Pollution from on-site sewage disposal systems and injection wells is impacting coral reefs worldwide. Through onsite testing and reef surveys at Puakō, Hawaiʻi Island, researchers from the University of Hawaiʻi at Hilo, UH Mānoa and other organizations found sewage pollution was moderate on the offshore reef from seeps, and that water motion mixed and diluted the pollutant.
The study “Detection and impact of sewage pollution on South Kohala’s coral reefs, Hawaiʻi,” was published in Marine Pollution Bulletin in March 2023, and led by UH Hilo alumnus Devon Aguiar, who holds a master of science degree from the tropical conservation and environmental science program. Aguiar is currently a fish and habitat monitoring specialist for the Hawaiʻi Division of Aquatic Resources.
Study authors believe the observed sewage conditions likely contribute to the dominance of turf algae cover, and the severity and prevalence of growth anomalies and algal overgrowth on corals. The study revealed that water motion was necessary to assess sewage pollution and identify environmental drivers associated with impaired coral health conditions.
Further, the researchers note the methods they used in this study could be utilized by natural resource managers to identify and reduce human-caused problems to coral reefs.
“In addition to describing the impacts of sewage pollution in South Kohala, our study also emphasized the use of multiple research methods,” said Aguiar. “Drawing from the disciplines of ecology, microbiology, and oceanography, we were able to provide an enhanced perspective on reef and benthic water conditions in South Kohala. It is my hope that these results can support efforts to reduce anthropogenic nutrient inputs on reefs within and outside of Hawaiʻi.”
The goal of the research with this project and the past ones was to document current water quality and coral reef health conditions at Puakō, with an eye toward the future when onsite sewage disposal systems will be removed, per Hawaiʻi State Act 125 (2017).
Aguiar’s mentor Tracy Wiegner, a professor of marine science at UH Hilo who is an expert in sewage pollution in marine environments, is a co-author.
Other UH Hilo co-authors are marine scientists Steven Colbert, John Burns and James Beets; alumnae Leilani Abaya and Jazmine Panelo; and research assistant Julia Stewart.
Additional co-authors are Kristina Remple and Craig Nelson from UH Mānoa, and Courtney Couch of the National Oceanic and Atmospheric Administration’s Pacific Islands Fisheries Science Center in Honolulu. The Nature Conservancy also collaborated on this research.
Read more at UH Hilo Stories.
—By Susan Enright