Plant organisms, bacteria and animals such as freshwater sponges have fouled the sheath of an electric cable in a canal. Photo: CC BY-SA 4.0/ Lamiot
New marine antifouling technologies could help keep marinas clean and stop ships being turned away from New Zealand ports.
An independent science organisation is investigating how to control the marine organisms that grow on underwater surfaces.
The research is timely - four cruise ships have been found in breach of biofoul standards since December, because of algae and barnacles growing on their hulls.
Cawthron Institute biosecurity manager Patrick Cahill said antifouling methods were typically used on boats, rather than static structures like pontoons. Unlike vessels, these structures did not have to adhere to biofoul standards, he said, despite being where a lot of invasive marine organisms first established before spreading.
To combat this, the organisation was investigating whether air bubbles blown onto underwater surfaces could prevent organisms from attaching.
"The bubbles basically act as a barrier to stop things settling, and then when things do settle, they sort of disrupt them and scour them off," Cahill said.
A field trial was underway at Waikawa marina in Marlborough, while earlier pilots in the North Island had shown promising results.
A diver inspecting biofoul Photo: Supplied/ Ministry for Primary Industries
The technology also had applications for boats that sat static for long periods of time, Cahill said, because these vessels were still required to adhere to biofoul standards.
"That's a real challenging situation for those boats," he said.
"These boats have got a traditional antifouling coating on them, but a lot of those coatings require the boat to be moving reasonably consistently to be effective."
However, researchers were also considering the cost associated with any potential solutions, and continuously applying bubbles to all marina structures would be energy intensive and require a fair amount of infrastructure, Cahill said.
The organisation was therefore also working with researchers at Durham University in the UK to invent a surface that could trap a microscopic layer of air.
"You could apply this new surface on the underside of your pontoons and then you'd, in theory, just have to very occasionally turn the bubbles on to replenish this trapped air layer, which we think makes it potentially a lot more scalable."
When asked whether the owners of such structures would be likely to want to dig into their own pockets to fund the preventative methods, Cahill said marina and port companies he had spoken with seemed very keen on it in principle.
"One thing we often hear is that boats, as we've seen with the cruise ships, are increasingly being regulated to be clean," he said.
"They'll be going to a marina or port environment and, you know, their boat has to be clean but all of the surfaces around them are not.
"So, I think there's a pressure from users of ports and marine environments. I think there is at least an interest from regulators to move towards it as well."
Another strand of the research was looking at how traditional antifouling coatings could be changed to be more environmentally friendly. Current coatings came in a paint form and included a toxin, usually based on copper.
Instead, the agency was working with researchers at the University of Auckland to develop a 'biocide' based on peptides, or short pieces of protein, made by many animals naturally.
"They can be effective like copper is, but when they get released into the environment they are very benign," Cahill said.
"They break down into amino acids, which are what peptides are made of, and basically that's the building block of life."
The project had been three years in the making and was now ready for real-world testing.
Finally, the institute was also looking at eco-engineering, which involved making marine environments more attractive to native species, like greenshell mussels.
Native growth would then stop invasive species from being able to settle.
If successful, the solutions would likely be welcomed by tourism operators, who had this summer faced a string of cancellations as cruise ships missed stops, took detours or postponed trips to be cleaned.