Words by Ellie Parker, Marine Officer, Solent Seagrass Restoration Project.
“Hidden beneath the surface of the Solent are underwater gardens of seagrass. Seagrasses are the only marine flowering plants. They typically occur along shallow, sheltered marine coastlines and estuaries, from the Tropics to the Arctic Circle. They have roots, grass-like leaves and produce flowers and seeds. Under the right conditions, they can grow to form flourishing, green underwater meadows which provide food and shelter for an array of marine life.
The seagrass meadows in the Solent are of international importance. They support rich biodiversity, including amazing species such as sea anemones, stalked jellyfish, sea slugs, pipefish and seahorses. They act as nursery grounds for commercially important fish species such as cod and sea bass. Seabass spend up to seven years growing in the Solent. Cuttlefish visit the meadows to breed, attaching their black eggs, known as ‘sea grapes’, to the seagrass leaves. Seagrass also provides a major food source for brent geese, which make the 3000-mile journey from Siberia to the Solent every year.
Seagrasses are incredibly important allies in the fight against climate change. They absorb massive amounts of carbon dioxide from the surrounding seawater and their long leaves slow the flow of water, encouraging settlement of carbon-rich sediment down into the seabed, where it is buried and locked away. They also improve our water quality and protect our shores from coastal erosion: slowing wave energy with their leaves and stabilising soft seabed sediments with their roots.
However, seagrass is disappearing. Globally, it is estimated that we lose an area of seagrass around the same size as two football pitches every hour. In UK it is estimated that we have lost up to 92% of seagrass over the past century.
In the 1920s and ‘30s a significant proportion of seagrass in the UK died from a wasting disease. There has not been much recovery since those days. Now, modern day pressures, including physical disturbance – from dragging anchors and chain moorings – and human-induced threats such as pollution, and excess nutrients from sewage and intensive agricultural practices, are putting our seagrass meadows under significant pressure.
Historically, seagrass is recorded to have been very large and abundant from Southampton up the River Hamble to Bursledon. However, when the Hamble was surveyed for seagrass in 2011 not a blade was found.
At the trust we want to protect and restore these vital marine habitats, creating a wilder Solent for both people and wildlife. That’s why in April 2021 we joined forces with marine engineering company Boskalis Westminster and the University of Portsmouth to undertake a seagrass restoration project in the Solent.
Together with an army of fantastic Solent Seagrass Champion volunteers we have been monitoring and surveying our existing seagrass meadows, identifying their extent and recording which ones are growing and flowering well. The data we collect feeds into current conservation measures to protect seagrass beds, and into our restoration work – providing a good indication of when and where to collect the seagrass seed.
Developing seagrass seed is found in special flowering shoots called spathes. In July and August we sustainably collect these spathes through snorkelling and wading at low water.”
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As you’re writers, I wanted to share what it’s like being one of the volunteers who helps to collect seagrass seeds.
First person account by Helen Salsbury, Volunteer
“We met at the second Farlington Marshes car park and collected our gear (boogie board, mud pattens to strap to our feet and a tub with a handle). We were covered in waterproofs and wellies. Ellie showed us pictures of what we were looking for, the various stages of the seagrass seed development and which ones were ready to pick. Then she led us down a rough footpath, then down the steeply-angled concrete of the harbour wall and onto the mudflats.
We could only collect during a short window each side of low tide. We walked a long way out onto the onto the mudflats following the path of tidal rivulets. At the Seagrass bed, we lowered the boogie boards and could either kneel on all fours or lie prostrate, as we slowly and methodically searched for mature Seagrass Seeds.
It takes time to get your eye in and to distinguish the different stages of seed development. You have to be really gentle with the seagrass as you sort through because you don’t want to harm it. It’s a subtle, meditative process, which is occasionally rewarded by a spathe of mature seeds. Often when you find one – you find others nearby.
When you take a break and look up you are truly in the wilderness. A wilderness I’ve never seen before. I suspect few people have.”
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And now back to the the official talk (words by Ellie Parker, Marine Officer, Solent Seagrass Restoration Project):
“The collected seeds are taken to the aquarium tanks at the University’s Institute of Marine Science. The seeds are left to mature and release from the decaying spathes – a process known as rotting out – over a period of two to three months. Once this has completed, the seeds are cleaned, sorted and processed ready for planting.
We have completed five seagrass deployments since December 2021 across two sites – Farlington in Langstone Harbour and Seaview on the Isle of Wight. We have planted a grand total of 33,500 Zostera marina seeds and 23,000 Zostera noltei seeds using two restoration methods – hessian seed pods and dispenser injection seeding.
The seed pod method involves packing a small amount of sediment and 30 to 45 seagrass seeds into each small hessian bag. These are then buried into the sediment.
The dispenser injection method involves the use of caulking guns, which are filled with a mix of sieved sediment and seagrass seeds. The sediment-seed mixture is injected directly into the mudflat or beach.
We are seeing early signs of success from our restoration work and are continuing to monitor our sites for seedling growth as well as to collect seeds for our next deployment.
By protecting and restoring seagrass habitats, we hope to create a wilder Solent, supporting increased biodiversity and sustainable fisheries, promoting greater ecosystem services, cleaner water and a natural carbon solution to mitigate the effects of climate change.”