The impact of bleaching on disease susceptibility and defence in reef building corals

Lead Research Organisation: Newcastle University
Department Name: Sch of Biology

Abstract

Most scientists agree that sea temperature increases due to global climate change have already caused mass mortality of corals throughout the tropics over the last 5-10 years. Given the current climate change predictions from organisations like the Hadley Centre in the UK, it appears likely that increases in sea temperatures will cause the complete collapse of these ecosystems within only a few decades. These estimates may be too pessimistic, because corals are able to adapt to rising temperatures using a variety of mechanisms. However, at the same time coral diseases have become increasingly common, as they have in many other systems and groups of organisms. Several scientists have proposed that these increases in disease are linked to climate change and we aim here to test whether temperature stress increases a corals' susceptibility to disease by monitoring indicators of health, antimicrobial defences and bacterial community structure and function. There are other possible causes of the recorded increase in diseases, however, such as increased transport and transfer of micro-organisms via tourists or ships' ballast water, for example. It is therfore vital that we understand the disease process so that appropriate and effective measures can be used to improve the health of coral reefs.

Publications

10 25 50

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Leggat W (2007) The hologenome theory disregards the coral holobiont in Nature Reviews Microbiology

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Palmer CV (2010) Levels of immunity parameters underpin bleaching and disease susceptibility of reef corals. in FASEB journal : official publication of the Federation of American Societies for Experimental Biology

 
Description The study used an holistic approach to investigate both the host defenses and microbial pathogens associated with reef coral diseases, a major cause of coral reef decline globally. We were able to show that: 1) Coral immunity, measured via a suite of indicator variables, is strongly correlated to coral disease and bleaching susceptibility. 2) Pathogen community shifts occur rapidly (within min.) of a threshold being reached following exposure to stress, during which little change to associated communities occurs. Disease is neither a result of 'imbalance' in associated microbial communities, nor delivery of novel pathogens, but a loss of host defenses allowing invasion of microbes to the normally virtually sterile tissues. 3) Ciliates (single-celled eukaryotes) are involved in several of the common coral diseases and may allow invasion of bacterial pathogens that further weaken host defenses.
Exploitation Route Our work has been disseminated and exploited at two levels: 1) a policy approach facilitated through international research networks and applied policy forums at international level (supported by the GEF/World Bank) and 2) an industrial approach within the UK and overseas aquarium trade, including both public aquaria and the commercial aquarium trade. These initiatives are aimed at reducing wild harvest and improving husbandry of captive corals. This work has been facilitated through a NERC Knowledge Exchange programme (Coral Aquarist Research Network) and collaborations with a number of public aquaria. Future work will investigate the potential for genetic selection and husbandry as a a viable means of combatting climate change impacts in coral reef environments. Our further studies have since shown that antibiotic treatment is an effective control for coral diseases, although unfortunately this is not a feasible (or ethical) treatment on regional/global scales. Our immunity studies suggest that both different host species and genetic variants have strikingly different levels of investment in immune defenses and different susceptibilities to temperature stress (which is increasing due to climate change and correlated to increased bleaching and disease). Thus, artificial selection for heat-tolerant corals may be a pragmatic solution to climate change impacts in tropical reef systems.
Sectors Environment

URL http://www.ncl.ac.uk/biology/staff/profile/john.bythell#tab_profile
 
Description Outcomes of the research contributed to policy development and further research in a major international collaboration funded by GEF/World Bank. The 10-year findings of this group were published in 2010(http://www.gefcoral.org/LinkClick.aspx?fileticket=zv3UV2E9Dzg%3d&tabid=3260?uage=en-US).
First Year Of Impact 2000
Sector Education,Environment
Impact Types Societal,Economic,Policy & public services

 
Description Coral Reef Targeted Research
Amount £45,193 (GBP)
Funding ID CRTR-BWG 
Organisation World Bank Group 
Department Global Environment Facility
Sector Public
Country United States
Start 01/2007 
End 12/2007
 
Description Coral Reef Targeted Research
Amount £45,193 (GBP)
Funding ID CRTR-BWG 
Organisation World Bank Group 
Department Global Environment Facility
Sector Public
Country United States
Start 01/2007 
End 12/2007
 
Description Re-evaluation of the importance of ciliates in coral disease
Amount £323,988 (GBP)
Funding ID NE/H020616/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2011 
End 07/2013
 
Description Coral Aquarist Researcher Network (CARN) 
Organisation University of Essex
Country United Kingdom 
Sector Academic/University 
PI Contribution Engaged in collaboration with CARN led by NERC KE Fellow Philippa Mansell (Essex Univ), including major representatives of UK aquarium trade and public aquarium operators with coral reef experts.
Start Year 2009
 
Description Coral Reef Targeted Research 
Organisation World Bank Group
Department Global Environment Facility
Country United States 
Sector Public 
PI Contribution 12-member international research network collaboration, funded by GEF/World Bank
Start Year 2007
 
Description Coral Reef Targeted Research 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Web site for dissemination to policy makers, decision makers and practitioners at local/regional, national and international levels - see http://www.gefcoral.org/Howwework/gefcoralv3/Meetourpeople/WorkingGroups/tabid/3290/Default.aspx. Various types of outputs and activities e.g http://www.gefcoral.org/VideoGallery/VideoPlayer/TabId/3700/VideoId/131/CRTR-Bleaching-Working-Group-Heron-Island-2009.aspx
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,
URL http://www.gefcoral.org/