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Coral Bleaching

1 . Global (2004)
CORAL BLEACHING AND GLOBAL CLIMATE CHANGE

Summary of Recovery After the 1998 Bleaching Event
This episode was the largest coral bleaching and mortality event ever recorded on coral reefs globally, with major effects in the Arabian/Persian Gulf, Eastern Africa, throughout the Indian Ocean, in Southeast Asia, parts of the western Pacific and the Caribbean and Atlantic region. Overall, it was estimated that 16% of the world’s area of coral reefs was severely damaged; some areas no longer resembled coral reefs. Approximately half of the reefs in the Indian Ocean and around South Asia were reported to have lost most of their living corals. The Status 2000 and particularly the 2002 reports indicated significant recovery of many affected reefs, especially areas that were remote or within well managed MPAs.

Summary of Coral Bleaching from 1999 - 2004
There has been no repeat of the massive global-scale bleaching of 1998 in the subsequent 6 years, although several minor bleaching events have been reported in many regions worldwide. Coral bleaching has also occurred outside the tropics. In mid to late 1999, there was extensive mortality of 28 species of non-symbiotic gorgonians, sponges, ascidians, bryozoans, and bivalves mainly in South-Eastern France. Two symbiotic corals Oculina patagonensis (invasive) and Cladocora caespitosa (native) bleached because there were prolonged elevated temperatures of 22.0°C to 23.9°C (1.2°C above summer maxima). Similar mortality had been seen in La Spezia, Italy, in September 1997 and August 1998, likely caused by high temperature bleaching and pathogens.
Source: Goldberg, J. and C. Wilkinson , 2004 , Global Threats to Coral Reefs: Coral Bleaching, Global Climate Change, Disease, Predator Plagues, and Invasive Species. . p: 67-92. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

Coral Bleaching

2 . Africa (2000)
The bleaching threshold for corals was exceeded for both hard and soft corals, but it was not excessive. Most corals on the reefs grow at 12m or deeper, which may have protected them from warmer temperatures in surface waters. Soft corals are more prevalent on shallow reef tops, with more conspicuous bleaching.
Source: Wilkinson, C.R. (Ed) , 2000 , Status of coral reefs of the world: 2000. . Australian Institue of Marine Science, Cape Ferguson, Queensland, 363 p. (See Document)

Coral Bleaching

3 . Eastern Africa (2004)
Eastern Africa

Bleaching in 1998: Africa’s coral reefs were severely affected by bleaching and mortality levels varied from <1% in South Africa to 80% or greater on reefs in Tanzania and Kenya. Recovery of affected reefs continues but improvements have been very patchy and hindered by chronic and
local threats, including over-fishing, COTS infestations, and repeated minor bleaching events.

Bleaching from 1999-2004: Minor bleaching was reported in northern Tanzania and Kenya during 2003. Mortality was generally minimal and in some cases the species that suffered the most bleaching damage in 1998 showed less bleaching than other species, such as Pocillopora damicornis and some Acropora species. Reefs that had high coral diversity prior to 1998 have recovered to less than one quarter of their previous coral cover. Degraded reefs with low coral cover outside MPAs have generally recovered half to all of the pre-bleaching cover. The highest coral recruitment has been on protected reefs with reasonably healthy stocks of parent corals nearby. Recovery is higher on shallow reefs than in deeper water and reefs within MPAs have shown better recovery than those outside, especially on Chumbe Island, Zanzibar, and Mombasa Marine Park, Kenya. Most of the new recruits are Pocillopora species, with the highest densities of more than 20 per m2 at Mafia, Tanzania, and Kiunga, Kenya, whereas on most other reefs the range is 1-3 new recruits per m2.

South West Indian Ocean

Bleaching in 1998: In the southern Indian Ocean islands of Madagascar, Mauritius and Reunion, most corals recovered immediately after the bleaching and mortality was minor. Recovery and new coral growth on Madagascar is encouraging, but in many areas this recovery merely balances damage from anchors and pollution from the land. The major impacts of this bleaching event were in the Comoros and Seychelles. Reefs in the Comoros appear to be recovering well, for example the corals in the Moheli MPA have recovered about half of their former coral cover (to about 20%) by early 2002, with even better prospects as recruitment was strong in 2002. The situation is less encouraging in the Seychelles with very low rates
of natural recovery, even in the protected areas, and most recovery is in deeper water. In Mauritius, the 1998 bleaching event was widespread yet relatively mild. The main cause of bleaching was an increased SST and solar radiation, exacerbated by increased rainfall leading to decreased salinity and increased terrestrial runoff. The synergy of factors is most likely responsible for the observed bleaching. Acropora species were found to be more affected on the reef flat yet non-Acropora were more susceptible on the reef slope.
Source: Goldberg, J. and C. Wilkinson , 2004 , Global Threats to Coral Reefs: Coral Bleaching, Global Climate Change, Disease, Predator Plagues, and Invasive Species. . p: 67-92. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

