Could bubbles be a blow to biofouling?
Millions of bubbles could soon be solving an age-old problem for boaties and help stop the spread of marine pests around New Zealand.
For centuries, sailors have battled biofouling (unwanted organisms) on their boats. Biofouling creates havens for troublesome sea critters, and increases the boat’s drag and fuel consumption.
Traditional anti-biofouling coatings such as tributyltin, contain biocides that stop marine organisms attaching themselves, but aren’t good for the environment. Now a trial at Port Nelson, led by Cawthron’s biosecuirty team, is testing whether sending a vigorous curtain of bubbles up marine structures could stop the problem altogether.
Cawthron marine ecologist Dr Grant Hopkins says the method, tested by the Australian Navy for use on its vessels, could reduce the numbers of marine pests making their way around the country.
“No-one’s actually tried to keep marine structures clean as a matter of routine,” he says. “That’s a new direction. All these marinas, wharf piles and port infrastructure can become a bit of a reservoir for biofouling critters, and our theory is if you can reduce the biomass of that, you can have flow-on benefits, meaning less fouling on boats and less spread of marine pests.”
The biosecurity team have rigged up two sets of underwater testing panels at Port Nelson, made of alternating concrete and acrylic. One set of panels has a fast curtain of bubbles jetting up the surface, and the other is a control, free of bubbles.
The bubbles in action at Port Nelson Marina
The experiment has many more months to run, but Dr Hopkins says things are looking quite promising, with divers already noticing the bubbled panels had less fouling build-up compared to the others. “Preliminary investigations are that it’s working.”
The acrylic panels have been coated with a very smooth, non-toxic, silicone-based paint, known as ‘fouling release coating’. If painted onto a hull, it enables biomatter to slough off once the vessel reaches a certain speed. “We’re hoping the super-smooth paint and bubbles will result in a winning combination.” Dr Hopkins says if the trial is successful, the technology could be retrofitted to existing pontoons, or new ones could be specifically designed to incorporate it.
This is one of three projects Cawthron is developing to keep marinas and ports fouling-free, with the other two to be trialled later on. The project is supported by Bellingham Marine, one of New Zealand’s largest marina manufacturing companies, as well as Monumental Plastics, paint producer Akzo Nobel, local engineering and diving companies, Port Nelson and the Northland Regional Council; Northland has seen an increase in the number of marine pests lately, and contracted Cawthron to test the technology.
Bellingham Marine provided the concrete panels for the project, and operations manager David Lamont says they’re pleased to be supporting a project to try and rid New Zealand of a major issue.
“Biofouling is a big concern in the marine industry at the moment, and as marina manufacturers we’d like to be part of the solution for coming up with ideas and prevention methods,” he says.
The trial is “groundbreaking” says Northland Regional Council biosecurity senior programme manager Don McKenzie.
“It could help the marine industry and our environment, and it could help clean hulls, clean structures, stop infection, and stop hulls carrying this around,” he says. “We think it has huge promise and it should be a flagship for how well New Zealand could position itself as a centre of excellence in this kind of technology.
“Cawthron is doing a fantastic job and we’re pleased to be a catalyst for that.”
Listen to Dr Hopkins talk about marine biosecurity on Cawthron's radio show.