Stressed female corals become male

Chew Bakar SG

Emily Sohn

Discovery News

A new study has found that mushroom corals can switch from male to female and back again, the first to show that coral can change sex in either direction.

Understanding why and when some corals make the switch may eventually help scientists protect them from the stresses of a changing environment.

For now, the study remains a fascinating window into the biology and evolution of these corals.

"We know in detail the reproductive patterns of more than 500 coral species, but no one reported before on the fact that some coral species may change sex," says lead author professor Yossi Loya, a zoologist at Tel Aviv University.

"I believe this was quite a big surprise to all coral reef scientists."

Mushroom corals belong to a family called Fungiidae. They are solitary, mobile species that live throughout the Pacific and Indian Oceans.

Mushroom corals are abundant and diverse, but how they reproduce is something scientists haven't known much about.

To learn more, Loya and a colleague travelled to a patch reef near Okinawa, Japan. The reef is home to tens of thousands of mushroom corals, representing a dozen species.

In 2004, the researchers collected, weighed, measured, and tagged about 15 individuals from two species. Each coral then got its own aquarium in the lab.

That July, about five days after the full moon, the mushroom corals did what many corals do - simultaneously release sperm and eggs.

In the ocean, these gamete explosions produce larvae that drift off to become new corals. In the lab, the scientists collected the gametes and looked at them under a microscope. Then, they returned the corals to the sea.

Initial analyses showed that each coral produced either sperm or eggs. Some types of corals are hermaphroditic, with both male and female parts. But mushroom corals appeared to be just one or the other.

The researchers repeated the same experiment in 2006 and 2007 - with both the same individuals and new ones. The results grew increasingly surprising.

In 2006, about 25% of one species and 50% of the other had changed sex since they'd been tagged two years earlier.

In 2007, 80% of the corals had changed sex from the year before. A quarter of those had reverted back to the sex they had originally been in 2004.

The results appear in the journal Proceedings of the Royal Society B .

"They went back to their notebooks because they thought they had made a mistake," says Professor Robert van Woesik, a marine biologist at the Florida Institute of Technology.

"We never realised in our wildest dreams that these corals can undergo sex changes. This is really exciting."

When mushroom corals are small, it makes more sense to be male, says Loya, because it takes less energy to produce sperm than to produce eggs. When the corals reach some critical size, however, it's better to be female.

Loya says some plants do the same thing, making this study interesting from an evolutionary perspective. Corals may look plant-like, but they belong to the Animal Kingdom.

The transition from male to female seems to be a natural progression with growth, van Woesik adds.

But the fact that the corals sometimes switch back from female to male, might be a sign that they are in distress and need to conserve resources.

Ocean organisms face stress from a number of source, including pollution and climate change. If environmental pressures push too many mushroom corals towards maleness, a skewed sex ratio could threaten their future.

Stage SG

O.o

Chew Bakar SG

lol

Bangulzai SG

incest can happen

Chew Bakar SG

incest can happen

More like monosex.

Bangulzai SG

More like monosex.

the own cock and the own cheebai see each other simultaneously ar

Tbee SG

Woah amazing... LOLOL!

lianamaster SG

Interesting!

EarlNeo SG

so... does that mean male can take stress better?

Chew Bakar SG

so... does that mean male can take stress better?

Male make the female pressured?

lianamaster SG

Cannot everything blame the male...

Bangulzai SG

Wednesday, June 17, 2009

Banning or restricting the use of certain types of fishing gear could help the world's coral reefs and their fish populations survive the onslaughts of climate change according to a study by the ARC Centre of Excellence for Coral Reef Studies at James Cook University, the Wildlife Conservation Society, and other groups.

The international team of scientists has proposed that bans on fishing gear - like spear guns, fish traps, and beach seine nets – could aid in the recovery of reefs and fish populations hard hit by coral bleaching events.

Around the world corals have been dying at alarming rates, due to unusually warm water events resulting from global warming.

Research carried out in Kenya and Papua New Guinea has shown that certain types of gear are more damaging to corals, to coral-dependent fish and to the key species of fish that are needed to help reefs recover from bleaching or storm damage.

"This is creating a double jeopardy for both the corals and certain types of reef fish. They are already on the edge because of overfishing– and the additional impact caused by a bleaching can push them over" Dr Cinner explains. The result can be an accelerated decline of the reef, its fish populations – and their ability to sustain local people.

"From an ecological perspective, the best response to bleaching is to close reefs to fishing entirely. But that is not feasible everywhere and is a particularly hard sell among the impoverished fishers in developing countries" says co-author Dr. Tim McClanahan of the Wildlife Conservation Society. "In areas where fishery closures are impractical, managers don't have many options and haven't been able to do much but watch the reef die and often not recover."

