Can Migrating Corals Outpace Ocean Warming and Acidification?

Discussing:  Couce, E., Ridgwell, A. and Hendy, E.J. 2013. "Future habitat suitability for coral reef ecosystems under global warming and ocean acidification". Global Change Biology 19: 3592-3606.

According to Couce et al. (2013), "there is concern that the growing frequency and severity of mass bleaching episodes may lead to species composition shifts and functional collapse in coral reefs in the near future." On the other hand, they also note global warming "has the potential to improve currently marginal environmental conditions and extend the range of tropical coral reefs into higher latitudes," as is "demonstrated in the fossil record in response to warmer geological periods (e.g., Lighty et al., 1978; Veron, 1992; Precht and Aronson, 2004; Greenstein and Pandolfi, 2008; Woodroffe et al., 2010; Kiessling et al., 2012)."

But what if ocean acidification occurs concurrently?

To investigate this potential situation, Couce et al. employed "a suite of statistical models based on the environmental factors thought to be limiting to the present equilibrium distribution of shallow-water coral reefs, perturbing them with Earth System Model projected future sea surface temperatures and aragonite saturation changes (the simulations used in Turley et al., 2010)," while considering "a range of potential future CO2 emissions scenarios," but focusing on "the consequences of the 'A2' scenario (characterized by regionally oriented economic development and high population growth, expecting ca. 850 ppm CO2 by 2100)."

After all was said and done, the three UK researchers found, "contrary to expectations, the combined impact of ocean surface temperature rise and acidification leads to little, if any, degradation in future habitat suitability across much of the Atlantic and areas currently considered 'marginal' for tropical corals, such as the eastern Equatorial Pacific." And they note, in this regard, that "these results are consistent with fossil evidence of range expansions during past warm periods."

In terms of the nitty-gritty here-and-now, Couce et al. conclude by stating that their results "present important implications for future coral reef management, as they suggest that more emphasis should be placed on conservation efforts on marginal reefs as they are not necessarily a 'lost cause'."

SOURCE

 Coral reefs in Palau surprisingly resistant to naturally acidified waters
   

          
Ocean researchers working on the coral reefs of Palau in 2011 and 2012 made two unexpected discoveries that could provide insight into corals' resistance and resilience to ocean acidification, and aid in the creation of a plan to protect them.
               
 The team collected water samples at nine points along a transect that stretched from the open ocean, across the barrier reef, into the lagoon and then into the bays and inlets around the Rock Islands of Palau, in the western Pacific Ocean. With each location they found that the seawater became increasingly acidic as they moved toward land.

"When we first plotted up those data, we were shocked," said lead author Kathryn Shamberger, then a postdoctoral scholar at Woods Hole Oceanographic Institution (WHOI) and a chemical oceanographer. "We had no idea the level of acidification we would find. We're looking at reefs today that have levels that we expect for the open ocean in that region by the end of the century."

Shamberger conducted the fieldwork in Palau with other researchers from the laboratory of WHOI biogeochemist Anne Cohen as well as scientists from the Palau International Coral Reef Center (PICRC).

While ocean chemistry varies naturally at different locations, it is changing around the world due to increased levels of carbon dioxide (CO2) in the atmosphere. The ocean absorbs atmospheric CO2, which reacts with seawater, lowering its overall pH, and making it more acidic. This process also removes carbonate ions needed by corals and other organisms to build their skeletons and shells. Corals growing in low pH conditions, both in laboratory experiments that simulate future conditions and in other naturally low pH ocean environments, show a range of negative impacts. Impacts can include juveniles having difficulty constructing their skeletons, fewer varieties of corals, less coral cover, more algae growth, and more porous corals with greater signs of erosion from other organisms.

The new research, published in Geophysical Research Letters, a journal of the American Geophysical Union, explains the natural biological and geomorphological causes of the more acidic water near Palau's Rock Islands and describes a surprising second finding – that the corals living in that more acidic water were unexpectedly diverse and healthy. The unusual finding, which is contrary to what has been observed in other naturally low pH coral reef systems, has important implications for the conservation of corals in all parts of the world.

