Radio waves mussel in on marine pest
Radio waves are an environmentally friendly way of killing the pesky zebra mussel - a close relative of the black-striped mussel that has come close to invading Australia, US researchers report.
Dr Matthew Ryan, from Purdue University Calumet in Hammond, Indiana,
told the 222nd meeting of the American Chemical Society this week of experiments in which a whole population of zebra mussels died within 40 days of being exposed to low-energy radio waves.
The technique has potential as a new method for controlling outbreaks of marine pests in Australia, said Dr Nic Bax from CSIRO's Centre for Research on Introduced Marine Pests.
"The infrastructure is set-up to quell infestation problems quickly, but action is limited by current technologies," said Dr Bax.
"In some cases we may not have the luxury of pest outbreaks in closed marinas, and new techniques will have to be investigated."
Australia's marine pest control systems were tested in April 1999, when the black-striped mussel, Mytilopsis sallei - a cousin of the zebra mussel - was found in three Darwin marinas. It was quickly eradicated with chlorine and copper sulfate.
"We were lucky with the black-striped mussel," explains Dr Bax, "because the infestation occurred in closed marinas, so the damage was limited."
Small, closed marinas can be easily quarantined so chemicals can be maintained at concentrations high enough to poison invading species.
Zebra mussels have caused great damage in the Great Lakes Region of North America, costing the United States around US$600 million a year in remedial engineering.
The prolific freshwater critters absorb large quantities of nutrients, leaving little for other organisms, and lay their eggs near the intake pipes of electricity generating stations, clogging the pipes to the point of unusability.
Chemicals such as chlorine and bromine have been used to remove zebra mussels, but there is growing concern that overuse might be polluting lakes and streams.
In the US study, 1,100 zebra mussels in large fish tanks were exposed to low-energy radio waves. All exposed mussels died within 40 days, while in an unexposed group only 10 per cent died.
Importantly, the radio waves did not significantly affect other organisms, such as fish, crabs and crayfish.
The water left over from the dead mussels was found to be high in calcium, leading Dr Ryan to conclude that the radio waves caused the mussels to surrender calcium needed to maintain their shells.
Marine pests can be introduced to Australian coastal waters as stowaways on the hulls of boats, and in the ballast water of ships.