Summary of Abstract Submission

Abstract Submission No. IO50-04-0002PresentationOral

RESILIENCE OF THE CORAL REEFS OF THE PADANG SHELF REEF SYSTEM, WEST SUMATRA, INDONESIA, AFTER THE 1997 MASSIVE CORAL DIE OFF ASSOCIATED WITH THE INDIAN OCEAN DIPOLE

Norman Quinn*1

1 Ministry of Fisheries and Marine Affairs, Indonesia

ABSTRACT :

Quantitative surveys of west Sumatran coral reefs began at the end of the 20th century. At that point as many as 50% of the reefs were classified as degraded with less than 50% live coral cover, primarily because of blast fishing. In 1997, reefs in the Padang Shelf Reef System (PSRS) experienced a massive die off associated with the Indian Ocean Dipole where an upwelling caused by unusually strong winds increased nutrient levels in the ocean and a drop in water temperature. Together with aeolian Fe from wildfires in Sumatra, oceanic nutrient levels were elevated to a point where a massive red tide event caused by the dinoflagellate, Gonyaulax spinifera, occurred and persisted for six months. PSRS live coral cover declined to 0% to a depth of at least 10-15m. In 2014, after nearly 17 years the reefs were resurveyed. All the surveyed reefs experienced increased live coral cover although the dominant coral species were not the same. The previously dominant branching Acropora formosa and A. nobilis of Gabuo Reef, Pandan Island and Pieh Island were extirpated. A total of 26 coral genera were observed at the sites with 19 observed in the long term monitoring transects. Pieh Island N was the most diverse site with 17 genera while Pandan Island N was the least diverse with three genera. Montipora was the dominant genus at all the sites. Blast fishing has ceased, but branching Acropora rubble previously damaged by blast fishing has yet to completely consolidate and was inhibiting resettlement.