Seagrass meadows in Southern Guimaras: Immediate Post-Oil Spill Status


by: *Maria Frances J. Nievales


The M/V Solar 1 Oil Spill damaged the ecology of southern Guimaras. Bunker fuel floated meters from shore for weeks hovering over critical ecological habitats including seagrass meadows. This study looked at the ecological status of seagrass meadows in the southern section of Guimaras Island immediately after the oil spill event;  and, attempted to track temporal changes in monitoring stations exposed to varying degree of oiling to clarify potential short term responses of seagrasses. Nine (9) species in 6 genera of seagrasses were encountered in various meadows which included Thalassia hemprichii, Enhalus acoroides, Halophila ovalis, H, minor, Cymodocea rotundata, C. serrulata, Halodule uninervis, H. pinifolia and Syringodium isoetifolium. Majority of the meadows were mixed species assemblage with T. hemprichii generally as the dominant species. Poor seagrass cover (<5%) and sparse shoot density (<50 shoots/sqm) characterized monospecific beds dominated by E. acoroides along the channel (UP Channel) or protected muddy embayments (e.g. Alman, Panobolon Is. lee, Sabang). More open meadows are species-rich with good cover (> 60%) (e.g. Panobolon Is. Front, Natunga Island). Shoots were densest (>3000 shoots/ sqm) in monospecific Halodule beds near estuaries (e.g. Igang, Alegria) with likely broadly fluctuating salinities. The meadow adjacent to the oiled shoreline with minimal clean up (i.e. CALAPARAN) had the least seagrass cover (17.4+ 1.4), shoot and blade densities (293+ 94, 948+ 203) and dry above-ground biomass (34.0+ 15.5) compared to less impacted meadows or the Reference Site between December 2006 to March 2007. In CALAPARAN, seagrass cover and shoot density were lower 2 to 7 months after the oil spill event compared to its 2 weeks post oil spill or year ago levels. Seagrass stations within TINMR in November 2006, showed disturbingly high proportion of dying seagrass blades relative to the Reference Site or to more hydrodynamically open, impacted sites distant from the point source of the oil spill. These were clear suggestions of stress in oil-impacted seagrass meadows but must be distinguished from natural temporal fluctuations though longer-term monitoring.

Keywords: Seagrass, oil spill, Guimaras