Ancient Corals Hold New Hope for Reefs

Huon Peninsula raised reef terraces. (Credit: Photo by John Pandolfi)

ScienceDaily (Mar. 2, 2010)

Fossil corals, up to half a million years old, are providing fresh hope that coral reefs may be able to withstand the huge stresses imposed on them by today’s human activity.

Reef ecosystems were able to persist through massive environmental changes imposed by sharply falling sea levels during previous ice ages, an international scientific team has found. This provides new hope for their capacity to endure the increasing human impacts forecast for the 21st century.

In the world’s first study of what happened to coral reefs when ocean levels sank to their lowest recorded level — over 120 metres below today’s levels — a study carried out on eight fossil reefs in Papua New Guinea’s Huon Gulf region has concluded that a rich diversity of corals managed to survive, although they were different in composition to the corals under more benign conditions.

“Of course, sea levels then were falling — and today they are rising. But if we want to know how corals cope with hostile conditions, then we have to study what happens under all circumstances,” explains Professor John Pandolfi of the ARC Centre of Excellence for Coral Reef Studies and The University of Queensland. “We’ve seen what happens to corals in the past when sea levels rose and conditions were favourable to coral growth: we wanted to see what happened when they fell and conditions were adverse.”

“When sea levels drop you get a catastrophic reduction in coral habitat and a loss of connectivity between reefs. Well, those circumstances are in some respects similar to what corals are experiencing today due to human impacts — so there are useful parallels.”

“Although it is little asked, the question of where reef species go when faced with extreme environmental situations is highly relevant for understanding their prospects of survival in the future — and what we need to do to give them the best chance,” Prof. Pandolfi suggests.

In the Huon region, the team found, coral reefs survived the hard times low of sea levels with as much richness of species — but with a different composition to what they had during the good times. “As a rule the coral colonies during the period of low sea levels were closer to the sea floor and slower-growing in comparison with times of high sea levels.”

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