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  BBC 6 Jan 05
Marine reserves 'good' for reefs
By Helen Briggs BBC News science reporter

EurekAlert 5 Jan 06
How marine reserves are giving coral reefs a helping hand

National Geographic 5 Jan 06
Predator Fish Help Coral Reefs Rebound, Study Shows
John Roach for National Geographic News

The return of a top predator in a Bahamas marine reserve is proving unexpectedly beneficial to coral reefs there, according to a new study.

The finding is a relief to scientists, who were concerned that the reserve's population of predatory Nassau grouper would swell at the expense of the already vulnerable reefs, which are quickly disappearing due to disease, hurricanes, and warming oceans.

"Actually there really is no cause for concern," said Peter Mumby, a marine biologist at the University of Exeter in England and lead author of the study. Mumby and his colleagues conducted the study in the Bahamas' Exuma Cays Land and Sea Park, which was established in 1959 and closed to fishing in 1986.

They found that while the reserve has allowed Nassau grouper to flourish, large species of parrotfish have thrived as well. This discovery surprised scientists, because parrotfish are prey for the Nassau grouper.

Parrotfish are also crucial to the health of coral reefs, because they are one of the few creatures that graze on seaweed. Left uneaten, the seaweed suffocates the corals and prevents reef growth.

The research is reported in tomorrow's issue of the journal Science.

Complex Interaction

Mumby's team feared that larger numbers of grouper in the reserve would cause the parrotfish population there to crash, to the detriment of the reef.

"The reserves are working very well for the predators," said Dan Brumbaugh, a senior conservation scientist with the American Museum of Natural History in New York and a study co-author. In fact the researchers found twice as many parrotfish predators--mostly Nassau grouper--inside the park as they did outside it.

"Despite that, we're not getting the negative impact on the grazers, which are so important to keep the [seaweed] in check," Brumbaugh added.

Mumby and his colleagues found that larger parrotfish, which are vulnerable to fishing outside the reserve, have thrived in the protected area along with the grouper.

The researchers also found that large parrotfish escape predation by grouper, because they are too big for the predators to eat. Once parrotfish reach a length of about 11 inches (28 centimeters), they become too big for even the largest grouper to swallow, the scientists explained.

So while the grouper preyed more on smaller parrotfish species, populations of larger parrotfish have grown. And these big parrotfish eat the most seaweed.

As a result, the researchers found that grazing within the reserve has doubled, which corresponds to a fourfold reduction in seaweed cover compared to outside the reserve.

"Those are the conditions necessary to help corals return to the reef and grow free of competition from [seaweed]," Mumby said.

In an accompanying article Ove Hoegh-Guldberg, a marine scientist at the University of Queensland in Australia, writes that the findings "illustrate some of the complexity of how marine protected areas might influence coral reef ecosystems."

Vulnerable Corals

Mumby and his colleagues were initially concerned about a potential decline in parrotfish numbers in the reserve, because a mysterious disease wiped out a species of sea urchin there in 1983.

The sea urchins were the only other species known to eat the seaweed that grows on the coral reefs. Without either the sea urchins or the parrotfish, the coral would almost certainly suffer.

For coral reefs to grow, larval coral must settle on dead coral or rock, Mumby explained. "The first thing a lot of seaweed does is reduce the amount of space corals have to settle on, and even if they do settle, they can be overgrown by [seaweed]," he said.

Worried that further stress on the reefs could prove devastating, Mumby and his colleagues were skeptical at first that marine reserves could protect reefs.

Now, armed with this new research, Mumby and his colleagues are ready to further investigate how protected areas can help save the world's fast-disappearing reefs.

"The use of reserves to protect fish stock is totally compatible with using them to protect corals," he said.

EurekAlert 5 Jan 06
How marine reserves are giving coral reefs a helping hand

It may be no surprise that marine reserves protect the fish that live in them, but now scientists from the University of Exeter have shown for the first time that they could also help improve the health of coral reefs.

In a paper in the prestigious journal Science, Dr Peter Mumby and colleagues looked at how a marine park in the Bahamas was affected by the return of the reef's top predator, the Nassau Grouper.

Researchers were concerned that an increase in groupers could have an adverse effect, because they feed on parrotfish which play a vital role in maintaining the reef ecosystem. Dr Peter Mumby, from the School of Biosciences at the University of Exeter, said:

"While an increasing number of larger predators is essentially good news we had concerns that this might result in a decrease in the numbers of parrotfish, which could ultimately damage the health of the reef. More than 20 years ago sea urchins in the Caribbean were wiped out by disease, leaving parrotfish as the main grazer of reef surfaces. The fish use their teeth to remove seaweed from the reef which allows new corals to settle and grow.This grazing process is essential to the health of the system."

"Caribbean reefs are still trying to recover from the devastating effects of an El Nino bleaching event in 1998 which caused widespread damage to coral around the world. What we have found is that marine reserves might provide exactly the right conditions to allow this to happen. Interestingly, once parrotfish reach a length of around 28 cm, they become too big for even the largest grouper to swallow. This 'escape' from a risk of predation means that most reserves are unlikely to reduce the amount of grazing even after the number of predators rises."

Peter added, "Diving in the Exuma Cays Land and Sea Park was fun because a large number of sharks turned up to watch us work. Sharks have been heavily fished on most coral reefs so it's always a thrill to visit one of their sanctuaries."

BBC 6 Jan 05
Marine reserves 'good' for reefs
By Helen Briggs BBC News science reporter

Marine reserves give a boost to coral reefs as well as fish stocks, new research shows.

Scientists had been concerned that large fish returning to protected areas of the Caribbean could disturb the delicate balance of reefs. They feared that larger predators would eat the smaller fish which graze on coral and keep down harmful algae.

But a study published in the journal Science found that coral in a marine reserve in the Bahamas is flourishing.

Rather than eating all the parrotfishes - the main creatures that clean up the reef - the returning predators, such as the Nassau grouper, only eat the smaller species. Parrotfish bigger than about 25 cm (10 inches) long are able to escape the predators' jaws, and do a more efficient job at removing algae from coral, stopping it from being smothered.

This is critical for Caribbean reefs, which were hit by the mass death of sea urchins, the main creatures to feed on the algae, in 1983, due to disease.

No-fishing zone

Parrotfish have become the dominant grazers on most Caribbean reefs but numbers have dwindled in areas where fishing is allowed. This had led to concerns about their fate in marine reserves, which focus on restoring habitat for large predators at the top of the food chain.

"The answer quite clearly is that this is not going to be a problem," said Peter Mumby of Exeter University in the south of England, who led the study.

He said marine reserves have a very beneficial effect for coral and will help reefs withstand the impact of climate change, coral bleaching and other threats. "This is the first time that anyone has shown that allowing a reserve to be successful in allowing fish to recover can reduce the amount of seaweed on the reef, which (in turn) increases the ability of coral to recover from things like hurricanes, tsunami and coral bleaching," Dr Mumby told the BBC News website.

The study looked at the Exuma Cays Land and Sea Park, which lies near the centre of the Bahamas archipelago. It was established in 1959, and has been a no-fishing zone for 20 years.
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