Please stay off the grass – it’s needed to help reduce greenhouse gases
Article by Denise Cullen, Cosmos Magazine
11 May 2023
This factoid might surprise people everywhere: tourism operators took the seagrass meadows out of the water in the resorts of the Maldives to give a picture of perfect, white ocean sand.
Now, they’re putting it back.
Seagrass is easily overlooked. If you stroll past the multimillion-dollar superyachts to the edge of a floating pontoon moored at Coral Sea Marina, at Queensland’s Airlie Beach, you’ll find two small tanks filled with submerged pots of seagrass.
Located just metres from the marina’s Ocean Club, where boaties come to cook, shower and check their email, these aquariums might look innocuous, but their contents could be a secret weapon in the fight against global warming.
In 2019, the United Nations Environment Program noted seagrass could absorb carbon, describing it as “one of the most threatened yet overlooked ecosystems on Earth”.
“Seagrass accounts for 10 per cent of the ocean’s capacity to store carbon so-called ‘blue carbon’ – despite occupying only 0.2 per cent of the sea floor, and it can capture carbon from the atmosphere up to 35 times faster than tropical rainforests,” the UNEP report states.
However, it pointed out seagrass meadows worldwide were threatened by urban, industrial, and agricultural run-off, coastal development, dredging, unregulated fishing and boating activities, and climate change. In some locations, the likelihood of recovery without intervention was poor.
According to Seagrass Watch, a not-for-profit that monitors the status of seagrass globally, there are as many as 72 different species of seagrass.
“Seagrass accounts for 10 per cent of the ocean’s capacity to store carbon so-called ‘blue carbon’ – despite occupying only 0.2 per cent of the sea floor, and it can capture carbon from the atmosphere up to 35 times faster than tropical rainforests.”
Beyond their capacity to sequester carbon, they help to prevent coastal erosion, filter out nutrients from land-based run-off, and oxygenate the water. Seagrass meadows are scattered along most of Australia’s coastline.
The test seagrass nursery at Coral Sea Marina was set up a little more than a year ago, established in collaboration with CQUniversity, Reef Catchments and the Great Barrier Reef Foundation. It followed a 2019 project by CQUniversity which explored which seagrass meadows in the region were at risk of being lost or degraded and how well they might recover.
The project is seeking to restore the seagrass meadows in nearby Pioneer Bay, which have been battered by sediment run-off, anchor and propeller damage, increased storm activity, and multiple years of La Niña climate events.
“We got involved through discussions with Reef Catchments about available space in the marina to house the nursery,” says Joscelyn O’Keefe, Head of Marketing and Business Development at Coral Sea Marina.“The seagrass meadows at risk are adjacent to the marina rock wall so participation was a no-brainer.”
The project is part of the Reef Islands Initiative, a 10-year program to establish a network of climate change refuges to protect critical habitats on Great Barrier Reef islands.
Traditionally, seagrass restoration has been undertaken through transplants, but this was time-consuming and often risked damage to the donor meadow. Instead, community volunteers have assisted researchers from CQUniversity’s Coral Marine Ecosystem Research Centre (CMERC) by collecting seagrass flowers and cultivating them within the nursery at Coral Sea Marina. The seagrass seeds are then harvested before being re-seeded in disturbed meadows. This system produces less damage to the donor meadows, facilitates greater genetic diversity and allows for expansion on a larger scale.
In a statement, CMERC Director Associate Professor Emma Jackson says seagrass meadows provided valuable nursery habitat to more than a fifth of the world’s largest 25 fisheries. They were also valuable grazing grounds for Australia’s dugongs, which can consume up to 40 kilograms of seagrass every day.
“Seagrass meadows are susceptible to urbanisation, due to the fact they grow in sheltered parts of the coast and estuaries where urban development occurs,” Jackson says.
Jackson, a self-professed seagrass nerd who had seagrass flowers in her wedding bouquet, says opportunities exist to use this development to the benefit of seagrass rather than their detriment.
“Our work is aimed at both improving our understanding of this vital marine plant, as well as developing new ways of restoring seagrass meadows with materials from CMERC’s seagrass nurseries.”
The next step in CMERC’s research is to look further into how the seeds are stored, germinated and then dispersed so that the restorations can be scaled up even further and continue with minimal impact on the meadows. It also means that in the event of a completely lost seagrass meadow, one could be recreated through the harvested seeds.
So far, CMERC has found the best environment in which to germinate seeds replicates the temperature, acidity and other aspects found in the stomach of a dugong, while the best way to disperse them is to plant them in sticky yet nutritious mud balls.
“They take them back out to Pioneer Bay (where they’re dropped) like little bombs,” O’Keefe says.
The Coral Sea Marina nursery is one of a multitude of projects designed to support these productive underwater pastures across the nation and the globe. For example, in Sydney Harbour, the Operation Posidonia project led by the UNSW and Sydney Institute of Marine Science is seeking to revegetate an endangered seagrass, Posidonia australis, which has become scarce due to boat mooring scars on the seafloor. To avoid damaging existing Posidonia meadows, a local ‘seagrass storm squad’ comprised of citizen scientists is being assembled to collect living donor shoots washed ashore after storms.
On the other side of the continent, a team led by the University of Western Australia and Murdoch University has just finished a one-hectare seagrass restoration site in Shark Bay, by transplanting 5,000 cuttings and deploying more than 1,500 seagrass snaggers and wieners (sand-filled hessian socks). In the Maldives, the Six Senses Laamu is working with Australian scientists to restore the seagrass meadows tourist resorts once removed to give the illusion they were built over unbroken white sand and turquoise lagoons. Since Six Senses Laamu started this work in 2018, a further quarter of the country’s high-end resorts have joined the campaign to protect their own seagrass meadows.
More recently, data provider Planet Labs has joined environmental not-for-profit The Nature Conservancy to launch the Blue Carbon Explorer, a new digital tool to map and monitor mangrove and seagrass blue carbon around the world. The tool also enables governments and coastal managers to make data-informed decisions on the protection and restoration of coastal ecosystems.
Lindsey Smart, a climate and ocean scientist at The Nature Conservancy, says: “These ecosystems really are a great ocean-climate link, and part of our strategy is to unlock this blue carbon potential for climate mitigation.”
The Blue Carbon Explorer is a Google Earth Engine app developed by The Nature Conservancy that leverages field-collected data from drone and satellite imagery, including Planet’s SkySat and PlanetScope, to help identify critical areas for restoration and protection.
The tool helps to visualise if these ecosystems are degraded or healthy, enabling analysts to determine the best management decisions to aid in their conservation and restoration. This collaborative work has already started to reveal insights into changing coastal habitats throughout the Caribbean, Indonesia, and Papua New Guinea.