An endangered seagrass which supports seahorses, blue swimmer crabs and fishlike snapper is being successfully rehabilitated thanks to the help of citizenscientists and UNSW scientists.
A study led by UNSW Science PhD student Giulia Ferretto from UNSW’s School ofBiological Earth and Environmental Sciences and published in BiologicalConservation, enlisted the help of 80 citizen scientists to restorePosidonia australis in Port Stephens.
“We have been restoring Posidonia australis in mooring scars in PortStephens, the second most impacted estuary by boat moorings in NSW,” MsFerretto says. “We launched Operation Posidonia – a collaboration betweenUNSW, Sydney Institute of Marine Science, the NSW Department of PrimaryIndustries, and UWA – in 2018 and engaged over 5000 people through our socialmedia channels and guided seagrass meetings with local groups and highschools. Over two years, our ‘army’ of volunteer citizen scientists – a ‘StormSquad’ of beach goers, dog walkers and kayakers – collected a total of 1500naturally detached Posidonia australis shoots washed up on the beach afterstorms, strong winds and high tides.”
Ms Ferretto says when conditions were favourable, a citizen scientist on aone-hour beach walk could collect as many as 30 viable seagrass fragments.
The shoots were kept in large floating boxes before being replanted by diversin the scars caused by boat moorings.
Ms Ferretto says most transplanted fragments produced new shoots after only afew months and are beginning to re-establish on their own, expanding in nearbyareas.
“We found that fragments planted in winter survived better that those plantedin summer, with some replanted areas reaching 70 per cent survival after oneyear,” Ms Ferretto says. “This is a great result considering that otherwisethose fragments wouldn’t have had another chance than drying up at sun.”
The team is now expanding Operation Posidonia in Lake Macquarie and BotanyBay, two of the estuaries where Posidonia australis is formally listed asendangered.
The method of collecting washed up, naturally detached fragments ofPosidonia australis (from heaps known as wrack), was adapted from anItalian study which also used Posidonia.
“One of the main problems with restoring an endangered plant is obtaining thematerial for the revegetation,” Ms Ferretto says. “ Posidonia [species] havean interesting distribution, they are only found in Australia and in theMediterranean Sea. The idea of using storm-generated fragments for restorationwas initially developed by a group of scientists in Italy and applied to[their] local seagrass, Posidonia oceanica. “We then combined this idea withthe use of citizen science to speed up the collection of the fragments.”
Posidonia australis is a foundation species of seagrass which creates acomplex and three-dimensional habitat that supports and sustains hundreds ofother species, Ms Ferretto says.
“It provides food and shelter to many species of fish and invertebrates, whichlive amongst seagrass leaves to look for food or find protection frompredators,” she says. “Some of the more famous species supported by Posidoniaaustralis are the endangered White’s seahorse and commercially importantspecies like blue swimmer crabs, bream, snapper and luderick. Seagrass meadowsare also extremely effective at capturing and sequestering carbon and can slowdown climate change by storing carbon more efficiently than terrestrialforests, as well stabilising sediments and protecting our shorelines fromerosion.”
She says the trouble is that Posidonia australis’s preferred habitat – ofclear waters and sheltered coves – is also the preferred habitat forrecreational 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 upto form larger uninhabitable zones.
Some of these mooring sites, around Port Stephens, have been replaced by lessdestructive environmentally friendly moorings and it’s these sites that theteam is restoring.
Ms Ferretto says the response from the Port Stephens community to the projecthas been awesome.
“The planting moment for me was the best part, especially when the marine lifejust started to swim around us divers,” she says. “There was one site inparticular where every time we’d dive there, there was a group of cuttlefishfollowing us from the moment we would jump in until the end of the dive, as ifthey were checking if we were doing a good job. Turning around after a longdive and seeing that patch that before had only sand now having beautifulgreen Posidonia australis leaves gave me a wonderful sensation every time.”
Image: UNSW Science’s Giulia Ferretto planting Posidonia australis into oldboat mooring scars in Port Stephens. Photo Grumpy Turtle Creative.
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