tagged w/ Coral Bleaching
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A sobering study released today shows more than half of Australia's Great Barrier Reef has disappeared over the past 27 years.
Scientists from the Australian Institute of Marine Science in Townsville have found the loss of coral is caused mainly by cyclones and crown-of-thorns starfish.
Coral bleaching is also to blame.
The study, published in the Proceedings of the National Academy of Sciences, warns the rate of the reef's decline has been higher than previously thought.
It says if current trends continue, its coral cover could halve again by 2022 and it may lose the biodiversity for which it was listed as a World Heritage Area.
The study argues that stopping the progress of the crown-of-thorns starfish is crucial to the recovery of the 3,000km-long reef.
But scientist John Gunn says the future of the ecosystem could be under threat if the loss of coral is not stopped.
"Accumulative impacts of storms and crown-of-thorns and two bleaching events have had a quite devastating effect over the last three decades," he said.
"We're very concerned that this is a bit of a crossroads for the reef and this data is very authoritative.
"I can't pretend that if we had this type of impact continuing and we had some of the possible impacts of climate change in the future that the Great Barrier Reef really is at threat."
Cumulative impacts
Mr Gunn, chief executive of the institute in Townsville, says damage to the reef is patchy, with some areas affected more than others.
"There are parts of the reef that are still pretty much as we'd like the whole of the reef to be, and they give us some hope that that's what we could achieve with the whole of it.
"These are areas north of Cooktown and they're pretty healthy reefs, in fact they're beautiful.
"It's the areas that really have these cumulative impacts, the three factors that we take account of in the study that have really come under sort of major pressure.
"But even there, there are reefs that are still very, very lovely to visit."
Last week AM reported a Climate Commission study that found global warming was putting increasing pressure on the Great Barrier Reef, potentially causing more bleaching events.
AIMS research director Dr Jamie Oliver says stopping the crown-of-thorns starfish could be the key to the reef's long-term survival.
"Now this is a native species which outbreaks in enormous proportions, killing off large proportions of the reef, and this is something that we may be able to take some action on," he said.
"If we can at least disrupt these outbreaks, that may give the reef a chance to recover from the other factors that we describe such as cyclones and coral bleaching."
More at the link, as well as video interview with John Gunn.A sobering study released today shows more than half of Australia's Great Barrier... more
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By 2030, more than 90% of coral reefs could be threatened by local activities like overfishing and global-wide events like climate change, say researchers at the World Resources Institute.
Destruction of these valuable ecosystems would be a devastating environmental and economic tragedy. While only 0.1% of total ocean area, coral reefs host around 25% of marine life. They also help drive economic activity from fishing, tourism and help protect communities from storm surges — providing a benefit that stretches far beyond the oceans.
Different reefs are at risk for different reasons. The World Resources Institute has been working on tracking damages to these ecosystems for the last three years, providing detailed maps and data on the health of reefs in different regions of the world.
Researchers at WRI just put together a fascinating video using Google Earth maps to illustrate how reefs in the Caribbean, Middle East, Indian Ocean, Southeast Asia, Australia and the Pacific are fairing — and what kind of impact that could have to communities in those regions.
At 14 minutes long, the video is quite long. But it’s worth a watch. If you don’t have time to see the whole thing, check out the range of maps and charts on the health of these reefs.
More at the linkBy 2030, more than 90% of coral reefs could be threatened by local activities like... more
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Despite what you may read or see in the mainstream media, out in the real world, massive and rapid changes are taking place in many ecological systems as a result of global warming. The Earth seems to be already convinced of global warming and is responding quickly.
Perhaps the most significant, and likely most enduring, are the shifts taking place in the Earth's oceans. Whilst many readers may have read or heard about Ocean Acidification, there are numerous other changes taking place in the oceans which should be equally as concerning. One such phenomena to appear in the last few decades is mass coral bleaching, a consequence of the continued warming of the oceans. Once vast stretches of colourful reefs teeming with marine life are being reduced to lifeless rubble covered in seaweed or slime. Many areas are not recovering, and the scale and frequency of bleaching worldwide is getting worse. In fact, early reports suggest 2010 may have witnessed the largest single bleaching event ever recorded.
