What's the story behind mysterious "halos" of bare sand that surround coral reefs?

When reefs are healthy an unusual phenomenon occurs: a perimeter of bare sand forms around the corals. These so-called halos, or bright circles of sand that are devoid of vegetation are visible to satellites miles above Earth.

But until now, scientists didn’t fully understand exactly how they formed, and why some were bigger than others. Now, two new studies may help answer the mystery of how halos take shape and what conditions make them grow. [In Photos: Diving in a Twilight Coral Reef]

Mysterious halos

Halos occur when fish and invertebrate inhabitants eat algae and seagrass growing near the reef. Over time, all vegetation in this zone is cleared away; these empty stretches of sand can measure from hundreds of square feet to hundreds of thousands of square feet, and create a footprint around the reef that's visible from space.

Researchers in the two studies recently took a closer look at these halos. Not only did they observe reef animal activity that unexpectedly extended the perimeters of the halos, the researchers also determined that the halos could be used as barometers for reef health. Learning how to interpret halos from satellite images could help scientists monitor hard-to-access reefs, the study authors reported.

In one study, published online today (April 24) in the journal Frontiers in Ecology and Evolution, the scientists found complicated species interactions shaped halos in Australia's Great Barrier Reef.

Remote underwater video camera traps revealed that herbivorous fish weren't the only reef dwellers enlarging halos — fish that hunted burrowing invertebrates played a part as well. By digging in the sand for their prey, these carnivorous fish nudged sand-dwelling algae farther away from the reef and widened the halos' boundaries, the researchers reported.

A pattern emerges

More clues about the halos emerged when the scientists examined high-resolution satellite images of coral reefs, publishing their findings today (April 24) in the journal Proceedings of the Royal Society B. They reviewed 1,372 reefs throughout the Great Barrier Reef, measuring features in 214 reefs; each of these contained hundreds to thousands of small, isolated coral platforms that were capable of being surrounded by a halo.

The study authors also conducted underwater surveys with camera traps at 22 halo locations, for three weeks.

The scientists were then able to directly compare halo patterns in waters where fishing was permitted — which would therefore have fewer predatory fish — and in waters that were protected, where predators would be plentiful.

The study authors suspected that in predator-rich protected waters, herbivorous fish would be more cautious and would graze close to the coral reef; the halos would therefore be smaller. In reefs that were open to fishing and had fewer predators, the scientists expected that grazing fish would be bolder, and that halos would reach farther from the reef, or would even be overgrown and disappear. But halos in both protected and unprotected waters turned out to be pretty much the same size, the study authors reported.

However, they discovered that halos were more likely to form in protected marine areas, "especially the older protected areas where predator populations have had longer to recover from previous fishing," lead study author Elizabeth Madin, an assistant research professor with the Hawaii Institute of Marine Biology at the University of Hawaii at Manoa, told Live Science.

That demonstrated to the researchers that halos could be a reliable indicator of stability in a reef's predator-prey populations, "which is an indicator of a healthy reef ecosystem," Madin said.

Their findings present new evidence showing how laws prohibiting fishing near reef communities can improve reef health, according to the study.

Coral reefs are typically monitored by divers that count species and evaluate the condition of corals and other life. However because halos are visible from space, satellite images could complement those surveys by providing snapshots of how reef halos change over time, Madin explained.

They also offer a glimpse at reefs that are inaccessible to divers, she added.

"We can look at them almost anywhere from satellite imagery, so this will give us a much broader view than what we could ever hope to do with the traditional monitoring methods. It would complement and scale what we can see," Madin said.

• Image Gallery: Great Barrier Reef Through Time
• Pretty in Pink: Photos of Bubblegum Coral
• Photos: The Secret Lives of Corals

Originally published on Live Science.

Coral reefs are large underwater structures composed of the skeletons of colonial marine invertebrates called coral. The coral species that build reefs are known as hermatypic, or "hard," corals because they extract calcium carbonate from seawater to create a hard, durable exoskeleton that protects their soft, sac-like bodies. Other species of corals that are not involved in reef building are known as “soft” corals. These types of corals are flexible organisms often resembling plants and trees and include species such as sea fans and sea whips, according to the Coral Reef Alliance (CORAL), a nonprofit environmental organization.

Each individual coral is referred to as a polyp. Coral polyps live on the calcium carbonate exoskeletons of their ancestors, adding their own exoskeleton to the existing coral structure. As the centuries pass, the coral reef gradually grows, one tiny exoskeleton at a time, until they become massive features of the marine environment.

Corals are found all over the world's oceans, from the Aleutian Islands off the coast of Alaska to the warm tropical waters of the Caribbean Sea. The biggest coral reefs are found in the clear, shallow waters of the tropics and subtropics. The largest of these coral reef systems, the Great Barrier Reef in Australia, is more than 1,500 miles long (2,400 kilometers).

Scientists have explored only about 20 percent of the ocean's floor, according to the National Oceanic and Atmospheric Administration (NOAA). As such, ocean explorers continue to discover previously unknown coral reefs that have likely existed for hundreds of years.

The lives of coral

There are hundreds of different species of coral, according to CORAL. Coral have a dazzling array of shapes and colors, from round, folded brain corals (named for their resemblance to a human brain) to tall, elegant sea whips and sea fans that look like intricate, vibrantly colored trees or plants.

Corals belong to the phylum cnidaria (pronounced ni-DAR-ee-uh), a group that includes jellyfish, anemones, Portuguese man o' war and several other gelatinous and stinging marine invertebrates.

Corals feed by one of two ways. Some species catch small marine life, like fish and plankton, by using the stinging tentacles on the outer edges of their bodies. Most corals, however, depend on algae called zooxanthellae to provide energy via photosynthesis.

The corals have a symbiotic, or mutually beneficial, relationship with the zooxanthellae, according to the U.S. Environmental Protection Agency (EPA). These algae live inside the coral polyp's body where they photosynthesize to produce energy for themselves and the polyps. The polyps, in turn, provide a home and carbon dioxide for the algae. Additionally, the zooxanthellae provide the coral with their lively colors — most coral polyp bodies are clear and colorless without zooxanthellae.

Some coral species, such as brain coral, are hermaphrodites, which means they produce eggs and sperm at the same time. Sexual reproduction occurs during a mass coral spawning event that, for some species, happens only once a year.

Other species, such as elkhorn coral, are gonochoric, which means they create colonies composed of either all males or all females. Within each coral colony all the polyps will produce only eggs or only sperm. For successful reproduction, the colony must rely on a neighboring colony that produces the other reproductive cell.

The world of coral reefs

Most of the substantial coral reefs found today are between 5,000 and 10,000 years old, according to CORAL. They are most often found in warm, clear, shallow water where there's plenty of sunlight to nurture the algae that the coral rely on for food.

Coral reefs cover less than 1 percent of the ocean floor — all the reefs combined would equal an area of about 110,000 square miles (285,000 square km), only about the size of the state of Nevada. Nonetheless, they are among the most productive and diverse ecosystems on Earth.

About 25 percent of all known marine species rely on coral reefs for food, shelter and breeding. Sometimes referred to as "the rainforests of the sea" for their biodiversity, coral reefs are the primary habitat for more than 4,000 species of fish, 700 species of coral and thousands of other plants and animals, according to CORAL.

Coral reefs are typically divided into four categories, according to CORAL: fringing reefs, barrier reefs, patch reefs and atolls. Fringing reefs are the most commonly seen reef and grow near coastlines. Barrier reefs differ from fringing reefs in that they are separated from the coastlines by deeper, wider lagoons. Patch reefs typically grow between fringing and barrier reefs on the island platform or continental shelf. The rings of coral that make up atolls create protected lagoons in the middle of the oceans, typically around islands that have sunk back down into the ocean.

Coral reefs under siege

Coral reefs are critical marine habitat on which many ocean species depend. Additionally, coral reefs provide an estimated $30 billion annually in direct economic benefit to people worldwide though food, fisheries and tourism, according to the Hopkins Marine Station of Stanford University.

But coral reefs are imperiled by several threats.

The increasing acidification of the ocean — caused when oceans absorb immense amounts of carbon dioxide released into the atmosphere through the burning of fossil fuels — inhibits coral's ability to produce the calcium carbonate exoskeletons they rely on for shelter.

Water pollution, too, is wreaking havoc on coral reefs. Agricultural pesticides and fertilizers, oil and gasoline, sewage discharge and sediment from eroded landscapes make it difficult for coral to thrive, and therefore damage the complex relationships that exist among the plants, coral and other animals that are part of the reef ecosystem.

As the temperatures of the world's oceans increase due to global warming, coral polyps expel the zooxanthellae they depend on for food. Once the zooxanthellae are gone, the coral loses its brilliant color, and all that can be seen is the white exoskeleton; this is referred to as coral bleaching. Coral colonies subject to bleaching usually die off, according to CORAL.

Fishing practices such as cyanide fishing (spraying cyanide in the water stuns the fish to make them easier to catch), "blast fishing" with explosives and overfishing with trawlers can destroy a thousand-year-old coral reef in a matter of minutes.

"Overfishing, ocean acidification and pollution are pushing coral reefs into oblivion," Roger Bradbury, an ecologist at the Australian National University in Canberra, wrote in his New York Times opinion article. "Each of those forces alone is fully capable of causing the global collapse of coral reefs; together, they assure it."

The future of the Great Barrier Reef

The largest coral reef in the world, the Great Barrier Reef, is home to at least 400 individual species of coral and thousands of different species of fish, mollusks, sea snakes, sea turtles, whales, dolphins, birds and more. As with the other coral reefs of the world, this incredible ecological hotspot is under threat.

A heat wave in 2016 caused a large percentage of the corals in the Great Barrier Reef to undergo severe bleaching and death. A 2018 study in the journal Nature Communications found that in just the northern third of the reef, over 60 percent of the shallow-water corals (those below 49 feet, or 15 meters) experienced some degree of bleaching, and 30 percent of the coral died. The study also found that even in the deeper, less-explored areas of the reef (down to about 131 feet or 40 m), nearly 40 percent of the corals had at least partial bleaching.

Healthy reefs lead to healthy oceans, and healthy oceans are vital to all life on Earth. The destruction facing not only the Great Barrier Reef, but also every reef around the world, can lead to the extinction of thousands of species of marine life. In turn, coastlines currently protected by reefs would more readily flood during storms, some islands and low-lying countries would vanish under the water, and the $30 billion industry that coral reefs provide could collapse.

The Australian government has put forth a long-term plan to sustain the Great Barrier Reef. The plan outlines efforts to greatly reduce and eventually eliminate dumping materials and chemicals, reduce fishing and poaching, and monitor the water quality of run-off directed toward reef.

There are also many attempts to rebuild the reef. Scientists are working to breed stronger species of coral that are less susceptible to the warmer waters and grow at an accelerated rate, reported the New York Times. They grow various coral species in the lab and place them in experimental environments designed to reflect the predicted temperature and acidity of the ocean decades from now.

Another group of coral reef ecologists are experimenting with growing corals on steel frames placed over the damaged parts of a reef. Electrical currents sent through the steel frames, accelerates the corals' growth by three to four times, reported New Scientist. It's possible this technique could help rebuild the reef and make the coral more likely to survive bleaching events.

The climate is changing, and so are the turtles.

A study published yesterday (Jan. 8) in the journal Current Biology about green sea turtles that nest along island beaches near Australia's Great Barrier Reef found that turtles born in areas most heated by climate change are 99.8 percent female. Turtles born farther south, along a cooler beach, are only about 65 percent female.

The result isn't surprising if you know a bit about turtle biology, but it is alarming. Sea turtles, like these green sea turtles (Chelonia mydas), don't have genetically determined sexes, the way mammals do. Instead, the researchers wrote, "In sea turtles, cooler temperatures produce more male hatchlings while warmer temperatures produce more females."

An egg in hot sand is more likely to produce a female turtle, and an egg in cool sand is more likely to produce a male. [In Photos: Tagging Baby Sea Turtles]

The pivot temperature where a population will turn out 50 percent females and 50 percent males is based on genetics and varies with species and even individual nesting groups, the researchers wrote. Turtles  seem to target their breeding periods to times when the sand is slightly warmer than their pivot temperatures, resulting in populations moderately skewed female. But shift the temperature of that period just a few degrees and the resulting baby turtles will be not just a bit female — instead, hardly a male will appear in the whole group.

Due to climate change, Raine Island — the site of the key breeding ground in this study — has warmed significantly since the 1990s, the researchers wrote, likely accounting for the hard female skew.

So, the researchers developed a new technique: Studying the turtles' hormones.Proving that the increasing temperatures actually changed the turtle population proved challenging, though. Turtles don't wear signs of their sex as obviously as humans; researchers can't tell just by looking between their legs. And the easiest method — cutting them open — isn't really an ethical way to approach an endangered turtle population.

A genetic test won't offer any insight into a given turtle's sex, since sea turtles don't carry their sexes in their genetic code. But the researchers found that if they brought blood plasma samples back to their lab, they could use hormonal differences to distinguish male and female turtles.

It's not clear yet, the researcher wrote, how exactly the wild female swing will impact the sea turtles' future. Males breed far more often than females, but researchers don't know to what extent the handful remaining can make up for all their missing brothers. It's also possible, the researchers wrote, that females will seek out mates in cooler climates to the south.

