UH Hilo marine scientist says take heed of today’s Dept of Health brown water advisory

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Faculty and student researchers at UH Hilo have been testing coastal waters in Hilo for years, consistently finding harmful bacteria, including staph and fecal indicator bacteria. It gets worse during storm run-off. 

Aerial view of Hilo Bay.
Hilo Bay. (File photo by Hollyn Johnson for UH Hilo)

By Susan Enright/UH Hilo Stories.

A marine scientist at the University of Hawaiʻi at Hilo, who has done extensive studies on water quality issues that plague Hawaiʻi Island coasts, says the Brown Water Advisory issued this morning by the Hawaiʻi Department of Health should be taken seriously.

Tracy Wiegner business portrait in outdoor setting.
Tracy Wiegner

“When the water is brown, turn around,” says Tracy Wiegner, professor of marine science and an aquatic biogeochemist who serves as a chemical oceanographer in UH Hilo’s Department of Marine Science.

Wiegner says research by UH Hilo students since 2007 has consistently found when the water in Hilo Bay is brown, bacteria concentrations are high.

“These bacteria get washed down from the watershed and can potentially pose a health risk to recreational water users such as swimmers, paddlers, surfers,” says Wiegner. “These bacteria include those indicative of wastewater pollution from cesspools, as well as pathogens known to cause serious skin infections.”

Faculty and student researchers at UH Hilo have been testing the waters in Hilo for years, consistently finding harmful bacteria, including staph and fecal indicator bacteria or FIB.

It gets worse during storms and heavy run-off.

“So, out of an abundance of caution, it is best not to go into the water when it is brown following heavy rains, or if you do, make sure you don’t have any open cuts and rinse off immediately,” says Wiegner in response to today’s Department of Health advisory.

Research findings

In 2019, a team of scientists from UH Hilo published a paper in the prestigious Journal of Environmental Quality on how rainfall-driven runoff increases concentrations of harmful bacteria in Hilo Bay.

The paper is titled “Rainfall and Streamflow Effects on Estuarine Staphylococcus aureus and Fecal Indicator Bacteria Concentrations.” The authors are Louise Economy, an alumna of UH Hilo’s tropical conservation and environmental science graduate program who is currently employed by the Hawaiʻi Department of Health; Professor Wiegner; Ayron Strauch, a hydrologist with the Department of Land and Natural Resources; Jonathan Awaya, professor of biology at UH Hilo; and Tyler Gerken, a UH Hilo alumnus and a graduate research assistant at the University of Washington at the time of publication.

The scientists used culture-based methods to quantify the presence of Staphylococcus aureus (known informally as “staph”), methicillin-resistant Staphylococcus aureus (abbreviated MRSA), and fecal indicator bacteria in Hilo Bay and in soils, sands, rivers, wastewater, and storm water within the Hilo watershed. These pathogen concentrations were then compared with rainfall and river discharge levels and water quality data. The results showed that staph and FIB concentrations increased with rainfall and river discharge. In terms of water quality, high turbidity (water cloudiness) was associated with higher bacteria concentrations, and high salinity with lower bacteria concentrations.

A study published last year, “Detection and modeling of Staphylococcus aureus and fecal bacteria in Hawaiian coastal waters and sands” (Water Environment Research, May 2024), led by UH Hilo marine science alumna Maria Steadmon, presents water quality data from six popular spots at and near Hilo bay. Results of the multi-student and faculty project, conducted between the years 2016-2019, show staph in water and sand at the Hilo beaches, following a dismal trend.

The authors of the study — including Wiegner and UH Hilo anthropology colleague Lynn Morrison, along with several UH Hilo students, alumni, and UH Mānoa scientists — say that microbial pollution of recreational waters leads to millions of skin, respiratory, and gastrointestinal illnesses globally. But, they point out, even though fecal indicator bacteria are monitored to assess recreational waters, they may not reflect the presence of Staphylococcus aureus, a global leader in bacterial fatalities.

Since many community-acquired staph infections are associated with high recreational water usage, the study measured and modeled S. aureus, methicillin-resistant S. aureus (MRSA), and FIB (Enterococcus spp., Clostridium perfringens) concentrations in seawater and sand at six beaches in Hilo over 37 sample dates from July 2016 to February 2019 using culturing techniques.

The researchers discovered S. aureus and FIB concentrations were roughly 6–78 times higher at beaches with freshwater discharge than at those without.

“This may be due to the fact that not only humans can carry staph but animals as well,” says Steadmon in an interview with Hawaiʻi Public Radio. “We both can shed the bacteria in the soil and that can be washed into streams and the watershed and then discharged into the coast.”

In the recently published Hilo study, seawater concentrations of Enterococcus spp. were positively associated with MRSA but not S. aureus. Elevated S. aureus was associated with lower tidal heights, higher freshwater discharge, onsite sewage disposal system density, and turbidity.

The authors go on to say that regular monitoring of beaches with freshwater input, utilizing real-time water quality measurements with robust modeling techniques, and raising awareness among recreational water users may mitigate exposure to S. aureus, MRSA, and FIB.

Story by Susan Enright, public information specialist for the Office of the Chancellor and editor of UH Hilo Stories. She received her bachelor of arts in English and certificate in women’s studies from UH Hilo.

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