The lowdown on coral bleaching
Reef-coral are actually a symbiosis (a mutually beneficial relationship) between the coral polyp, an anemone-like creature, and tiny algae called zooxanthellae. The coral provide shelter and nutrients for the algae , and in exchange the algae provide carbohydrates (food) to the polyp, using energy from the sun (photosynthesis) and the nutrients provided by the coral. These algae live in the skin tissue of the polyp and produce the coloured pigments which make coral reefs so visually spectacular. When this partnership breaks down the polyps expel the algae, which leads to the "bleached" effect. Although the polyp does feed using its tentacles to snare food, the bulk of its nutrition (90%+) comes from the algae, and they are a critical component of coral skeleton formation and therefore reef maintenance and growth. Without symbiotic algae, the coral can die from starvation, or become so weakened by a lack of food, that it succumbs to harmful bacteria (Mao-Jones 2010), and/or seaweeds which can poison and kill coral on contact.
Because reef-coral have adapted tolerance to a narrow band of environmental conditions, bleaching can occur for a number of reasons, such as ocean acidification, pollution, excess nutrients from run-off, high UV radiation levels, exposure at extremely low tides and cooling or warming of the waters in which the coral reside. Typically these events are very localized in scale and if bleaching is mild, the coral can survive long enough to re-acquire new algal partners. So bleaching in itself is not something new, but mass coral bleaching on the huge scale being observed certainly appears to be, and represents a whole new level of coral reef decline.
Ocean warming is driving mass coral bleaching
As coral reefs operate very near to their upper limit of heat tolerance (Glynn & D'Croz 1990), bleaching en masse happens when the surface waters get too warm above their normal summer temperature, and are sustained at this warmer level for too long. The intensity of bleaching corresponds with how high, and how long temperatures are elevated and, as one might expect, the intensity of bleaching affects the rate of survival. Small rises of 1 -2 degree C, for weeks at a time, usually induce bleaching.
This episodic ocean warming has been most pronounced worldwide during El-Nino events, when the Pacific Ocean exchanges heat to the atmosphere and surface waters. In recent years though, severe mass bleaching is happening outside of El-Nino because of the "background" ocean warming. The huge mass bleaching in the Caribbean in 2005, a non El-Nino year, and again this year is a prime example of this (Eakin 2010) . Evidence connecting warm surface waters and mass coral bleaching has strengthened to the extent that the National Oceanic and Atmospheric Administration (NOAA) has a coral bleaching alert system in place. This alert system accurately forecasts mass coral bleaching based on satellite data of sea surface temperatures.
Hot water + Coral = Dead coral
So how does hot water kill coral?. It requires both high water temperatures and sunlight. Oxygen is released as waste during photosynthesis and like all chemical processes this is affected by temperature, speeding up as more energy (warmth) is applied. When water temperatures rise too high the protective mechanisms to prevent heat damage, employed by the coral and the algae, are overwhelmed. The zooxanthellae algae produce high levels of oxygen waste which begin to poison the coral polyp. In acts of self-preservation the coral kick out the algae, and in doing so become susceptible to starvation, opportunistic diseases, competitive seaweeds and macroalgae (slime to you and me) . Coral can succumb to the effects of bleaching years later, and for those coral that survive, growth effectively ceases and full recovery can take anything up to a decade.
Coral resilience is futile
On a world scale coral reefs are in decline, and it makes for rather depressing reading for an avid diver like myself. Over the last 30-40 years 80% of coral in the Caribbean have been destroyed (Gardner 2003) and 50% in Indonesia and the Pacific (Bruno & Selig 2007). Bleaching associated with the 1982 -1983 El-Nino killed over 95% of coral in the Galapagos Islands (Glynn 1990), and the 1997-1998 El-Nino alone wiped out 16% of all coral on the planet. Globally about 1% of coral is dying out each year. Not all of this continual decline is solely down to bleaching of course, pollution and other human activities are also contributing, but bleaching is speeding up the loss of coral.
cont.Despite what you may read or see in the mainstream media, out in the real world,... more
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By now, both candidates agree that global warming is a reality but they don't necessarily agree on what to do about it. In our Collective Journalism special "U.S.: Killing the Earth?" we look at the affect climate change has on the environment and on the Presidential election. We investigate alternative energy sources, the growing green collar job sector, consequences of dramatic climate change and potential solutions to the crisis.
This special features the work of Collective Journalism contributors around the country, from Missouri to California, from Florida to Minnesota.
Collective Journalism, Current's citizen journalism program, works by combining perspectives from contributors like you around the world. All month until Election Day, CJ will be airing special investigations into the most important issues of this election.By now, both candidates agree that global warming is a reality but they don't... more
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