Ancient corals hold new
hope for reefs
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." "What we have found suggests that reef systems are
able to survive adverse conditions given suitable shallow rocky habitat.
An interesting finding of this study is that complex coral ecosystems
were maintained during the less optimal periods of low sea level. These
may have been critical to the re-establishment of nearby reefs once
environmental conditions began to improve." "The fossil record shows
that reefs have been remarkably successful in surviving large
environmental disturbances.
However, the combination of drastic environmental changes that we're
seeing today, such as degraded water quality, depleted fish stocks,
coral bleaching, ocean acidification and loss of habitat are
unprecedented in the history of coral reefs.
Although this study clearly highlights the resilience of reef
ecosystems, it is important not to underestimate the magnitude of the
challenges that reefs are currently facing.
"Prof. Pandolfi says we somehow have to find ways of preventing or
offsetting each of these impacts if we expect our reefs to ride out the
major climatic changes of the 21st century in as good condition as they
have in the past.
- Science Daily
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