The small seed that is hoped will bring the coast back to life

News imageBBC A pair of hands holds a shoot which contains three pale seeds in contrast to the dark green of the seagrass.BBC
Seagrass seeds are found in pod-like structures called spathes

Forget the worm, this early bird was after the seed - and a very special one at that.

It meant an 04:00 BST alarm and, for some of the other 20 or so volunteers I joined at Calshot Beach near Southampton, even earlier.

A particularly low tide in the Solent meant the sea would reveal a crop on which conservationists are pinning their hopes to rebuild a depleted coastline.

Seagrass seeds.

Just like trees and plants, seagrass has a superpower - it can absorb massive amounts of carbon dioxide.

The same area of seagrass can absorb 35 times the amount a tropical rain forest can.

It locks in carbon and releases oxygen back in to the environment.

Seagrass also creates structure and habitat for thousands of species.

The UK has lost more than 90% of its seagrass meadows over the last century.

Disease, disturbance and pollution have meant vast swathes of once vibrant green seabed have been left bare.

News imageA group of people are spread in ankle deep water crouching down to look for seagrass seeds as the tide begins to come back in
Volunteers made the most of an exceptionally low tide to sift through the seagrass meadow looking for seeds

After a briefing in a nearby car park, we troop down to the water's edge clutching white plastic buckets to begin the hunt.

Leading the morning's fingertip search was seagrass supremo Tim Ferrero, from Hampshire and Isle of Wight Wildlife Trust.

"Seagrasses are the only marine flowering plants," he explains as we slowly work our way through the seagrass meadow.

"They do everything that a plant does on land. They flower, they pollenate, they set seed, all underwater basically.

"So, what we're doing is, we're collecting seed from an existing seagrass meadow so that we can then plant that seed somewhere else to recreate seagrass meadows."

News imageA woman with blonde hair and a white top crouches down in very shallow water sifting through seagrass which lays flat on the beach at low tide.
Sophie Whitemoor was one of about 20 volunteers gathering seeds at Calshot

For the experienced seagrass seed collectors, buckets soon begin to fill with the tips of stems.

For those new to the low tide trawl, they are few and far between to begin with.

Finding the right part of the plant, with seeds at the right stage for picking, takes a little while to get your eye in.

The pod-like leaf called a spathe is slightly rounder and paler than the darker, flatter blades of seagrass.

The seeds, when ready to pick, sit neatly in a row, slightly raised from the surface.

News imageA man with a beard and glasses wearing a white lab coat puts a handful of green seagrass into a blue tub
Handfuls of picked seagrass are transferred into rotting tubs, which separate the seeds from the stems

"Sometimes, it's just about feeling around and you can kind of feel these short stems that feel like they've got a pack of Tic Tacs in them," says volunteer Sophie Whitemoor.

Crouching alongside is fellow volunteer James Harper.

"I'm still building on my personal technique," he says. "It's just a case of looking for the most round stems, really."

The group are incredibly upbeat, considering the time of their early morning search.

"It's just a passion for me, really," says Jackie Mellan. "Any opportunity I can come out and help with restoration projects then I do."

For the next hour or so, the volunteers sift through the seagrass as it lays flat on the shore.

But it is a race against the clock and a turning tide means the small army of people gathering the harvest eventually beats a retreat to the shore.

The buckets are gathered back in the car park and the crop is carefully placed in a barrel of cool seawater to be taken for processing.

The seagrass seeds are taken to the University of Portsmouth's Institute of Marine Sciences at Eastney.

Placed in large blue tanks of seawater, the spathes begin a process which will release the seed from the stem.

"We call it rotting out," says Fererro, now wearing a white laboratory coat as he adds handfuls of seagrass to the Calshot tank. "It takes about between eight to 12 weeks to complete."

The decayed plant turns black and is caught in a sieve, allowing the seeds to fall to the bottom of the catching tub.

Once separated, the seed goes into storage in high-salinity water tanks for the winter, kept at a chilly 1-3C (34-37F).

Come the spring, volunteers will again be setting their alarms, this time to sow their precious crop.