Coral Bleaching

4 . Eastern Africa (2004)
ECOLOGICAL STATUS OF REEFS

The reporting on the status of the coral reefs in East Africa has been dominated by the damage caused by the coral bleaching and mortality during the El Niño event in 1998 and subsequent recovery. The coral cover recovery has been wide ranging at locations along the coastline and is now at 50 to 100% levels. However, many of the reefs that have shown ‘full recovery’ to prebleaching levels had displayed signs of human induced degradation prior to the bleaching. The apparent rate of recovery was more rapid on these degraded reefs, but only on coral communities that already had lost many slow growing and vulnerable coral species and was instead dominated by opportunitistic (Pocillopora, Stylophora, branching Porites) and stress resistance species (massive Porites, Coscinaraea, Pavona). In contrast, the reefs showing the least recovery since 1998 are those that were in better health prior to bleaching. Recovery on these reefs has been affected by chronic and local threats, including over-fishing, crown-of-thorns starfish (COTS - Acanthaster planci) infestations and repeated minor bleaching events.
Source: Obura, O., J. Church, C. Daniels, H. Kalombo, M. Schleyer and M. Suleiman , 2004 , Status Of Coral Reefs In East Africa 2004: Kenya, Tanzania, Mozambique And South Africa. . p: 171-188 in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

Coral Bleaching

5 . Eastern Africa (2004)
The long-term damage from coral bleaching and mortality are becoming apparent with increased rates of coral reef erosion. Surveys in Mozambique in 2004 showed that some reefs had small decreases in coral cover, attributed to a collapse in the reef framework, while coral diversity and community complexity was still increasing. There are examples of coral tables and plates that died in 1998 subsequently collapsing due to bioerosion. These are now being observed elsewhere in the region, such as southern Tanzania, The Maldives and the Chagos Archipelago.
Source: Obura, O., J. Church, C. Daniels, H. Kalombo, M. Schleyer and M. Suleiman , 2004 , Status Of Coral Reefs In East Africa 2004: Kenya, Tanzania, Mozambique And South Africa. . p: 171-188 in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

Coral Bleaching

6 . Eastern Africa (2002)
Coral bleaching and mortality during the El Niño event of 1998 was most severe in Kenya, northern Tanzania and parts of northern Mozambique, and diminished to virtually nothing in the south (Table 1). The bleaching started in the south in February-March 1998, and finished in May in the north, following the path of the solar zenith during the southern Summer. The most severely damaged reefs suffered levels of coral mortality between 50-90%. Coral cover on lagoon patch reefs and fore-reef slopes in southern Kenya dropped from an average of 30% to 5-11% within and outside MPAs (Obura et al., 2000; Obura, 2001a; McClanahan et al., 2002). There was similar bleaching in northern Kenya in shallow areas, but below 10m depth coral mortality was often less than 50%. There was high bleaching (60- 90%) at Tutia reef in Mafia Island Marine Park, Tanzania and Misali reef on the west coast of Pemba, whereas there was 10% or less bleaching on Unguja Island, Zanzibar (Mohammed et al., 2000, this volume). The most extensive bleaching in Mozambique was on exposed reefs in the north, with up to 99% mortality on some patch reefs (Motta et al., 2000, this volume). Reefs in sheltered bays, where there are naturally higher levels of nutrients and turbidity, and more variance in water temperatures, were least affected. Bleaching of hard corals in 1998 was absent in South Africa because most reef corals grow at 12m or deeper (Schleyer & Celliers, 2000; Schleyer & Celliers, this volume).

Coral mortality during the 1998 El Niño event was more intense on the fast growing genera Acropora, Pocillopora, Stylophora and Seriatopora, as well as Galaxea and Echinopora, with up to 100% bleaching and mortality (Obura, 2001b; McClanahan et al., 2001). In some other genera (e.g. Fungia, Coscinaraea,, anemones) there was high bleaching, but high rates of immediate recovery. Many other coral groups (e.g. Montipora, Astreopora, faviids, agariciids, poritids, siderastreids, and most octocorals and zoanthids) bleached at variable levels, but the full impacts are difficult to determine in these relatively rare corals. Thus, there will be a shift in the structure of the coral community in the short to medium term away from species that grow and reproduce most rapidly to slower growing, massive species. Recovery will depend on available parent stock for new recruitment and no short-term repeats of these damaging El Niño events. Higher coral recovery rates in MPAs suggest that a healthy parent stock improves local coral recruitment and regrowth potential, though these factors are yet to be tested in East Africa.

Recovery since 2000 has been patchy in all countries. For example in northern Kenya, shallow reefs are generally recovering from the bleaching while deeper reefs have suffered stasis or further declines in coral cover (Obura, 2002, Table 1). This variability in recovery also occurs between adjacent reefs, with some showing good recovery while their neighbours do not. In general, reefs within MPAs have shown higher recovery rates of coral cover, especially on Chumbe Island off Zanzibar (Mohammed et al., 2002). This has also been true in Kenya, though the higher prebleaching coral cover on MPA reefs means the time to full recovery may be greater (McClanahan et al., 2002). Recruitment has also been variable, with peak values of >20 per m2 being recorded for Mafia (Tanzania, Mohammed, this volume) and Kiunga (Kenya, Obura, this volume), though average levels are much lower in the range of 1-3 per m2. Recruitment is overwhelmingly dominated by Pocillopora,.

In Mozambique, reefs affected by bleaching have shown little recovery to 2002, though inaccessible reefs (in the north) and those in MPAs showed greatest improvements in coral cover and had the most complex fish populations (Motta, this volume). Some recovery has been recorded, howver, in the form of primary colonisation by soft corals.

In Kenya and Mozambique in particular, recovery from the El Niño has been reversed on significant reef areas by new threats, which are outlined below.
Source: Obura, D. , 2002 , Status of Coral Reefs in East Africa. . in Linden, O., D. Souter, D. Wilhelmsson, and D. Obura (eds.). Coral degradation in the Indian Ocean: Status Report 2002. CORDIO, Department of Biology and Environmental Science, University of Kalmar, Kalmar, Sweden.pp 15-20 (See Document)

Coral Bleaching

7 . Southwest Indian Ocean (2004)
Some coral reefs of the countries of the South Western Indian Ocean are showing recovery from the coral bleaching event of 1998 that reduced live hard coral cover on many reefs to less than 5%. However, recent bleaching events and subsequent mortality of the new recruits are impeding this recovery. Some exceptional sites are proving to be highly resilient to the bleaching damage, while at other sites, anthropogenic stresses including excessive sedimentation, pollution and trampling are compounding the effects of natural disturbances, such as cyclones, and increasing reef degradation. There is considerable effort to increase the capacity to manage and to improve decision making. It is encouraging that certain states are reporting increased resistance of Acropora to coral bleaching, as these coral species are a critical component of the 3-dimensional structure of reefs, and for creating complex habitats for fish and other reef species. The region is described as a biodiversity ‘hot spot’, with a large number of endemic species.
Source: Ahamada, S., J. Bijoux, L. Bigot, B. Cauvin, M. Kooonjul, J. Maharavo, S. Meunier, M. Moine-Picard, J.-P. Quod and R. Pierre-Louis , 2004 , Status of the Coral Reefs of the South West Indian Ocean Island States. . p: 189-212. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

Coral Bleaching

8 . Southwest Indian Ocean (2004)
Most coral reefs in the region are slowly recovering from the damage caused during the 1998 mass coral bleaching event. However, several new bleaching events on Reunion and the Seychelles in 2003 and 2004 have reversed some of this recovery and served as a warning that the 1998 bleaching was not an isolated event.
Source: Ahamada, S., J. Bijoux, L. Bigot, B. Cauvin, M. Kooonjul, J. Maharavo, S. Meunier, M. Moine-Picard, J.-P. Quod and R. Pierre-Louis , 2004 , Status of the Coral Reefs of the South West Indian Ocean Island States. . p: 189-212. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

