SPECIAL REPORT SR-2022-01
Microbial Indicators, Sewage Markers, and Human Pathogens in Hawaii Streams
Marek Kirs
September 2021, vi+71 pp.
ABSTRACT
The overarching goal of this study was to support and improve application of protective and meaningful microbiological recreational water quality standards in Hawaii. Eighty samples were collected from a total of nineteen watersheds on Hawaii Island, Kauai, Maui, and Oahu. The samples were analyzed for concentrations of indicator bacteria (total coliforms, Escherichia coli, enterococci, Clostridium perfringens, F+ and somatic coliphages) and pathogens (Salmonella and Campylobacter) by cultivation-based methods, and for concentrations of sewage markers (crAssphage, HF183, HPyV, PMMV) and human enteric viruses (adenoviruses, enteroviruses, noroviruses GI and GII, rotaviruses) by molecular methods (qPCR and RT-qPCR). High concentrations of enterococci (78.8% samples exceeding the 130 MPN/100 ml Beach Action Value, averaging from 47 to 6,801 MPN/100 ml) were observed in the watersheds. Ten out of nineteen (53%) watersheds were positive for at least one human marker. In the samples positive for sewage markers (32.5%), sewage input appears to be relatively low as no enteric viruses (adenoviruses, enteroviruses, noroviruses GI and GII, rotaviruses) were detected. This prevented application of risk analyses models. Clostridium perfringens and somatic coliphage concentrations appear to discriminate between the samples impacted or not impacted by sewage as well as between the samples positive or not positive for Salmonella and Campylobacter, supporting its value as a sewage tracer. Although limited rainfall was observed, concentrations of sewage markers and bacterial pathogens were not influenced by rainfall, while concentrations of indicator bacteria were. From all the microbial parameters studied, F+ coliphage concentrations correlated positively with the onsite sewage disposal systems (OSDS) density. Novel qPCR assays for F+ RNA coliphage subgroups were developed and used to analyze the samples. Improving the recovery of enteric RNA viruses would strengthen further studies.