"Our study highlights the need for immediate management strategies aimed at lowering incubation temperatures at key rookeries," the researchers wrote, "to boost the ability of local turtle populations to adapt to the changing environment and avoid a population collapse — or even extinction."

Originally published on Live Science.

Its biodiversity may be priceless, but the Great Barrier Reef has a real economic value — 56 billion Australian dollars ($42.5 billion) of real economic value, to be precise, a new report finds.

The report, published by the financial consultancy Deloitte Access Economics, also found that the enormous coral reef off of Queensland, Australia, supports 64,000 jobs in that country and contributed AU$6.4 billion ($4.9 billion) to Australia's economy in the 2015 to 2016 fiscal year. But the reef is under threat from climate change, with back-to-back bleaching episodes threatening the survival of vast swaths of coral.

"This report sends a clear message that the Great Barrier Reef — as an ecosystem, as an economic driver, as a global treasure — is too big to fail," Steve Sargent, the director of the Great Barrier Reef Foundation, said in a statement. [Image Gallery: Great Barrier Reef Through Time]

Economic boon

The Great Barrier Reef Foundation commissioned the report, which drew from publicly available economic data as well as surveys of Australian residents. The analysis counted direct economic benefits, such as income made by tour-dive companies or commercial fishing supported by the reef. If also included indirect economic benefits, like the boon to restaurants and hotels near the Queensland coast and the economic value of the research being done on the Great Barrier Reef.

Ninety percent of the AU$6.4 billion the reef brought into Australia between 2015 and 2016 came from direct tourism activities. [Images: Colorful Corals of the Deep Barrier Reef]

Iconic value

Beyond the direct and indirect benefits to Australia's economy, the reef also provides what Deloitte Access economists called "indirect" or "non-use" value. This is the value the Great Barrier Reef has by simply existing: its social value, its importance for biodiversity and its importance as a point of Australian identity and pride.

Researchers used a survey of 1,000 Australians and 500 non-nationals to try to estimate this indirect value. They found that 54 percent of Australians and 63 percent of international respondents said they'd be willing to pay to protect the Great Barrier Reef. Of those people, most said they were motivated by protecting the reef for future generations (70 percent of Australians) or because the reef is "important to the planet" (62 percent of international respondents). Of those who said they wouldn't be willing to be levied to protect the Great Barrier Reef, most said they couldn't afford such a tax, and others said the funding should come from another source. Only 2 to 3 percent said they did not think the Great Barrier Reef was important or under threat.

The AU$56 billion ($42.5 billion) valuation comes from extrapolating the direct and indirect economic benefits of the reef over the next 33 years, until 2050. Over that time period, the direct-use benefit from tourism is AU$29 billion ($22 billion). Other contributors to that number include ecosystem services, like the ecological functions the reef conducts to cycle nutrients and protect the coastline, and the "brand value" of the reef in raising Australia's reputation as an international destination.

The reef also has value that can't be estimated in dollars, the economists concluded. It's an important place for indigenous Australian cultural and religious heritage, and archaeological sites along the reef have revealed artifacts, such as stone tools and rock art, that hint at the earliest occupants of Australia.

Original article on Live Science.  

Two-thirds of the length of the Great Barrier Reef is suffering from bleaching, a condition likely to cause mass coral die-offs.

The Australian Research Council (ARC) announced yesterday (April 10) that 900 miles (1,500 kilometers) of reef have bleached in 2017, meaning the symbiotic (and often colorful) algae within the coral's tissues are expelled. The most severe impacts were seen on the middle third of the reef's length; the entire reef stretches for 1,430 miles (2,300 km) off northeastern Australia.

Bleaching doesn't necessarily kill corals outright, but leaves them crippled in their ability to get enough nutrients to survive. The algae within the corals, called zooxanthellae, provide the corals with crucial nutrients and help the corals remove waste. Without them, the corals are more vulnerable to disease. If the algae are unable to recolonize the corals, the corals are also vulnerable to starvation. [See Images of the Great Barrier Reef Through Time]

"This is the fourth time the Great Barrier Reef has bleached severely — in 1998, 2002, 2016 and now in 2017," James Kerry, a marine biologist with the ARC Center of Excellence for Coral Reef Studies, said in a statement. "Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss."

Lost hope

In 2016, aerial surveys conducted by the ARC Center of Excellence revealed the most severe bleaching on record at the time. That bleaching event was partially spurred by El Niño, which brings warm water to reefs. High temperatures are a major source of stress for corals, which respond by expelling their algae, according to the National Oceanic and Atmospheric Administration (NOAA). During last year's bleaching event, scientists found some hope in that the lower two-thirds of the Great Barrier Reef had not been badly affected, and said that the bleached areas might bounce back.

"It's really just a matter of whether or not we get another bleaching event in the next 10 years that would impede recovery," Rebecca Albright, a marine biologist with the Carnegie Institution for Science in Washington, D.C., told Live Science at the time.

That second bleaching event has already arrived, and in a non-El Niño year, to boot.

"Mass bleaching events 12 months apart offer zero prospects of recovery for reefs that were damaged in 2016," Kerry said.

New damage

Whereas, the new damage to the reef is most severe in the middle third, in 2016, the northern end of the reef took the most damage, the ARC reported. Tropical Cyclone Debbie, which made landfall in Australia last month, worsened the situation by  damaging a swath of reef 62 miles (100 km) wide.

But scientists are most concerned about the main culprit in reef bleaching events: global warming. Climate change not only heats up the oceans, it increases ocean acidification, another stressor for coral. Changes in ocean currents might affect reefs, as well, while altered precipitation patterns can influence runoff into vulnerable areas, according to NOAA.

Already, 80 percent of hard coral cover in the Caribbean is gone, a 2003 study in the journal Science reported. The Indo-Pacific, home to 75 percent of the world's reefs, lost approximately 1 percent of its coral each year over the past 20 years, according to a study published in the journal PLOS ONE. In the 1980s, the PLOS ONE study authors reported, coral cover in the Indo-Pacific averaged 42.5 percent, an average that dropped to 22.1 percent by 2003. Before-and-after pictures show the rapid pace of change globally.

Original article on Live Science. 

Large sections of the Great Barrier Reef are already dead, and scientists warn that the rest of the coral organisms that make up the sprawling reef ecosystem will die if global warming continues unabated.

After a yearof record-high-breaking temperatures in 2016, the Great Barrier Reef experienced its worst coral bleaching event on record, as the tiny coral animals evict their color-giving partners — algae that photosynthesize and are the reason for vibrantly hued reefs. Now, scientists have returned to the reef to measure the coral bleaching that has occurred this summer (which begins in December in the Southern Hemisphere) compared to last summer.

Scientists from 10 research institutions across Australia, representing the National Coral Bleaching Taskforce, will spend the next few weeks conducting air and underwater surveys of the Great Barrier Reef. [Image Gallery: Great Barrier Reef Through Time]

"We're hoping that the next 2-3 weeks will cool off quickly, and this year's bleaching won't be anything like last year," Terry Hughes, lead author of a study describing the team's findings and the convener of the task force, said in a statement. "The severity of the 2016 bleaching was off the chart."

Hughes, who is also a marine ecologist and director of the Australian Research Council Centre of Excellence for Coral Reef Studies, noted that 2016 was the third major bleaching event, and most devastating, to affect the Great Barrier Reef. The catastrophic bleaching last year impacted a region of the reef approximately 500 miles (800 km) in length. (The entire reef is about 133,000 square miles, or 344,400 square kilometers.) Heat waves in 1998 and 2002 also caused massive bleaching of the reef.

Past exposure to bleaching does not make coral reefs any more tolerant to new bleaching events, Hughes said. Once measurements of the bleaching extent this year are completed, they may reveal that 2017 was the fourth major event, Hughes added.

"It broke my heart to see so many corals dying on northern reefs on the Great Barrier Reef in 2016," Hughes said. "With rising temperatures due to global warming, it's only a matter of time before we see more of these events. A fourth event after only one year is a major blow to the reef."

Bleaching occurs when corals are stressed from phenomena such as warmer-than-average waters for an extended period of time. In response, corals, which are actually little organisms called coral polyps, expel the algae that lend them their color and provide them with food. This gives the coral a bleached appearance, and if bleaching continues for too long, the algae may not be able to recolonize the coral.

Though overfishing and poor water quality can also stress coral reefs, climate change — and the resulting warmer oceans — is the leading cause of bleaching, said study co-author David Wachenfeld, director of reef recovery at the Great Barrier Reef Marine Park Authority.

"Global warming is the No. 1 threat to the reef," Wachenfeld said. "The bleaching in 2016 strongly reinforces the urgent need to limit climate change as agreed by world leaders in the Paris Agreement, and fully implement the Reef 2050 Plan to boost the reef's resilience." (The Reef 2050 Plan aims to sustain and conserve the Great Barrier Reef, including annual reef health reports and denying development projects that might harm the reef.)

Details of their research on the Great Barrier Reef bleaching events were published online yesterday (March 16) in the journal Nature.

Original article on Live Science.

More than 300,000 years ago, a colossal undersea landslide sent huge amounts of debris sliding down the Great Barrier Reef, generating a 90-foot-high (27 meters) tsunami, researchers have discovered.

Perhaps luckily for creatures in the area, that tsunami wave would have been dampened by the surrounding reefs, the researchers said.

The slide would have sent about 7.6 cubic miles (32 cubic kilometers) of rubble plunging down a slope of the Australian reef. (For comparison, the volume of the Great Pyramid of Giza is about 91 million cubic feet, or less than one-100th of a cubic mile. That means a volume of some 12,000 Great Pyramids plunged to the seafloor during the prehistoric landslide event.)

The culprit of the slide? "We believe an earthquake of sufficiently large magnitude was the most likely trigger for such a landslide event," study researcher Robin Beaman of James Cook University in Queensland, Australia, told Live Science in an email. "As for, 'Would a similar phenomenon happen today?' the continental slope sediments appear stable under current conditions." [Infographic: Tallest Mountain to Deepest Ocean Trench]

The researchers discovered the remnants of the giant submarine landslide while mapping the seafloor along a margin of the Great Barrier Reef using 3D multibeam sonar, in which sound waves are bounced off the seafloor. In one spot, called the Queensland Trough, which was supposed to be relatively flat, they found eight knolls, some of which rose 330 feet (100 meters) above the seafloor with lengths of more than 9,800 feet (3,000 m), the researchers said.

That series of knolls, now called the Gloria Knolls Slide complex, were the result of the ancient landslide, the researchers found. 

Their geological sleuthing involved more seafloor mapping and coral sampling.

Samples from the knolls, which were submerged under nearly 4,000 feet (1,200 m) of water, revealed both living and fossil corals, Beaman said. The corals took up residence along the knolls sometime after the hilly terrain formed. "The oldest fossil coral we found, using isotope dating techniques, was 302,000 years old, therefore, making the landslide event that caused these knolls to be older than that age," Beaman told Live Science.

From the detailed, 3D maps of the area, the researchers reconstructed, or modeled, the landscape that would have existed before the slide. "So we can then simply do a before/after analysis of the volume of sediment that has been removed from this pre-slide surface," Beaman wrote.

The research, detailed in the March 2017 issue of the journal Marine Geology, was conducted by Beaman, lead author Angel Puga-Bernabéu of the University of Granada, Jody Webster of the University of Sydney, Alex Thomas of the University of Edinburgh, and Geraldine Jacobsen of the Australian Nuclear Science and Technology Organization.

The researchers noted that more research is needed to determine the risk of tsunamis related to these types of underwater landslides on the Queensland coast.

Original article on Live Science.

Behind Australia's iconic Great Barrier Reef hides another large, doughnut-shaped reef, according to a recent study.

Using laser data from the Royal Australian Navy, scientists found a large field of unusual circular mounds behind the familiar Great Barrier Reef. Upon further research, they discovered that the structures are Halimeda bioherms — geological formations created by green algae. [Images: Colorful Corals of the Deep Barrier Reef]

"We've known about these geological structures in the northern Great Barrier Reef since the 1970s and '80s, but never before has the true nature of their shape, size and vast scale been revealed," Robin Beaman, a research fellow at James Cook University in Australia and part of the team that discovered the reef, said in a statement.

The scientists called the discovery "vast," as they've mapped about 2,300 square miles (6,000 square kilometers) of the reef. Each doughnut-shaped mound measures 650 to 980 feet (200 to 300 meters) across and up to 33 feet (10 m) deep at the center.

The structures form "a significant inter-reef habitat" covering a greater area than nearby coral reefs, said Mardi McNeil, lead author of the new study and a marine geoscience research student at the Queensland University of Technology.

This bioherm field raises questions about the effects of climate change and the reef's vulnerability, because Halimeda may be susceptible to ocean acidification and warming, the scientists said. Warmer ocean temperatures cause coral bleaching — a phenomenon that occurs when coral are stressed by the warmer-than-average waters,. This causes the coral to expel the algae that live in them, which can be fatal to the reef if bleaching continues for too long and algae are unable to recolonize. Earlier this year, Australia's National Coral Bleaching Taskforce (NCBT)announced that more than 90 percent of the Great Barrier Reef shows signs of bleaching, which has been accelerated by record heat this year.