"When you move from a high pH reef to a low pH neighboring reef, there are big changes, and they are negative changes," said Cohen, a co-author on the paper and lead principal investigaor of the project. "However, in Palau where the water is most acidic, we see the opposite. We see a coral community that is more diverse, hosts more species, and has greater coral cover than in the non-acidic sites. Palau is the exception to the places scientists have studied."

Through analysis of the water chemistry in Palau, the scientists found the acidification is primarily caused by the shell building done by the organisms living in the water, called calcification, which removes carbonate ions from seawater. A second reason is the organisms' respiration, which adds CO2 to the water when they breathe.

"These things are all happening at every reef," said Cohen. "What's really critical here is the residence time of the sea water."

"In the Rock Islands, the water sits in the bays for a long time before being flushed out. This is a big area that's like a maze with lots of channels and inlets for the water to wind around," explained Shamberger. "Calcification and respiration are continually happening at these sites while the water sits there, and it allows the water to become more and more acidic. It's a little bit like being stuck in a room with a limited amount of oxygen – the longer you're in there without opening a window, you're using up oxygen and increasing CO2."

Ordinarily, she added pushing the analogy, without fresh air coming in, it gets harder and harder for living things to thrive, "yet in the case of the corals in Palau, we're finding the opposite.  "What we found is that coral cover and coral diversity actually increase as you move from the outer reefs and into the Rock Islands, which is exactly the opposite of what we were expecting."

The scientists' next steps are to determine if these corals are genetically adapted to low pH or whether Palau provides a "perfect storm" of environmental conditions that allows these corals to survive the low pH. "If it's the latter, it means if you took those corals out of that specific environment and put them in another low pH environment that doesn't have the same combination of conditions, they wouldn't be able to survive," said Cohen. "But if they're genetically adapted to low pH, you could put them anywhere and they could survive."

"These reef communities have developed under these conditions for thousands of years," said Shamberger, "and we're talking about conditions that are going to be occurring in a lot of the rest of the ocean by the end of the century. We don't know if other coral reefs will be able to adapt to ocean acidification – the time scale might be too short."

The scientists are careful to stress that their finding in Palau is different from every other low pH environment that has been studied. "When we find a reef like Palau where the coral communities are thriving under low pH, that's an exception," said Cohen. "It doesn't mean coral reefs around the globe are going to be OK under ocean acidification conditions. It does mean that there are some coral communities out there – and we've found one – that appear to have figured it out. But that doesn't mean all coral reef ecosystems are going to figure it out."

"In Palau, we have these special and unique places where organisms have figured out how to survive in an acidified environment. Yet, these places are much more prone to local human impacts because of their closeness to land and because of low circulation in these areas," said co-author Yimnang Golbuu, CEO of the PICRC. "We need to put special efforts into protecting these places and to ensure that we can incorporate them into the Protected Areas Network in Palau."


http://phys.org/news/2014-01-coral-reefs-palau-surprisingly-resistant.html

Great Barrier Reef: Governments say world heritage site not in danger from development

Australia has argued it is making substantial progress on the United Nations' requests for better protection of the Great Barrier Reef and that it should not be listed among world heritage sites "in danger".

In a progress report to the UN World Heritage Committee, the federal and Queensland governments say the natural values the reef was protected for are still largely intact, although in parts - such as inshore areas south of Cooktown - they are declining.

The report was delivered to the UN on Saturday, a day after final approval was granted to dump in the reef's waters 3 million cubic metres of dredging sludge from the expansion of coal export terminals at Abbot Point.

The World Heritage Committee has threatened to put the reef on a list of world heritage sites considered "in danger" after becoming concerned in 2012 about the effect of numerous resource projects slated for the reef's coast.

Australia needs to show significant progress on UN recommendations for better reef management to avoid a downgrade. Tourism operators warn an "in danger" listing will damage the reef's international reputation and their businesses.

The governments' report points to several programs to reduce threats, including a sustainability strategy, water quality measures and a draft Queensland ports strategy.

Federal Environment Minister Greg Hunt said there was genuine improvement in reef indicators in regard to dugongs, turtles, seagrass and coral. The Coalition had rejected Labor's multiple new-port strategy and was containing development to five existing port areas, he said.

"It is a permanent task for every Australian government to protect and maintain the reef. Nobody can ever rest on that, but there should be no way the reef can and should be considered 'in danger'," Mr Hunt said.