"Selective gear restrictions offer reef managers and fishers alike some middle ground, reducing pressure on the reef and its fish while it is in the recovery phase, while also providing fishers with some options for their livelihood" Dr Cinner says. This middle way is also more likely to be taken up by fishers. "In other research we've found that fishers themselves prefer gear restrictions to total closures, because most fishers use several types of gear so they can still earn a living when the use of one sort of gear is banned. They are more likely to comply."

The team investigated the effects of five main types of gear on different types of fish: spear guns, traps, hook and line, beach seine nets and gill nets.

They found that spear guns were the most damaging of all – to corals themselves, to susceptible fish species and to the fish needed to help reefs recover, such as parrot, surgeon and trigger fish, which keep seaweeds and urchins in check while the coral re-grows.

"Spear guns target a high proportion of species that help maintain the resilience of coral reefs, but also can result in a surprising amount of damage to the corals themselves. When a fish is shot with a spear gun, it often hides in the reef, so some fishermen break the corals in their attempts to get it." Dr Cinner says.

But in developing countries, spear guns can be the fishing tool most used by the poorest fishers because they are cheap to make and the yield can be high, so they are an important source of income for poor fishers.

"You can't simply impose an arbitrary ban on their use – you need to consider issues like compensation, other fishing options, or alternative livelihoods for the affected fishers," says co-author Dr. Shaun Wilson of the Western Australian Department of Environment and Conservation. "One key issue may be educating fishers about the importance of reef habitat and the species that help to maintain reef quality – and the need to be selective in what they shoot. This would mean fishers could still use this cheap and effective fishing tool without necessarily damaging habitat and reef resilience."

Fish traps also targeted both the most susceptible reef fish and the ones most involved in reef recovery. Beach seine nets didn't target as many key fish species as gill nets, traps, or spear guns, but were damaging both to corals directly and took large amounts of juvenile fish.

"Where people really depend on reef resources, it may not be possible to permanently ban all of these types of gear. By creating temporary bans for specific types of gear following a coral bleaching event, reef managers could ease pressure on the reef and its fish population for a time when corals ecosystems are most sensitive without causing undue hardship to the human populations that depend on it." Dr Cinner says

"Of course, where the conditions are right, managers and fishers don't have to wait for a bleaching event- preventative gear bans are a good idea, particularly in areas that are highly susceptible to the impacts of bleaching," says co-author Dr Nick Graham. "And our new research provides managers with some ideas about the trade-offs involved in banning certain gear."

Dr Cinner says that temporary bans or imposing permanent restrictions on the use of various types of gear can apply to virtually any coral reef management – whether in the developing world or in developed countries such as on Australia's Great Barrier Reef.

"In principle, it can be used anywhere. It offers both communities and reef managers much greater flexibility. Around the world, communities are increasingly making their own decisions about how to protect their reefs and they could impose voluntary bans on certain gears.

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Wildlife Conservation Society

Thanks to Wildlife Conservation Society for this article.

Bangulzai SG

Reef boom beats doom

Thursday, April 23, 2009

Corals Bleaching

Coral Beds Dominated By Algae

Corals Restored In 2008

Marine scientists say they are astonished at the spectacular recovery of certain coral reefs in Australia's Great Barrier Reef Marine Park from a devastating coral bleaching event in 2006.

That year high sea temperatures caused massive and severe coral bleaching in the Keppel Islands, in the southern part of the GBR. The damaged reefs were quickly smothered by a single species of seaweed – an event that can spell the total loss of the corals.

However, a lucky combination of rare circumstances meant the reefs were able to achieve a spectacular recovery, with abundant corals re-established in a single year, says Dr Guillermo Diaz-Pulido, from the ARC Centre of Excellence for Coral Reef Studies (CoECRS) and the Centre for Marine Studies at The University of Queensland.

Dr Diaz-Pulido explains that the rapid recovery is due to an exceptional combination of previously-underestimated ecological mechanisms.

"Three factors were critical. The first was exceptionally high re-growth of fragments of surviving coral tissue. The second was an unusual seasonal dieback in the seaweeds, and the third was the presence of a highly competitive coral species, which was able to outgrow the seaweed.

"But this also all happened in the context of a well-protected marine area and moderately good water quality", said Dr Diaz-Pulido.

"It is rare to see reports of reefs that bounce back from mass coral bleaching or other human impacts in less than a decade or two," he adds

"The exceptional aspect was that corals recovered by rapidly regrowing from surviving tissue. Recovery of corals is usually thought to depend on sexual reproduction and the settlement and growth of new corals arriving from other reefs. This study demonstrates that for fast-growing coral species asexual reproduction is a vital component of reef resilience" says Dr Sophie Dove, also from CoECRS and The University of Queensland.