Further study of the new reef could offer new avenues of research into the impact of climate change and coral bleaching, Beaman said.

"For instance, what do the 10- to 20-meter-thick [33 to 66 feet] sediments of the bioherms tell us about past climate and environmental change on the Great Barrier Reef over this 10,000-year timescale?" he said. "And what is the finer-scale pattern of modern marine life found within and around the bioherms now that we understand their true shape?"

Similar to the rings of a tree, coral rings can offer scientists information about the age of the coral and the environment in which it formed. Beaman added that further research of the site would include taking sediment samples and continuing more detailed surveys of the area. The research team will also use autonomous underwater vehicles to investigate the physical, chemical and biological processes of the structures.

The study was published online Aug. 24 in the journal Coral Reefs.

Original article on Live Science.

Australia's Great Barrier Reef corals are in trouble.

The northern part of the world's largest coral reef ecosystem is experiencing "the worst mass bleaching event in its history," according to a statement released Tuesday (March 29) by the Australian Research Council.

Documented by the National Coral Bleaching Taskforce (NCBT) in aerial surveys, observations of more than 500 coral reefs spanning 2,485 miles (4,000 kilometers) showed that the majority of reefs were undergoing extensive and severe bleaching.

"Almost without exception, every reef we flew across showed consistently high levels of bleaching, from the reef slope right up onto the top of the reef," said Terry Hughes of the NCBT, calling the surveys "the saddest research trip of my life." [Worst Coral Reef Bleaching on Record for the Great Barrier Reef | Aerial Video]

Bleaching happens when corals are exposed to stresses such as warmer-than-average waters for prolonged periods of time. The corals respond to the stress by expelling the algae that provide them with their color, which makes the corals look like they've been bleached white. Bleaching can be fatal for corals if the stress is too intense, or if it continues for too long and the algae are unable to recolonize them.

Ecosystem at risk

Australia's Great Barrier Reef (GBR) covers 134,364 square miles (348,000 square kilometers), making it larger than the U.K., Switzerland and the Netherlands combined, according to the Great Barrier Reef Marine Park Authority. Recognized as a World Heritage Area in 1981, the reef contains 400 types of coral and hosts 1,500 types of fish and 4,000 mollusk species, as well as other marine life such as large green turtles and dugongs ("sea cows").

The GBR experienced bleaching events in 1998 and in 2002, but the current mass bleaching is much more severe, experts are saying. Rebecca Albright, a marine biologist with the Carnegie Institution for Science in Washington, D.C., has studied the GBR since 2011. Albright told Live Science that 95 percent of the GBR's northern reefs are currently showing signs of extreme bleaching, compared with 18 percent that experienced bleaching in 2002.

Even the more robust corals are affected, Albright said, another sign that this event is particularly serious. She cautioned that it's still too early to assess the long-term impacts of bleaching on the corals, though estimates of coral mortality anticipate losses of about 50 percent.

Two factors are responsible for stressing the corals, Albright said: climate change, which is driving ocean temperatures upward, and a strong El Niño  — a cyclical climate event associated with warmer-than-average sea surface temperatures in the tropical Pacific. And with El Niño conditions expected to extend through 2016, that doesn't bode well for the corals' recovery.

"Corals are sensitive to not only the anomaly in temperature — how high it goes — but also the duration of that exposure," Albright told Live Science. "This kind of perfect storm of all these factors coming together makes this a catastrophic scenario right now." [Images: Colorful Corals of the Deep Barrier Reef]

A global event

But what's happening to the GBR is only part of the picture. A global bleaching event prolonged by El Niño is currently underway — "the longest coral die-off on record," according to a statement released by the National Oceanic and Atmospheric Administration (NOAA) on Feb. 23.

Mark Eakin, coordinator of the NOAA Coral Reef Watch program, told Live Science that the event, which began in 2014 in the Pacific, could linger through 2017.

"We consider it a global bleaching event if it's widespread in all three of the major ocean basins — Indian, Atlantic and Pacific," he said. Eakin described current reports of bleaching that extend over half of the Southern Hemisphere, with severe bleaching in New Caledonia, Fiji and southern Indonesia, as well as in the GBR.

Even fast-growing corals take decades to develop, so damaged reefs will need time before they're restored to their former level of health, Eakin said.

And recovery time may be in short supply. Global bleaching events have been expanding their reach and increasing in severity since the first event was documented in 1998, Eakin told Live Science.

"We’re seeing prolonged high temperatures that cause bleaching coming back repeatedly. We're seeing areas that have seen high temperatures for two to three years in a row. There's no time for corals to recover," he said.

The 1998 global bleaching event was associated with a strong El Niño — the strongest on record — but as ocean temperatures rise, even a mild El Niño can trigger a devastating effect on the world's corals. And the global bleaching event that's underway right now began in 2014, before the current El Niño was active, Eakin said.

For the GBR, in spite of the extreme bleaching there may yet be some hope for its recovery. The upper part of the reef that sustained the most damage was in very good shape beforehand, which should improve its prospects for "bouncing back," according to Albright.

"And the lower two-thirds of the GBR is still in very good shape — not a lot of bleaching in those areas. So a lot of people are holding on to that as another piece of hope," Albright said.

"It’s really just a matter of whether or not we get another bleaching event in the next 10 years that would impede recovery," she added.

Follow Mindy Weisberger on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

NASA is about to get up close and personal with Earth's corals: The space agency will use airplanes and water instruments to survey these delicate structures and capture the most detailed views ever of the planet's corals.

Corals are crucial to Earth's ecosystem, but they are typically studied only occasionally, during diving expeditions. This means that many of the world's reefs have never been surveyed. Yet coral reefs host one-quarter of all ocean fish species, shelter shorelines from storms and are a source of food for millions of people.

The new NASA campaign is aptly named CORAL (short for COral Reef Airborne Laboratory), and aims to assess the condition of these vulnerable ecosystems and to collect data on the size and quality of the reefs. [Images: Colorful Corals of the Deep Barrier Reef]

"Right now, the state of the art for collecting coral-reef data is scuba diving with a tape measure," Eric Hochberg, CORAL principal investigator and a scientist at the Bermuda Institute of Ocean Sciences in St. George's, said in a statement. "It's analogous to looking at a few trees and then trying to say what the forest is doing."

As part of the campaign, CORAL researchers will visit the Great Barrier Reef and other reefs in Australia, as well as reefs in Florida, Hawaii, Palau and the Mariana Islands.

The scientists will use an airborne instrument called the Portable Remote Imaging Spectrometer (PRISM), which was created at NASA's Jet Propulsion Laboratory in Pasadena, California. The spectrometer will be used with on-site instruments in the water to monitor the reef's condition.

One of PRISM's tasks will be to record the ratio of algae to reef on a coral. When corals die, algae numbers typically increase, and the spectral signatures of corals and algae show up differently in the spectrometer, NASA said.

Based on the limited data available so far, scientists think 33 percent to 50 percent of Earth's coral reefs are degraded or dead. Some reef scientists think that reefs could all but vanish by the middle of the century.

Though it will be comprehensive, the three-year CORAL campaign will cover only 3 percent to 4 percent of the world's reefs.

"Ideally, in a decade or so, we'll have a satellite that can frequently and accurately observe all of the world's reefs, and we can push the science — and, most importantly our understanding — even further," Hochberg said.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

This article was originally published on The Conversation. The publication contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

Reef historian Iain McCalman, in Sydney, and reef scientist Stephen Palumbi, in California, are monitoring reef degradation from opposite sides of the planet. They compared notes.

Iain McCalman: A recent report found that the Great Barrier Reef had lost 50% of its living coral. This was mainly from cyclones and the damages of Crown of Thorns starfish. Then there are the new threats of coral bleaching and acidification.

Are the problems you are finding in the US old ones that have mounted up and intensified? Or are they new challenges coming from human-stimulated climate change?

Steve Palumbi: All coral reefs in the world suffer from the same problems – they’re smothered by sediment, choked by weedy algae, blasted, dug up and stripped of most of their fish. Then there’s climate change making the oceans hot, sour and stormy.

Worst off are the reefs of the Caribbean, suffering from more than 500 years of incremental impact from western civilization, mostly in the form of poor stewardship. But even the far-flung reefs of the Pacific that the US manages have some combination of local stresses.

It seems to me that what the Great Barrier Reef has – that US reefs do not – is a central place in the hearts and minds of the public. Sure, most people in the US like corals and fish, but our reefs have not reached celebrity status. What kind of extra oomph does celebrity give the Great Barrier Reef? Has it been important in keeping it healthy?

Iain McCalman: The Great Barrier Reef’s popularity has helped control some things such as tourist pollution and the overfishing of parrot fish that graze on algae and keep corals clean.

Yet we haven’t been able to deter our governments from building massive new Reef ports and there are more and bigger coal ports on the way.

What worries me, too, is that waters warmed by greenhouse gases will cause big outbreaks of coral bleaching this coming summer, with stressed corals turning white as they expel the symbiotic algae that normally live within them. Another one degree or so will hurt corals that have been hit before: this time they may not recover.

Steve Palumbi: I’m also worried about coral bleaching. This week along the US Pacific coast we have had record temperatures on land and in Monterey Bay – well, it is still very cold by Great Barrier Reef standards, about 60F (16C), but it is warm for us! And a look at the latest map of ocean temperatures shows a lot of red – these are places where the ocean is 1-2 degrees warmer than the usual annual maximum.

Iain McCalman: We are predicting something similar, especially because we seem to be entering an El Niño weather phase when the Pacific is generally warmer anyway, though Charlie Veron, one of our great coral scientists, says that every year is becoming an El Niño year in Australia as far as corals are concerned.

Steve Palumbi: Every year is a hot one … that seems to be what the world is seeing across the continents and the seas. Way back when people first stumbled on the fact that corals bleached when the temperature rose too much, they found something else: corals in warmer climates near the equator bleached at a higher temperature than corals living in cooler waters.

We have seen this on a small scale in American Samoa where we work, and have shown that individual coral colonies living in warm water acclimate to the heat by changing their physiology. And whole populations of corals adapt to heat by having the right genetic makeup across about 100 genes.

Can we use this discovery? Turns out we can in two ways. We can locate and protect these heat-resistant corals. And we can try transplanting them to see if they in fact retain their heat resistance. We expect them to lose a little ground. How much is the question.

I’d love to think this will give us a leg up in replanting future reefs. I am not sure yet, because reef restoration has been so difficult. Does the Great Barrier Reef have any successful restored, replanted reefs?

Iain McCalman: Not that I know of. Moreover, with a government skeptical about climate change, a good deal of the work of this kind on adaptation is being shelved. Five of the Directors of the Great Barrier Reef Marine Park Authority recently resigned in protest against the cutting of programs concerned with responding to climate change.

Five directors of the Great Barrier Reef Marine Park Authority recently took redundancy packages, among them its former climate change director Paul Marshall, who said budget cuts have left the agency without a dedicated climate program.

But I also wanted to ask you about acidification. As the amount of CO₂ in the atmosphere rises, oceans absorb more and it turns into carbonic acid in seawater. How do you rate the mounting acidification of the oceans from absorption of CO₂ as a threat to corals?

It seems to be the elephant in the room: its consequences go beyond endangering corals to threaten other marine species as well. Some scientists seem to think it will deliver the death blow to coral reefs, if other things don’t get them first. What’s your feeling?

Steve Palumbi: Acidification is not the elephant in the room yet, it’s the elephant on the bus … due to get here any time now. The best data suggest that acidification has huge effects, from slowing down coral growth to changing the behavior of coral reef fish so that they get eaten more easily. Those effects are not strong yet, but they are coming quickly as CO₂ builds up in the atmosphere.

CO₂ and acidification takes 50 years to reverse. Think of stopping distance – a speeding car takes a long time to stop. So too with acidification.

And that is what I worry about. Because by the time the effect of that CO₂ is killing corals, it will be too late to do anything about it. It’s like cancer treatment. If you’re lucky, they find a tumor when it is small and maybe isn’t even bothering you. But that tiny tumor is a huge threat, and we jump on it to fix it.

But I want to circle back to something you brought up at the beginning. Australia is selling coal to China, I hear. What is going on?

Iain McCalman: This issue of coal lies at the heart of current threats to the Great Barrier Reef, and symbolizes an economic mindset that reef lovers everywhere are up against. Our government has decided that Australia’s economic future lies in selling cheap coal to China and India. To do this the Federal and Queensland state governments need to expand existing coal ports on the Reef because these provide the cheapest and quickest shipping routes to Asia.

Quite apart from discouraging investment in renewable energy by backing fossil fuels, this decision has fraught implications for the health of the Reef and its waters.

Because the reef is too shallow for massive container ships, the new coal ports all entail extensive dredging of the seafloor. Thankfully public agitation has temporarily deflected the government’s original plan to dump three million cubic meters of dredged silt from Abbot Point into the reef channel, where it would choke corals and swamp sea grasses. Even so, dredging will stir up immense amounts of sediment as well as coral-threatening bacteria.

The vastly increased tonnage of container ships churning up and down the tricky reef channel represents a further threat from reef accidents and oil spillages, both of which have occurred a number of times in the recent past. There are plans, too, for several new mega-sized coal mines to be opened nearby, requiring similar access to the Great Barrier coastline and lagoon.

To call this policy short-sighted is an understatement. It sacrifices one of the wonders of the world and a substantial economic asset for Australian tourism; and this at a time when even China is trying to wean itself from using polluting coal.

The Great Barrier Reef might be an icon for us in Australia, as you said, Steve, but we seem to have governments that are proud to be icon bashers.

Steve Palumbi: I am thinking about a wonderful passage in your book, about Captain Cook navigating the Great Barrier Reef’s intricate tributaries, straining his considerable navigational skills to delicately thread his small ship up coral-filled canals. Now blast a modern coal ship through there, and what would you expect to happen? Cook’s ship was threatened by the Great Barrier Reef. Now the tables have turned.

I can’t help also to think about one of the last major threats to the whole Great Barrier Reef - the crown of thorns starfish. It wasn’t too long ago that this voracious predator was wasting reefs all along Australia. The way you describe the dangers of mining and ports makes me want to call this new threat the Coal of Thorns.

The Coal of Thorns may prove to be an even bigger threat - because it is something the reef has never seen and it is on an industrial scale that could threaten even this biggest biological structure on Earth. And all to help China pollute their own air! What happens after you build all these ports, you export the coal and China turns to their vast supplies of natural gas? Dead reef and a dead exporting business.

When the coral-eating Crown of Thorns began devastating the Reef in the 1960s, people tried everything to stop it. Folks picked them up by the thousands and burned them. They poisoned them. They fought them up and down the length of Australia. They would have loved to have the problem solved by simply passing a law.

This threat from coal is a problem created specifically by people. And it could be solved by people in a way that was never available for the starfish scourge – a simple sign of a pen could do away with this major threat.

This article was amended on October 28, 2014, to clarify the circumstances of the departure of the five former directors of the Great Barrier Reef Marine Park Authority.

Iain McCalman receives funding from Australian Research Council.

Stephen Palumbi receives funding from the U.S. National Science Foundation, the Gordon and Betty Moore Foundation and the David and Lucile Packard Foundation.

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.

Brilliant shades of blue and aqua coat the iridescent lips of giant clams, but these shiny cells aren't just for show, new research finds. The iridescent sheen directs beams of sunlight into the interior of the clam, providing light for algae housed inside.

In a symbiotic return, the algae use that sunlight to power photosynthesis, resulting in energy for the giant clam. "It ends up being a large part of the energy budget of the clams," said study researcher Alison Sweeney, an assistant professor of physics and astronomy at the University of Pennsylvania.

Essentially, the oversize mollusks, which can measure more than 4 feet (1.2 meters) long, have a natural solar energy system hiding in their shells.

Most iridescent cells — including those that impart a vivid blue to the morpho butterfly, the glittery colors of beetles and the shine of birds' feathers — are dead, much like fingernails and human hair. But the iridescent cells of squid and giant clams are alive. [Marine Marvels: Spectacular Photos of Sea Creatures]

So, the researchers wondered, "What on Earth is a giant clam doing with a living iridescent cell?" Sweeney said.

Giant clams have a dull outer shell, as well as a weighted shell hinge that helps them point their lips up toward the sunlight. Perhaps the iridescent cells, called iridocytes, play an optical function, the researchers reasoned.

The team traveled to Palau, an island east of the Philippines in the tropical Pacific Ocean, to gather information about the giant clams. "We put this into a computer model about how we think light propagates through the clams," Sweeney said. "[But] nobody actually believed it," she added, referring to how the light was reflected back into the shells of the clams.

So, they returned to Palau to take detailed measurements of light inside the clams — Tridacna derasa, T. maxima and T. crocea — with the help of a fiber-optic probe. The iridescent cells reflected a remarkable amount of light into the clam, more than the scientists had initially expected, Sweeney said. Clam tissue with iridocytes has about fivefold more particles of light, called photons, deep inside the tissue than clam tissue without iridocytes does, they found.

"We're very excited by our surprising discovery," said study researcher Dan Morse, a professor of biomolecular science and engineering, and director of the Marine Biotechnology Center at the University of California, Santa Barbara.

"The brilliantly reflective cells of the giant clam actually redirect photons from sunlight deeper into the clam's tissue, gently and uniformly illuminating millions of symbiotic algae that live there, so they can provide nutrients to their animal host by photosynthesis," Morse wrote in an email to Live Science.

The algae's configuration is also efficient, the researchers found. If the algae were spread horizontally across the clam's tissue, only the top layers of algae would get light. The giant clam, however, doesn't have this obstacle. Instead, the algae are piled into vertical columns that allow the reflective cells to shine light along the sides of the columns — not just the algae on top.

The reflected light is also less intense than direct sunlight, so the algae don't get fried, Sweeney said.

The study is "very interesting," Euichi Hirose, a professor of invertebrate biology at the University of the Ryukyus in Japan, told Live Science in an email.

"Now, we know the giant-clam mantle has a more sophisticated function than we expected," said Hirose, who was not involved in the current study. "The colorful mantle reflects useless light for photosynthesis (green and yellow) and scatters useful light (red and blue) forward, and laterally, into deep tissue."

The giant clams' colorful and sparkly sheen may one day inspire new forms of clean technology, the researchers said. For instance, traditional solar cells work well in direct sunlight, but not when they get too hot. With the clam's design, a reflective sheen could help solar cells stay cool even when they're exposed to intense sunlight, Sweeney said.

The study was published yesterday (Sept. 30) in the Journal of the Royal Society Interface.

Follow Laura Geggel on Twitter @LauraGeggel and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Healthy coral reefs, known for their brightly colored spiny and soft layers, may act as critical refuges and food sources for hungry sharks swimming through Australia's Great Barrier Reef, reports a new 10-year study that captured underwater footage of sharks.

Coral reefs cover just about 5 percent of the habitats in the Great Barrier Reef, but about 95 percent of the shark sightings happened near the reefs, the study found.

"Sharks need healthy reefs," Mario Espinoza, the study's lead researcher and a Ph.D. candidate in environmental science at James Cook University in Queensland, Australia, told Live Science in an email. "It's a simple but powerful message."

Beginning in 2000, researchers deployed more than 2,500 remote underwater video stations in the Great Barrier Reef Marine Park to document its marine biodiversity. In all, the research team documented 21 shark species. [Great Barrier Reef Sharks Take The 'Cam' Bait | Video]

"It's a fabulous paper," said Demian Chapman, an assistant professor of marine biology at Stony Brook University on Long Island, who was not involved with the study. "It's one of, if not the largest, the most comprehensive studies of its kind."

The baited camera stations reached depths of between 23 and 377 feet (7 and 115 meters) — deeper than most divers studying sharks, Chapman said. The method also left the sharks alone, except for giving them a free snack of crushed oily sardines.

"It was completely unobtrusive to the sharks, because it was all done with cameras," Chapman said. "Other studies catch sharks."

Sharks appear in footage from 614 of the stations and in about a quarter of the videos, a percentage comparable to other studies, such as one Chapman did in Belize, he said. "They are top predators and they move around a lot," he said.

The recordings also showed what types of habitat the sharks preferred. For each video, the researchers noted the proportion of coral cover, plants and algae, filter feeders such as clams and sponges, soft coral and bare sand or mud, Espinoza said. They also assessed coral complexity, or the topographic contours and sizes of the reefs. [On the Brink: A Gallery of Wild Sharks]

"For example, some sites that had more coral cover and that were more complex usually had more sharks than those that were all sandy and muddy without any live cover," Espinoza said. "Sites with more corals also tend to have more fish, and more fish means more food [and] resources for sharks."

No fishing

The researchers also saw more sharks in areas that were closed to fishing. However, many shark species still preferred areas with high coral cover within these protected areas, suggesting that both no-fishing zones and healthy coral reefs are vital for improving shark numbers, Espinoza said.

"This is particularly important because recent findings from a study published by scientists at AIMS [the Australian Institute of Marine Science] had shown a 50 percent decline in coral cover on the Great Barrier Reef since 1985," Espinoza said. "This large decline of coral cover is likely to have negative effects on a wide range of marine species, including shark populations."

The Great Barrier Reef no-fishing zones installed in 2004, as well as other marine management rules, such as enforcing catch limits and allocating fishing licenses, may help threatened shark species rebound, the researchers said. 

A few years after the no-fish zones went into effect, the number of grey sharks increased, said Marc Nadon, a fishery assessment specialist at the University of Hawaii, who was not involved with the study. But the zones did not appear to help the tiger shark species (Galeocerdo cuvier), which swim long distances and often leave protected areas, he said.

Nadon noted that the underwater cameras recorded more sharks farther from the Australian coast. "To me, it seems like it's a factor of isolation," Nadon said. "The farther away you are from people, the more sharks you have."

Sharks are often demonized in popular culture, but studies like this remind the public that sharks are needed in the ocean, said Simon Pittman, director of Seascape Analytics, a marine consulting company, and a scientist with the U.S. National Oceanic and Atmospheric Administration's biogeography branch, who was not involved with the study.

"We need to remember as ecologists that sharks are top predators, and they're key to maintaining ecosystem integrity," Pittman said. "You can see them as canaries in a coal mine. They're sensitive to how we manipulate the system. If we're overfishing, not only are we taking sharks themselves, but we're taking the food of the sharks."

Future studies may determine exactly how sharks interact with coral reefs and other habitats they frequent, experts said.

"It could be that you need a healthy reef to have healthy shark populations," Chapman said. "Or some people say you need sharks to have a healthy reef. Whether it's the chicken or the egg, we don't know in this case."

The study was published today (Sept. 10) in the journal PLOS ONE.

Follow Laura Geggel on Twitter @LauraGeggel and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Some of Madison Stewart's earliest memories come from the Great Barrier Reef: the school of bream she saw while snorkeling at age 6, the moray eel that made her leap from the water "like a penguin."

But it's sharks that have shaped Stewart's life. At 14, she noticed an eerie lack of these apex predators on a dive in the reef. Now 20, this conservationist and filmmaker stars in a new documentary drawing attention to the plight of the animals she thinks of as family.

"My digging helped me find out that there was a legal shark fishery in the Great Barrier Reef, and it's been operating for more than 20 years now," Stewart told Live Science. About two-thirds of the reef is open to fishing, and 80,000 sharks per year can be caught legally from the water. The fins are exported, she said, and most of the meat is sold in Australia, often labeled "flake." The data on the sustainability of this fishery, however, is lacking.

"Right now, we fish blind," Stewart says in the documentary, "Shark Girl," which premieres June 15 on the Smithsonian Channel. [8 Wild Facts About Sharks]

Becoming a voice for sharks

The ocean feels like home to Stewart, who lived on a yacht with her family at age 2; by the age of 18, she had logged more than 450 dives, most of them with sharks. At 14, alarmed by the changes she could see in the Great Barrier Reef, she left school to be homeschooled and to advocate for sharks.

"When you take the sharks, the apex predators, the boss, when you take them out of the equation, everything seems to collapse," Stewart said of the reef ecosystem. Sharks, for example, prey on large fish that would otherwise eat fish hatchlings and cause ecological imbalances.

One of Stewart's main goals is to combat people's fear of sharks; in the new documentary, she moves through shark-infested waters with ease. Shark species have different personalities, like dog breeds, she told Live Science. The big tiger sharks are curious but cautious; the lemon sharks are "quite cheeky." Leopard sharks have no teeth, but enjoy swimming up to divers for a scratch, she said.

One segment in the documentary, in particular, perhaps drives Stewart's point home the strongest: She and a guide feed a gaggle of 20 to 30 sharks out of a bait box in the Bahamas. Needless to say, no one loses an arm. The scene is an antidote to sensational news stories about shark attacks, which kill, on average, one person each year in Australia, according to Taronga Conservation Society Australia. Still, such attacks get outsized attention in the media, Stewart said.

"It should be celebrated that there are sharks in our waters," she said. "But it's not."

Protecting predators

The documentary traces Stewart's activism in Australia, where she projects films of her dive onto a wall in Chinatown to draw attention to shark finning, and meets with executives from the Woolworths grocery chain to discuss high levels of mercury found in shark meat from the Great Barrier Reef sold in the chain's stores. (Ultimately, Woolworths declined to comment on the product, Stewart said.)

As apex predators, sharks concentrate mercury pollution found in the tissue of their prey. The metal is a potent neurotoxin. Other research has found high levels of another neurotoxin called BMAA in shark fins, the main ingredient in shark fin soup.

Stewart also visits Mexico, which in 2011 enacted a ban on shark fishing during the breeding season in order to protect shark populations. (This year, the country also banned the catch of great white sharks.). The documentary goes to the island country of Palau, too, which has banned shark fishing altogether and turned its waters into a shark sanctuary.

Against a backdrop showing pictures of bloodied shark corpses, Stewart and the researchers in the documentary point out that the public would never meet the slaughter of charismatic creatures such as dolphins or elephants with such indifference. Consumers can help sharks by refusing to eat shark fin soup and by knowing where their shark meat comes from, Stewart said. Consumers should also make careful decisions about the other fish they eat, she said, as sharks are often caught up in nets meant for tuna and other catches.

"I'm not saying you have to love [sharks], but at least respect them," Stewart said. "You can be terrified of sharks and still have a deep respect for them."

