Is there a case for the “bacterial bleaching hypothesis’? Oculina patagonica / Vibrio shiloi revisited

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The idea that mass coal bleaching is caused by bacteria bleaching as opposed to temperature stress has been quite a contentious issue over the past decade. Despite the fact that massive amounts of evidence that have accumulated that support the idea that thermal stress has driven the mass episodes of coral bleaching (pigment loss associated with the dissociation of the symbiosis between coral and their dinoflagellates) over the past 30 years, some oxygen has been given to the alternative idea that mass coral bleaching is triggered by the presence of bacteria from the genus Vibrio.The idea that bacteria were involved in triggering coral bleaching originated from work done on the temperate coral Oculina patagonica from the Mediterranean sea (an invading species from the Atlantic coast of South America) seemed to suggest that the annual coral bleaching was due to a bacterial infection from a putative pathogen, Vibrio shiloi.

This discussion focuses on recent work done by my laboratory and which was published in the Nature journal ISME (download here) and which suggests that bacteria are not responsible for triggering mass coral bleaching (in O. patagonica or anything else). We are interested in your thoughts and hope that you will comment in the hope of resolving debate over this issue for once and for all.

The Bacterial Bleaching Hypothesis is based on a series of eloquent microbiological investigations conducted by Eugene Rosenberg and his group revealed the intra-cellular penetration, multiplication and subsequent cellular lysis of zooxanthellae by V.shiloi resulted in the annual bleaching of O.patagonica in temperatures above 28ºC. Since then, the bacterial bleaching hypothesis has been extrapolated as an explanation for global mass coral bleaching, and more recently, the coral ‘probiotic hypothesis’ (link). To some (including Eugene Rosenberg), the workplace emphasis onto bacteria rather than climate change as the cause for mass coral bleaching – the implications for the future of coral reefs would be highly significant if Rosenberg were correct.

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2008 is International Year of the Coral Reef

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Marianas Variety, 21st Jan 2008

Different environmental groups and government agencies gathered on Friday at the SandCastle of the Hyatt Regency Hotel Saipan to declare 2008 as the International Year of the Coral Reef.

Gov. Benigno R. Fitial and Lt. Gov. Timothy P. Villagomez attended the event, with the chief executive urging the community to become more aware and action-oriented in the protection and conservation of the islands’ coral reefs.

Villagomez said the threat to coral reefs is not only a national or regional concern, but a global matter, especially in light of global warming.

Students, academicians, and other concerned individuals joined the event and got to hear Peter Houk, Division of Environmental Quality’s biologist, John Starmer, Coastal Resources Management biologist, and other invited speakers discuss the importance and possible solutions to the growing concerns regarding the coral reefs of the islands.

The symposium also recognized the medicinal value of reef organisms, and the different threats to coral reefs such as improper watershed development, sedimentation, marine debris, over-fishing, global warming, among other problems.

Global warming is the increase in the average temperature of the Earth’s near-surface air and oceans. One of the effects of global warming, according to experts, relates to the evaporation of water — the warming of the air will cause more water to evaporate into the atmosphere.

The participants in the symposium likewise acknowledged the need for an increased public awareness and for greater responsibility in protecting coral reefs for future generations.

The symposium was organized and sponsored by the Coastal Management Resources Office, the Division of Environmental Quality, the Division of Fish and Wildlife, the Coral Reef Initiative Program, the U.S. Environmental Protection Agency, the Marine Monitoring Program and the Mariana Islands Nature Alliance.

Isobel Bennett, Australian coral reef pioneer dies

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It is with great sadness that I post that Isobel Bennett, a pioneer and founder of coral reef science in Australia and author of the book “The Great Barrier Reef” has passed away this week (see below for an obituary from The Age newspaper). Isobel was a truely unique person and one of Australia’s most distinguished marine sciences, and her death comes as a true loss to the scientific community. Click here for a link to an extensive interview conducted by the Australian Academy of Science detailing the life of one of “the last great naturalists”.

Seashore and reef expert dies at 98

The Age, January 14th 2008

A PIONEERING marine scientist who had a coral reef named after her has died at 98.

Isobel Bennett, who left school at 16 and went on to become a seashore expert, passed away at a nursing home in Mona Vale, in northern Sydney, yesterday.

Len Zell, a lecturer in marine and tropical biology at James Cook University, said Ms Bennett was schooled in the “university of life”, and had an insatiable curiosity. “She achieved high standing as an Australian marine scientist, not by education, but by sheer hard work, determination, attention to detail, and a never-ending curiosity that tired me out lifting boulders on many reef flats,” he said.

“The last time I was on Heron Island with her she was in her 80s, and we spent hours out on the reef flat turning boulders and photographing and discussing the critters there.”

Ms Bennett, who was awarded an honorary doctorate by NSW University, was born in Brisbane in 1909 and, as the eldest of four children, left school at 16 to enter the workforce.

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Humans Have Caused Profound Changes In Caribbean Coral Reefs

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ScienceDaily, January 9th

Coral reefs in the Caribbean have suffered significant changes due to the proximal effects of a growing human population, reports a new study.

“It is well acknowledged that coral reefs are declining worldwide but the driving forces remain hotly debated,” said author Camilo Mora at Dalhousie University, Halifax, Canada. “In the Caribbean alone, these losses are endangering a large number of species, from corals to sharks, and jeopardizing over 4 billion dollars in services worth from fisheries, tourism and coastal protection,” he added.”The continuing degradation of coral reefs may be soon beyond repair, if threats are not identified and rapidly controlled,” Mora said. “This new study moves from the traditional localized study of threats to a region-wide scale, while simultaneously analyzing contrasting socioeconomic and environmental variables,” he added.

