A French researcher says last month's passage of tropical cyclone Oli caused substantial damage to the coral reefs of French Polynesia.
The storm had wind gusts of 260 kilometres an hour when it hit the Austral islands.
The researcher in Moorea, Serge Planes, says a starfish pest in the past three years has weakened the corals and deprived them of the cavities for small fish but the cyclone has now washed away dead coral branches which were important for the regeneration of the reefs.
He says it will take years for the coral to recover, possibly up to 15 years.
At worst, it could take decades if algae manage to dominate marine life in the medium term.