University of NSW PhD student Giulia Ferretto said she has been "very impressed" with the Port Stephens results of study she is leading on restoring Posidonia australis.

"We have been restoring Posidonia australis in mooring scars in Port Stephens, the second most impacted estuary by boat moorings in NSW," Ms Ferretto said.

"We started with Port Stephens because it is a good, healthy estuary where Posidonia has been really affected by moorings but where there are also a lot of fragments we could use.

"We knew we could test different techniques in Port Stephens and find the best method for transplanting in a healthy estuary. Port Stephens was our proof of concept. Seeing the results, we have been able to expand."

Giulia Ferretto transplanting shoots of Posidonia australis back into the seabed in Shoal Bay. Video by Grumply Turtle Creative:

Operation Posidonia is a collaboration between UNSW's Sydney Institute of Marine Science, the NSW Department of Primary Industries and University of Western Australia.

It was launched in 2018 and used social media and meetings with local community groups and schools to engage with 5000 citizen scientists.

During a period of two years the citizen scientists made up of beach-goers, dog walkers and kayakers collected about 1500 naturally detached Posidonia australis shoots that had washed up on the beach after storms, strong winds and high tides.

In Port Stephens, about 80 people helped to collect shoots. Ms Ferretto and her team held talks with volunteers to help them collect the best possible fragments.

Hundreds of viable fragments in favourable conditions were collected and delivered to a floating box at the Anchorage in Corlette. This box was regularly emptied by NSW DPI Fisheries staff, who kept the fragments alive at the Taylors Beach institute.

In 2019 and early 2020 Ms Ferretto and a team of divers began to transplant those fragments back into seagrass gardens around Shoal Bay.

Ms Ferretto said most transplanted fragments produced new shoots after a few months and quickly re-established. Many expanded into new areas.

"We found that fragments planted in winter survived better that those planted in summer, with some replanted areas reaching 70 per cent survival after one year," she said.

"This is a great result considering that otherwise those fragments wouldn't have had another chance than drying up at sun.

"Collecting seagrass from the beach and planting it back is quite risky but survival has been quite high. So far, I'm very happy, in particular about the growth."

Ms Ferretto said heavy rainfall and flooding in the area in October 2020 did not have a negative impact on the transplanted shoots in Shoal Bay. The team has not been able to monitor the plots so far in 2021. They have not seen whether the March 2021 floods, which decimated sea beds and marine life in Nelson Bay, has had an impact on the plots in Shoal Bay.

The team is now expanding Operation Posidonia in Lake Macquarie and Botany Bay, two of the estuaries where Posidonia australis is formally listed as endangered.

The Posidonia seagrass species are only found in Australia and in the Mediterranean Sea.

"The idea of using storm-generated fragments for restoration was initially developed by a group of scientists in Italy and applied to [their] local seagrass, Posidonia oceanica," Ms Ferretto said.

"We then combined this idea with the use of citizen science to speed up the collection of the fragments."

Posidonia australis is a foundation species of seagrass which creates a complex and three-dimensional habitat that supports and sustains hundreds of other species. It provides food and shelter to many species of fish and invertebrates, which live amongst seagrass leaves to look for food or find protection from predators.

"Some of the more famous species supported by Posidonia australis are the endangered White's seahorse and commercially important species like blue swimmer crabs, bream, snapper and luderick," Ms Ferretto said.

"Seagrass meadows are also extremely effective at capturing and sequestering carbon and can slow down climate change by storing carbon more efficiently than terrestrial forests, as well stabilising sediments and protecting our shorelines from erosion."

But the challenge is that Posidonia australis's preferred habitat of clear waters and sheltered coves is also the preferred habitat for recreational boating.

The traditional mooring of these boats, which involves a chain and concrete block that harrows the seagrass bed, creates raw 'sand scars', which join up to form larger uninhabitable zones.

Some of these mooring sites, around Port Stephens, have been replaced by less destructive environmentally friendly moorings and it's these sites that the team is restoring.

Ms Ferretto said the response from the Port Stephens community to the project has been awesome.

"The planting moment for me was the best part, especially when the marine life just started to swim around us divers," she said.

"There was one site, in particular, where every time we'd dive there, there was a group of cuttlefish following us from the moment we would jump in until the end of the dive, as if they were checking if we were doing a good job.

"Turning around after a long dive and seeing that patch that before had only sand now having beautiful green Posidonia australis leaves gave me a wonderful sensation every time."

Our journalists work hard to provide local, up-to-date news to the community. This is how you can access our trusted content: