Coral Bleaching

Coral Bleaching Working group

Many international forums have stressed the urgent need to improve our understanding of the mechanisms, ecological outcomes and economic ramifications of the impacts of global climate change on coral reefs. This understanding will be critical for strategies designed to minimise degradation of coral reefs and to protect the socio-economic benefits they provide to reef-dependent communities. It is also important to understand the relative cost and practicality of various mitigation options. Bleaching is a particularly dramatic and important manifestation of the impact of climate change on coral reefs.

Background

Early in 2002, large scale bleaching affected the world’s largest continuous coral reef. More than 60 percent of the Great Barrier Reef bleached and up to five percent was severely damaged as a result. Bleaching events have also been recorded in many important reef systems worldwide, particularly those in the Caribbean region.

Bleaching refers to the loss of symbiotic dinoflagellate algae, Symbiodinium, within the coral host leading to a bleached, white appearance. Bleaching is a response of the coral host and associated with elevated seawater temperature. Over extended periods bleaching can result in death of the coral.

Our Research

Research Activities

The CRTR Bleaching Working Group’s (BWG) research is focused on filling critical information gaps with respect to coral bleaching and mortality. It is examining specific physiological mechanisms for coral bleaching as well as the local ecological factors that precipitate bleaching and its after-effects, and differences between direct human stressors and those related to climate change. It has drawn together international experts to investigate these critical issues that surround the impact of global climate change on the world’s coral reefs.

The knowledge needed by management to be effective is by nature enormous and diverse. The BWG will deliver critical information that will enable management to better understand and predict the outcome of climate change on coral reefs, focusing on four key areas representing the most urgent information gaps:

A more complete understanding of the susceptibility and tolerance of corals to rising sea temperatures.
A more accurate model of the impact of global climate change on coral reef ecosystems.
Management tools by which to identify and monitor stress on coral reefs.
Better scenarios of the socio-economic implications of global climate change on coral reefs.

Research Update

The Bleaching Working Group is one of the most prominent groups working on the impacts of global warming on coral reefs and continues to bring together and lead research efforts in the area of coral bleaching and ecological change research. Key outcomes from the Group in the past year include:

Population dynamics of coral populations under environmental change
The Group has made strong progress on the ecological and environmental monitoring under this sub-project. 18 sites have now being set up at the four regional Centres of Excellence in the Philippines, Zanzibar, Mexico and Australia – to establish an integrated understanding of coral population dynamics.

Fundamental mechanisms of coral bleaching
Progress on understanding the fundamental mechanisms of coral bleaching has now progressed to a point whereby the Group is writing a review, which will summarise the advances in this research area from the past three to five years.

Effects of bleaching on coral and fish communities in the western Indian Ocean
This sub-project has made excellent progress with the compilation of the Indian Ocean coral cover data coming to completion. The data set includes ~ 1,000 times x sites of coral cover from 1957 to 2005. In addition, a compilation of all species lists of corals in the Indian Ocean has occurred. There are now plans to analyse coral cover, rates of mortality and numbers of taxa to determine the priority reefs in this region.

Geographical diversity of Symbiodinium
Research into the geographical diversity of Symbiodinium has found different strains in approximately 800 coral species from Zanzibar, Thailand and surrounding regions. Early results from DNA extractions, PCR-DGGE analyses and DNA sequencing of the 550 coral samples from the under-studied Thailand region indicate many new and unusual coral-algae symbioses. While a definitive assessment of how water quality affects these associations is premature, many of the same species of symbiont are being found at mainland and island locations. A conspicuous feature of the region is the occurrence of clade D species (a group that appears to be thermally tolerant) whose presence is not restricted to turbid inshore areas as previously thought, but which is also found on offshore islands where water clarity is greater.

Functional diversity of Symbiodinium
The project looking at the functional diversity of Symbiodinium and its role in explaining differences in stress susceptibility among reef-building corals and their symbionts is preparing to publish a paper describing 1600 gene products. This is a very important step forward for the project as Working Group members are now focusing on a number of projects looking at genetic responses of corals to stress. It is also a world-first as no other cDNA libraries of the key symbiont inhabiting reef-building corals have been published.

Tools for Management

The Group has produced a number of tools or findings relevant to managers and policy-makers. These tools will have significance for reef managers in that they will assist them to understand and respond to mass coral bleaching. On a broader policy front, the research being produced by the Group is confirming the extreme threat that unrestrained global warming and ocean acidification hold for the world’s coral reefs. The tools are:

Colour cards to monitor coral bleaching: colour cards have been produced in partnership with The University of Queensland to monitor coral bleaching across reefs. NGOs, tourist companies and reef enthusiasts in Australia and several other countries are now utilising these cards.
Members of the Bleaching Working Group contributed to the ‘A Reef Manager’s Guide to Coral Bleaching’ co-authored by Paul Marshall and Heidi Schuttenberg. This Guide provides brings together the latest scientific knowledge and managem experience to assist managers in responding effectively to mass coral bleaching events.
‘The Carbon Crisis: Coral Reefs under Rapid Climate Change’: This article was produced by the CRTR and published in Science in December 2007. It provides a comprehensive message highlighting the urgent action required to protect coral reefs from rising concentrations of carbon dioxide in the Earth’s atmosphere.

Who we are

Working Group Members

Working Group members bring international experience to this targeted research.

Project Partners

Working Group partners bring capacity to this research endeavour.
The IOC/UNESCO supports annual training exchanges with Semerang University, Indonesia

Contact

Coral Bleaching and Local Ecological Responses Working Group:

Chair: Professor Ove Hoegh-Guldberg
University of Queensland, Australia

Co-chair: Professor Yossi Loya
Tel Aviv University, Israel

Project Executing Agency:

Global Coral Reef Targeted Research and Capacity Building for Management Program
The University of Queensland
Brisbane QLD 4072
Australia
Tel: +61 7 3346 9942
Fax: +61 7 3365 4755
Email:

Information Resources

Poster: CRTR Program Bleaching Working Group [download]
Brochure: CRTR Program Summary [download]
Research Update, July 2008 [download]
Effects of Climate and Seawater Temperature Variation on Coral Bleaching and Mortality: reprint from Ecological Monographs 2007 [download]
Long-term changes in coral colony size distributions on Kenyan reefs under different management regimes and across the 1998 bleaching event: reprint from Marine Biology [download from Springer website]
Proceedings of the Bleaching Working Group Inaugural Workshop - Puerto Morelos - May/June 2005 The Workshop, held over a three week period, covered coral bleaching and disease and new techniques in the physiology of stress. Involving over 60 students and scholars from 10 nations, the proceedings cover issues of environmental stress and coral reefs. While very much a work in progress, the discussions and presentations represent cutting edge opinions and research but are not peer reviewed.
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- Download full report [PDF, 5.25MB]