The study monitored coral reefs, including corals, fishes and macroalgae, in 322 sites across 13 countries throughout the Caribbean. The study was complemented with a comprehensive set of socioeconomic databases on human population density, coastal development, agricultural land use and environmental and ecological databases, which included temperature, hurricanes, productivity, coral diseases and richness of corals. The data were analyzed with robust statistical approaches to reveal the causes of coral reef degradation in that region.

The study showed clearly that the number of people living in close proximity to coral reefs is the main driver of the mortality of corals, loss of fish biomass and increases in macroalgae abundance. A comparative analysis of different human impacts revealed that coastal development, which increases the amount of sewage and fishing pressure (by facilitating the storage and export of fishing products) was mainly responsible for the mortality of corals and loss of fish biomass.

Additionally, the area of cultivated land (a likely surrogate for agrochemical discharges to coral reefs) was the main driver of increases in macroalgae. Coral mortality was further accelerated by warmer temperatures.

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“Stop the warming disinformation”

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One of the most astute “letters to the editor” i’ve seen in a while:

Re “Gore’s cult of global alarmism,” commentary, Dec. 26: I was astounded to see The Bee print such a profoundly ignorant column about the climate change issue. Columnist Cal Thomas claims that the scientific debate on the issue hasn’t even begun, because those who believe global warming is a serious issue won’t debate with their critics.

If there was ever a scientific consensus on an issue, it’s this one. This year’s Intergovernmental Panel on Climate Change report is its fourth major scientific conclusion on the issue in recent decades, and it is the most alarming yet. People like Thomas can always find a scientist or two trying to poke holes in the views of the overwhelming majority, but the truth of the climate situation is abundantly clear to anyone willing to examine the evidence.

Thomas cites a report by the Republican staff of a Senate committee. With the current Republican administration’s track record of blocking action on climate change, that is a laughable source.

Thomas even presents as fact ExxonMobil’s claims that it cares about climate change, and that it doesn’t fund global warming skeptics. Just how gullible does Thomas think we are? The time for debate is over. It’s time to get serious about addressing climate change.

Climate Shifts

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The concept of Climate Shifts originated after reading a blog of a colleague of mine at the University of Queensland, Professor John Quiggin. Since going online on the 10th July, Climate Shifts (“a topical commentary regarding climate change, natural ecosystems, politics and the environment”) has attracted a total of 17,670 readers. Thanks largely to StumbleUpon, our highest traffic was 792 unique visitors in a 24hr period (26/10/07). Geographically, here is what a typical day at Climate Shifts looks like:

From recent keywords (people searching on google, yahoo and others), it seems people are finding Climate Shifts for current events (e.g. “the aims of the climate summit that concluded this week“, “coral reef spawning great barrier reef november 2007“), up to date information on coral reef threats (e.g. “coral dying bleaching co2 in the water“, “what happens when we destroy coral reefs“) and a few words from our climate skeptic friends (e.g. “institute for public affairs oil industry funding” and “piers akerman lies“).

My initial reason for starting the blog was as follows:

1) My concern about our rapidly shifting climate, and its impacts on both natural ecosystems and the people within.

2) To improve how science is communicated – to ensure its wide dissemination while maintaining its neutrality and impartiality.

Expect some large changes to the blog along these lines in 2008: technological advances in the blogging world, active science and ongoing commentary – watch this space! Thanks also to Casper Henderson at Coral Bones, Rick McPherson at Coral notes from the field and Simon Donner and others in the blogosphere.

Finally, although nothing grandiose, i’ve somehow landed on Wikipedia under “Ove Hoegh-Guldberg (biologist)“, which I guess is better than people mistaking me for Ove Høegh-Guldberg, the Danish Prime Minister between 1772-1784!

Climate change 2007 – a year in review

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A somewhat belated happy new years to everyone reading – welcome back after the Christmas break. Not only has 2007 been quite a year in the politics of climate change (more on this from me later), there have been quite a few climatic extremes – see the article below from the Associated Press. As skeptics have been all too eager to point out, there have been plenty of examples of cold weather in 2007 (and hence global warming must be false). However, as the article clearly states: “Individual weather extremes can’t be attributed to global warming, scientists always say. However, ‘it’s the run of them and the different locations‘ that have the mark of man-made climate change, said top European climate expert Phil Jones, director of the climate research unit at the University of East Anglia in England.” After all, a single heatwave doesn’t prove global warming to be ‘true’.

2007 – A Year of Climate Surprises

Associated Press (1st January 2008)

When the calendar turned to 2007, the heat went on and the weather just got weirder.

January was the warmest first month on record worldwide — 1.53 degrees above normal. It was the first time since record-keeping began in 1880 that the globe’s average temperature has been so far above the norm for any month of the year.

And as 2007 drew to a close, it was also shaping up to be the hottest year on record in the Northern Hemisphere.

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Coral in Crisis – Science Friday interview with Ken Caldeira

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Below is a great interview by Science Friday of my colleague, Dr Ken Caldeira on the topic of ocean acidification of the worlds coral reefs (as a co-author on the recent science paper, Ken clearly echoes my sentiments on this issue) – click below to listen.

“The world’s coral reefs are in great danger, threatened by climate change and rising carbon dioxide levels. In an article published in the journal Science, researchers provide provide three different scenarios for the fate of reef-building corals worldwide as they face higher concentrations of atmospheric carbon dioxide and the related ocean acidification that slows coral calcification, the process needed for a reef to grow. Increasing CO2 levels have the potential to greatly shift the chemistry of ocean waters, threatening the existence of most coral species.

The fragile corals also face a phenomenon known as ‘bleaching,’ caused by rising temperatures, and damage from overfishing, pollution, and oil and gas exploration. We’ll hear about the forecast for the future of the world’s coral”

[audio:https://climateshifts.org/sciencefriday.mp3]