Flourishing coral sanctuary discovered off East Africa

The coral sanctuary is a wildlife hotspot where species are thriving despite warming events that have killed their neighbours

The coral refuge, which stretches from Shimoni, 50 miles south of Mombasa, in Kenya to Dar es Salaam in Tanzania, is fed by cool water from deep channels formed thousands of years ago by glacial runoff from Kilimanjaro and the Usambara mountains. Outside that area, the corals are bleached and dying. But inside the area, of around 400 sq km [150 sq miles] they retain their colour and their health.

Tim McClanahan, the author of a study on the refuge published this month in Advances in Marine Biology, told the Guardian he had an “epiphany” when he realised why the reef was so rich in wildlife.

The coastline has the highest density of dolphins in east Africa, and coelacanths, fish once believed extinct, swim in its deep waters. I thought ‘why are all the animals here?’ And I realised it was because of Kilimanjaro.

The cool water appears to protect the corals from episodic warming events like El Niño. The major reef habitats-island and fringing reefs are also protected from the open ocean storms and the strong inter-annual current temperature variability.

McClanahan has been looking for coral sanctuaries in the west Indian Ocean for more than a decade. He said he has found three potential coral sanctuaries in the western Indian Ocean, but only for this one is the available scientific evidence “pretty strong”.

Initially, McClanahan succumbed to a feeling of despair about the future of the reefs, "then you sort of pull up your socks and go see what you can do," he said. “I’m very excited about it. It gives us something to hope for. Some good news in gloomy times.”