Australian scientists nervously watch Great Barrier Reef

Tuesday 25th Jan 2011 by theWeather Club

As the flood waters in Queensland begin to recede, scientists' eyes are following the water into the sea and towards the region's greatest natural feature, the Great Barrier Reef. This is the world's largest reef system, and it supports a tourist trade worth several billion dollars per year as well as a multitude of marine organisms. It means the reef's welfare is a genuine concern for parts of Australia far removed from Queensland.

"Freshwater kills corals, and there is nothing we can do about it," says Katharina Fabricius, principal research scientist with the Australian Institute of Marine Science. The northern rivers are presently seeing flow rates way above normal and as the extra water floods into the sea west of the reef, it freshens the water more than normal which is not good news for the coral. And it is not just the water that is an issue. The sediment it brings also hurts the reef by blocking sunlight and covering the coral fronds. This run-off degrades the reef at the best of times; but in flood conditions, it becomes much more serious

But there is another problem, one caused by Queensland being a largely agricultural state: chemicals. Pesticides, herbicides and fertilisers, washed off the farms, are carried onto the reef. And it is the fertilizers that are actually a major issue. Just like on land they stimulate growth and for the coral this is a problem. Marine plants smother the growing coral, choking it to death. "The young corals are highly sensitive to exposure to organically enriched sediments," Dr Fabricius told the BBC. "My own research has also shown that increasing levels of nutrients can lead to more seaweed - up to a five-fold increase - and reduce coral biodiversity, with half of the coral species potentially lost from the exposed sites."

Scientists monitoring the coral say they have already seen indications of coral damage, but that it is too early to tell how big the impact is likely to be. The continuing threat of bad weather means that travel to the reef is difficult, meaning it is likely to be several weeks at least before scientists are able to gauge the true scale of the flood's impacts. Everyone is hoping - for economic as well as ecological reasons - that it will prove to be a short term hit from which corals, fish and everything else can recover quickly.