To dive more deeply into Madsion Stewart's motivations, watch our full, uncut interview Part 1 and Part 2 (Links Below).

And check out what happens when Madison feeds our American video producer some Australian Vegemite!

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

A new four-year study of tiger sharks off the coast of Australia has revealed patterns in the animals' mysterious migratory wanderings, including curious differences based on the gender and age of the sharks.

The study, led by Jonathan Werry, a researcher at Griffith University in Australia, tracked 33 tiger sharks (Galeocerdo cuvier) using satellite and acoustic transmitters as they traveled across the Coral Sea, which lies between the Great Barrier Reef, off the east coast of Australia, and the Pacific island of New Caledonia. The sharks ranged in length from 5 feet (1.5 meters) to nearly 13 feet (4 m).

The researchers found that mature female sharks tend to be the ones making long-distance journeys across the Coral Sea — between the deep ocean and the more shallow, coastal waters — while adult males and younger females were found to linger in oceanic reefs away from the coasts. [In Images: Tracking Tiger Shark Migrations in the Coral Sea]

"In the reef system in the center of the Coral Sea, 500 nautical miles [575 miles, or 930 kilometers] from either coastline, we saw extraordinary year-round residency for mature males and pre-reproductive females," Werry told LiveScience. "This is quite interesting, because it's a reverse of the behavior we see when these animals are in the coastal areas."

Previous research on the migration of tiger sharks discovered that these animals are typically transitory along coastal reef systems, and do not seem to remain at, or return to, particular sites for long periods of time, he added. The results of the new study, however, indicate that tiger sharks may actually favor certain regions farther out in the deep ocean, where food sources may be more abundant.

"What you get in coastal areas is a very sporadic group of large sharks, and then it looks like mature females are the ones migrating between coastal areas and oceanic reefs — something that's probably driven by their pupping cycle," Werry said. "This tends to suggest these oceanic regions are vital to their ecology."

The findings also indicate that tiger sharks do not have uniform traveling habits.

"Sometimes, you can look at species as a whole for migratory patterns, but tiger sharks have quite a complex life history strategy that varies dramatically between males and females, and between when they are immature and mature sharks," Werry said.

Migration mysteries

Researchers are beginning to unravel some of the mysteries of tiger sharks' migration patterns, but many unanswered questions remain. For instance, Werry and his colleagues are investigating whether oceanic reefs function as important mating spots, which could help explain why adult males choose to remain in the area for extended periods of time.

The new study also examined shark migratory patterns in three dimensions, which included recording measurements of how deep the sharks dived. "Instead of just looking at movements from one place to another, we also looked at how the sharks use the water column," Werry explained.

In one instance, a female shark dove to a depth of more than 3,700 feet (1,100 m).

"That's an extraordinarily deep dive for a large shark," Werry said. "These three-dimensional measurements give us insight into the range of environments that sharks are using, and point out the importance of oceanic habitats, in addition to coral reefs."

Keys to protection

Understanding the migratory habits of tiger sharks, and which areas of the marine environment are most crucial to the animals, is critical for the management and protection of the species, the researchers said. Tiger sharks are classified globally as "near threatened" by the International Union for Conservation of Nature, the world's main authority for the conservation status of wildlife.

"Management strategies need to consider the wide-ranging movements of large (subadult and adult) male and female tiger sharks at the individual level — in particular, when fidelity to specific coastal reefs may be consistent across groups or individuals," Werry said in a statement. "The importance of oceanic Coral Sea reefs should be a priority for future research."

The new study, performed in collaboration with the French government, was published online today (Jan. 8) in the open-access journal PLOS ONE.

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.

Deep Blue Sea

A research project led by Jonathan Werry, of Griffith University in Australia, examined the migration patterns of tiger sharks across the Coral Sea, which is located between the east coast of Australia and the Pacific island of New Caledonia.

Here, Werry and a colleague release a tiger shark that has been tagged with satellite and acoustic transmitters.

Say Cheese!

Researchers restrain a tiger shark underwater.

Chomping at the Bit

Researchers prepare to release a 13-foot-long (3.9 meters) tiger shark after it was tagged. The black pipe in the shark's mouth is used to calm the animal.

Swimming with the Sharks

Jonathan Werry, a researcher at Griffiths University in Australia, swims with a tiger shark after it was tagged with acoustic and satellite transmitters.

Into the Wild

A 10-foot-long (3 meters) tiger shark swims in the Coral Sea, off the eastern coast of Australia.

With a mouse click, viewers anywhere can be transported to the serene underwater world of the Great Barrier Reef.

Google Street View has partnered with scientists to create 360-degree panoramas of the world's coral reefs, called Google Street View Oceans. New ocean sites continue to be added to the project, which was released in 2012. The science team hopes to develop a rigorous system for monitoring the coral's health while giving the public a chance to explore these beautiful but vulnerable ecosystems.

"Coral reefs are some of the most endangered ecosystems on the planet," said Ove Hoegh-Guldberg, a reef scientist at the University of Queensland, Australia, who is leading the research in collaboration with the Catlin Seaview Survey. "I realized that if we formed a partnership, we could start to look at those images and understand why coral reefs are going downhill." [Photos: Underwater Google Street View Reveals Stunning Corals]

Using a human-driven, underwater scooter equipped with a set of sophisticated cameras, the team snaps photos of the reefs and stitches them together into panoramas.

Next, the team uses advanced image-recognition software to monitor the coral and other sea creatures within these images. The same technology that allows computers to pick a face out of a photo of a crowd can be applied to coral and other reef organisms, Hoegh-Guldberg told LiveScience. The team will present its research at an international ecology meeting in London this week.

The team has already explored the Great Barrier Reef and is currently surveying the Caribbean. "The Caribbean is in a very poor state," Hoegh-Guldberg said, adding that coral cover in the region has declined from more than 50 percent in the 1970s to less than 5 percent now.

The causes of coral decline are complex. Climate change is warming and acidifying the oceans, threatening the health of the organisms that support reef ecosystems. As carbon dioxide enters the oceans, it produces acid that dissolves the minerals corals use to grow.

Coastal development presents other problems. Deforestation allows more nutrients and sediment to run off into the ocean, damaging reefs. And overfishing is stripping the reefs of the fish that keep harmful algae growth in check.

"Fish are not just there for enjoyment and to be eaten,"Hoegh-Guldberg said. "They act as gardeners."

But most people probably don't know what's being lost: Less than 1 percent of humans have ever dived on a coral reef, Hoegh-Guldberg said.

With this new project, reef worlds that were once the province of the few are now accessible to anyone with an Internet connection. In fact, regular people will be able to aid scientists in their efforts to monitor these ecosystems. For example, a young student interested in turtles could count the turtles in the images.

Next year, Hoegh-Guldberg and his team plan to map the Coral Triangle in Southeast Asia, a major center of biodiversity. "It's a very valuable part of the ocean, but it's also under extreme pressure," Hoegh-Guldberg said.

Follow Tanya Lewis on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on LiveScience.

Coral Reef Street View

Google Maps has teamed up with the Catlin Seaview Survey to create 360-degree panoramas of coral reefs around the world.

Coral Reef Health

The underwater images will help researchers measure the health of coral reefs.

Great Barrier Reef

The team has explored the Great Barrier Reef off the coast of Australia and is currently exploring the southern Caribbean.

Dying Coral

Climate change and coastal development pose a serious threat to coral reef ecosystems.

Underwater Cameras

A human-driven underwater scooter equipped with sophisticated cameras is used to capture the photos.

Virtual Exploration

Anyone with Internet access can virtually explore these vibrant coral reef environments.

Coral Reef Life

Coral reefs are home to many different species, including tropical fish and manta rays.

Overfishing

Overfishing is taking a toll on reefs, which depend on fish to keep algae populations in check.

Mammal Life

The reef is home to mammals as well.

Citizen Scientists

Regular citizens can help scientists keep track of the wildlife that call the reefs home.

Image Recognition

Scientists are using image recognition software to identify corals and other organisms.

Appreciating Coral Reefs

Less than 1 percent of humans have ever dived on a coral reef, according to project leader Ove Hoegh-Guldberg, a reef scientist at the University of Queensland, Australia.

Public Awareness

One of the project's aims is to increase public awareness of the threats coral reefs face.

Monitoring Reefs

Over time, scientists will be able to measure how the reefs respond to pressures from the environment.

Ahead of the meeting of the United Nations Educational, Scientific and Cultural Organization's (UNESCO) World Heritage Committee in Cambodia next month, the UN has warned the governments of Australia and Queensland state that the Great Barrier Reef could be added to the List of World Heritage in Danger, if certain actions and plans aren't put in place by those governments, the Sydney Morning Herald reports.

Government representatives are not happy about the possibility and are working to prevent the listing. "Australia would be the only developed country in the world to have a world heritage site on [the] endangered list. It would be a huge international embarrassment and it would be a big blow to our tourism industry," Queensland Greens Senator Larissa Waters said, as quoted by the Morning Herald.

Federal Environment Minister Tony Burke said the report published by the UN didn't take into account several government initiatives and that Australia was working with the World Heritage Committee to ensure the protection of the reef.

The UNESCO World Heritage List is a group of 962 spots that have particular cultural or natural value. A list of those sites considered to be endangered by armed conflict, natural disasters and development is also kept to draw attention to their plight.

Follow Andrea Thompson @AndreaTOAP, Pinterest and Google+. Follow OurAmazingPlanet @OAPlanet, Facebook and Google+.

Updated on Jan. 3 at 7:18 p.m. ET.

Even four times as deep as most scuba divers venture, the Great Barrier Reef  blooms. A new exploration by a remote-operated submersible has found the reef's deepest coral yet.

The coral Leptoseris is living 410 feet (125 meters) below the ocean's surface, a discovery that expedition leader Pim Bongaerts of the University of Queensland called "mind-blowing."

Coral reefs are made of colonies of polyps which secret a rock-like exoskeleton. The polyps have a symbiotic relationship with algae that provide them nutrients using photosynthesis. Because this process requires light, coral reefs thrive in clear, relatively shallow water.

"The discovery shows that there are coral communities on the Great Barrier Reef existing at considerably greater depths than we could have ever imagined," Bongaerts said in a statement.

Coral colonies

The 410-foot distance is surprising for the Great Barrier Reef, where scuba divers find stunning coral displays at depths down to 100 feet. But corals are known to live deep elsewhere. In the Gulf of Mexico, researchers have found the coral Lophelia pertusa thriving 2,620 feet (799 m) down. Lophelia doesn't need sunlight to survive. In Puerto Rico, light-dependent corals survive as far down as 500 feet (150 m).

Bongaerts and his colleagues received funding from insurer the Catlin Group Limited to explore the Great Barrier Reef as part of an effort to understand how climate change is altering the oceans.

On the outer edge of the Ribbon Reefs, off the northern Great Barrier Reef, the researchers hit unusually calm seas and were able to deploy a remote-operated vehicle, or ROV, off the edge of the Australian continental shelf, where the ocean floor plummets hundreds of feet. It was a tough dive, said expedition member Paul Muir, a taxonomist from the Museum of Tropical Queensland. [See Photos of the Deep Reef Corals]

"With more than 250 meters of cable out to provide power and communications with the ROV, it was a real struggle to collect a specimen of one of these corals," Muir said in a statement.

The deep reef

The team persevered and brought one precious Leptoseris coral sample back to sea level. Typically, such corals peter out in the Great Barrier Reef above 330 feet (100 m), replaced by non-light-dependent sponges and sea fans. Using the ROV, the team also found the deepest Staghorn Acropora, a type of coral that makes up the majority of most of the world's reefs.

"These discoveries show just how little we really know about the reef and how much more is yet to be discovered," Bongaerts said. "This poses lots of questions for us, but now we have specimens, we'll be able to analyze them much more closely and can expect our findings to reveal a far greater understanding of just what is going on to enable reef corals to survive at such extreme depths."

The Great Barrier Reef has been in decline, with half of it vanishing in the last 27 years, according to a study released in the journal Proceedings of the National Academy of Sciences last October. Climate change is boosting the temperature of the oceans, causing some of the damage. Another reef foe is the crown-of-thorns starfish, which eats coral. The starfish populations have exploded because of nutrient runoff from agricultural fertilizers.

Editor's Note: This article was updated to correct the name of Leptoseris.

Follow Stephanie Pappas on Twitter @sipappas or LiveScience @livescience. We're also on Facebook & Google+.

ROV Expedition

A researcher lowers a remotely operated submersible vehicle into the waters of the Great Barrier Reef.

Ribbon Reef

A scuba diver swims among colorful fish and coral in the northern Great Barrier Reef's Ribbon Reef. Researchers exploring the deep edges of the reef recently found coral living at 410 feet (125 meters).

ROV at Ribbon Reef

The remotely operated vehicle (ROV) sits on a cliffside at Ribbon Reef in the northern Great Barrier Reef.

Deep Coral

Coral was found lower than ever seen before in the Great Barrier Reef. The corals are four times deeper than most scuba divers can dive.

Deep Coral Reef

The corals are found in a place that is difficult to explore because of bad weather.

Deep Great Barrier Reef

Deep corals found in the northern Great Barrier Reef.

