Climate Change, Coral Bleaching and the Future of the World's Coral Reefs

Topics: Coral reef, Photosynthesis, Coral Pages: 84 (24988 words) Published: October 16, 2008
and the
of the
ISBN 90-73361-52-4
Sea temperatures in the tropics have increased by almost
1oC over the past 100 years and are currently increasing at
the rate of approximately 1-2oC per century. Reefbuilding
corals, which are central to healthy coral reefs,
are currently living close to their upper thermal limit.
They become stressed if exposed to small slight increases
(1-2oC) in water temperature and experience coral
Coral bleaching occurs when the photosynthetic
symbionts of corals (zooxanthellae) become increasing
vulnerable to damage by light at higher than normal
temperatures. The resulting damage leads to the expulsion
of these important organisms from the coral host. Corals
tend to die in great numbers immediately following coral
bleaching events, which may stretch across thousands of
square kilometers of ocean. Bleaching events in 1998, the
worst on record, saw the complete loss of live coral from
reefs in some parts of the world.
This paper reviews our understanding of coral bleaching
and demonstrates that the current increase in the intensity
and extent of coral bleaching is due to increasing sea
temperature. Importantly, this paper uses the output from
four different runs from two major global climate models
to project how the frequency and intensity of bleaching
events are likely to change over the next hundred years if
greenhouse gas emissions are not reduced. The results of
this analysis are startling and a matter of great concern.
Sea temperatures calculated by all model projections show
that the thermal tolerances of reef-building corals are
likely to be exceeded within the next few decades. As a
result of these increases, bleaching events are set to
increase in frequency and intensity. Events as severe as the 1998 event could be become commonplace within twenty
years. Bleaching events are very likely to occur annually
in most tropical oceans by the end of the next 30-50 years.
There is little doubt among coral reef biologists that an
increase in the frequency of bleaching events of this
magnitude could have drastic consequences for coral reefs
everywhere. Arguments that corals will acclimate to
predicted patterns of temperature change are
unsubstantiated and evidence suggests that the genetic
ability of corals to acclimate is already being exceeded.
Corals may adapt in evolutionary time, but such changes
are expected to take hundreds of years, suggesting that the
quality of the worldÕs reefs will decline at rates that are faster than expected.
Every coral reef examined in Southeast Asia, the Pacific
and Caribbean showed the same trend. The worldÕs largest
continuous coral reef system (AustraliaÕs Great Barrier
Reef) was no exception and could face severe bleaching
events every year by the year 2030. Southern and central
sites of the Great Barrier Reef are likely to be severely
affected by sea temperature rise within the next 20-40
years. Northern sites are warming more slowly and are
expected to lag behind changes in the southern end of the
Great Barrier Reef by 20 years. In summary, the rapidity
and extent of these projected changes, if realized, spells
catastrophe for tropical marine ecosystems everywhere
and suggests that unrestrained warming cannot occur
without the complete loss of coral reefs on a global scale.
C L I M A T E C H A N G E , C O R A L B L E A C H I N G A N D T H E F U T U R E O F T H E W O R L D Õ S C O R A L R E E F S 1
Executive summary
The environmental and economic importance of the
worldÕs coral reefs
Coral reefs are the most spectacular and diverse marine
ecosystems on the planet today. Complex and productive,
coral reefs boast hundreds of...