Australian Coral Reef Society president Peter Mumby said many people had argued convincingly that the reef was in the worst shape since monitoring began. He said the progress report downplayed industrial development threats, including port and agriculture expansion, that could add as much as another 14 million tonnes a year of damaging sediment to reef waters.

University of Queensland coral reef ecologist Selina Ward said the Abbot Point decision was dangerous because the best modelling showed dumped sediment would drift to outer areas, damaging coral and seagrass.

The government progress report said extreme weather and climate change were the biggest threats to the reef. It also pointed to nutrient and sediment run-off from land clearing and agriculture, and associated spikes in crown-of-thorns starfish numbers.

It said pollution from other sources, including port development and dredging, "is minor but may be highly significant locally and over short time periods".

Queensland Resources Council chief executive Michael Roche said the governments' progress report had identified the port development impacts as being minor and temporary.

http://www.smh.com.au/environment/great-barrier-reef-governments-say-world-heritage-site-not-in-danger-from-development-20140202-31v3p.html

Coralline algae in a high CO2 world:  How do they cope?

Discussing:  Ragazzola, F., Foster, L.C., Form, A.U., Buscher, J., Hansteen, T.H. and Fietzke, J. 2013. "Phenotypic plasticity of a coralline algae in a high CO2 world". Ecology and Evolution 3: 3436-3446.

Ragazzola et al. (2013) introduce their study by noting that coralline algae have been shown to be a major contributor to the formation and stabilization of coral reefs and in enhancing coral larvae settlement, citing Chisholm (2000). And due to what they call "their crucial role in shallow water ecosystems and their worldwide distribution," they say that "understanding the impact of ocean acidification on calcifying algae is fundamental," especially since "their high-Mg calcite skeleton is the most soluble polymorph of CaCO3 (50% more soluble than calcite and 20% more soluble than aragonite)," and that coralline algae are therefore "likely to be particularly sensitive to a reduction in Ω," which is the calcium carbonate saturation state of seawater, citing Ries (2011), Burdett et al. (2012) and Martin et al. (2013).

Due to the fact that "species with wide geographic ranges, such as coralline algae, are in general very plastic and able to acclimatize to a variety of habitats through morphological and functional responses (Brody, 2004)," Ragazzola et al. cultured Lithothamnion glaciale, one of the main maerl-forming species in the northern latitudes, under different elevated CO2 levels (410, 560, 840, 1120 ppm = 8.02, 7.92, 7.80, 7.72 pH ) for a period of ten months, but with initial analyses of the various parameters they measured being conducted at the three-month point of the study, as reported by Ragazzola et al. (2012).

In doing so, the six scientists report that the growth rates of the plants in the three CO2-enriched treatments after the first three months of their study were not significantly different from either each other or from those of the ambient-treatment plants.

At the end of the ten-month experiment, however, the CO2-enriched plants' growth rates were approximately 60% lower than that of the ambient-treatment plants. On the other hand, they found that the individual cell wall thicknesses of both inter and intra filaments at the three-month point of the study were significantly thinner than those of the control plants, whereas at the end of the ten-month study they were equivalent to those of the control plants.

In discussing these findings, Ragazzola et al. (2013) write that a possible explanation for them is "a shift from what could be termed a 'passive' phase during the first three months to an 'active' phase by the end of ten months," whereby "during the 'passive' phase, the increased energy requirement for calcification due to higher CO2 results in a reduction in the amount of calcite deposited in each cell well," but during the 'active phase,' L. glaciale reduces its growth rate so that the cell wall structure can be better maintained.

Noting that maintaining skeletal integrity is one of the main priorities of marine organisms living in high CO2 environments, the German and UK researchers say "the results of this study indicate that seawater chemistry can drive phenotypic plasticity in coralline algae," and that "the ability to change the energy allocation between cell growth and structural support is a clear adaptive response of the organism," which they say "is likely to increase its ability to survive in a high CO2 world."

SOURCE

Signs of coral recovery for the Great Barrier Reef

Great Barrier Reef Marine Park Authority scientists say baby corals are blooming on the Great Barrier Reef

GBRMPA and Queensland Parks and Wildlife Service have carried out their second inspection of a series of reefs between Townsville and Tully, in the wake of cyclone Yasi.

