Thousands of seed bags planted in bid to restore seagrass meadows off coast

Nina Massey, PA Science Correspondent

Researchers are hoping to change Plymouth’s seabed with the planting of four hectares of a “super plant” seagrass which can help in the battle against climate change.

As part of work on England’s seagrass planting effort the last of thousands of seed bags were placed in Plymouth Sound National Marine Park on Wednesday.

Experts estimate the UK may have lost at least 44% of its seagrasses since 1936, 39% since the 1980s, and that the losses over longer time spans may be as high as 92%.

Seagrass meadows provide homes for young fish and protected creatures such as seahorses and stalked jellyfish.

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The plant also has an integral role in stabilising the seabed, cleaning the surrounding seawater and capturing and storing significant amounts of carbon.

Experts say it captures carbon up to 35 times faster than rainforests, and while it only covers 0.2% of the seafloor, it absorbs 10% of the ocean’s carbon each year.

The last of 16,000 seagrass seed bags and 2,200 seedling bags will be planted in Plymouth as part of a four-year project aiming to plant a total of eight hectares of seagrass meadows.

The process involves dropping biodegradable hessian bags, containing 30 seeds in a nutrient rich sediment, down a plastic tube onto the seafloor up to 10 metres below.

Within three weeks the seagrass will break through the bag which will break down itself in five weeks.

In a year the plants will have matured and researchers will dive down to see how it is growing.

Four hectares will be in Plymouth Sound and four hectares in the Solent Maritime Special Area of Conservation.

Dr Emma Nolan, seagrass cultivation officer at the Ocean Conservation Trust, said: “Seagrass is a super plant, it traps carbon from the atmosphere up to 35 times more efficiently than the rainforest, capturing carbon in its sediment.”

Mark Parry, development officer at the Ocean Conservation Trust, said the project is sort of like a wildflower meadow for the sea.

He added: “Within the marine environment you get animals coming in and recruitment of different marine life quite quickly.

“So we are hoping that when we kickstart this process and our seeds grow, then we get all of the associated benefits with it quite quickly.

“One of the big things at the moment is about blue carbon, and really that’s just carbon that is stored by the sea – so we could be part of that carbon cycle.”

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He added: “We are looking to restore four hectares in this area.

“Historically, could it be larger? We don’t have a record for larger areas of it.

“But yes, this is the first time on record that the eastern side of Plymouth Sound will have shown an abundant, healthy, seagrass bed.”

Dr Nolan told the PA news agency: “To think that this could potentially be self-sustaining, if what we do works and it starts to reproduce and regrow itself, then if you restore four hectares, that could become eight, which could become 16 – that is the dream.

“But I think there is a lot of work to do before getting to that position.”

Mr Parry said the project had only been possible because of all the hard work of the partners in the LIFE Recreation ReMEDIES project.

He added: “These events have taken over 12 months of planning and include a combination of volunteers who have visited the National Marine Aquarium creating our planting units and our dive volunteers.

Seed bags sitting on the seabed
Seed bags sitting on the seabed (Ocean Conservation Trust/PA)

“This truly is a community effort.”

The LIFE Recreation ReMEDIES project is being led by Natural England, with the planting being carried out by project partner the Ocean Conservation Trust.

Seagrass is delicate and can be damaged by activities such as the anchoring, mooring and launching of leisure boats, as well as other shore- and water-based activities.

Therefore, as well as planting new seagrass meadows, the project is working to protect existing ones by helping recreational users to minimise impacts on these sensitive habitats.

Natural England and ReMEDIES partners plan to extend the benefits of this work beyond the UK to assist with international marine recovery efforts. Techniques and evidence gathered will be captured and shared with marine conservation

ReMEDIES is funded by the EU LIFE programme and led by Natural England in partnership with Ocean Conservation Trust, Marine Conservation Society, Royal Yachting Association and Plymouth City Council/Tamar Estuaries Consultative Forum.