The natural context of changes in the Great Barrier Reef - The Great Barrier Reef: An Environmental History - page 39

environmental factor that has caused changes in coral reefs; in particular, affecting
fragile corals such as Acropora species, although other species are also susceptible
to storm damage. Documentary sources refer to noteworthy tropical cyclones
at Green Island (1858), Cooktown (27 January 1899 and 4-5 March 1899)
and Low Isles (March 1911) (Almond, 1899, p1025; Mackay, 1911, p1187) . 2
While travelling in the Great Barrier Reef, Agassiz (1898, p115) referred to
Saville-Kent's observation of 'the wreckage of the fringing reef by a hurricane at
Saddleback Island'. For some locations, a time series of tropical cyclones has been
reconstructed; for example, Loch (1991, p5) showed that severe tropical cyclones
affected Michaelmas Cay in March 1878, January 1906, March 1911, February
1920, February 1927, March 1934 and 1948, in addition to many smaller storms.
Another record of this type of naturally-occurring damage stated that the jetty at
Green Island was destroyed by a tropical cyclone in 1946 and was reconstructed
by the Cairns Harbour Board . 3
The GBRC expedition to the Great Barrier Reef in 1936 described other
instances of damage to corals that were attributed to tropical cyclones. For
example, observers on that expedition stated that Mackay Cay was 'severely
damaged' by a tropical cyclone in 1934 and, at the reef between Ingram and
Beanley Islands, the same report indicated that 'the sandy surface of this reef was
caused by the destruction, through a cyclone, of a former cay' (Steers, 1938, pp70,
84). The observers found that Night Island had been devastated by a tropical
cyclone within the preceding 20 years. Since that event, Steers (1938, pp94-5)
stated:
To the north-west of the reef the mangrove mud has spread, and seems to
have killed much of the reef. Incidentally, much of the whole area covered
by the mangroves was sandy; there was also abundant Thalassia . […] Whilst
the upper surface of the reef seems to be largely moribund, the general
appearance of much of the cay and mangrove area is one of recovery and
rejuvenation after a severe blow.
Moreover, the impacts of tropical cyclone damage were not restricted to the
northern Great Barrier Reef. For instance, Steers (1938, p54) described the major
transformation of Lady Elliot Island reef that he attributed to the tropical cyclone
of March 1936, which 'appears to have been responsible for building the outer
ridge' of the reef.
Oral history sources provide additional details of the impacts of tropical
cyclones on coral reefs. One informant, a geomorphologist, recalled the visible
effects of the storm that struck the Bowen area in 1918, affecting the coral reefs
at Stone and Holbourne Islands. At Stone Island, he reported that almost no
coral had survived, even where coral communities would now be expected to be
found . 4 C onsiderable damage also occurred at Holbourne Island when the reef
moat was breached by a storm, leading to a dramatic change in water level . 5 The
informant stated: