ScienceDaily (Feb. 23, 2010) — Will coral reefs disappear? This is the title of a symposium presented at the American Association for the Advancement of Science (AAAS) annual conference in San Diego, California. And it’s a topic that should not be taken lightly.

NSERC-funded researcher Dr. Simon Donner, an assistant professor in the department of geography at the University of British Columbia, talked about the vulnerability of coral reefs to climate change due to higher ocean temperatures.

Dr. Donner studies coral bleaching. Corals get most of their energy from microscopic algae that live in their tissue. These algae are colourful and are what gives corals their vivid hue. When environmental factors go out of the range that corals are used to (such as warming water), the symbiosis between the coral and the algae breaks down and corals effectively expel the algae and turn white. The coral is then deprived of its source of energy, and dies.

Dr. Donner studies the frequency of coral bleaching events, their consequences and the link to unusually warm oceans. He says that mass coral bleaching events were thought to be extremely rare as far back as 30 years ago.

At the AAAS conference he talked about the predicted occurrence of bleaching events under different climate scenarios and, according to Dr. Donner, it doesn’t look good.

“Even if we froze emissions today, the planet still has some warming left in it. That’s enough to make bleaching dangerously frequent in reefs worldwide,” he says.

Given the hundreds of millions of people living in the tropics who depend on coral reefs for food, income, tourism and shoreline protection, the loss of reefs is a serious issue.

“Obviously, there’s an aesthetic concern because people see Finding Nemo and they’re worried about what’s going to happen to the world’s coral reefs, but the key thing is that there are hundreds of millions of people who depend on them for their livelihood,” says Dr. Donner.

However, the outlook isn’t completely bleak. Dr. Donner says that no one is predicting that coral reefs will go extinct; they will continue to survive, but only in certain habitats, such as shaded areas. The reality is a general loss of coral cover and a breakdown of the physical structure of reefs.

In order to see what the future of reefs might be, Dr. Donner is pursuing fieldwork in the central equatorial Pacific, because the islands and reefs in that area are affected by repeated El Nino events. Because of this, they’ve experienced higher year-to-year temperature variability than other areas on the planet. Dr. Donner is studying the corals in these areas to understand how the reefs are biologically different, and how that has allowed them to persist through warm water events that would kill coral in other areas of the planet.

“It’s a natural model for the future,” he says.

Marine Science Program, Department of Environment and Conservation, Kensington, WA, Australia, 2UMR 5244 CNRS-EPHEUPVD, 3 Coral Reef Studies, James Cook University, Townsville, Queensland, Australia, Thuwal, Saudi Arabia, University of Technology, Sydney, NSW, Australia, de Recherche pour le Développement (IRD), Marseille, France, Australia, School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia, 4ARC Centre of Excellence for 5King Abdullah University of Science and Technology,6Woods Hole Oceanographic Institution, Woods Hole, MA, USA, 7Department of Environmental Sciences,8Agrocampus Ouest, Laboratory of Computer Science, Rennes, France, 9Institut10Australian Institute of Marine Science, Townsville, Queensland,11Australian Institute of Marine Science, c/– The Oceans Institute, University of Western Australia, Crawley WA, Australia,12 
Evolutionary Biology, University of Western Australia, Crawley WA, Australia, United Nations University, International Network on Water, Environment and Health, Dubai, United Arab Emirates, 13Centre of14Marine Lab, University of Guam, Mangilao, Guam,15 Biosciences, University of Exeter, UK, CA, USA, et Observatoire de l’Environnement, Moorea, French Polynesia, National Center for Ecological Analysis and Synthesis, Santa Barbara, CA, USA, 16Marine Spatial Ecology Lab, School of 17Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara,18Centre d’Océanologie de Marseille, Université de la Méditerranée, Marseille, France, 19Centre de Recherches Insulaires 20Marine Programs, Wildlife Conservation Society, Bronx, NY, USA,21 and Department of Zoology, Stockholm University, Sweden, 22National Coral Reef Institute, Nova Southeastern University, Florida, USA23Department of Ecosystem Studies, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan  *Author for correspondence (shaun.wilson@dec.wa.gov.au) 
Accepted 3 November 2009   Summary 
Expert opinion was canvassed to identify crucial knowledge gaps in current understanding of climate change impacts on coral 
reef fishes. Scientists that had published three or more papers on the effects of climate and environmental factors on reef fishes 
were invited to submit five questions that, if addressed, would improve our understanding of climate change effects on coral reef 
fishes. Thirty-three scientists provided 155 questions, and 32 scientists scored these questions in terms of: (i) identifying a 
knowledge gap, (ii) achievability, (iii) applicability to a broad spectrum of species and reef habitats, and (iv) priority. Forty-two per 
cent of the questions related to habitat associations and community dynamics of fish, reflecting the established effects and 
immediate concern relating to climate-induced coral loss and habitat degradation. However, there were also questions on fish 
demographics, physiology, behaviour and management, all of which could be potentially affected by climate change. Irrespective 
of their individual expertise and background, scientists scored questions from different topics similarly, suggesting limited bias 
and recognition of a need for greater interdisciplinary and collaborative research. Presented here are the 53 highest-scoring 
unique questions. These questions should act as a guide for future research, providing a basis for better assessment and 
management of climate change impacts on coral reefs and associated fish communities. 

Ivana Vu¹, Gillian Smelick¹, Sam Harris¹, Sarah C. Lee¹, Ernesto Weil², Robert F. Whitehead³, John F. Bruno^1*

1 Department of Marine Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America, 2 Department of Marine Sciences, University of Puerto Rico, Lajas, Puerto Rico, United States of America, 3 Center for Marine Science, The University of North Carolina Wilmington, Wilmington, North Carolina, United States of America

Introduction 

Infectious disease outbreaks are a major cause of coral loss and reef degradation. In the Caribbean, outbreaks of white band disease in the early 1980s nearly extirpated the then dominant species Acropora cervicornis and Acropora palmata [1]. The white band pandemic led to the regional collapse of coral cover [2], [3] with wide-raging effects on reef inhabitants, geomorphology and ecosystem processes. Evidence from paleontological studies and ecological monitoring indicate that coral disease prevalence, variety, host range, and impacts have increased substantially over the last 30 years [4]–[6].

There are several potential explanations for the observed increase in the severity and impacts of coral diseases. For example, there is evidence that nutrient pollution [7]–[9] and anomalously high ocean temperature [10]–[12] can increase within- and among-colony spread rates of several coral diseases. These and other environmental stressors could increase pathogen virulence and decrease host resistance [13]–[15]. Another widely discussed yet largely untested explanation for increased coral disease is that decades of overfishing [16] have disrupted the balance of coral reef ecosystems, making corals more susceptible to disease outbreaks and other disturbances [17]–[19]. Specifically, the removal of herbivores has led to substantial increases in benthic macroalgae on some reefs [20], which could facilitate disease outbreaks either by acting as pathogen reservoirs or vectors [21] or by increasing the concentration of Dissolved Organic Carbon (DOC)[22].

A recent study found that algae can cause rapid mortality of small coral fragments in closed containers [22]. Related laboratory studies of the effects of DOC on coral health [23], [24] support a potential mechanism through which algae could indirectly cause coral disease outbreaks. Yet many ecologists remain skeptical of a mechanistic link between fishing, macroalgae and coral disease [25], [3], in part due to the paucity of evidence from field experiments.

The purpose of this study was to test the hypothesis that changes in coral reef trophic dynamics and benthic community structure are a cause of increased coral disease severity. Specifically, we asked whether the presence of macroalgae can influence within- and among-colony spread rates of Caribbean Yellow Band Disease (CYBD) in Montastraea faveolata, a major reef-building species in the region. We also measured the effects of macroalgae on coral growth and survival. Our results suggest that, at least in these short-term field experiments, macroalgae has no effect on the severity and dynamics of CYBD.