Marine research expedition finds severe damage to coral reefs from rising sea temperatures off Madagascar.

Research has revealed that the coral reefs of Madagascar’s south west coast have suffered massive damage from coral bleaching, including a number of reefs that lost up to 99% of their coral cover.

 

The research team, led by the conservation organisations Blue Ventures and the Wildlife Conservation Society and funded by Conservation International, also discovered a few hopeful signs. The researchers also found a few small reefs with corals that seemed to be resilient to the rising sea temperatures, so it may ultimately be possible to reseed the damaged reefs. These reefs might provide valuable information about how to save corals from future damage.

Several coral bleaching events, when rising sea temperatures causes corals to turn white and ultimately die, have hit the south-west coast of Madagascar recently, with particularly bad years in 1998 and 2000.

Previous surveys discovered that the north coast of Madagascar escaped from some bleaching events due to cool water currents from nearby deep ocean areas.

The south west coast of Madagascar has not been so lucky.
Where the reef had been bleached, algae had started to take over and fish diversity was poorer than on healthy reefs.

Madagascar is thought to have some of the highest diversity of marine species in the Indian Ocean.

Researchers recorded 386 fish species on the south-western reefs. Twenty of these species had never been recorded for Madagascar and 1 may be a new species altogether. They also recorded 164 species of hard coral, including 19 that are new records in Madagascar’s waters. 4 coral species may be new to science.

The number of coral species found was significantly lower than those previously found along the north west coast of Madagascar, probably as a result of the mass bleaching events of 1998 and 2000.

‘Global warming is a major threat to the world’s coral reefs, but there are other more direct threats as well that can be more immediately addressed,’ said Alasdair Harris, research director of Blue Ventures. ‘Destructive fishing practices and nutrient runoff from villages and resorts are also killing these incredible underwater systems that provide vital resources for the people of Madagascar.’

Over fishing and nutrient runoff have decreased the number of plant-eating species found on the coral reefs, allowing damaging algae to grow on corals that are already stressed by increasing sea temperatures. By boosting the number of herbivores, damaging algae can be controlled and coral settlement and growth can increase.

Harris said it is vital that government agencies, NGOs and local villages all work together to create marine protected areas that will prevent over fishing and other damaging activities. The development of alternative and sustainable incomes, like ecotourism, will also help local villages that rely on these dwindling marine resources.

Scientists hope their findings will be used by the government in its plan to expand the amount of protected areas in Madagascar, including increasing the total size of the country’s protected marine habitats from 2 to 10 thousand square kilometres.