Great Barrier Reef 'overrun by weeds'

Nicole Butler, ABC 5 Jan 10;

It is one of the natural wonders of the world but the Great Barrier Reef is almost constantly at risk.

Scientists say farming chemical run-off is threatening the Reef, which is also battling climate change, coral bleaching and the crown of thorns starfish.

Now experts at the Australian Research Council (ARC) say around 43 per cent of the inshore reef is being overrun by seaweed, a claim hotly disputed by local tourism operators.

James Cook University marine biology Professor David Bellwood, who is also an ARC expert, says a shift from a coral-dominated reef to one overrun by weed shows the health of the ecosystem is in decline.

"What we can say is at the moment there is a lot more weed than we expected and that this weed does constitute a potential threat," he said.

"It certainly rings a few warning bells, the biggest implication is whether this weed starts to expand.

"So we need to know its history and that's what we're currently trying to find out. Does this constitute a change? Because if it is a change then it is very worrying."

Professor Bellwood warns if the weed is taking hold it is a difficult condition to reverse.

"There is always going to be some algae on the reef, it's just what makes it spread and that's what we're trying to understand - why is there so much weed on inshore reefs and what are the primary factors driving it?" he said.

"The main indication is that it's the fish that determine the distribution of the weed. If you've got lots of fishes eating the weed, the weed doesn't spread."

Professor Bellwood says it is critical to protect browsing and grazing fishes and he has written to the Federal Government urging it to develop a national policy.

"We've got to protect our herbivorous fishes - that's the only thing that is clear at this point in time that we can do that is a step towards protecting the reef," he said.

"And the other thing is, even though the weed is out there, it doesn't mean to say the reef is rotting, what it means is things are different, it's still a beautiful place and if people get a chance they should go out and look at it."

'A load of rubbish'

But the Research Council's report has raised the ire of tourism operators who rely on the reef for their livelihoods.

The sector normally supports most conservation measures but this time it has dismissed the study as a load of rubbish.

Col McKenzie, head of the Association of Marine Park Tourism Operators in far north Queensland, says the findings are inaccurate.

"For a scientist to come out and say that 40 per cent of the reef has been taken over by seaweed, I just think that he needs to rethink where his control sites are," he said.

"He might have one or two reefs somewhere. For him to pick on those two reefs and say that's indicative of the whole Great Barrier Reef which is 2,500 kilometres long is just absolutely ludicrous."

Mr McKenzie says the ARC are exaggerating the figures and using "scare tactics" to try to step up protection of the reef.

"The scientists tend to think that if they can show dramatic results, or say that this is going to be a really negative thing ... they can get more research money," he said.

"I think over a period of time it desensitises the Australian population and it presents a message that look, this is buggered and we're not going to be able to fix it, and so why should we continue to spend all the money and time and effort doing so?

"The reality is, the reef is not that far gone, we can save the Great Barrier Reef, we've just got to get the water quality right."

Seaweeds take over reefs
ARC Centre of Excellence for Coral Reef Studies
Science Alert 6 Jan 10;

A new scientific study has found that seaweeds have claimed large areas of the coastal shelf of Australia’s Great Barrier Reef (GBR).

Part of a global effort to record and understand changes in coral reefs worldwide, the study has found that more than 40 per cent of inshore reefs on the GBR are dominated by seaweeds (macroalgae) – but that the mid-shelf and outer reefs are virtually free of weed.

“The Great Barrier Reef is widely regarded as the world’s most intact large reef system – and that’s the way we aim to keep it,” says Professor Dave Bellwood of the ARC Centre of Excellence for Coral Reef Studies and James Cook University. “As part of that goal, it is important to study what makes up the reef, in order to monitor any changes that may occur and understand what is causing them.”

Worldwide, many scientists consider that a shift from coral-dominated reefs to weed-dominated reefs signals a decline in the health of coral ecosystems – and is exceptionally difficult to reverse. Much therefore depends on keeping coral-dominated reefs in as weed-free a condition as possible, Prof. Bellwood suggests.

“We carried out two major censuses in the northern and central regions, sampling reefs close to the shore, in the mid GBR lagoon, and on the outer GBR, in which we swam more than 500 10-metre transects, taking careful note of the reef composition.

Seaweed cover was greatest on inner-shelf reefs – around 43 per cent per cent were dominated by weeds – and decreased markedly to around 4 per cent on mid-shelf and outer-shelf reefs in both regions of the GBR.