GBRMPA's Climate Change and Ecosystems Manager Roger Beeden has been heading up the survey and says that the coral bloomings are a positive sign of recovery.

"We are seeing baby corals in some of the shallows and also in some of the deeper areas," he said.

"It is showing that even though it has had multiple impacts in the last few years, it is able to bounce back.

"It has got that natural resilience to recover, provided it doesn't get hit with too many other events."

Mr Beeden says many parts of the reef looked like "moonscapes" when they surveyed after cyclone Yasi.

"Even though coral are animals it was akin to seeing a whole forest knocked down in lots of places," he said.

"That was really, almost heart breaking for many of us to see, and yet two years on we are beginning to see lots of the early signs of recovery."

Mr Beeden says it is not just wind from the cyclones that causes damage to the coral.

"During cyclone Yasi ... there were some monitoring stations that are out on reefs and there was actually mixing in the water down to 200 metres in some places," he said.

"So it was a huge event in terms of moving water around and it is that water movement that caused the damage to about 15 per cent of the Great Barrier Reef."

Mr Beeden says it is good news for fast growing coral, but there are slower growing coral that need more time.

"In the fast growing ones we can begin to see quite good recovery in 5-10 years, but in the really big ones, the kind of huge, great big trees if you like, actually can take decades to centuries to recover," he said.

"What we are seeing now is actually the ones that are 2 or 3 years old, so they are actually the ones that have spawned after cyclone yasi and you can actually visibly see them now on the reef."


http://www.abc.net.au/local/stories/2013/12/13/3911244.htm

Hoagy is at it again

After his own research showed that corals recover rapidly from damage, Hoagy went quiet for a couple of years -- but it looks like he is back at his old stand now.  And even his fellow Warmists are  predicting a temp rise of less than 4 degrees.  And guess where corals thrive best  -- in the warmest waters!  Hoagy is a crook!

RISING sea temperatures might sound nice for us wanting to go for a warmer dip, but it could kill off the Great Barrier Reef by the end of the century, a scientist claims in a new book.

The coral would have to move 4000km southward over 100 years to survive scientists' worst-case scenario of a 4C degree rise in sea temperatures by 2100, Professor Ove Hoegh-Guldberg says.

In his book, Four Degrees of Global Warming: Australia in a Hot World, the University of Queensland reef specialist says the outlook for the reef is bleak.

"In a four-degree world, the Great Barrier Reef will be great no longer. It would bear little resemblance to the reef we know today," he wrote.

"There is little evidence that marine resources like the Great Barrier Reef possess the resilience to withstand the impacts of a dramatically warming world." Even a more conservative 2C temperature rise estimate would likely be too much for the reef to handle, he wrote.

The death of the almost 2300km-long reef would destroy its $6 billion tourism industry as well as other areas like fishing. The book looks at how Australia will adapt to a warmer and drier climate in the next 100 years.

Warmer and more acidic seawater is a knock-on effect of increased atmospheric carbon levels.

Prof Hoegh-Guldberg wrote that sea temperatures rose by 0.5C in the 20th century but the effect is expected to speed up this century.

The result is that coral cannot move fast enough to cooler southern seas or genetically adapt fast enough to stay where they are.

"Unless we dramatically reduce carbon dioxide emissions which are acidifying our oceans and leading to their warming, we will face the destruction of the Great Barrier Reef and serious decline in our marine resources," he wrote.

SOURCE

Coastal developments approved in Qld.

Greenies will all be holding their breath at the moment  -- building up to a massive tanty.  Note that Gladstone is South of  the GBR anyway.  There is no reef to speak of offshore from Gladstone

Several massive resource projects have been approved on the Great Barrier Reef coast by the federal government including the dredging and dumping of spoil near the reef and a new coal export terminal.

Environmentalists have hit out at the decision, with the WWF and the Greens saying it further industrialises and threatens the world heritage protected icon. Environmental campaigners Greenpeace, Friends of the Earth and the Australian Marine Conservation Society, dressed as Nemo and turtles, will protest against the approval in Brisbane's CBD on Wednesday.

The projects approved by Environment Minister Greg Hunt late on Tuesday include the dredging of 3 million cubic metres of spoil - which will be dumped in the reef's waters - for the development of three coal export terminals at Abbot Point.