Coral Bleaching

9 . Pacific (2005)
Federally sponsored coral reef surveys conducted between 1979-2004 reveal that all PRIAs have experienced coral bleaching during the past 25 years. Pre-2000 observations by Maragos (1979, 1994) include reports and photographs of localized coral bleaching of the ocean reefs at Wake in mid-1979 and mass coral bleaching in progress at Rose off all reefs to depths of 25 m in April 1994. NOAA and USFWS scientists who visited Wake in 1998 did not report any bleaching. Several USFWS visits and surveys of Rose between 1995-1999 and recent surveys of Rose in 2002 and 2004 sponsored by the National Oceanic and Atmospheric Administration (NOAA) reveal that corals are still recovering from a mass bleaching event of 1994. Coral bleaching was also reported at Johnston and Kingman in the 1990s (P. Jokiel, pers. Comm.). The four NOAA and USFWSsponsored expeditions to Baker, Howland, Jarvis, Kingman, and Palmyra between 2000-2004 strongly suggest that mass bleaching occurred within the few years before 2000, and that corals have remained in recovery phase since then. Additional evidence on recent bleaching at Palmyra reveal that the reefs off the broad western reef terrace at Palmyra supported thriving Acropora staghorn coral thickets in 1987 (Maragos, 1988) that died and degenerated to rubble deposits by November 1998 (Molina and Maragos, 1998). The distribution of large Porites heads and numerous small Pocillopora coral heads present on the terrace in late 1998 suggest mass coral bleaching in the mid-1990s rather than coral mortality caused by storm waves at Palmyra.

During 12 benthic surveys at Johnston Atoll in January 2004, mild bleaching of relatively few coral colonies were found at eight of the 12 sites. Mild bleaching was observed on Montipora patula, M. capitata, and Acropora cytherea.

During much of June through December 2002, both remotely sensed and in situ measurements of SST around Jarvis Island, Baker Islanda, and Howland Island were extremely high, at time 2˚C or more above maximum mean coditions, for prolonged periods (Figure 12.2). Prolonged temperature anomalies such as these have been implicated in most widespread coral bleaching events. Due to their remote nature, these reefs were not surveyed during or immediately after this period of SST increase. Biological monitoring by experienced scientists in early 2004 did not yield visual evidence that widespread coral mortality had occurred in the wake of a possible bleaching event in 2002.
Source: Brainard, R., J. Maragos, R. Schroeder, J. Kenyon, P. Vroom, S. Godwin, R. Hoeke, G. Aeby, R. Moffitt, M. Lammers, J. Gove, M.Timmers, S. Holzwarth, and S. Kolinski , 2005 , The State of Coral Reef Ecosystems of the Pacific Remote Island Areas. . p.338-372 in Waddell, J. (ed.), 2005. The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2005. NOAA Technical Memorandum NOS NCCOS 11. NOAA/NCCOS Center for Coastal Monitoring and Assessment’s Biogeography Team. Silver Spring, MD. 522 pp. (See Document)

Coral Bleaching

10 . Pacific (2004)
Southwest Pacific

Bleaching in 1998: Coral bleaching and mortality was not a significant problem during the major global bleaching event in 1998 but there have been several bleaching episodes since then, particularly in Fiji, Tuvalu, and Vanuatu.

Bleaching from 1999-2004: In Taveuni (Somosomo Straits), there has been no recent bleaching and recovery from 2000 bleaching is variable but clearly evident, with many non symbiotic corals in high abundance. In Bligh Water, the pillar reefs are in excellent condition, and there is vigorous recovery of dead areas from earlier bleaching, including patches of table and branching Acropora. In Lomaiviti, there is regeneration of hard corals everywhere, including much vigorous growth. Kadavu (south Great Astrolabe Reef, Madava to Ono) has some high coral cover, but generally very low coverage and sparse regeneration. (from Les Kaufman, lesk@bu.edu).

There was an average of 70% bleaching of the Acropora corals in Funafuti Lagoon, Tuvalu in 2000, when water temperatures were 30.5°C to 32°C. But there was less than 10% for the Agariciidae, Faviidae and Mussidae (from Samasoni Sauni, sauni_s@usp.ac.fj and Ron Vave).
Source: Goldberg, J. and C. Wilkinson , 2004 , Global Threats to Coral Reefs: Coral Bleaching, Global Climate Change, Disease, Predator Plagues, and Invasive Species. . p: 67-92. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

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