The potential impacts of pollutants, including caffeine, the herbicide glyphosate and the broad-spectrum antibiotic sulfamethoxazole, on microbial communities in stream and coastal environments was the focus of Sofia Suesue’s senior thesis research in the University of Hawai‘i (UH) Mānoa Global Environmental Science (GES) bachelor’s degree program in the Department of Oceanography.
Suesue’s findings suggest that caffeine degrades in concentration from the inland portion of the stream to the nearshore and it may have an impact on microbial metabolism. Her research also showed that glyphosate and sulfamethoxazole were stable in both marine and freshwater systems with higher concentrations in nearshore sections of the stream, suggesting they can be delivered into coastal areas where they may persist.
“Observing potential pollutant attenuation by microbes only within inland, non-channelized portions of the stream system suggests that inputs from all other areas may be more likely to export into coastal waters which could lead to the increased occurrence of environmental and public health concerns connected to pollutant presence,” said Suesue.
Guided by School of Ocean and Earth Science and Technology mentors Henrietta Dulai, Earth Sciences professor, and Craig Nelson, associate researcher in the Department of Oceanography and Hawai‘i Sea Grant, Suesue surveyed the Kahaluʻu-ʻĀhuimanu stream system on the windward side of O‘ahu to measure how the concentration of the three contaminants changed from inland to coastal environments.
After this survey, the researchers selected four sites across the stream system and two within Kāne‘ohe Bay. They conducted a lab experiment wherein they added contaminants to the water samples collected from these areas and observed changes in the contaminant concentration and microbial density over the course of two weeks.
“If we observe a decrease in contaminant concentration and significantly higher cell density, that may suggest that a contaminant was being used as an energy source for microbes,” said Suesue. “This is what we observed in the samples to which we added caffeine. It appears that it may have an impact on microbial metabolism in that system.”
One intriguing finding of the research was the observation that, of the three pollutants tested, only caffeine degraded over a month-long incubation, and then only with freshwater microbial decomposers.
“When caffeine was added to marine waters we saw no evidence of degradation, suggesting that the marine microbial decomposers could not break down this molecule rapidly,” explained Nelson.
The team was struck by how persistent all three compounds were in marine ecosystems, remarking that “these experiments add to the growing concern over the long-term persistence of chemicals associated with human pollution sources.”
From summer course to career path
Prior to joining SOEST, Suesue was pursuing an associate’s degree in natural sciences at Windward Community College (WCC) and enrolled in a summer oceanography course at UH Mānoa, Halau Ola Honua’s Mauka to Makai, that focused on the management of watersheds on O‘ahu.
“Through the Mauka to Makai course, I became more interested in studying oceanography and found pursuing a career in research to be a more possible aspiration than I originally thought,” said Suesue. “Also, with my experience in the course I believed I could utilize what I would learn [in GES] to one day help with some of the environmental issues in our coastal areas.”
Raised on the windward side of O‘ahu, environmental science had always intrigued Suesue. Michael Guidry, summer course co-coordinator and director of the GES program, encouraged her to transfer to SOEST after graduating from WCC.
Connecting with Dulai, who has substantial experience in contaminant surveys and hydrology, and Nelson, whose focus is microbial ecology, provided Suesue mentors with expertise that perfectly complimented her interests and guided a meaningful research project.
Suesue defended her undergraduate GES research thesis in August 2022 and is now participating in the Conservation Leadership Development Program run by the local sustainability training nonprofit Kupu. Through this program she serves at the USFWS Pacific Islands Refuges and Monuments Office as a biological science technician with the Pacific Seabird Monitoring Program.
“In the future, I’d like to continue to research environmental factors that could affect coastal conservation efforts across the Pacific,” Suesue said.
Original article written by Marcie Grabowski for SOEST News.