Mr Hunt also approved the building of a new coal terminal at Abbot Point by Indian mining giant Adani.

Approval was also given to a new processing plant for coal seam gas on Curtis Island, which includes 1.4 million cubic metres of dredging at Port Curtis and the mouth of the Calliope River near Gladstone. A pipeline to the plant - being proposed by Arrow Energy - was also approved.

In making the decision Mr Hunt said he had imposed 148 strict environmental conditions on the Abbot Point and Curtis Island developments. They included conditions to ensure the water quality impact from the dumping of dredging spoil was offset.

Mr Hunt said the offsets - which would stop sediments entering the Great Barrier Reef marine park from land sources such as farm runoff - would require an overall gain in water quality.

"It is important to note that each of these sites is already heavily industrialised and that the processes were highly advanced at the change of government," Mr Hunt said.

"The conditions I have put in place for these projects will result in an improvement in water quality and strengthen the Australian government's approach to meeting the challenges confronting the reef."

Water quality is a significant problem for the Great Barrier Reef with increasing pollutants and nutrients resulting in damage to corals, sea grass and other important marine habitats. There is also emerging evidence that poor water quality can encourage populations of a damaging starfish know as crown of thorns that has plagued the reef.

The World Heritage Committee has also been alarmed by increasing development on the reef's coast - with a number of major resource projects approved in recent years - and will consider in 2014 whether it should be placed on an "in danger" list of world heritage sites.

Richard Leck from WWF said Mr Hunt had failed the reef and had turned his back on scientific evidence of the damage dredging would cause.

"Approving a massive amount of sediment to be dumped at a time when the reef's health is so low, it really is against what the science tells us," he said.

Queensland Resources Council chief executive Michael Roche welcomed the decision and said it confirmed that industry could co-exist with the reef.

SOURCE

Mega-pesky! New paper 'unexpectedly' finds CO2 and 'acidification' dramatically IMPROVED fish reproduction in coral reefs

A paper published today in Global Change Biology finds that increased dissolved CO2 and decreased pH [so-called "acidification"] had the completely unexpected result of dramatically increasing reproduction [by 82%] in a coral reef fish. According to the authors, "This study provides the first evidence of the potential effects of ocean acidification on key reproductive attributes of marine fishes and, contrary to expectations, demonstrates an initially stimulatory (hormetic) effect in response to increased pCO2."

Increased CO2 stimulates reproduction in a coral reef fish

Gabrielle M. Miller et al

Abstract:

Ocean acidification is predicted to negatively impact the reproduction of many marine species, either by reducing fertilization success or diverting energy from reproductive effort. While recent studies have demonstrated how ocean acidification will affect larval and juvenile fishes, little is known about how increasing partial pressure of carbon dioxide (pCO2) and decreasing pH might affect reproduction in adult fishes. We investigated the effects of near-future levels of pCO2 on the reproductive performance of the cinnamon anemonefish, Amphiprion melanopus, from the Great Barrier Reef, Australia. Breeding pairs were held under three CO2 treatments (Current-day Control (430μatm), Moderate (584μatm) and High (1032μatm)) for a 9-month period that included the summer breeding season. Unexpectedly, increased CO2 dramatically stimulated breeding activity in this species of fish. Over twice as many pairs bred in the Moderate (67% of pairs) and High (55%) compared to the Control (27%) CO2 treatment. Pairs in the High CO2 group produced double the number of clutches per pair and 67% more eggs per clutch compared to the Moderate and Control groups. As a result, reproductive output in the High group was 82% higher than the Control group and 50% higher than the Moderate group. Despite the increase in reproductive activity, there was no difference in adult body condition between the three treatment groups. There was no significant difference in hatchling length between the treatment groups, but larvae from the High CO2 group had smaller yolks than Controls. This study provides the first evidence of the potential effects of ocean acidification on key reproductive attributes of marine fishes and, contrary to expectations, demonstrates an initially stimulatory (hormetic) effect in response to increased pCO2. However, any long-term consequences of increased reproductive effort on individuals or populations remains to be determined.

