Status of Coral Reefs of the World 2000

Status of Coral Reefs of the World: 2000
trochus being an important food and income source for remote areas such as atolls. In
Tonga during 1990-91, new stocks of giant clams (Tridacna gigas and Hippopus hippopus)
were introduced to replace previously over-harvested giant clams and mariculture projects
for the giant clam, Tridacna deresa was established during the 1980s. Four species of
Tridacnidae occur throughout Kiribati and Tonga, but there is only one species in French
Polynesia, Tridacna maxima. This species is abundant in some closed lagoons of the
Tuamotu Archipelago and is eaten for food, but is not yet over-exploited or exported.
NATURAL DISTURBANCES AND IMPACTS
Volcanic Activity
Several new islands have formed during the last 20 years on the volcanic arc of the Pacific
and Australian plates, but most of these have re-submerged. The only recent volcanic
activity in the region occurred in Tonga. The last eruptions of Niuafo’ou were in the late 30s
and early 40s, and Kao and Tofua are potentially active. The small island of Mehetia (east of
Tahiti) in the Society archipelago is close to a hot spot and was probably active a few
thousands years ago. While there are corals growing on the island, a fringing reef has not
yet formed.
Cyclones
These occur throughout the region, but are more frequent in the west than the east to west
and in the north rather than the south e.g. cyclones are relatively frequent in Kiribati, but rare
in French Polynesia. The major recent cyclones took place during: 1982, 1995, 1997, 1999,
and 2000 in Tonga; 1958, 1960, 1968 and 1979 in Niue; and in 1982-1983, 1991 and 1997 in
French Polynesia. The impacts of cyclones are thought to be less damaging to coral reef
areas where there is a high prevalence of storms due to adaptation, however it appears that
cyclones do more long-term damage to reefs that experience cyclones infrequently. This
was the case in French Polynesia which witnessed dramatic destruction of coral reef lagoons
and outer slope areas from 6 cyclones that occurred during the El Niño years of 1982-1983
Crown-of-thorns Starfish Infestations
Acanthaster planci outbreaks and elevated numbers were reported in almost all of the
Polynesian countries in the late 1970s and early 1980s. But since that time, populations
appear to be stable with only sporadic outbreaks in some places e.g. Rarotonga and
Aitutaki during 1998.
Coral Bleaching Events
These appear to have been more frequent and severe during the past 20 years, although
there are few data for most of these countries before this time. Bleaching was reported for
about 80% of the Acropora species during March 2000 in Rarotonga, Cook Islands. In Tonga
and Fiji bleaching occurred in February, 2000, where up to 90% of the Goniastrea and
Platygyra colonies bleached and coral death on the outer slope was reported to be about
2-5%. Only slight bleaching was reported in Kiribati in 2000. Considerable information on
bleaching and mortality has been recorded in French Polynesia where there was major
mortality in 1991 (20% of colonies died on the outer slopes of many islands), 1994 (major
bleaching, but most colonies recovered), and 1999 (high bleaching and mortality, with
great variability at the inter-and intra-island scale).
188