The Birth Of Coral

We know what is putting the world’s coral reefs in peril today, but what ideal conditions created them in the first place and how can they be maintained?

- Sheena Harvey

A ragged crescent of land ringed by the sharp peaks of relatively young volcanoes encloses Kimbe Bay on the north coast ofthe island of New Britain in the southern Pacific.Part of Papua New Guinea, this island, and in particular that bay, is known by marine scientists for its astonishing biodiversity. Within the shelter of a geologically turbulent land mass, awe-inspiring coral reefs teem with oceanic life. This is thought to be the evolutionary birthplace of the world’s coral reefs. What gave rise to this theory is the particular set of topographical features around the bay and the actions of the area’s ocean currents.

New Britain lies north of the Solomon Sea and cups the Bismarck Sea. South of the island, and parallel to it, is the Bougainville Trench, one of the deepest in the region, dropping to more than 9,000m (30,000ft) – deeper than Everest is high. The trench is a long narrow depression in the seabed, marking where a plate in the Earth’s crust is sliding under another, like a wrinkle in a piece of cloth.

Perfect conditions

Trenches gather detritus containing organic matter, nitrogen and phosphorous. Powerful ocean currents stir up that nutrient-rich sediment and carry it to shallower areas. In New Britain and Kimbe Bay, the nutrients from the Bougainville Trench are carried upwards by the South Equatorial Current and northwards around the island.

As the current follows the land’s contours, it swirls around the shallow shelf that forms Kimbe Bay and nutrients gather there at a time of year when the waters are at the optimum temperature to promote life. Blown by the trade winds from across the Pacific, the current is also oxygen-rich. Together, these conditions promote coral growth. And with coral comes a plethora of marine life, from the microscopic to the mega. Surveys in Kimbe have recorded 400 types of coral, 860 varieties of fish and at least 10 cetacean species.