See full version: Coral Reefs Are Fighting Back Against Global Warming
The discovery marks the first time that an animal has been found to produce DMSP. Previously, scientists thought it was the algae living in the coral that made the gas, but the new research found that the coral itself can churn it out. And, perhaps more importantly, corals’ DMSP production goes up when the coral gets stressed. more
The idea of “DMS-as-climate-regulator,” says Hannah Waters for her blog, Culturing Science, “rose to fame when it starred in one infamous Earth-as-organism idea—the Gaia hypothesis—just a few decades ago.” more
Coral reefs are on the receiving end of the battering ram that is anthropogenic climate change. With their vibrant colors and exotic fish, they’re the poster child of ocean degradation, and they get a lot of attention because they’re on the front lines—their habitats are among the most sensitive to the warming waters. But new research, led by Jean-Baptiste Raina, has found that coral are fighting back: coral can release a chemical, dimethylsulphoniopropionate (DMSP), that helps them engineer their environment and stave off global warming.
The discovery that corals can pump out dimethylsulponiopropionate, and hence DMS, say the researchers in their study, adds another reason to worry about their decline. Raina et al: [links]
"Understanding the immune system of reef-building corals will help to reduce the impact of coral diseases and environmental stresses," says Caroline Palmer, lead author of the publication. "Potentially, this will enable us to more accurately predict the vulnerability of coral reefs to disease and bleaching, before there are obvious signs of stress."
Two of the main factors that cause corals to bleach are attacks by disease-causing microbes and temperature stress. It is currently estimated that between three and six per cent of corals in the Great Barrier Reef (GBR) are affected by coral diseases, and up to a third of corals at a given location can be affected by temperature stress in a warm year. Temperature stress is a growing concern due to global warming.
"Variation in levels of immune function among different species is likely dependent on the energy they assign to it. As energy is vital for an effective immune response, corals that utilise energy to grow and reproduce rapidly have less to spare for their immune response," says Caroline Palmer. "These corals, like the staghorns, Acropora, are the colonies most vulnerable when challenged by temperature stress or disease." here
Australian researchers are a step closer to understanding the rapid decline of our coral reefs, thanks to a breakthrough study linking coral immunity with its susceptibility to bleaching and disease.
But, “we also find some genes that are different between corals from the two different habitats,” Palumbi says. “It has nothing to do with where the corals are living. It has only to do with where the corals are from.” Those differences are probably the result of genetic adaptation that happened a long time ago, he says. here
Corals from the waters that stayed below 90°F acclimated somewhat to the higher, more-variable heat conditions, though they never were quite as heat-tolerant as the corals native to the fluctuating waters. Palumbi’s team then looked at the corals’ genetics—which genes they carried and the degree to whichcells were using those genes (gene expression). here
Three days of heating activates a battery of 250 different stress genes in the typical coral. In the Ofu lagoon, the corals keep about 60 of these “heat genes” operating at high capacity all the time. Some of these corals seem to be born with these guardian genes turned on, but others only turn them on when moved by scientists to the reef’s hottest region. Some never activate the crucial genes; these colonies simply die. The cumulative result is a small band of survivors thriving in a small backreef lagoon a quarter mile across, growing in the intense sun and heat. [links]
Palumbi and his colleagues studied A. hyacinthus corals that live off Ofu Island in the National Park of American Samoa. This species is one of the main builders of Ofu Island’s reefs, and it’s particularly sensitive to environmental stress, such as high heat. But some of these corals manage to thrive in spots where the water see-saws between 84° F (29°C) and 95°F (35°C), the latter when the tide is low and the sun is high. The corals don’t have to survive long in that high heat—just a few hours until the tide rises—but those conditions should be beyond the organism’s normal tolerance. The researchers wanted to find out how these corals manage to survive. more
The new study finds that at least one species of coral may be able to cope with the higher heat. “As the environment warms, [corals] will adjust and evolve to match it,” says the study’s lead author, Stanford University marine ecologist Stephen Palumbi. But the ability of corals to acclimate and adapt to warmer and warmer waters may stop at some point, he warns. “What we don’t know is how far that process can go and where it will max out.” more
More importantly, corals are squeezed between two impacts of rising greenhouse pollution that local officials like Austin are powerless to regulate: Ocean acidification and warming. The oceans absorb roughly a third of humans’ carbon emissions. By mid-century, this will make surface waters worldwide twice as acidic as they were prior to the Industrial Revolution, according to NOAA. Acidic water can erode the corals’ framework and impede their ability to reproduce. here
So what’s causing the die-off? Corals everywhere are fragile and obviously unable to run away from adverse conditions; they can be smashed by severe waves and boats and poisoned by polluted runoff from the land. Overfishing is a major problem; fish graze on the algae that live on reefs, keeping it trimmed down and allowing sunlight to reach the zooxanthellae. Without help from the fish, the coral get out-competed by the algae and can die. Austin said his office is in a constant battle to keep people from fishing algae-grazers, and the government recently passed a sweeping conservation law that will set aside up to half of the island’s coastal waters as no-fishing zones for this reason (only about 15 percent are so designated today). here
The silver lining to bleaching events is that they allow conservation-minded scientists like Austin to gauge the effectiveness of local protective policies; after the 2009 event, local scientists found that coral cover was roughly seven percentage points higher—and suffocating algae 14 points lower—inside protected no-fishing zones. Having a healthy fish population helped the coral better cope with warming water; in other words, local conservation provided an effective roadblock against global climate change. [links]
“Anybody who’s been diving in Grand Cayman for a long time would agree that it’s very different today,” he said. “But it’s a very slow death. These things are dropping apart and no one is really aware of it.” more
A study published last October found that on reefs around Little Cayman, a kind of suburb island adjacent to Grand Cayman, coral cover fell from 26 to 14 percent just between 1999 and 2004. Since the early 1980s, coral cover across the entire Caribbean has plummeted 80 percent, so that living corals now cover only 10 percent, on average, of available surface area. And a 2011 report from the World Resources Institute that labeled reefs around Grand Cayman as highly threatened found that what’s happening there is a microcosm of a global trend: 90 percent of the world’s coral will be at risk of disappearance by 2030, thanks primarily to ocean acidification and global warming, both products of greenhouse gases released by human activity. more