Some structural changes of seagrass meadows in Taklong Island National Marine Reserve, Guimaras, Western Visayas Philippines after an oil spill

Abstract

In August 2006, over 2 million liters of bunker fuel spilled from a sunken cargo vessel off Panay Gulf, Western Visayas Philippines. Floating oil found its way in the coastline of southern Guimaras including that of a marine protected area, Taklong Island National Marine Reserve (TINMR) (10o24’ to 10o26’N, 122o29’ to 122o31’ E). Most shorelines adjacent to seagrass beds were heavily covered with bunker fuel for weeks before manual clean up were initiated. This study describes temporal changes in structure between 2 adjacent seagrass meadows within TINMR, one with extensively oiled shoreline (CALAPARAN) and the other visually unoiled (KALIROHAN). Seagrass features in TINMR sites were compared to a reference site (LAWI) ～15 km north off the oil spill path. All 3 sites have mixed species dominated by Thalassia hemprichii. Sampling of the seagrass meadows following the oil spill indicate impact in the meadows with oiled shoreline (CALAPARAN). These impacts included: (1) a decrease in seagrass cover and shoot density; (2) generally lower seagrass cover, shoot and blade densities, and above-ground biomass within a year after the oil spill when compared to the other 2 sites; (3) a lower mid-year peak in seagrass cover as part of a bimodal seasonal pattern; and (4) a prolonged decline in shoot and blade densities within a year of the oil spill compared to KALIROHAN.