SOURCE

Woe! Australia has not "reported" to that great heap of corruption that is the United Nations

Just Greenies at work trying to impose their anti-human values on everyone else.  To them, no proof is needed that human activity is harming the reef.  That is just axiomatic to them -- they just  want to stop everything.  There's no such thing as a happy Greenie

THE Great Barrier Reef is set to be named as a World Heritage Site in danger by UNESCO next month.

A long-awaited assessment of the reef by UNESCO and the International Union for Conservation of Nature (IUCN), released on Friday evening, says decisive action must be taken to avoid a listing in June.

The report claims the federal and Queensland governments have failed to improve water quality or halt coastal developments that could impact the reef.

Only one annual water quality report card has been published, in 2011, which covered 2009.  A second report card was due in early 2012, but it's yet to be delivered.

The report also says there's been no clear commitment by the either federal or Queensland governments to limit port developments near the reef.  Instead about 43 proposals are under assessment.

"The above-mentioned issues represent a potential danger to the outstanding universal value of the property," the report said.

"The World Heritage Centre and IUCN ... recommend that the committee consider the Great Barrier Reef for inscription on the list of World Heritage in Danger ... in absence of a firm and demonstrable commitment on these priority issues."

Prime Minister Julia Gillard said the Federal Government was committed to keeping the reef a great heritage area for the world.

"In the last couple of weeks I announced a $200 million reef rescue commitment," she told reporters in Melbourne.  "We are very committed and we'll continue to pursue those kind of commitments in the future."

But Greens Senator Larissa Waters called on Liberal and Labor to support a Senate bill which would adopt the World Heritage Committee's recommendations as law.

"The Newman and Gillard governments have continued to fast-track mega industrial ports alongside the reef," she said.  "Protecting the Great Barrier Reef must be beyond politics and all parties should support my bill."

World Wildlife Fund spokesman Richard Leck said UNESCO had put Australia in the sin bin.  "We will likely see a reef showdown this June," he told AAP.

The only other world heritage sites in danger that aren't in a developing country or an active war zone are the UK's Liverpool Maritime Mercantile City and Florida's Everglades.

SOURCE

Scientists find heat-tolerant coral reefs that may resist climate change

Amid all the flim-flam below there is only one solid fact:  Corals can survive higher temperatures -- as has often been shown elsewhere

 Experts say that more than half of the world's coral reefs could disappear in the next 50 years, in large part because of higher ocean temperatures caused by climate change. But now Stanford University scientists have found evidence that some coral reefs are adapting and may actually survive global warming.
                   
"Corals are certainly threatened by environmental change, but this research has really sparked the notion that corals may be tougher than we thought," said Stephen Palumbi, a professor of biology and a senior fellow at Stanford's Woods Institute for the Environment.

Palumbi and his Stanford colleagues began studying the resiliency of coral reefs in the Pacific Ocean in 2006 with the support of a Woods Institute Environmental Venture Project grant. The project has expanded and is now being funded by Conservation International and the Bio-X program at Stanford.
"The most exciting thing was discovering live, healthy corals on reefs already as hot as the ocean is likely to get 100 years from now," said Palumbi, director of Stanford's Hopkins Marine Station. "How do they do that?"

Coral reefs form the basis for thriving, healthy ecosystems throughout the tropics. They provide homes and nourishment for thousands of species, including massive schools of fish, which in turn feed millions of people across the globe.

Corals rely on partnerships with tiny, single-celled algae called zooxanthellae. The corals provide the algae a home, and, in turn, the algae provide nourishment, forming a symbiotic relationship. But when rising temperatures stress the algae, they stop producing food, and the corals spit them out. Without their algae symbionts, the reefs die and turn stark white, an event referred to as "coral bleaching."

During particularly warm years, bleaching has accounted for the deaths of large numbers of corals. In the Caribbean in 2005, a heat surge caused more than 50 percent of corals to bleach, and many still have not recovered, according to the Global Coral Reef Monitoring Network, an international collaboration of government officials, policymakers and marine scientists, including Palumbi.

Havens of healthy reefs

In recent years, scientists discovered that some corals resist bleaching by hosting types of algae that can handle the heat, while others swap out the heat-stressed algae for tougher, heat-resistant strains. Palumbi's team set out to investigate how widely dispersed these heat-tolerant coral reefs are across the globe and to learn more about the biological processes that allow them to adapt to higher temperatures.

