Status of Coral Reefs of the World 2000

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Status of Coral Reefs of the World: 2000 EASTERN AUSTRALIA GBR Far Northern Section These reefs are fairly remote, so there is relatively little regular monitoring; 9 reefs were surveyed by manta tow in 1999. They had average reef-wide coral cover of about 26% (range 12 - 40%) which is slightly higher than the long term average for the GBR. Crown-ofthorns starfish (COTS) were present at very low densities on most reefs. GBR Cairns Section This section includes some of the most accessible reefs on the GBR. Much of the adjacent hinterland receives high rainfall, causing reefs closer to shore to be regularly subjected to low salinities, high sedimentation and potentially, enriched nutrient levels. In 1999, 49 reefs were surveyed by manta tow and had mean reef-wide hard coral cover of 21% (range 3- 40%); a low value caused by extensive COTS outbreaks on mid-shelf reefs. Coral bleaching affected inner-shelf reefs in this section in 1998, which caused some mortality. Video surveys of sites on the northeast sides of 19 reefs showed a similar picture, with outer shelf reefs in the north of the Section having some of the highest coral cover on the GBR (53- 61%). GBR Central Section This section also includes the accessible reefs for tourists and fishers in the Whitsunday Islands. Manta tows of 33 reefs found reef-wide coral cover to be 23% (range 3-51%). This is because inshore reefs in the north of the section suffered some mortality from the bleaching in 1998. Intensive surveys of NE facing sites on 18 reefs estimated hard coral cover at 32%. Outbreaks of COTS are occurring in the North of the Section. This pattern of outbreaks appearing first in the north of the Cairns Section, followed by a wave of outbreaks moving south was observed in the 1980s. It is presumably driven by southerly drift of larvae with the East Australian Current. GBR Mackay-Capricorn Section This most southerly section of the GBR contains some remote reefs in the Pompey Group and the Swain Reefs as well as the Capricorn-Bunkers which are some of the best-known because of research stations on Heron and One Tree Islands. There was high average coral cover on all parts of 12 reefs of 33% (range 16-49%), with consistently high reef-wide coral cover on outer-shelf reefs in the Pompey Group and the Capricorn-Bunkers (above 36%). Intensive surveys of NE facing sites on 11 reefs reflect this, with mean hard coral cover estimated at 41%. There are chronic outbreaks of COTS on some Swain reefs, which do not follow the episodic pattern of outbreaks in northern sections. Elizabeth and Middleton Reefs These are large atolls about 120km north of Lord Howe Island and well south of the GBR. Surveys in the 1980s and 1990s showed there was more diversity and more tropical species than on Lord Howe. Crown-of-thorns starfish did some damage throughout the 1980s, but the full impacts are not known. Human impacts are negligible, but storms can cause substantial changes. 144
Status of Coral Reefs of Australasia INTERPRETATION OF VALUES FOR CORAL COVER This report refers frequently to percent coral cover. The average reef-wide cover of hard coral on GBR reefs was estimated at 23% in 2000, with values ranging from 3- 51%. More precise estimates from underwater video records on a range of NE facing slopes show relatively higher cover of hard coral with a mean value of 28% and range of 4-68%. These relatively low values reflect fairly frequent disturbances such as cyclones and crown-of-thorns starfish outbreaks during the last few decades. Much of the change in coral cover on the GBR is due to growth and destruction of table Acropora spp. (e.g. A. cytherea and A. hyacinthus). These table corals live in areas of high water movement and grow rapidly to cover a large area, but they become increasingly susceptible to storm damage as they grow. On reefs close to the equator, where cyclones are rare, such corals cover much of the reef and average values for coral cover will be higher (up to 80% or more in places). Thus different disturbance regimes will lead to different norms for the extent of coral cover. Therefore, it is essential to know the environmental regime of an area to interpret coral cover. An estimate of 30% on the GBR is often an indication that the reefs are in excellent health as storms and COTS tend to keep coral populations down. Whereas in other areas, cover of 30% would be viewed with alarm, as reefs in parts of the Red Sea, the Maldives, Indonesia, and parts of the Caribbean often have levels way over 70%, due to a lack of tropical storms or they are in protected waterways like the Red Sea. Lord Howe Island This high volcanic island (14.6km 2 ) is 603km off the east coast of Australia and one of the most southern coral fringing reefs in the world (31 o 40’S). The reefs have low species diversity, but good coral cover on the rocky slopes in passes and lagoons. The island and surrounding seas were declared a World Heritage Area in 1982, a Marine Park was declared in June 2000, and a reef-monitoring program is being implemented. Two previous surveys found significant differences in the composition of coral species between 1978 and 1993, suggesting some turnover of rare species. There was an increase in crown-of-thorns starfish numbers in the early 1990s and some coral bleaching in the late 1990s, but impacts have been minimal and the condition of the reefs is good. Fish, plants and invertebrates have a mix of tropical and temperate species and a number of endemic species. There is a management plan to protect the World Heritage values while allowing recreational fishing, and fishing to supply locals and tourists. There is coral growth on rocky reefs south of the GBR in southern Queensland: the Gneering Shoals (26 o S), Flinders Reefs (27 o S) and northern New South Wales (28 o S 30’S) on rocky reefs with populations of corals up to 50% coral cover. 145
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FOREWORD Over the past few years, I
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CONTENTS COUNTRIES, STATES AND TERR
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COUNTRIES, STATES AND TERRITORIES A
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Countries, States and Territories T
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EXECUTIVE SUMMARY CLIVE WILKINSON T
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Executive Summary CORAL BLEACHING I
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Executive Summary South Asia Most r
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Executive Summary parts of Fiji and
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Executive Summary management and mo
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Executive Summary tourism developme
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Executive Summary problem is loomin
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Status of Southeast and Central Pac
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Status of Southeast and Central Pac
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12. STATUS OF CORAL REEFS OF AMERIC
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Status of Coral Reefs of American S
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15. STATUS OF CORAL REEFS IN THE NO
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Status of Coral Reefs in the Northe
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17. STATUS OF CORAL REEFS IN THE EA
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Status of Coral Reefs in the Easter
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18. STATUS OF CORAL REEFS IN SOUTHE
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Status of Coral Reefs in Southern T
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19. SPONSORING ORGANISATIONS, CORAL
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Sponsoring Organisations, Coral Ree
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LIST OF ACRONYMS AGRRA AIMS ASEAN B
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