Fighting elite off to a-salt enemy seaweed
Worth their salt ... Able Seaman Clearance Diver Adam Goodwin goes seaweed hunting at Careel Bay, Pittwater, yesterday. Photo: Rick Stevens
By James Woodford, Environment Writer
Some of the fiercest warriors in the Australian military have been called on to spend two days sprinkling salt on seaweed.
A team of Royal Australian Navy clearance divers began yesterday their task of taking out the noxious seaweed Caulerpa taxifolia, which is taking over the state's estuaries and is considered one of the greatest threats to water life.
Already the weed is taking over coastal lakes such as Burrill, Narrawallee and Conjola. Botany Bay is also infested, as are parts of Pittwater, Lake Macquarie and Lord Howe Island.
[an error occurred while processing this directive]NSW Fisheries called on the navy to help it spread swimming pool salt on an infested area of about 300 square metres in Pittwater.
In return, the navy gets to give its diving team valuable, though relatively unchallenging, time under water.
Working at depths of less than two metres, the divers are expected to take 48 hours to complete the job.
It is the first large trial of the effectiveness of increasing salinity as a way of killing Caulerpa. Scientists have already found through small tests that the seaweed cannot cope with small changes in salinity. Salt has also been successfully used against Caulerpa beds, which are devastating huge areas of the Mediterranean Sea.
The navy divers are dumping 75 kilograms of salt per square metre, which seems to leave desirable seaweed species and other water life unscathed.
The deputy director of NSW Fisheries, Paul O'Connor, said the salt dumped on the weed dissolved within a few hours but that was enough to kill the Caulerpa.
"It can't handle the change," Mr O'Connor said. "They lose their moisture and collapse. If it is effective on this large scale it will be quite exciting because it provides another arrow to our bow."
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