References: 60. Goenaga, C., Vicente, V., and Armstrong, R. (1988) Aposymbiosis in Puerto
Rican zooxanthellate cnidarians
61. Goreau, T.J. and Hayes, R.M. (1994) Coral bleaching and ocean "Hot spots".
62. Goreau T.J., Hayes R.M., and Strong, A.E. (1997) Tracking south pacific coral
reef bleaching by satellite and field observations
63. Goreau, T.J. (1964) Mass expulsion of zooxanthellae from Jamaican reef
communities after hurricane Flora
64. Goreau, T. J. (1992) Bleaching and Reef Commumity Change in Jamaica:
1951 - 1991
65. Goreau, T. J., and MacFarlane, A. H. (1990) Reduced growth rate of
Montastrea annularis following the 1987-1988 coral-bleaching event
66. Harriot, V.J. (1985) Mortality rates of scleractinian corals before and during a
mass bleaching event
67. Harrison, PL and Wallace, CC. (1990) Reproduction, dispersal and recruitment
of Scleractinian corals [Coral Reefs]
68. Hatcher, B.G. (1988) Coral Reef Primary Productivity: AbeggarÕs Banquet.
69. Hoegh-Guldberg, O. (1989) Regulatory Biology of Endosymbiosis Ph.D.
70. Hoegh-Guldberg, O. (1994) The population dynamics of symbiotic
zooxanthellae in the coral Pocillopora damicornis exposed to elevated ammonia.
71. Hoegh-Guldberg, O. and Pearse, J. S. (1995) Temperature, food availability
and the development of marine invertebrate larvae
72. Hoegh-Guldberg, O. (1995) The mass bleaching of coral reefs in the Central
Pacific in 1994
73. Hoegh-Guldberg, O. (1994) Mass bleaching of coral reefs in French Polynesia,
April 1994
74. Hoegh-Guldberg, O. (1999) The impact of increased concentrations of
ammonium and phosphate on coral growth and survivorship under field
75. Hoegh-Guldberg, O., and Jones, R. (1999) Diurnal patterns of photoinhibition
and photoprotection
76. Hoegh-Guldberg, O. and Salvat, B. (1995) Periodic mass bleaching of reef
corals along the outer reef slope in Moorea, French Polynesia
77. Hoegh-Guldberg, O. and Smith, G.J. (1989) The effect of sudden changes in
temperature, irradiance and salinity on the population density and export of
zooxanthellae from the reef corals Stylophora pistillata (Esper 1797)and
Seriatopora hystrix (Dana 1846)
78. Hoegh-Guldberg, O., Berkelmans, R. and Oliver, J. (1997) Coral bleaching:
Implications for the Great Barrier Reef Marine Park
79. Houghton, J. T., Callander, B. A. and Varney, S. K. V. (eds) (1992) Climate
Change 1992
80. Houghton J.J., Meiro Filho L.G., Callander B.A., et al. (eds) (1995) Climate
change 1995: The science of climate change: contribution of working group I to
81. Hughes, T. P. (1989) Community structure and diversity of coral reefs: the role
of history
82. Hughes, T. P. (1994) Catastrophes, phase shifts, and large-scale degradation of
a Caribbean coral reef
83. Hughes, T. P. and Jackson, J. B. C. (1985) Population dynamics and life
histories of foliaceous corals
84. Hughes, T.P., Reed, D.C., and Boyle, M. (1987) Herbivory on coral reefs:
community structure following mass mortalities of sea urchins.
85. Hurrell, J. W., and Trenberth, K. E. (1997) Spurious trends in the satellite MSU
temperature record arising from merging different satellite records
87. ICRS (Dec 1998) Statement on Global Coral Bleaching in 1997-1998,
International Coral Reef Society, December 1998.
88. Iglesias-Prieto R. (1995) The effects of elevated temperature on the
photosynthetic responses of symbiotic dinoflagellates
89. Iglesias-R., Matta, W.A., Robins, W.A. Trench, R.K.(1992) Photosynthetic
response to elevated temperature in the symbiotic dinoflagellate Symbiodinium
90. Jameson, S. C., McManus, J. W., and Spalding, M. D. (1995) State of the
Reefs: Regional and Global Perspectives
91. Jokiel, P. L. (1980) Solar ultraviolet radiation and coral reef epifauna. Science
207:1069 1071.
92. Jokiel, P.L., and Coles, S.L. (1990) Response of Hawaiian and other Indo-
Pacific reef corals to elevated temperatures
93. Jokiel, P. L., and Coles, S. L. (1977) Effects of temperature on the mortality
and growth of Hawaiian reef corals
94. Jokiel, P. L. and York, R. H. Jr. (1982) Solar ultraviolet photobiology of the reef
coral Pocillopora damicornis and the symbiotic zooxanthellae
95. Jones, R.J. (1995) Sublethal stress assessment in scleractinia and the regulatory
biology of the coral-algal symbiosis
96. Jones, R.J. (1997a) Zooxanthellae loss as a bioassay for assessing stress in
97. Jones, R.J. (1997b) Changes in zooxanthellar densities and chloro-phyll
concentrations in corals during and after a bleaching event
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Coral Reefs and Bleaching Phenomenon Essay
  • Coral Reef Climate Change Essay
  • Coral Reefs Essay
  • Coral Bleaching Essay
  • Bleaching Away the Beauty of Coral Reefs Essay
  • How Does Climate Change Affect Coral Reefs Essay
  • Essay on Coral reef
  • Coral Reef Essay

Become a StudyMode Member

Sign Up - It's Free