In 2006, Palumbi and graduate student Tom Oliver, now a postdoctoral researcher at Stanford, traveled to Ofu Island in American Samoa. Ofu, a tropical coral reef marine reserve, has remained healthy despite gradually warming waters.

The island offered the perfect laboratory setting, Oliver said, with numerous corals hosting the most common heat-sensitive and heat-resistant algae symbionts. Ofu also has pools of varying temperatures that allowed the research team to test under what conditions the symbionts formed associations with corals.

In cooler lagoons, Oliver found only a handful of corals that host heat-resistant algae exclusively. But in hotter pools, he observed a direct increase in the proportion of heat-resistant symbionts, suggesting that some corals had swapped out the heat-sensitive algae for more robust types. These results, combined with regional data from other sites in the tropical Pacific, were published in the journal Marine Ecology Progress Series in March 2009.

Global pattern

To see if this pattern exists on a global scale, the researchers turned to Kevin Arrigo, an associate professor of environmental Earth system science at Stanford and an expert on remote satellite sensing of marine microalgae. Arrigo gathered worldwide oceanographic data on a variety of environmental variables, including ocean acidity, the frequency of weather events and sea-surface temperature.

Oliver then compiled dozens of coral reef studies from across the tropics and compared them to Arrigo's environmental data. The results revealed the same pattern: In regions where annual maximum ocean temperatures were above 84 to 88 degrees Fahrenheit (29 to 31 degrees Celsius), corals were avoiding bleaching by hosting higher proportions of the heat-resistant symbionts.

Most corals bleach when temperatures rise 1.8 F (1 C) above the long-term normal highs. But heat-tolerant symbionts might allow a reef to handle temperatures up to 2.6 F (1.5 C) beyond the bleaching threshold. That might be enough to help get them through the end of the century, Oliver said, depending on the severity of global warming.

A 2007 report by the United Nations International Panel on Climate Change concluded that the average surface temperature of the Earth is likely to increase 3.6 to 8.1 F (2 to 4.5 C) by 2100. In this scenario, the symbiont switch alone may not be enough to help corals survive through the end of the century. But with the help of other adaptive mechanisms, including natural selection for heat-tolerant corals, there is still hope, Oliver said.

"These findings show that, given enough time, many corals can match hotter environments by hosting heat-resistant symbionts," he explained. "While hopeful, the work also suggests that modern environments are changing so rapidly that corals may not be able to keep up. It comes down to a calculation of the rates of environmental change versus the rates of adaptation."

Heat-resistant corals also turn out to be more tolerant of increases in ocean acidity, which occurs when the ocean absorbs excess carbon dioxide from the atmosphere--another potential threat to coral reefs. This finding suggests that corals worldwide are adapting to increases in acidity as well as heat, Oliver said, and that across the tropics, corals with the ability to switch symbionts will do so to survive.

Future protection

The problem of coral bleaching comes down to a collapse of the algae at the cellular level, Oliver explained. But the molecular biology of corals and their zooxanthellae under stress is shockingly understudied, he added.

To examine the corals and their symbionts at the molecular level, the researchers are collaborating with John Pringle, a professor of genetics at Stanford. Pringle and his lab have set up tanks where anemones, corals and their algae are exposed to a variety of treatments, including changes in temperature, acidity and light. That research is ongoing.

"What I hope is that we will learn some really deep and interesting things about the cellular and genetic mechanisms that allow this symbiosis to function, and about the mechanisms that come into play when the symbiosis is breaking down under stress," Pringle said. "The longer-range hope is that having that understanding will contribute to efforts in coral conservation."

The ultimate goal is to find protein biomarkers that indicate signs of heat stress and potential heat resistance, Oliver explained. Then coral reef managers could go to a reef, take small coral samples and test for the presence of the biomarkers to see how resilient the reef will be to higher temperatures.

"With this tool, managers could identify existing populations that may be more resistant to climate change and potentially prioritize their protection from everything else that kills coral reefs, like fishing and [agricultural] runoff," Oliver said.

"Although we are doing things to the planet we have never done before, it's hard to imagine that these corals, which have existed for a quarter of a billion years, only have 50 years left," Palumbi said. "And part of our job might be to figure out where the tougher ones live and protect those places."

SOURCE