A Site Investigation of Pollution Along the Bantayan-Piapi Coastline, Dumaguete City, Philippines

Abstract

Physico-chemical and bacteriological analyses were conducted on samples from the mouth of Mojon Creek at the north end of Silliman Beach, and sewer outfalls along the Bantayan-Piapi coastline. At each of the seven sampling stations, two samples were collected: one from the river mouth or outfall and a second from seawater located at least 20 m offshore. A supplementary underwater fish density and biomass survey was conducted in the shallow seagrass areas.

Extremely high levels of bacteria were detected in the samples, with concentrations of E. coli and enterococci ranging from one to five orders of magnitude exceeding the referenced standards and criteria. The concentrations of ammonia in all samples exceeded the referenced standards and criteria, thereby contributing to a toxic environment for aquatic organisms. Outfall effluent samples had non-detect to low dissolved oxygen (DO) levels, which were matched by high biochemical oxygen demand (BOD). A few outfall samples exceeded standards for oil and grease, total suspended solids (TSS), and phosphates. Based on a transect survey in the seagrass beds, the fish biomass and population density were notably low. The results of this study indicate significant pollution in the study area. This is supported by other recent data obtained by the Silliman University Angelo King Center for Research & Environmental Management (SUAKCREM). A concurrent, collaborative study on microplastics in fish gut confirmed the results of earlier studies by SUAKCREM on the occurrence of microplastics in local fish catch.