Biological-Physical Modeling to Predict the Dynamics of a Pathogenic Bacterium, Vibrio Vulnificus, in an Urbanized Estuary in Hawaiʻi

The south shore of Oʻahu, Hawaiʻi is one of the most visited coastal tourism areas in the United States with some of the highest instances of recreational waterborne disease. The pathogenic bacterium, Vibrio vulnificus, proliferates in the warm temperature and intermediate salinity waters of the estuarine Ala Wai Canal in Honolulu. Heavy rainfall has been shown to transport V. vulnificus from the canal into the nearshore coastal system threatening human and ecological health, as well as the state’s tourism-based economy. Water quality monitoring of human pathogens requires abundant and consistent resources for highly technical training, laboratory facilities, and extensive knowledge of the biology of microbial indicator organisms. We developed a biological-physical numerical model to predict pathogen dynamics from environmental conditions that can be easily measured with oceanographic sensors. We employed a novel approach that involves community engagement and assimilates data from the Regional Ocean Modeling System (ROMS), in situ profile sampling, deployed instrument time series from the Pacific Islands Ocean Observing System (PacIOOS), and multifactorial growth and mortality laboratory experiments. Monthly surveys were conducted to characterize biogeochemical gradients in high spatial and temporal resolution for model validation. This work, funded by the University of Hawaiʻi Sea Grant College Program, integrates the microbiological, biogeochemical, and hydrological processes of the estuarine and nearshore oceanographic dynamics in an effort to provide easily assessable and interpretable model products available to health agencies and the general public. Model forecasting will assist mitigation strategies in the face of imminent anthropogenic impacts, including planned sediment dredging and construction for flood mitigation within the canal as well as long-term climate change that will continue to alter water temperature and precipitation patterns in this region.