The war against marine pests will rapidly get easier if we can prevent them from growing on artificial structures like marina pontoons and wharf piles. The Marine Biosecurity Toolbox – a New Zealand led research programme - has some promising leads. We talk with Oliver Floerl, co-lead of the Marine Biosecurity Toolbox research programme with the Cawthron Institute about extensive research underway in New Zealand to make this happen.
An interdisciplinary team of scientists are working to develop new ways to prevent the buildup of marine pests on infrastructure. It is exploring three strands, any of which could play an important part in the future of marine biosecurity.
Air bubbles as antifoul
One promising line of enquiry the Cawthron Institute has pursued for five years is the use of bubble streams around underwater infrastructure like marina pontoons and wharf piles.
“We shroud infrastructure in small air bubbles that creates a barrier to the larvae of marine organisms so they can’t settle,” explains Oliver.
Working with Northland Regional Council and Auckland Council they have piloted bubble stream generation systems that have proven they are able to keep surfaces clean for several months. A prototype for a retrofitted system that will work on a marina pontoon is about to be trialed in Picton. Longer term, and in partnership with a pontoon manufacturer, they aim to establish a purpose-built, ‘bubbled’ pontoon in Auckland, one of the country’s invasion hotspots.
“The objective is to develop a perpetual and environmentally benign mechanism that will keep structures clean,” explains Oliver. The team’s research and testing is currently funded for the next three years.
Ecological engineering – giving native species a helping hand
Cawthron scientists recently showed that artificial coastal infrastructure (ports, marinas, civic urban facilities) currently occupies on average half of the total coastline associated with New Zealand’s main urbanised harbours, replacing natural reefs, beaches and mudflats. One of the conundrums of marine biosecurity is that marine pests, which have often successfully travelled long distances onboard a vessel hull, are well suited to living on artificial structures, and colonise these more rapidly than native species.
This means marine pests can quickly come prolific in some of the places we really don’t want them – like marinas and ports, subduing the population of native species.
The Marine Biosecurity Toolbox is investigating ways to enhance native species on structures at the expense of marine pests. The native species can, once successfully established in a location, provide invasion resistance, as well as a range of ecological benefits that aren’t realized when they are absent.
The Marine Biosecurity Toolbox program is working with materials scientists, surface chemists and a team of biologists and 3D printing experts to replicate high-value natural habitat surfaces artificially.
Oliver explains: “Green-lipped mussels have become decimated in many urban harbours. We are developing surfaces inspired by 3D scans of rock and other surfaces in healthy natural mussel beds. We know mussels like these surfaces and cluster there and our prototypes appear to reflect that.”
By retrofitting these units to existing coastal structures, and rewilding them with native species, the team believes it may be possible to reap ecological and cultural benefits, along with increased invasion resistance.
“Our aim is that native species will occupy that space and help to keep the number of marine pests down,” he says. “Ecological engineering has been successfully used to enhance marine biodiversity in other parts of the world. We specifically want to enhance native kaimoana species and use that as a barrier to marine pest establishment. It will be a challenge to do that at a larger scale and we are taking small steps.”
3D-printed models of healthy green-lipped mussel beds are being used to examine habitat preferences of juvenile and larval mussels. This information can then be used to develop surface characteristics into coastal infrastructure that will attract and retain native mussels and, eventually, also other valued native and kaimoana species. In the image, juvenile mussels can be seen to be attracted to the tips of 3D models.
Shellfish as robot cleaners? The potential of Biological Control
Scientists at Cawthron Institute have shown that native grazing species, such as paua and marine snails, have the ability to graze on the biofilm that develops on an artificial surface and thereby reduce the development of biofouling.
“The biocontrol ‘agents’ are able to do the job – but is there sufficient food for them to support the densities we may need? Over the next years we are now determining if there is sufficient sustenance on a pontoon or piling to keep them alive, and designing systems that they won’t fall off.”
“I am confident we will be able to showcase the performance of our developing technologies via longer-term trials,” says Oliver. The team behind the Marine Biosecurity Toolbox programme includes economists that are determining the cost-benefit of their technologies so that those who own and operate marine structures – whether councils, marina developers, port operators or the aquaculture industry – can accurately calculate the benefits relative to the investment needed or the cost of managing marine pests in other ways.
“We’ve had challenges, like everyone else, in the last two years with getting out and doing the work. We are proud of what we’ve managed to achieve to date - we have made a lot of progress and are tracking well. We are excited about this year having further results to share.
Keen to know more?
The Marine Biosecurity Toolbox website has more detailed information on all of these projects, the partner organisations involved, other research areas, latest news and progress, and key contacts that are happy to answer questions. Visit www.biosecurity-toolbox.org.nz/news/