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.”