Reef Faunal Assemblages & Seagrass-associated Echinoderm Populations in Oil Spill-affected Waters in Southern Guimaras, Philippines: A Comparison between Pre-spill and Post-spill Years

Data on reef and seagrass bed assemblages from previous surveys (2000-02) in the TINMAR are compared with similar data collected after the oil spill in August 2006 (2006-08). Sea urchin densities showed a large reduction from levels observed in 2000-02, while sea stars showed a 50% increase in abundance from observed levels in 2000-01. The opposing trends may reflect long term natural fluctuations of grazer populations in seagrass beds and may not necessarily be the effect of a specific disturbance. It is within the context of natural seasonal and between year patterns in variability that any meaningful impact of events such as the oil spill should be assessed. Observed abundance levels of reef fish assemblages from 2006-07 were 60% lower than levels observed in previous surveys. Overall abundance remained low even twenty (20) months after the oil spill, although reef habitat quality (live hard coral cover and macroepifaunal assemblages) did not show any difference from pre-spill (2000-02) conditions. This suggests that the reduction in reef fish abundance may have been caused by or in addition to other factors. The need for coordination with other monitoring studies, e.g. capture fisheries, is stressed