Tracking natural seepage and wastewater effluent in and around Boracay Island, Philippines

Caroline Marie Jaraula1, Diana Aga2, Mishel Valery Rañada1, Shyrill Mae Mariano1, Jhun Marc Salvador1, Luisa Gillian Angeles2, Mary Antoinette Limen1, Emmanuel Artuz1, Florybeth La Valle3, John Burtkenley Ong4 and Alasdair Cohen5, (1)Marine Science Institute, University of the Philippines, Metro Manila, Philippines, (2)University at Buffalo, Department of Chemistry, Buffalo, NY, United States, (3)University of California, Berkeley, Department of Environmental Science, Policy, and Management, Berkeley, CA, United States, (4)Ateneo de Davao University, Davao City, Philippines, (5)Virginia Tech, Department of Population Health Sciences, United States
Abstract:
Porous limestone bedrock of tropical islands such as Boracay, have complex and dynamic hydrological connections susceptible to wastewater seepage. Sampling campaigns were conducted in 2018 to capture baseline data during the island’s six-month closure to tourism, and in September 2019 after tourism to the island resumed, coinciding with a period of relatively high precipitation and runoff. Sewage pipes were traced and water samples collected along the length of the outfall pipes and, by way of comparison, in ambient waters. Stable isotopes of water, pharmaceutical and personal care products (PPCP), and microbial water quality parameters were measured as indicators of wastewater effluent. Stable isotopes of Hydrogen and Oxygen indicated pond, natural seepage, and very shallow nearshore areas with meteoric water sources, signifying rapid infiltration and rainfall runoff into the limestone bedrock as well as outflow on the surface, or as submarine groundwater discharge. During the closure to tourism, only caffeine and acetaminophen were detected in ponds and sites of natural seepage to the marine environment. PPCP analyses are ongoing for the samples recently collected. Fecal indicators were analyzed using IDEXX®Quanti-Tray/2000® for both fresh and seawater systems; 3M™PetriFilm™ Coliform Count Plates, as well as a DelAgua testing kit, were also used to analyze freshwater samples. Natural inland catchments including lagoons and wetlands evidenced high loading of E. coli and fecal coliforms. Consistent high counts of fecal indicator bacteria in marine waters suggest recent and/or ongoing contamination. Areas with live-aboard boats and commercial sewage pipe outflows are also likely sources of contamination. In order to better understand sources and distribution of wastewater effluent in the near-shore environment, water sampling will be repeated during high tourism and low precipitation conditions in December, 2019 as well as during a warmer period in April, 2020.
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