“We got quite a shock when we saw how much of the inner reefs were dominated by weed,” Prof Bellwood – who has dived the GBR for several decades – admits. “Forty-three per cent is a surprisingly big number – but it is their natural state or not? There is a lack of historical data to tell us for sure. It needs close scrutiny to find out.”

He called on Australians who may have been photographing inshore reefs since the 1950s to provide whatever pictorial evidence they may have of weed and coral cover, provided the photos are clearly dated and the location they were taken is known. This may help scientists establish whether the seaweed is on the increase or not.

As yet there is much to learn about what causes reefs to become dominated by algae, although nutrients from the land are one suspect and herbivorous fish are unquestionably an important factor in keeping weeds in check.

“In our survey the corals of the mid-shelf reefs were in much better condition – and one of the things we can clearly do is make sure they stay that way. It would be tragic if macroalgae started to spread on them,” he adds.

Key to this, Prof. Bellwood says, is maintaining strong populations of browsing and grazing fishes, like parrot, surgeon, rabbit and bat fish, which keep the weeds down by ‘mowing’ them and preventing them from getting a foothold. “There is overwhelming scientific evidence from Australia and round the world to show that herbivores are vital to the overall health of coral reefs,” he adds.

However Australia has no legislation to protect this vital group of fishes and their central role in helping to conserve the Great Barrier Reef.

Prof. Bellwood has written to the Rudd Government suggesting the need for a national policy – but has yet to receive a positive reply.

“This is a win-win politically, as well as for the environment,” he says. “Protecting Australia’s herbivorous fishes would offend few people – but would have major benefits in keeping our reefs clean and healthy and so supporting the $5 billion in activities that rely on them.”

Finally, Prof. Bellwood urges those diving the reef to visit the weedy inshore reefs: “They aren’t all coral, but they can be spectacularly beautiful in their own way, and you will see a mix of species inshore that you can see nowhere else. In my eyes they rival anything you can see in a dive on the outer barrier reef – yet they are so much easier to gain access to.”

For those who regularly dive the inshore reefs and take pictures, Prof Bellwood, urges them to keep careful records of date and place. “We really need to know whether or not these reefs are changing, and how fast. If anyone has records going back to the 1950s, that would be brilliant.”

Seaweed chokes Australia's Great Barrier Reef
Yahoo News 6 Jan 10;

SYDNEY (AFP) – Australian natural wonder the Great Barrier Reef is overgrown in places by seaweed in what could be a worrying indication of the health of the coral structure, scientists said on Wednesday.

Surveys of the World Heritage-listed reef, already at risk from global warming, found that more than 40 percent of areas closest to shore were dominated by green weed, Professor David Bellwood said.

"We knew there would be some weed there, we were just surprised how much," Bellwood, a marine biologist from James Cook University, told AFP.

"We are concerned about it because it does look like a lot of weed and in other places in the world, weed is an indication of decline."

Bellwood said the offshore reefs, those at least 20 kilometres (12.4 miles) from Australia's eastern coast, were largely untouched by the algae but that some of those closer to shore were choking with weed.

While the reason for the build-up of greenery was not known, Bellwood said he suspected it was because algae-eating fish have died out in those areas.

"The question is, does this mean the Barrier Reef is in real trouble? That the reef is rotting from the inside out? Or does it mean to say that that amount of weed is natural? And the answer is: it's hard to say," he said.

Bellwood, from the Centre of Excellence for Coral Reef Studies, said the best defence for the reef would be clean water and the existence of herbivorous fish which could graze on the weeds.

"The Great Barrier Reef is in the best condition of any reef in the world," he said.

"However, it is suffering. And it has suffered significant declines in coral cover in the last few years. The presence of that weed is just another little red light."

Scientists have already warned that the 345,000-square kilometre (133,000-square mile) attraction is in serious jeopardy as global warming and chemical runoff threaten to kill marine species and cause disease outbreaks.

Bellwood said the seaweed could be just the latest problem for the reef.

"It's just that when you combine run-off and fertiliser and pesticides and climate change and human interaction and coastal erosion and coastal development and fishing and overfishing... these things are all starting to accumulate," he said.

The reef is believed to have deteriorated significantly since European settlement in 1788, after enduring coral disease, toxic blue-green algae and infestation by pestilent species such as the crown-of-thorns starfish.