October 30, 2014

Maldives Expedition Looks at Recovery from 1998 Bleaching Event

\"\"By Dr. Jean-Luc Solandt, Reef Check Maldives Coordinator

In September 2014, Biosphere Expeditions, in collaboration with the Marine Conservation Society, Maldives Research Centre, and Carpe Diem Maldives, carried out a very successful survey of the reefs of N Male Atoll, Maldives. They re-surveyed sites previously visited before the 1998 bleaching event to analyze marine ecosystem resilience. During the expedition, three people (one UK, two Maldivian) were trained as Reef Check EcoDiver Trainers and seven as EcoDivers.

Upon surveying the patch, channel, and outer reefs near Summer Island, they found that the patch reefs (e.g. Deh Giri) were the most significantly affected, covered by corallimorphs (Discosoma) carpeting more than 60% of the seabed. Another site, Reethi Rah, showed a significant Crown-of-Thorns starfish outbreak, which was concerning, particularly when coupled with recent disease outbreaks seen in previous surveys. Furthermore, there appeared to be more coral-eating cushion starfish and Drupella.

Outer forereef slope reefs appeared to show the greatest uniformity of good health, particularly Madi Gaa. Other more sheltered channel and patch reefs showed good coral cover and recovery from the 1998 bleaching event in shallow transects (<6m), but not for the deeper transects, most commonly at 10m. Dr. Jean-Luc Solandt, Reef Check Maldives coordinator and the lead scientist on the expedition, believes this is caused by the creation of rubble fields from the breakdown over the past 15 years of coral killed during the bleaching event; gravity is pulling the rubble down to the deeper, more sheltered waters of the reef slopes, which has been a pattern in their data for years now. These rubble-strewn areas appear to be poor surfaces for new corals to grow. Surprisingly, the surveys didn’t reveal more reefs (such as Deh Giri) that have then moved onto a different stable state that are dominated by opportunistic colonising lifeforms such as Discosoma.

In addition, the expedition found that commercial fish species were worryingly absent over these N Male reefs, and herbivorous parrotfish were also uncommon.

For more information on this expedition and its findings, you can contact Dr. Solandt