The natural context of changes in the Great Barrier Reef - The Great Barrier Reef: An Environmental History - page 40

A cyclone hit [Holbourne Island] in 1918; the island prior to this - or the
fringing reef - had a shingle ridge around the outer edge of the reef, which
moated the water at low tide. Within this moat, there was quite good […]
living coral. What happened during the cyclone was that the shingle rampart
was breached; water levels became much lower on the reef flat and a lot of
the living corals just died off. They are still there; they are high micro-atolls
and you can see - about 30 or 35 centimetres below that level - where coral
has grown since . 6
The recovery of Holbourne Island reef - in contrast to the reef at Stone Island
- was attributed, by that informant, to reduced sedimentation at Holbourne
Island, which is further offshore and more distant from terrestrial impacts than
is Stone Island.
Oral history evidence indicates that tropical cyclone damage to corals has been
witnessed by many observers, including catastrophic reductions in coral cover.
One informant, a coral reef scientist, reported seeing changes in coral reefs: 'from
incredibly rich coral communities with 50 to 75 per cent coral cover down to less
than five per cent coral cover'. However, the same informant described the rapid
recovery of offshore coral reefs from tropical cyclones, stating:
You just get huge recruitment and rapid growth of Acroporas . Going back in
five years' time after total devastation will show you what is apparently quite
a healthy reef, although, if you look closely, you'll see most of the corals are
less than half a metre in diameter. So you can get rapid recovery in exposed,
high-energy situations . 7
In contrast to offshore reefs, fringing reefs are particularly vulnerable to the
effects of tropical cyclones. The informant stated that 'a good cyclone reduces
them to rubble with virtually no coral cover' . 8 A s a result, historical changes in
fringing reefs can be over-written by the influence of successive storms, resulting
in changes to the structure of those reefs as coral rubble and larger coral pieces
are transported by wave action.
Many informants recalled the effects of particular tropical cyclones on specific
reefs. One informant, a sugar cane cutter and recreational fisher, referred to the
storm that struck Port Douglas in 1911; he also described the tropical cyclone
that occurred at Cape Tribulation on 12 March 193 4. 9 Another informant,
a shell collector, described the extent of the damage at Orpheus Island reef,
stating that:
I was in my early teens when we visited Orpheus Island, in the Palm [Island]
group, and saw first-hand what destruction the power of a tropical cyclone
can create: huge banks of broken coral metres deep cast high into the
vegetation in drifts. By sifting through this coral, we found lots of spectacular
shells we had only seen illustrated in Joyce Allen's Australian Shell s . 10