Deep Coral

At 410 feet (125 m), these corals are the lowest ever seen at the Great Barrier Reef, though many non-light-dependent corals can survive at thousands of feet below the ocean surface.

Coral Specimen

A single specimen of coral brought up from 410 feet (125 m).

Coral Specimen

The coral is of the genus Acropora, a common reef coral.

Research Team

The expedition team celebrates their collection of the deep coral specimen.

Flat Coral

A shallower dive reveals how corals spread flat at depth to catch more light.

Shallow Reef

A ruined. shallow section of the Great Barrier Reef damaged by storms.

The expansion of European settlement in Australia triggered a massive coral collapse at the Great Barrier Reef more than 50 years ago, according to a new study.

The study, published Nov. 6 in the Proceedings of the Royal Society B, found that runoff from farms clouded the pristine waters off the Queensland coast and killed the natural branching coral species, leaving a stunted, weedy type of coral in its place. The findings suggest that decades before climate change and reef tourism, humans were disrupting the ecology of the Great Barrier Reef.

"There was a very significant shift in the coral community composition that was associated with the colonization of Queensland," said study co-author John Pandolfi, a marine biologist at the University of Queensland Australia.

Europeans began to colonize Queensland, Australia, in the 1860s, cutting down forests to make way for sheep grazing and sugar plantations. By the 1930s, large amounts of fertilizer and pesticide-laden runoff poured from rivers into the nearby ocean.

Several recent studies have shown that snorkelers and climate change kill coral, and one study found that half of the majestic Great Barrier Reef has vanished over the last 30 years.

But Pandolfi's team wondered whether humans had been altering reef ecology for much longer.

To find out, the team drilled sediment cores, 6.5 to 16.5 feet (2 to 5 meters) long, from the seafloor at Pelorus Island, an island fringed by coral reefs off the Queensland coast. When coral dies, new coral sprout on the skeletons of old organisms and ocean sediments gradually bury them in place, Pandolfi told LiveScience.

By dating different layers of that sediment, the team reconstructed the story of the reef.

The fast-growing Acropora coral dominated the reef for a millennium. This massive, three-dimensional coral can grow to 16 feet (5 m) high and span 65 feet (20 m) across, forming a labyrinth of nooks and crannies for marine life to hide in, Pandolfi said. [Image Gallery: Great Barrier Reef Through Time]

"They're like the big buildings in the city, they house a lot of the biodiversity" he said.

But somewhere between 1920 and 1955, the Acropora stopped growing altogether and a slow-growing, spindly coral called Pavona took its place.

That spelled trouble for the panoply of animal species that shelter in the reef, and for the nearby coastline, because the native Acropora species provide wave resistance to shelter harbors.

The team believes that over time, polluted runoff clouded the normally pristine Pacific water and poisoned the native species. The same polluted water fueled an algal bloom that choked out the native coral species when they tried to grow back, he said.

"They just weren't able to come back after the 1950s."

While the findings suggest humans have been damaging reefs far longer than previously thought, the problem has a straightforward, local solution: Reduce polluted runoff into the ocean, Pandolfi said.

"Any kind of measures that are going to improve the water quality should help those reefs to recover."

Follow LiveScience on Twitter @livescience. We're also on Facebook & Google+. 

The daily routines of manta rays in the Great Barrier Reef of Australia have been exposed in a new study that reveals when these graceful fish eat, cruise and visit "cleaning stations" where smaller fish nibble off their dead skin and parasites.

The study focused on Lady Elliot Island, a small land mass in the Reef. Manta rays (Manta alfredi) congregate here year-round, but are more common in autumn and winter, the researchers report today (Oct. 3) in the journal PLoS ONE.

Using three years of observations, some by "citizen scientists" — local scuba divers and boat captains who volunteered to record manta ray sightings — researchers from the University of Queensland charted how ocean conditions influence where manta rays gather and what they do. They found that more manta rays cluster around the island when wind speeds are lower and when the moon is new or full.

Manta rays also commute to key locations for certain activities, the researchers found. Five of the seven ocean sites surveyed were used predominately for foraging. There, manta rays were most often seen swimming against the current, mouths open, filtering plankton from the water.

At the two remaining sites, manta rays were seen foraging but also engaged in the fishy equivalent of a car wash. During this behavior, rays were seen hovering over coral, staying relatively stationary as small "cleaner fish" picked parasites and skin detritus off of their bodies.

The research could be helpful in understanding why far-travelling manta rays go where they go, according to the researchers.

Follow Stephanie Pappas on Twitter @sipappas or LiveScience @livescience. We're also on Facebook & Google+.

Horseshoe reef

Horseshoe reef before crown-of-thorns invasion.

Horseshoe reef

Horseshoe reef after crown-of-thorns invasion.

Low Isands

Healthy reef at Low Islands.

Low Islands

Healthy reef at Low Islands.

Low Islands

Healthy reef at Low Islands.

Beaver reef

Damage to Beaver Reef by Cyclone Hamish.

Beaver reef

Crown-of-thorns damage on Beaver Reef.

Coral eating starfish outbreak

Population outbreaks of the coral eating starfish Acanthaster planci have been responsible for 42% of the over 50% decline in coral cover on the Great Barrier Reef between 1985 and 2012.

MacDonald reef

MacDonald reef before cyclone damage.

MacDonald reef

MacDonald reef after cyclone damage.

Damaged reef

Crown-of-thorns and cyclone damage.

Halfway Island

Bleaching at Halfway Island.

North Kepplel

Bleaching at North Kepplel.

Australia's Great Barrier Reef is a glittering gem — the world's largest coral reef ecosystem — chock-full of diverse marine life. But new research shows it is also in steep decline, with half of the reef vanishing in the past 27 years.  

Katharina Fabricius, a coral reef ecologist at the Australian Institute of Marine Science and study co-author, told LiveScience that she has been diving and working on the reef since 1988 — and has watched the decline. "I hear of the changes anecdotally, but this is the first long-term look at the overall status of the reef. There are still a lot of fish, and you can see giant clams, but not the same color and diversity as in the past."

To get their data, Fabricius and her colleagues surveyed 214 different reefs around the Great Barrier Reef, compiling information from 2,258 surveys to determine the rate of decline between 1985 and 2012. They estimated the coral cover, or the amount of the seafloor covered with living coral.

That overall 50-percent decline, they estimate, is a yearly loss of about 3.4 percent of the reef. [Photos of Great Barrier Reef Through Time]

They did find some local differences, with the relatively pristine northern region showing no decline over the past two decades.

Cyclones and starfish

The reef’s decline, detailed this week in the Proceedings of the National Academy of Sciences, can be chalked up to several factors, they found. The biggest factors are smashing from tropical cyclones, crown-of-thorns starfish that eat coral and are boosted by nutrient runoff from agriculture, and coral bleaching from high-temperatures, which are rising due to climate change.  (Coral bleaching happens when ocean temperatures rise and cause the corals to expel their zooxanthellae — the tiny photosynthetic algae that live in the coral's tissues.)

Other coral experts say the precipitous decline matches what they have found. "This is a really grim wake-up call," said John Bruno, a biologist at UNC Chapel Hill. "The GBR [Great Barrier Reef], which only 10 years ago was considered the world's most pristine and resilient coral reef is clearly not better off and no less threatened than any other reef. I am bullish on the long-term survival of reefs, but science like this is challenging that outlook."

Saving the reef

As for what can be done to save the reef, or what's left of it, some say reducing carbon dioxide (CO2) emissions is key. "International efforts to cap and reduce CO2 emissions are equally critical and must occur at the same time as cleaning up local impacts," said Les Kaufman, a biologist at Boston University who is part of an international consensus statement on climate change and coral reefs.

Fabricius says not much can be done in the short term about the climate-change-driven frequency of cyclones — five category 5 storms in the past seven years have pounded the reefs — or high temperatures. However, there are efforts in place to stem the damage from starfish, which can grow up to 3 feet (0.9 meters) in diameter and sport long venomous spines and 21 arms. Young starfish feed on coral-making algae, and leave behind the coral's skeleton.

One project encourages farmers to adopt practices that limit the amount of nutrient-rich runoff draining into reef areas. Another would allow tour operators to manually remove starfish from tourist areas, which Fabricius admits isn't a solution, just a temporary fix.

Another option is to examine ways of harnessing natural starfish diseases that typically keep starfish numbers low. "Starfish normally are rare," Fabricius said. "We want to help Mother Nature keep them rare." The research shows that the reef could rebuild itself in 20-30 years despite the cyclones and bleaching, if the starfish population died back.

The experts agree that doing nothing is not an option at this point. "The problem is entirely soluble, and coral reefs can be saved through concerted effort over this and the following two or three generations," said Kaufman. "There is absolutely no excuse for failure to do this, and if we do fail our generation will forever be remembered for unimaginable, unforgivable stupidity and sloth."

The waters of Australia's Great Barrier Reef are getting warmer, satellite measurements show, which spells bad news for the myriad creatures that dwell in this rain forest of the ocean.

The satellite measurements of ocean temperatures show that the waters in the reef have warmed by 0.36 degrees Fahrenheit (0.2 degrees Celsius) on average over the past 25 years. The change was even more pronounced in certain areas. For example, waters off the coast of Rockhampton, Australia, warmed by 0.9 F (0.5 C).

The warming increases the risk of coral bleaching, wherein the symbiotic organisms that allow coral to thrive are expelled.  

The changes at the Great Barrier Reef were mirrored in altered seasonal patterns. "In some areas summer is coming earlier and lasting longer; in others, both summers and winters are warmer than in the past," Natalie Ban, a researcher with the ARC Centre of Excellence in Coral Reef Studies, said in a statement. "This all affects the sea life."

The study, to be published in the October issue of the journal Conservation Biology, raises questions about how to best manage the world's largest reefand protect its wildlife.

"Some people think we ought to have the highest levels of protection for areas that are changing the least, so they remain as refuges to recharge the surrounding reef areas," Ban said in a statement. "Others argue the opposite — that the greatest protection should be afforded to the most vulnerable areas."

The authors hope the paper will help to come up with "the best and most flexible system for managing the [reef] through what will undoubtedly be momentous environmental change," Ban said.

Reach Douglas Main at dmain@techmedianetwork.com. Follow him on Twitter @Douglas_Main. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

Anyone who wanted to see the Great Barrier Reef up close but got hindered by factors like finances or asthma has a new chance. Google just unveiled underwater views of the reef. Just in time, too, as environmentalists fight a mine proposal that they say could destroy it all.

PHOTOS: The Unexpected Beauty of Coral Crustaceans

For the first time, Google Maps is showing underwater, 360-degree panoramic views of the Great Barrier reef and five other well-known reefs around the world. The images were made in collaboration with the Caitlin Seaview Survey, a scientific study intended to reveal ocean life and address questions about the changes associated with rapidly warming and acidifying oceans.

In addition to carbon pollution and warming, environmentalists have a new worry about the Great Barrier Reef's future. Nine coal mines, dubbed "mega-mines," have been proposed for the Galilee Basin in Queensland, Australia. The Guardian, calling the plans part of a "new Australian coal export rush," reported that the mines would produce 330 million tons of coal annually.

Greenpeace called the Australian mega-mine proposition "reckless" and potentially "catastrophic" in a report released last week. The organization predicts the coal basin will become the world's seventh-largest emitter of carbon dioxide pollution from fossil fuels. The CO2 emissions, the new port terminals, the seafloor dredging, and increased ship traffic through whale habitats would all put the Great Barrier Reef World Heritage Area in danger.

The Australian coal industry dismissed Greenpeace's numbers as "mythical" and accused the organization of scaremongering.

Recently the UN weighed in on the proposal. Its World Heritage Committee urged Australia not to permit any new port development or associated infrastructure beyond existing and long-established major port areas. Still, at least one part of the mega-mines proposal is moving ahead. In August, the $7.1 billion Alpha mine got state and federal approval.

PHOTOS: Ocean Artists Convey Horror and Magic

Pollution and politics aside, the Great Barrier Reef can be a dangerous place to visit in person. Last week a Chinese tourist drowned during a tour. For me, at least, a virtual visit seems like the safest way to see it. That said, if all the mega-mines get built, Google's underwater views might be all that remains.

This story was provided by Discovery News.

The coral diversity in the West Indian Ocean, especially around Madagascar, is greater than previously believed and it may even rival parts of the Great Barrier Reef, new research shows.

The study, published Sept. 19 in the journal PLoS ONE, is based on surveys of reef-building corals conducted from 2002 to 2011 by scientists with the Coastal Oceans Research and Development in the Indian Ocean (CORDIO).

The researchers identified 369 coral species in the West Indian Ocean, but estimated that further studies may show up to 450 species residing there, which would put it on par with India's Andaman Islands or the northern Great Barrier Reef.

The number of species is especially high in the northern Mozambique Channel, the waterway that separates Madagascar from Africa's west coast. The researchers said 250 to 300 species could be found at sites in this area. Meanwhile, there were 200 or fewer species in other parts of the West Indian Ocean, including waters off northern Kenya, the Gulf of Aden and the outer Seychelles islands.

Steve Katona, managing director of the Ocean Health Index for Conservation International, explained in a statement that healthy coral reefs can provide benefits like costal protection against storms, tourist attractions and food production.

