Initial assessment of the bacterial population of Guimaras waters and soil after the Solar I Oil Spill


by: Christopher Sombito, Gilda Lio-Po, resurrecio Sadaba and Romelie Torreta


A massive oil spill occurred near the shores of Guimaras Island, Philippines, in 11 Aug 2006 caused by the sunken MT Solar I vessel. The oil spill spread to neighboring towns of Guimaras damaging the marine coastal environment, consequently, causing health and economic problems, particularly, by affecting local fisheries, wildlife, and tourism. Hence, this study was conducted to assess, quantify, and isolate indigenous bacteria with potential petroleum hydrocarbon-degrading properties that could be used for bioremediation of oil spill contaminated areas in Guimaras and nearby provinces. Sampling were conducted in Oct and Nov 2006 to assess the level of both heterotrophic and hydrocarbon-degrading bacteria (HDB) from areas affected ( Tando, Taklong, Cabalagnan, Panobolon, Alegria, Sabang , Inampulugan) and unaffected (Lawi and Getulio) by the oil spill. Samples consisted of beach water and beach sand, mangrove surface soil and subsurface soil where levels of heterotrophic bacteria consisted of Total Aerobic Counts (TBC). Presumptive Vibrio Counts (PVC), Presumptive Aeromonas Counts (PAC) and Presumptive Pseudomonas counts (PPC) were determined. Likewise, the levels of hydrocarbon-degrading bacteria were also assessed. Results showed that heterotrophic bacteria were found in variable densities among the sampled sites with Nov soil and water samples, yielding higher counts than in Oct. The Significantly sample high density of total culturable bacteria yielded mean counts of 6.4 x 10 5 cfu/g from Taklong beach soil , 5.1 x 105 cfu/g from Alegria mangrove surface soil and 5.6 x 105 cfu/g from mangrove subsurface soil samples of Inampulugan in Nov 2006. The levels of Vibrio were highest in Getulio at 3.3 x 104 cfu/g and 2.4×104 cfu/g for beach and mangrove surface soil, respectively and in Sabang for mangrove sub-surface soil at 1.6 x104 cfu/g. The levels of Aeromonas were significantly highest in Alegria at 2.1 x 105 cfu/g for beach soil and in Getulio at 1.5 x105 cfu/g and 1.4 x 105 cfu/g for mangrove surface and sub-surface soil, respectively. The levels of Pseudomonas were significantly highest in Sabang for Mangrove surface soil at 2.3 x 104 cfu/g and in Cabalagnan at 1.4 x 105 cfu/g and 4.5 x 104 cfu/g for beach and mangrove sub-surface soil, respectively. Oil-degrading bacteria were also found in variable densities among the sampled sites including one of the oil spill unaffected sites but of low level. Although, some sites have relatively low levels and even some sites had undetectable level (<2.3 MPN/g or ml), Taklong beach soil yielded a significantly high level of hydrocarbon-degrading bacteria at 620 MPN/g. Thus, this study confirms the presence of petroleum hydrocarbon-degrading bacteria in some affected areas in Guimaras.

Keywords: oil spill, bacteria bioremediation, hydrocarbon-degrading bacteria, Philippines