13) in a few ways that we think are more appropriate for our laboratory.…”

“…However, our attempt to reproduce that method in our laboratory was prevented by the lack of availability (in the United States) of the proprietary extraction kit described in that report; we also noted that the concentrations of poliovirus they used in their seeding experiments (300 to 770 PFU/ml) were very high compared to what one might see in field samples, leading to questions about recovery at realistic field concentrations. We modified the Katayama et al (13) protocol to include a readily available extraction kit, different qRT-PCR parameters that we tested in a previous study to avoid inhibition (1), and a range of test virus concentrations at levels more realistic of realworld field samples. We also tested this modified protocol with both freshwater and seawater samples and compared the cellulose mixed-ester filter retention with the retention of more porous and freely flowing glass fiber filters used in a previous enterovirus field study (1).…”

“…We modified the Katayama et al (13) protocol to include a readily available extraction kit, different qRT-PCR parameters that we tested in a previous study to avoid inhibition (1), and a range of test virus concentrations at levels more realistic of realworld field samples. We also tested this modified protocol with both freshwater and seawater samples and compared the cellulose mixed-ester filter retention with the retention of more porous and freely flowing glass fiber filters used in a previous enterovirus field study (1). Overall, we found that our modified filter/qRT-PCR method was rapid and reasonably efficient for both fresh-and seawater samples, with the best efficiency found with the cellulose acetate/nitrate filters in freshwater and fine-pore glass filters in seawater.…”

Luminex detection of fecal indicators in river samples, marine recreational water, and beach sand

“…The entire procedure, including water filtration and nucleic acid extraction can be performed in a matter of hours; therefore, Luminex assays have the potential to meet the needs of water quality research. If DNA extraction and cataloguing of environmental sequence diversity can be improved, suspension arrays could provide a useful tool to multitiered analysis (Boehm et al, 2003;Noble et al, 2006) and epidemiologic studies of recreational water and sand quality. Median fluorescence intensity (MFI) of Luminex probes hybridized against DNA from a variety of bacterial cultures.…”

“…Rapid detection of multiple species could yield a "fingerprint" of water quality that would be a useful addition to fecal indicator enumeration. Such a multitiered approach (Boehm et al, 2003;Noble et al, 2006) could yield more information about the source of contamination, the potential health risk, and the best strategy for remediation. This approach could benefit environmental research, epidemiological studies, and routine water quality analysis.…”