UH Hilo alumnus publishes study he conducted as an undergraduate; findings show staph, MRSA in Hilo Bay watershed

The research team collected soil samples at urban, agriculture, and native-forest land uses in the Hilo Bay watershed. Staph, MRSA, and fecal indicator bacteria were present in soil from all land uses with the highest being in urban soils and the lowest in native-forest soils.

Tyler Gerken pictured
Tyler Gerken, a UH Hilo alumnus whose undergraduate research focused on bacterial contaminants in the Hilo Bay watershed, had his work published this summer in the Journal of Environmental Quality. (Courtesy photo)

By Susan Enright.

The senior thesis of a former environmental science major from the University of Hawai‘i at Hilo was published this summer in the Journal of Environmental Quality. During his undergraduate research at UH Hilo, Tyler Gerken investigated staph, Methicillin-resistant Staphylococcus aureus (MRSA), and fecal indicator bacteria (FIB) from soils of different land uses in the Hilo Bay watershed. MRSA is a public health concern because the infection is caused by a type of staph bacteria that’s become resistant to many of the antibiotics used to treat ordinary staph infections.

After graduating from UH Hilo in 2019, Gerken advanced his education and earned a master of science in environmental health in 2021 from the University of Washington School of Public Health where he continued similar research on Hawai‘i Island’s water and sand.

Gerken’s research interests include surveillance of environmentally-transmitted microbial pathogens, zoonotic diseases, antimicrobial resistance, water quality and water supply management, natural resource management, and incorporating Indigenous knowledge to answer scientific inquiries.

The budding scientist is from Kea‘au, Hawai‘i Island, and is a descendant of Kahuna Lā‘au Lapa‘au, masters of traditional Native Hawaiian healing practice. This heritage and his scientific interests have fueled his dedication to environmental justice.

Aerial of Hilo Bay
Hilo Bay. (Hollyn Johnson/UH Hilo)

Tracy Wiegner
Tracy Wiegner

While at UH Hilo, Gerken says he “assisted the marine science department with field and laboratory work collecting and analyzing water quality tests and parameters in nearshore environments.” One of his advisors and a co-author of the published study is Tracy Wiegner, UH Hilo professor of marine science and director of the tropical conservation biology and environmental sciences graduate program.

“Tyler worked to identify where in the watershed these bacteria were coming from that we find in Hilo Bay after storms,” says Wiegner.

A third co-author of the recently published study is Louise Economy, an alumna of UH Hilo’s tropical conservation and environment science graduate program employed by the Hawai‘i Department of Health. Economy was also part of the team during Gerken’s undergraduate research.

The study

MRSA and other fecal indicators increase in Hawai‘i’s streams and estuaries following storms and pose a health threat to recreational water users. The authors of the study write that to reduce this risk, watershed bacteria sources need to be identified for management actions.

“This study’s goals were to identify soil bacteria sources among different land uses and to determine if their concentrations were associated with different soil properties,” write the authors.

The research team collected soil samples at urban, agriculture, and native-forest land uses in the Hilo Bay watershed. Staphylococcus aureus, MRSA, and FIB were present in soil from all land uses with the highest being in urban soils and the lowest in native-forest soils.

Six petri dishes of soil samples.
Soil samples were collected from different land uses (urban, agricultural, and native forests) on Hawaii Island. The research found that levels of pathogenic bacteria are highest in urban and agricultural soils. (Tyler Gerken)

Staphylococcus aureus, MRSA, and FIB soil concentrations were positively correlated with each other and with soil temperature and pH, but inversely correlated with soil moisture and organic matter content.

“Our results demonstrate that soils are a watershed bacteria source and that some soil properties affect their concentrations. Identifying these sources is critical for implementing management actions to reduce pathogen loads to estuaries and transmission to recreational water users,” conclude the authors.

The undergraduate support for Gerken’s research was from the Louis Stokes Alliances for Minority Participation, Kamehameha Schools, the Pacific Internship Programs for Exploring Science, Students of Hawaiian Advanced Research Program, UH Mānoa Center for Microbial Oceanography Research and Education, and the UH Hilo Department of Marine Science. Additional support was from the Hau‘oli Mau Loa Foundation and the U.S. Geological Survey’s Pacific Islands Climate Adaptation Science Center.

Read more about the study at the Soil Science Society of American website.

Coming home

In a profile piece on the UW website done while Gerken was working on his master’s degree, he says that he would like to work with a state or federal agency, such as a department of health or department of ecology. He is currently an employee with the Federal Emergency Management Agency.

He also says in the UW interview, “Eventually, I plan on returning home to Hawai‘i to utilize the knowledge and skillset gained while at the UW to improve and expand upon environmental health within the Hawaiian archipelago.”

By Susan Enright, a public information specialist for the Office of the Chancellor and editor of UH Hilo Stories.