Great Barrier Reef tested for flood damage
Australian Geographic with AAP 19 Jan 11;
Authorities are monitoring for tell-tale signs of damage as muddy flood plumes smother 10% of the GBR.
TURBID FLOODWATERS FLOWING into the Great Barrier Reef (GBR) may cause an explosion in algal blooms and coral bleaching, authorities have warned.
The Fitzroy, Burnett and Thompson rivers have flushed floodwaters into the reef's inshore areas, particularly off the central Queensland coast near Rockhampton.
Though the reef runs for 2300 km down the coast of Queensland, research from James Cook University has revealed that the muddy plumes are already covering more than 10 per cent of its surface area.
The Great Barrier Reef Marine Park Authority (GBRMPA) is mapping the floodwaters and testing samples for pesticides, salinity, turbidity and temperature anomalies. So far the plumes are not affecting popular tourism locations in the Whitsundays, Cairns or Port Douglas, it says.
Immediate and long-term threats
The most immediate threat is from the freshwater itself which kills coral; nutrient- and pesticide-rich waters can also smother corals and encourage blooms of algae and other competitors.
The risk doesn't end when the floodwater stop flowing, according to Dr Britta Schaffelke, with the Australian Institute of Marine Science in Townsville. "After flooding we see an increased incidence of disease," she told the British science journal Nature this week.
"So even if the coral initially survive, over the next few months they might still die, or not reproduce, or reduce their growth rate," she said. "They would also be less resilient to any subsequent bleaching events caused by periods of very warm weather, an event that has already struck the reef twice in the past decade and is predicted to become more common due to climate change."
Time will tell
"It will be some time before we know the full extent of damage caused by the flood plume," says GBRMPA spokesman Andrew Skeat. "[But] even when ecosystems are exposed to freshwater plumes they do not necessarily die."
The flood run-off, full of sediment and nutrients, could spark increased algal blooms, coral bleaching and coral diseases, he agrees. It could also increase the productivity of some inshore species such as barramundi, mangrove jack, some prawns and sponges.
"Many plants and animals have mechanisms to cope ... however, this event has unusually large amounts of flood run-off with suspended material and the prevailing conditions may be different to previous events."
Disastrous impact
Environmental groups have also expressed wide concerns.
"The plumes of sediment and debris generated by flooding on this scale can have a wide range of impacts on marine habitats and species," said a statement released by the Australian Marine Conservation Society. "From entanglement of marine life in debris such as plastic bags to the smothering effects of large amounts of deposited sediments on sensitive habitats like seagrass meadows and coral reefs."
WWF-Australia, based in Sydney, has warned against the "disastrous impact" on corals and species including dugongs and turtles.
"In addition to the terrible costs to farmers and communities in Queensland, we will also see a major and extremely harmful decline in water quality on the Great Barrier Reef," says Nick Heath, program leader for water.
"Today's floods are bigger, dirtier and more dangerous from excessive tree clearing, overgrazing and soil compaction. As a result less water infiltrates deep into the soil, increasing the size and erosive intensity of floods," he adds.
Anxious wait for impact on Moreton Bay
Courtney Trenwith Brisbane Times 21 Jan 11;
Queensland environmentalists are anxiously waiting to see how much of Moreton Bay's "unique playground" will be destroyed by the unprecedented pollution that is still gushing down the Brisbane River.
Experts say turtles, dugongs and various fish species are certain to die as toxins kill their main food source, sea grass.
But just how many don't survive will depend on how quickly the bay can recover.
The bay is also likely to turn green as algal blooms develop, but the extent of algae damage will depend on how long it lingers.
On Wednesday, an team of marine scientists began the meticulous task of monitoring and assessing exactly what effect last week's floods are having on the bay and what the long-term damage may be.
The CSIRO's Andy Steven said the flood had given researchers a rare opportunity to understand how marine ecosystems respond to massive inputs of freshwater and sediments.
Dr Steven said a torpedo-like ocean glider, packed with sensors, would play a key role in helping to determine how the floods have affected marine ecosystems in Moreton Bay by monitoring the extent of the flood plume and assessing its impacts on marine life.
Experts have agreed that although the recent floods did not peak as high as in 1974, additional development since then meant it would cause greater damage to waterways.
Queensland Conservation Council executive director Toby Hutcheon said a clear picture would not be known until the contaminated sediment washing into the bay settled. That could take weeks or months.
Mr Hutcheon said the worst-case scenario would see the loss of the entire dugong and turtle populations.
The World Wildlife Fund has also has expressed concerns over the likelihood of dugong deaths.
"This is new to everyone," Mr Hutcheon said.
"We don't know anything about the [impact on the] wildlife ... it could be very serious.
"We need to be concerned. We're at the point now that, because the [Department of Environment and Resource Management] and the government have been focused on the clean-up, we haven't had an opportunity to assess some of the threats and damages yet so we don't know how serious it will be."