"At the same time," Katona said, "corals worldwide are threatened by warming sea-surface temperatures, ocean acidification, pollution by chemicals, nutrients and sediment, ultraviolet light, invasion by alien species and direct habitat destruction from unsustainable fishing techniques, divers, boat anchors, coral collection or mining and dredging."

The researchers said Mozambique Channel in particular, is facing pressures from population growth, overfishing, urbanization and energy exploration.

"Coral reefs of the Western Indian Ocean need careful management and protection if they are to realize their full potential for improving human well-being in this critical developing region," Katona said. 

Follow LiveScience on Twitter @livescience. We're also on Facebook & Google+.

The Great Barrier Reef is a mosaic of 2,900 individual reefs off the coast of Queensland in northeast Australia. The sprawling reef can be seen from space and is not only the world's largest coral reef system but also the largest structure on Earth made by living organisms.

Where is the Great Barrier Reef?

The Great Barrier Reef stretches more than 1,600 miles (2,575 kilometers) — a little more than the distance from Boston to Miami. It covers an area of 133,000 square miles (344,400 square km), reaching from the Torres Strait at it northernmost point to Fraser Island in the south. The reef includes Lady Elliot Island and the smaller Murray islands.

Great Barrier Reef animals

A coral reef consists of coral polyps, which are animals in the jellyfish family, along with algae called zooxanthellae. In return for a cozy, safe place to live, the algae provide the building blocks polyps need to survive and make limestone to build the reef structures. The vast structures that result do more than awe snorkelers. [Images: Colorful Corals of the Great Barrier Reef]

The Great Barrier Reef supports a vast array of life forms. Thirty species of whales, dolphins and porpoises have been recorded in the Great Barrier Reef, including the dwarf minke whale, Indo-Pacific humpback dolphin, and the humpback whale.

Large populations of dugongs, large marine mammals that are relatives of the manatees, make their home along the reef.

More than 1,500 fish species live on the reef, including the clownfish, red bass, red-throat emperor, and several species of snapper and coral trout. About 5,000 species of mollusks live on the reef.

Seventeen species of sea snake live on the Great Barrier Reef in warm waters up to 160 feet (49 meters) deep and are more common in the south than in the northern section.

Six species of sea turtles — the green sea turtle, leatherback sea turtle, hawksbill turtle, loggerhead sea turtle, flatback turtle, and the olive ridley — come to the reef to breed.

Saltwater crocodiles live in mangrove and salt marshes on the coast near the reef.

The Great Barrier Reef is home to 215 species of birds (including 22 species of seabirds and 32 species of shorebirds) that visit the reef or nest or roost on the islands. The white-bellied sea eagle and roseate tern are frequently sighted.

The 15 species of seagrass found along the reef attract the dugongs and turtles and provide habitats for the fish. The most common types of seagrasses are Halophila and Halodule. 

The reefs are vital to the survival of several endangered species, so much so that in 2004, the Great Barrier Reef Marine Park Authority (GBRMPA) increased the amount of highly protected zones by almost 30 percent.

How the reef formed

The Great Barrier Reef is about 500,000 years old, but it hasn't always looked as it does today. Reefs on Australia's continental shelf have taken on many forms, depending on the sea level, and the current formation is about 6,000 to 8,000 years old.

According to the Australian Institute of Marine Science and other scientific research, the current reef began to form during the Last Glacial Maximum. This period, which occurred from about 26,500 years ago to 19,000 to 20,000 years ago, ushered in significant environmental changes in the region, including a dramatic drop in sea levels.

The land that forms the base of the Great Barrier Reef is the remains of the sediments of the Great Dividing Range, Australia's largest mountain range. About 13,000 years ago, the sea level was 200 feet (61 meters) lower than the current level, and corals began to grow around the hills of the coastal plain, which had become continental islands. The sea level continued to rise during a warming period as glaciers melted. Most of the continental islands were submerged, and the coral remained to form the reefs and cays (low-elevation sandy islands) of today.

Variety of reefs

The Great Barrier Reef World Heritage Area is divided into 30 bioregions that consist of different types of reefs.

Cresentic reefs — shaped like crescents as the name implies — are the most common shape of reef in the middle of the system. These types of reefs are found surrounding Lizard Island as well as far north of the Great Barrier Reef Marine Park and in the Swain Reefs.

Flat reefs known as planar reefs are found in the northern and southern parts, near Cape York Peninsula, Princess Charlotte Bay and Cairns.

The northern part of the Great Barrier Reef features ribbon reefs, which are narrow and winding, and deltaic reefs, which, as the name implies, resemble river deltas.

Fringing reefs, which attach to the mainland, are infrequent. Most occur in the southern part of the Great Barrier Reef and are attached to high islands such as the Whitsunday Islands.

Lagoonal reefs are found in the southern Great Barrier Reef, and further north, off the coast of Princess Charlotte Bay. [Image Gallery: Great Barrier Reef Through Time]

Environmental concerns

A tourism hotspot, approximately 2 million people visit the Great Barrier Reef every year, according to the Australian government. There is widespread concern that such intense tourism might be harming the fragile reefs.

Pollution is another concern, as another oil spill occurred in 2010, when the Chinese coal-carrying ship Shen Neng1 ran aground on the reef, leaking a 1.86-mile-long (3 km) ribbon of oil and destroying precious coral and marine life.

Declining water quality is a major factor in the pollution of the Great Barrier Reef. During tropical floods, runoff containing fertilizer and pesticides is dispensed into the reef's waters and harms its delicately balanced ecosystem. The runoff problem is made worse by the loss of coastal wetlands along the Queensland coast, which act as a natural filter for toxins. The area of wetlands in the Great Barrier Reef catchment has decreased by over 50 percent, according to the Great Barrier Reef Coastal Wetlands Protection Program.

— Kim Ann Zimmermann, LiveScience Contributor

The Great Barrier Reef's amazing diversity of life gets a helping hand from distant underwater volcanic eruptions, a new study has found.

Submarine volcanoes can spit out trillions of pieces of floating rock upon which corals and other organisms hitch a ride to the world's largest reef, where they can thrive and multiply, according to research published this month in the journal PLoS One.

Study co-author Scott Bryan, a researcher at Queensland University of Technology in Brisbane, Australia, said these types of eruptions are rather frequent, occurring about once a decade or more, and helped form the reef in the first place, bringing in potentially billions of plants and animals.

The rock regatta

Shortly after the 2006 eruption of an underwater volcano near the Pacific island of Tonga, researchers found a wide variety of organisms hitching a ride on volcanic pumice, Bryan told OurAmazingPlanet. The volcano spit out many large chunks of pumice that initially covered 179 square miles (440 square kilometers) of ocean, but eventually  fragmented into at least 10 trillion small pieces, the largest being about 10 inches (25 centimeters) in diameter. [Images: A Trip to the Coral Triangle]

Almost all of these chunks, or clasts, had some sort of organism on them, Bryan said.

The floating rocks traveled more than 3,000 miles (5,000 km) over the next eight months, picking up more than 80 species of corals, anemones, barnacles, mollusks and crabs before ending up in the Great Barrier Reef and the coast of Australia, Bryan said.

The rock regatta picked up corals and other reef-building species while passing near reefs near Fiji, Vanuatu and elsewhere in the western Pacific along the journey, Bryan said.

"We have a diverse group of species present on the pumice in extremely high numbers, which means they are likely to succeed in colonizing a new environment," Bryan said.

Billions and billions of colonizers

Once on the reef, animals like crabs and mollusks can easily drop off into their new home. Corals can colonize the area if the pumice sinks to the bottom, or the coral may reach maturity while floating and release larvae into the reef.

"These things can grow on the pumice until they're ready to reproduce," said Judith Winston, a marine biologist at the Virginia Museum of Natural History, who wasn't involved in the study. "It's like a boatload of people landing on a desert island as opposed to one person."

This is the first "natural experiment" in which a huge raft of pumice has been followed over time until it started to wash up on the beaches, Winston said. The other research on pumice is mostly anecdotal and took place after pumice had already arrived somewhere, she said.

Life raft

Pumice rafting is an important way that life gets around. "It hasn't been considered nearly as important in spreading marine animals as it probably is, and probably has been," Winston said.

And since pumice rafts have likely been around since life itself, it's shaped the ocean and the world as we know it, said Martin Thiel, a researcher at Catholic University of the North in Chile who wasn't involved in the study. 

This influx of diversity into the reef likely helped originally build the reef, and may help replenish areas destroyed by human activity or hurricanes, Bryan said. Pumice rafting is a faster method of colonizing than the slow, step-by-step process previously assumed to predominate, in which coral larvae swim out from one reef into a nearby area, he said.

With pumice rafting, "You're basically colonizing the whole area instantaneously, as opposed to step by step," Bryan said.

The process could also bring in detrimental reef species, although this isn't likely to be an enormous threat since pumice rafting is a natural process that has been going on for a long time, Bryan said. 

Reach Douglas Main at dmain@techmedianetwork.com. Follow him on Twitter @Douglas_Main. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

Updated Friday, June 15 at 8:10 a.m. ET.

Scientists diving in the North Pacific were jarred when they heard mysterious sounds like spear guns being fired. The jolting noises turned out to be never-before-seen (or heard) head-butting bouts between some of the largest coral-reef fish, called parrotfish.

As they studied groups of the giant bumphead parrotfish (Bolbometopon muricatum), which can reach 4 feet (1.3 meters) long and 100 pounds (46 kg), the researchers were able to document the violent behavior with video and images.

The reef fish are named for their bulbous foreheads, which add to their eccentric, pouty lips and yellowish-to-pink faces. [See Photos of Head-Butting Fish]

"To us, it sounded like someone was firing a spear gun off close to our ears. Before we saw the behavior, we actually joked that the bumpbheads were head-butting like bighorn sheep," study researcher Roldan Muñoz, of the National Marine Fisheries Service, Beaufort Laboratory, in North Carolina, told LiveScience. "We were blown away when we actually witnessed the behavior."

During the summer of 2011, during about 100 hours of snorkel and scuba dives, the researchers witnessed several instances of the head-butting rituals off Wake Atoll. The male parrotfish swam head-on toward each other until they delivered their blow, head-bump to head-bump, a collision that is painful even to watch. Immediately after the head-on crash, the opposing parrotfish swam rapidly in a semicircle, trying to bite the back and flank of each other. [Video of bizarre head-butting parrotfish]

"Following circling, fish swam apart in opposite directions and then turned again face to face to initiate additional collisions," the researchers write this week in the open-access journal PLoS ONE.

Observations of the rowdy rituals revealed that most occurred on the days and in the locations of spawning.

As such, the researchers suspect sexual selection can explain the emergence of the so-called ossified ridge, or bump, atop the male parrotfish's head, along with the butting behavior. Sexual selection would favor the development of the hump and head-butting behavior if this trait and behavior increased a male's chances of successfully competing with other males, and ultimately mating with females.

"We believe that bumphead males head-butt to establish dominance and access to preferred territory that is then used to advertise to females that the males are available for mating," Muñoz said. In fact, in videos of the violent display, the male that wins the butting bout hovers over a particular spot, maintaining his place in the water column to await the females.

"No one has ever heard of any species of marine fish head-butting until now," Muñoz said.

But how could such boisterous behavior go unnoticed for so long?

Researchers have some thoughts on that. Since the behavior is the result of competition between males for access to the gals, it is likely to occur only in high-density populations of the fish. Many of the populations have dwindled and so would be unlikely to support the behavior.

The perfect spot for head-butting? The Great Barrier Reef, which holds the healthiest bumphead populations along its outer reefs.

"But one would have to be at the outer reef early in the morning, specifically trying to observe reproductive behavior, in order to have a chance of observing head-butting — and this is no small feat given the distance from shore of the outer reefs," Muñozsaid.

"At Wake Atoll, the outer reef is very close to shore, so we were easily able to put ourselves in the right place at the right time. But we were absolutely surprised."

The researchers plan to return to Wake Atoll to learn more about the bumphead population's mating behaviors.

Editor's Note: This article was updated to clarify a statement about sexual selection.

Follow LiveScience on Twitter @livescience. We're also on Facebook & Google+.

Things That Go Bump

While diving off Wake Atoll in the North Pacific, researchers discovered a bizarre head-butting behavior in the bumphead parrotfish that live there. The violent collisions occurred at spawning grounds. Shown here, a partial spawning aggregation of of the bumphead parrotfish consisting of 246 individuals.

Who's In Charge?

The second head-butt, shown here, between two male bumphead parrotfish. The butting makes such a loud sound that at first the researchers thought it sounded like a spear gun.

You Win

Here, following the fourth charge, the subordinate male (right) capitulates, rapidly fleeing the area with use of the caudal fin.

Bumpy Head

The dominant male, showing scale damage on back and side, is shown here following the head-butting bout. The giant bumphead parrotfish (Bolbometopon muricatum), which can reach 4 feet (1.3 meters) long and 100 pounds (46 kg), is named for its bulbous foreheads (shown here); its eccentric look gets a boost from the pouty lips and yellowish-to-pink face.

Different Foreheads

A female Bolbometopon (lower fish) and male (upper), illustrating the differences between the sexes in forehead and size; the female's forehead slopes caudal to the beak, but is nearly parallel with the beak in males. Males are also typically larger than females.