"Coral reefs globally are increasingly being damaged by mass bleaching and climate change, and their capacity to recovery from that damage is critical to their future," explains Prof. Ove Hoegh-Guldberg of CoECRS and The University of Queensland. "Our study suggests that managing local stresses that affect reefs such as overfishing and declining water quality can have a big influence on the trajectory of reefs under rapid global change."

"Clearly, we need to urgently deal with the problem of rising carbon dioxide in the atmosphere, but managing reefs to reduce the impact of local factors can buy important time while we do this," he says.

Understanding the different mechanisms of resilience is critical for reef management under climate change. "Diversity in processes may well be critical to the overall resilience and persistence of coral reef ecosystems globally," Dr Laurence McCook, from the Great Barrier Reef Marine Park Authority, says.

The research was partially funded by a Pew Fellowship in Marine Conservation awarded to Dr McCook, the Great Barrier Reef Marine Park Authority as well as the ARC Centre of Excellence program.

"This combination of circumstances provided a lucky escape for the coral reefs in Keppel Islands, but is also a clear warning for the Great Barrier Reef. As climate change and other human impacts intensify, we need to do everything we possibly can to protect the resilience of coral reefs," he adds.

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ARC Centre of Excellence in Coral Reef Studies

Thanks to ARC Centre of Excellence in Coral Reef Studies for this article.

Bangulzai SG

Tuesday, June 16, 2009

Emergency plans to counteract global warming by artificially shading the Earth from incoming sunlight might lower the planet's temperature a few degrees, but such "geoengineering" solutions would do little to stop the acidification of the world oceans that threatens coral reefs and other marine life, report the authors of a new study in the journal Geophysical Research Letters*. The culprit is atmospheric carbon dioxide, which even in a cooler globe will continue to be absorbed by seawater, creating acidic conditions.

"There would be a slight reduction in this problem, because land plants would be expected to be able to grow more vigorously in a high CO2, but cool world," says Ken Caldeira of the Carnegie Institution's Department of Global Ecology, a co-author of the study with lead author Damon Matthews of Concordia University, Canada, and Carnegie geochemist Long Cao. Land plants and soils would hold onto more carbon in this scenario, so less would find its way into the oceans. "However this expansion of the land biosphere, while it's a slight help to ocean acidification is not enough to make a big difference."

A widely-discussed proposal for countering warming with geoengineering involves injecting small, reflective particles into the upper atmosphere. This would partially block incoming sunlight before it reached the Earth's surface, lowering global temperatures just as volcanic ash from the Mount Pinatubo did following its eruption in 1991. But critics have warned that such a scheme might also alter rainfall patterns, damage the planet's ozone layer, or have other unexpected effects.

Until the current study, which used a computer model of the Earth's climate system and biosphere to simulate the effect of geoengineering on climate and the ocean's chemistry, the potential impact of such a scheme on ocean acidification had never been calculated. In the simulations, reduced sunlight cooled the planet as expected,,and it also slightly slowed the rise in atmospheric carbon dioxide, as more carbon was absorbed by natural sinks. But this slight change was not enough to significantly mitigate ocean acidification.

Ocean acidification rivals global warming as a threat to marine ecosystems, especially coral reefs, which need to be surrounded with mineral-saturated water in order to grow. Rising levels of carbon dioxide make seawater more acidic, leading to lower mineral saturation. Recent research has indicated that continued carbon dioxide emissions will cause coral reefs to begin dissolving within a few decades, putting the survival of these ecosystems at extreme risk.

Geoengineering's minimal effect on ocean acidification adds another factor to the debate over the advisability of intentionally tampering with the climate system. Some see geoengineering as a possibly necessary response to the prospect of devastating climate change caused by increased human emission of greenhouse gases. Others see it as reckless tinkering with the planet's complex and finely tuned climate system that could do more harm than good.

"Geoengineering approaches come with all sorts of risks," says Caldiera. "It is important we learn about the the full set of these risks and all of their implications." He considers deep cuts in human emissions of carbon dioxide to be the most effective safeguard against a global environmental crisis. "One of the good reasons to prefer CO2 emissions reductions over geoengineering is that CO2 emissions reductions will protect the oceans from the threat of ocean acidification, whereas these geoengineering options will not."

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Carnegie Institution

Thanks to Carnegie Institution for this article.

Chew Bakar SG

Too many conflicting articles, so doom or boom of corals?

Chew Bakar SG

Coral reef

Bangulzai SG

Too many conflicting articles, so doom or boom of corals?

it just means we have not have a clear understanding of nature as yet.

Chew Bakar SG

BenBenDeZhu SG

Will the char bor n ta por in sgf change sex when stressed?

BenBenDeZhu SG

Will the char bor n ta por in sgf change sex when stressed?