SEQ Healthy Waterways Partnership scientific program director Eva Abal said there would be impacts for all of the catchments in the flood path, including Oxley Creek, the Bremer River and Brisbane River.
Dr Abal said invertebrates that lived on the sediment would be scarred after being dragged along in the current.
The extent of the damage would depend on how much of the gunk that ended up in the waterways flowed out to Moreton Bay.
"[The suburban catchments] are acting as a drain, they're draining all this out into Moreton Bay," Dr Abal said.
"[The impact] will still be fairly significant in terms of water quality and whatever biodiversity they had."
Mr Hutcheon said there would also be issues with creek bed erosion due to the sudden surge of water.
He said the first priority was to clean-up the waterways, then assess the damage and determine how to recover from the natural disaster and ensure the ecosystem is better protected if there was another major flood.
"It's very important we don't just rebuild and do what we had in the past because with the climate changing it's very likely this sort of event can happen again," Mr Hutcheon said.
"[We need to] make sure that nature and biodiversity is more resilient."
Dr Abal said waiting to learn the cost of the floods was a nail-biting prospect.
"I'm very anxious because I love the bay but at the same time ... [I'm] hopeful parts of or all of the bay is resilient," she said.
"It's the only place in the world where you can stand on the bay adjacent to Moreton Island and look straight ahead and you see the city skyline but at the same time we have this very healthy population of dugong and turtles swimming around.
"It's a very unique playground ... [that will be] diminished. It's about how Moreton Bay is able to recover, we don't know because we've never had any event like this."
- with AAP
Reefs reeling from Queensland floods
Abbie Thomas for ABC Science Online 21 Jan 11;
Researchers say the recent Queensland floods are carrying tonnes of fresh water, nutrients and pesticides to the ocean, placing enormous stress on the Great Barrier Reef.
For the past five weeks, plumes of silt-laden fresh water have been flowing onto reefs off the Queensland coast.
The impact is so massive it can be seen in NASA satellite photographs.
Researchers list the Keppel Islands near Rockhampton, Moreton Bay and Fraser Island, north of Brisbane, as being most at risk.
Dr Alison Jones, from Central Queensland University in Rockhampton, has seen first-hand the impact of the floods on corals in Keppel Bay.
"You can't see anything at all from above," she said.
"As you take the camera down, it looks like a big brown soupy mess.
"Deeper down the water is a bit clearer and you can see bleached white [coral] colonies appearing out of the gloom."
Dr Jones checked five islands and found stressed coral around all of them.
"Halfway Island was much worse than North Keppel. It was just dead coral, killed by the fresh water," she said.
"There wasn't really a single thing alive.
"There also seems to be some temperature bleaching, believe it or not, from the ocean being warm, which is completely unrelated to the flooding."
Dr Britta Shaffelke, a researcher at the Australian Institute of Marine Science, says wind direction over the next few days will be crucial in determining the extent of the damage.
"At the moment the mud plume [from the Fitzroy River] is confined to the Keppel Bay area," she said.
"However if the wind turns around from the south east to the north, the plume might reach much further to the outer reefs such as Heron Island."
Floods damage corals in a number of ways.
Corals cannot survive in freshwater because their physiology is adapted to salt water.
Silt is also clouding the water and blocking out sunlight, stopping corals from photosynthesising and feeding themselves.
Nutrients such as nitrogen and phosphorous can kick start toxic algal blooms, which strip oxygen from the water and at the same time, provide food for the larvale of crown of thorns starfish.
Pesticides carried in floodwater call also kill corals.
Researchers are most concerned about the impact of the sediments.
"What has changed is that the load of sediment in the rivers has increased 4- to 10-fold since pre-European times," said AIMS scientist Dr Katharina Fabricius.
"Reefs exposed to high levels of nutrients and sediments have up to five-fold higher cover of seaweeds (which can smother corals) and half the biodiversity of species of coral - these are the long term effects of these floods," she says.
Dugongs at risk
Meanwhile, further south in Moreton Bay, experts are worried about the long-term impact on dugongs. In 1996, a flood left many dugongs starving, as sediment and nutrients overwhelmed and killed the seagrass beds in the area.
"For Morteton bay, the flooding event last week was significantly bigger for sediment deposition and fresh water than the flood of 1996," says Dr Eva Abal, chief scientific officer at the Great Barrier Reef Foundation.
"My expectation about the impact on the bay is that we will experience some seagrass loss, but it also depends on how quickly water clears up."
Shaffelke also points out that there are unusually vast amounts of turbid freshwater off the coast of Brisbane.
"That hasn't happened for many, many decades in the Brisbane area, so many plants and animals will imediately die or be very stressed," she says. "I expect there to be quite serious impacts as well."
"In relation to the floods in Rockhampton … that is certainly not typical or happens very often. For both humans and the enviroment this is an extraordinary event.
"For the marine environment, the events are still unfolding. The highest rainfall is actually in February, so we are certainly not at the end of this season."
