9 Apr 2016

Bubble curtain effective for repelling invaders

7:54 pm on 9 April 2016

Nelson marine scientist Grant Hopkins believes a new solution to an old problem around marine invaders has been found in something as simple as a curtain of bubbles.

A vessel is hauled at the Nelson Marina for regular anti-foul treatment on its hull.

A vessel is hauled at the Nelson Marina for regular anti-foul treatment on its hull. Photo: RNZ / Tracy Neal

Cawthron marine biosecurity team leader Grant Hopkins said trials at Port Nelson using bubbles to prevent marine pests sticking to underwater structures had been a success and could be extended to pontoons.

Grant Hopkins

Cawthron's team leader of marine biosecurity, Grant Hopkins. Photo: RNZ / Tracy Neal

The bubble curtain mechanism, developed by the Australian navy, blew millions of bubbles on to a non-toxic coating, making it too smooth for marine invaders to latch onto.

Dr Hopkins said the test acrylic coated panels had no fouling on them, and were the same as the day they were put in the water.

"On our first dive, only two to three weeks into the trial, the results are great - exactly what we expected.

"We hoped the treatments with the bubble curtains would have led to significantly less fouling and that was the case," he said.

The technology could end the use of toxic anti-fouling paints now used to prevent the spread of marine pests on boats.

Traditional marine anti-fouling material applied to the hulls of boats contained copper and other biocides which prevented marine organisms sticking to them.

In the 1960s and 1970s commercial vessels used paints that contained tributyltin, which was very toxic and harmful to marine life. It had since been banned.

"It means that the concept of using bubbles over surfaces to keep them free of fouling has merit and warrants further investigation.

"We hope it will generate more commercial interest in the idea, and expand the scope of the studies, because at the moment we're still at the proof of concept stage, but we'd love to get to the stage of applying this to whole pontoons rather than just a few panels," Dr Hopkins said.

A vessel is hauled at the Nelson Marina for regular anti-foul treatment on its hull.

A vessel is hauled at the Nelson Marina for regular anti-foul treatment on its hull. Photo: RNZ / Tracy Neal

Harbours and marinas were hubs for marine pests, and boats were the way they travelled around the country, he said.

He said the trials, commissioned by Northland Regional Council, would continue over winter and it was hoped the system might eventually be used by other councils and marina companies.

Northland council biosecurity manager Don McKenzie said there was a lot of interest in the trials from the New Zealand Marina Operators Association.

Mr McKenzie said new, environmentally appropriate tools were needed in the fight to stop the spread of marina invaders.

"We can't keep spreading these marine pests over all our best places."