March 1, 2011 – By Brett Leverett
Australians weren’t the only ones impacted by the flooding that occurred in January. An unexpected victim is the Great Barrier Reef and the marine life that depends on the reef for survival.
The greatest flooding to hit Queensland State in over 50 years has carried mass amounts of sediment from the Fitzroy, Burnett and Burdekin Rivers into waters at the southern end of the reef.
This sediment contains deadly pesticides and fertilizers which have caused a significant amount of damage to the coral. Based on past research, predictions look grim for the largest reef system in the world.
“Our work has shown that high levels of nutrients and sediments can reduce coral diversity and increase the cover of seaweeds on inshore reefs,” says Katharina Fabricius, a researcher at the Australian Institute of Marine Science.
Furthermore, previous large floods along the Burdekin, one of several rivers that have flooded in Queensland, have led to outbreaks of a starfish that can single-handedly overtake reefs.
The crown-of-thorns starfish has a nasty taste for eating coral and is considered to be the greatest cause of coral mortality in the reef. This starfish apparently thrives on the conditions created by flooding. The last 3 major floods to hit the reef are all correlated with the largest outbreaks of the crown-of-thorns.
Scientifically known as acanthaster planci, the crown-of-thorns live and prey on live corals; killing them in the process. Through this destructive feeding, crown-of-thorns can disrupt an entire reef’s ecosystem. There are numerous records of these starfish outbreaks, proving the massive amounts of damage they can cause. Unfortunately, coral reef ecologists have not discovered a good solution to deal with these harmful pests.
For the marine life caught up in the polluted waters, their fates look grim. Many of the bigger species of fish can swim away from the deluge of fresh water, but smaller coral reef fish may suffer the same fate as the corals they live around. This temporary loss of fish may be the cause of the crown-of-thorns population explosion. Many of the fish that typically live in the reef are the only form of predators to this starfish, and in the absence of these predators the crown-of-thorns has the chance to thrive.
Even with the threat of a crown-of-thorns population boom, their effect is not instantaneous and will take some time to fully develop. But the immediate aftermath of the flooding has lead to a potentially stressed coral system. The sediment that has affected the beds of sea grass can trigger a series of stressful events; killing off large sections of coral and leaving it vulnerable to further complications.
Michelle Devlin, a researcher at James Cook University in northern Queensland stated, “You get very stressed corals, you get stressed sea grass… So let’s just say that a big cyclone came along, knocked them all out. They might not recover so well because they are already very stressed.”
Unfortunately for the Great Barrier Reef, the cyclone Yasi struck the Queensland coast on February 3rd.
Typically, cyclones and coastal flooding are actually key components of a reef’s life-cycle. But the abnormal changes in water quality and the excessive volume of fresh water run-off have caused problems. Scientists fear that increasing levels of toxicity reaching the reef could start a downward spiral of destruction.
Coral realistically can’t compete with this level of pollution. Although despite the obvious destruction, the Great Barrier Marine Park Authority is optimistic. They believe that damaged portions of the reef could make a significant recovery in five to ten years. However, they point out that the full extent of the damage to the reef is still unknown.
Photo Credit: Rob and Stephanie Levy