Even some reefs badly damaged four years ago in a massive tsunami are showing a rapid growth of young coral, said the Wildlife Conservation Society in New York.

"This is a great story of ecosystem resilience and recovery," said Stuart Campbell, a spokesman for the society's Indonesia marine program.

The recovery has been aided by communities that have abandoned destructive fishing techniques and are transplanting healthy corals into damaged reefs, the BBC reported Saturday.

The 2004 tsunami killed an estimated 230,000 people. Prayers and ceremonies remembering the dead were held Friday in Indonesia, Thailand and India, the BBC noted.