A Year in the Life: Seagrass Restoration

Georgia Bennett, our Seagrass Restoration Assistant, takes us through how the team are working throughout the year to restore 30 hectares of lost seagrass meadow at Spurn Point as part of our newly launched Wilder Humber project.

At Spurn Point National Nature Reserve we are restoring the lost and fragmented seagrass meadow. What was once a large expanse of seagrass, measuring around 480 hectares, is now small, fragmented patches of meadow which are not able to naturally recolonise to their historic range.

Restoring seagrass is important because:

It can store vast quantities of carbon in the sediment, helping fight against climate change.
It is an amazing habitat for many animals and can increase biodiversity.
It helps stabilise the sediment and allows of succession of other habitats such as saltmarsh.
It protects against coastal erosion by dissipating wave energy.
It acts as a pollution filter and sink.

View of seagrass in the sea on a clear blue day.

Our annual restoration plan begins in July and follows the same process each year…

Seagrass spathes - seeds ready to be collected

July - September – Seed Collection

During summer, our dwarf eelgrass (Zostera noltii) plants begin flowering, following an increase in water temperature and irradiance (sunlight). After the flowers have been pollinated, seeds begin to develop in late July and August. This is our cue to go out and check the healthy seagrass bed to assess the progress of the seed development.

This step involves lying out on body boards so as not to damage any part of the mudflat or seagrass and collecting spathes (seed pods) from the meadow to be taken back to our lab and stored in oxygenated tanks.

The spathes then undergo what is known as the rotting phase, where the mature seeds are released and then sink to the bottom of the tank as they are very dense. We then meticulously sieve out all of the sediment, rotted seagrass fronds, snails and even crabs from the seeds so they can be stored in clean seawater in the fridge.

Seagrass hessian bags in the palms of two peoples' hands

October and November – Seed Bag Making and Round 1 of Planting

After all the seeds have been collected and sieved, they are ready for our first round of seed bag making and planting! Each seed is carefully wrapped in its own hessian parcel, ensuring that once it is planted, it remains in the same place in the sediment, and is less likely to be eaten by animals such as crabs or snails.

When half of the seeds collected are safely in hessian bags, the team goes out onto the bare mudflat and plants one seed bag per square metre using a tree planting tool called a pottiputki.

Three people with a seagrass planting tool planting seagrass bags in the shore beds

This works out at around 4000 seed bags per acre! These seeds will lay dormant in the sediment over winter, until they are naturally triggered during spring to germinate.

December to March – Seed Bag Making and Seed Germination. April – Round 2 of Planting

After our November planting season, we will continue to make seed bags with the other half of our seeds.

These will then be stored in tanks until a few weeks prior to April planting, when we will flush the seeds with fresh water and increase the water temperature. This is a trigger for the seeds to germinate inside their bags and to start growing fronds and rhizomes.

This means that when we go out in April to plant these seed bags, they will already have a head start to begin growing in the mud.

Once we have planted out these germinated seed bags, we will have restored a total of 10 acres every year!

May and June – Clean down and prepare to do it all again!

After all the planting is done, May and June is our quieter period, where we leave the seagrass to grow and continue other survey works such as wetland bird surveys, fyke netting of the finfish assemblage and water quality surveys.

Then in July it is time to check back on the seagrass to see how many of the seeds have germinated and grown into small seedlings.