Sexual Selection

Here, a closer look at the male parrotfish's ossified bump atop its head. The researchers suspect sexual selection played a role in the development of the bump and the head-butting behavior it allows.

Wake Atoll

The researchers conducted surveys on a biennial basis by the NOAA Coral Reef Ecosystem Division. Circles indicate the total number of fish observed at each location around Wake Atoll in the North Pacific Ocean.

The photo says it all: an alien-looking shark, adorned with mossy hairs and a flat face, with its mouth agape and a slender bamboo shark headfirst inside. Though not unusual for a shark to snack on another shark, it's not typical behavior — and it's certainly not common for humans to catch the action firsthand.

In fact, the researchers who came upon the shark-eat-shark scene on the fringes of Great Keppel Island on the southern Great Barrier Reef didn't realize at first what they were looking at.

"The white bamboo shark appeared first, and as we came closer, we suddenly realized that its head was not hidden under a ledge, as is usual, but in the mouth of the very well-camouflaged wobbegong," Daniela Ceccarelli of Australian Research Council Centre of Excellence (ARC) for Coral Reef Studies, told LiveScience, adding that "witnessing predation events like this is very rare."

Ceccarelli and David Williams, also of ARC, were conducting a fish census there on Aug. 1, 2011, when they spotted the sharks.

The eater in this party was a tasselled wobbegong shark (Eucrossorhinus dasypogon) more than 4 feet long (1.3 meter); the wobbegong's prey was a 3.2-foot-long (1 m) brown-banded bamboo shark (Chiloscyllium punctatum). Like other wobbegong species, this one is an ambush predator, lying in wait on the seabed and then attacking prey at high speed.

"It's not unusual for them to prey on other sharks, especially small sharks such as the bamboo shark, as they forage for invertebrates on the seabed," Ceccarelli said.

They watched the sharks for about 30 minutes, with neither shark moving during that stint. The wobbegong didn't further ingest the bamboo shark, the researchers note in a brief article published online Feb. 4 in the journal Coral Reefs. "We didn't observe the end of the predation event, but as the bamboo shark was most definitely dead, we assume that the wobbegong eventually consumed it," Ceccarelli said. The meal would likely have taken at least several more hours, the researchers point out in their paper.

Wobbegongs also have jaws that can dislocate, a large gape and sharp, rearward-pointing teeth, allowing them to grasp relatively large prey before swallowing it whole, the researchers noted.

Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

The Great Barrier Reef, like most other coral reefs around the world's oceans, is under threat from a number of sources, from the steadily acidifying waters of the sea to the impact of commercial fishing. But a new effort to collect samples from the reef has established the first frozen repository of Great Barrier Reef corals that could one day be used to restore coral populations.

Coral reefs are dynamic ecosystems made up of coral polyps, the hard skeletons they live in, the symbiotic algae that feed them and the myriad fish and other plants and animals that support and are supported by the corals.

Corals are under severe pressure due to pollution from industrial waste, sewage, chemicals, oil spills, fertilizer, runoff and sedimentation from land; climate change; acidification; and destructive fishing practices. Some marine scientists think that coral reefs and the marine creatures that rely on them may die off within the next 50-to-100 years, causing the first global extinction of a worldwide ecosystem since prehistoric times.

Collecting coral

A team of researchers spent two weeks at the end of November collecting sperm and embryonic cells during spawning from two species of coral that live in the Great Barrier Reef, to create a freezer bank of these valuable organisms.

"It turns out we can produce significant numbers of developing larvae using the thawed sperm and that those larvae actually settle," said Mary Hagedorn, a marine biologist at the Smithsonian Conservation Biology Institute.

Coral settling is the process in which a free-swimming, bowling pin-shaped coral larva metamorphoses into a single polyp baby coral.

"This is a huge milestone for us because if the larvae couldn't metamorphose and settle, we wouldn’t be able to successfully use the bank for conservation efforts, which is the driving force behind this important research," Hagedorn said.

Hagedorn has already successfully applied this technology to reefs in the Caribbean and Hawaii.

Coral in the bank

The new frozen bank includes samples of two reef-building species of coral, Acropora tenuis and A. millepora, from the Great Barrier Reef, which now reside in long-term storage at the Taronga Western Plains Zoo in Dubbo, Australia. [Images: Expedition to Great Barrier Reef]

Though they remain alive, the banked cells are in a stasis and researchers can thaw the frozen material in one, 50 or, in theory, even 1,000 years from now. The samples, if handled properly, could be placed back into ecosystems to keep the gene pool diverse, which serves to keep populations health and viable.

While scientists have successfully used frozen sperm from coral to fertilize fresh coral eggs, their next focus is on developing techniques to use frozen coral embryonic cells to help restore coral populations. In January, Hagedorn and her collaborators will focus on culturing frozen embryonic cells to see how long they can live.

"Right now there are no tools to help address some of the diseases most devastating to the reef," Hagedorn said. "If we can grow embryonic cells and keep them alive, this technology could be important in battling those coral diseases."

"The Sea in many places is here cover'd with a kind of a brown scum, such as Sailors generally call spawn; upon our first seeing it, it alarm'd us, thinking we were among Shoals, but we found the same depth of Water were it was as in other places."

Sailing through the Coral Sea outside the Great Barrier Reef , Captain James Cook made those observations on Aug. 28, 1770. His journals contain the first mention of the long brown filaments of cyanobacteria that are common along the Australian coast.

On Aug. 9, 2011, the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite captured this view of a similar band of brown between the Great Barrier Reef and the Queensland shore. Though it's impossible to identify the species from satellite imagery, such red-brown streamers are usually trichodesmium. Sailors have long called these brown streamers "sea sawdust."

Trichodesmium, a form of cyanobacteria, are small, usually single-celled organisms that grow in the ocean and produce food through photosynthesis like plants. They play an important role in Earth's oceans because they convert nitrogen gas from the atmosphere to ammonia, a fertilizer that plants can use to grow. At the same time, trichodesmium removes carbon dioxide from the atmosphere. Their blooms often occur in warm, nutrient-poor waters. Charles Darwin observed one such bloom from the HMS Beagle in 1832, marveling that "their numbers must be infinite."

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• Ocean in Bloom Around New Zealand

Although Australia's massive Great Barrier Reef is home to a dazzling array of marine life, its smaller and more remote regions are less crowded and less diverse. A new study from the Australian Institute of Marine Science (AIMS) and Australia's University of Adelaide reveals this kind of small-town living is dangerous for the local fish populations.

Professor Corey Bradshaw, director of Ecological Modeling at the University of Adelaide, said the first problem is that far-flung reefs, like many along the 1,600-mile (2,600-kilometer) stretch of the Great Barrier Reef, are less likely to receive visitors. In the fish world, immigration is key.

"We even have a name for it—the 'Rescue Effect,'" Bradshaw told OurAmazingPlanet. "If you're isolated you're less likely to have a fish find you, because you're far away."

Low immigration means the population stays small, which leaves it vulnerable to random events.

"If they get hit by something — let's say there's a bleaching event and all the coral dies, and then a cyclone hits — if there's a small population, it's far more likely to be wiped out," Bradshaw said.

In addition, low immigration means a lack of diversity, which itself poses a real threat to survival. Bradshaw likened a reef's rich mix of species to a healthy investment portfolio; the safest bet is to maintain a variety of stocks.

"A diverse system with lots of species keeps the overall system from collapsing," he said.

This new research has far-reaching implications for reefs facing crisis because of climate change.

"Our research suggests that conservation resources might be better allocated to the protection of large, connected habitats," said Dr. Camille Mellin, a Postdoctoral fellow from AIMS and the University of Adelaide's Environment Institute, and leader of the project.

The study's authors, using data collected over the last 15 years, produced a mapping tool that can be used for reefs all over the world. An "index of susceptibility," as Bradshaw called it, the map allows researchers to perform triage on the reefs, and predict which might stay alive.

"It's cutting your losses," Bradshaw said. "If we're going to lose reefs anyway, the ones we should be trying to protect are the reefs that are most likely to survive."

• Images: Incredible Coral
• Worlds Apart: A Cautionary Tale of Two Coral Atolls
• One of World's Most Pristine Coral Reefs Revealed

This article was provided by OurAmazingPlanet, a sister site to LiveScience.

Four newly identified worm species, including one that sports an unusual green color, have been found wriggling in the sands of the Great Barrier Reef.

The layer of sand that covers the floors of the Earth's oceans is actually home to a large diversity of marine organisms. Enterprising animals can take advantage of the water-filled spaces between sand grains.

The newfound creepy crawlies are members of the genus Grania, a group of worms found in marine sands throughout the world, from the tidal shore down to the deep ocean. Worms that belong to Grania, part of the class of annelid worms Clitellata, are typically about 0.8 inches long (2 centimeters) and mostly white in color.

Zoologist Pierre De Wit, of the University of Gothenburg in Sweden, found the four worm species while sieving samples of sand collected from Australia's Great Barrier Reef. One of the four, dubbed Grania colorata, is green, instead of the usual white.

"These worms are usually colorless or white, and we have not been able to work out why this particular species is green," De Wit said.

De Wit also found a previously unknown member of the Grania family in Scandinavia. The species, Grania occulta, was thought to be part of a known Grania species, but DNA analyses suggested otherwise.

"Species that were previously regarded as the same may prove to have a completely different function in the ecosystem, and have different tolerance of environmental toxins, for example. It is obviously important to know this in order to be able to take the right action to protect our fauna," De Wit said.

There are currently 71 species that have been described in the Grania genus. The new species are described in De Wit's Ph.D. thesis.

• Lowly Worms Wiggle With Style
• Images: Rich Life Under the Sea
• Worm Images and Information

Coral disease outbreaks have struck the healthiest sections of Australia’s Great Barrier Reef, and a new study has conclusively linked disease severity to ocean temperature and climate change for the first time.

“With this study, speculation about the impacts of global warming on the spread of infectious disease among susceptible marine species has been brought to an end,” said Don Rice, director of the National Science Foundation’s Chemical Oceanography Program, which helped fund the research.

The study tracked an infection called white syndrome in the Great Barrier Reef, the largest coral reef system in the world.

Coral colonies live atop limestone scaffolding, which is built from the secretions of the coral creatures called polyps. The vivid colors of the coral come from the symbiotic algae that live in the polyps and supply them with much of their nutrients.

When disease or stressful environmental conditions, such as changes in ocean temperature, strike the reef, the polyps expel their algae, making them appear pale.

Corals are critical to the survival of some commercial marine species and help buffer low-lying coastal areas.

“More diseases are infecting more coral species every year, leading to the global loss of reef-building corals and the decline of other important species dependent on the reefs,” said study lead author John Bruno of the University of North Carolina.

The stressful rise in ocean temperatures due to global warming, coupled with the close living quarters of corals may make it easy for infection to spread, according to the study published in the May 1 online issue of the journal PLoS Biology.

“We’ve long suspected that climate change is driving disease outbreaks,” Bruno said. “Our results suggest that warmer temperatures are increasing the severity of disease in the ocean.”

• Top 10 Surprising Results of Global Warming
• Coral Reef Damage Rising Worldwide
• Image: Stressed-Out Coral Reefs

Coral reefs in the central and western Pacific are disappearing twice as fast as rainforests are on land—faster than was previously thought, a new study says.

The reefs in this region, called the Indo-Pacific, are disappearing at a rate of 1 percent per year—nearly 600 square miles of reef have disappeared per year since the late 1960s, researchers found.

"We have already lost half of the world's reef-building corals," said study team leader John Bruno of the University of North Carolina at Chapel Hill.

The Indo-Pacific contains 75 percent of the world's coral reefs, including Australia's Great Barrier Reef, the largest single structure built by living organisms (it can be seen from space), and has the highest coral diversity in the world.

Bruno and his colleagues compiled and analyzed a database of 6,000 quantitative surveys of reefs performed between 1968 and 2004 on more than 2,600 Indo-Pacific coral reefs.

The surveys tallied coral cover, which is a measure of the density of living corals in a specific part of the ocean floor. Bruno's study found that coral cover had decreased from 40 percent in the early 1980s to about 20 percent in 2003.

The pattern of loss across the entire study area indicates that coral loss is a global phenomenon, likely brought on by large-scale stressors such as climate change, coral disease, predators, nutrient pollution and overfishing.

While reefs cover less than 1 percent of the ocean globally, they are an integral part of coastal communities because of their high biodiversity and the economic benefits they provide in tourism and protection of coastal land from storms.

"Indo-Pacific reefs have played an important economic and cultural role in the region for hundreds of years and their continued decline could mean the loss of millions of dollars in fisheries and tourism," said co-author Elizabeth Selig, a UNC graduate student. "It's like when everything in the forest is gone except for little twigs, a few lone trees."

Surprisingly, coral cover was similar in highly protected reefs and unprotected reefs, which Bruno says has implications for coral conservation and the improvement of protection measures, which apparently are not working well enough.

"We can do a far better job of developing technologies and implementing smart policies that will offset climate change," Bruno said. "We can also work on mitigating the effects of other stressors to corals including nutrient pollution and destructive fishing practices."

The study is detailed in the Aug. 8 edition of the online journal PLoS One.

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• Images: Incredible Coral