Grantee: Seawilding

Duration: January – May 2023

Background

The seagrass species, Zostera marina, also known as common eelgrass, is an essential keystone species that sequesters carbon and provides a vital inshore habitat and spawning ground for fish and other marine species. Simultaneously, seagrass roots bind to the seabed, reducing or mitigating against cliff and coastal erosion.

Although seagrass covers just 0.2% of the ocean floor, seagrass meadows support up to 25% of the world’s top fisheries by providing a 3-dimensional structure in what can otherwise be a barren marine landscape. Globally, 92% of seagrass that once existed has been lost, while in the UK, 95% of seagrass meadows have disappeared from coastal waters because of dredging, pollution and disease. In the fight against climate change and biodiversity loss, restoring seagrass offers a compelling solution.

Seawilding are a community-based charity working to restore degraded marine habitats and species through native oyster and seagrass restoration. Based in Loch Craignish, Argyll, they carry out pioneering work to restore lost biodiversity, sequester carbon, create green jobs and to mentor other community-based groups to manage their own inshore marine environments sustainably. They create citizen science and research opportunities with community groups and academics, as well as engaging and involving children from local schools.

In October 2022, HIEF awarded Seawilding a £15,000 grant to pilot a small-scale seagrass nursery.

Native Seagrass meadow in Loch Craignish. © Seawilding

The Project

Through germinating seeds in tanks, the project trialled different substrates and growing containers, with an aim to track improving germination rates.

Three nursery systems were constructed:

• Closed recirculation system using artificial seawater and sterile sediment.
• Closed recirculation system with a mixture of sterile and natural sediments.
• Open system with a constant through-flow of fresh seawater, using a mix of sterile and natural sediments

“We wanted to trial a system using artificial seawater as, if successful and straightforward, it would mean a future nursery would not need to be restricted to a shoreline site where power and other facilities may be difficult to find.”

Several important findings were made during the trial. Germination in the closed systems was unsuccessful, but promising in the open system. The use of hessian bags was confirmed to be ineffective, but hair and coir matting methodologies were found to benefit seagrass growth.

The organisation collaborated with a host of other specialist groups during this project, including universities, The Fieldwork Company in the Netherlands, Project Seagrass, and the Ocean Conservation Trust’s ‘Blue Meadows Project’. Data and findings were also shared with the Global Seagrass Nursery Network and vertical farming specialists who will be trialling seagrass seedlings in their own growth systems.

The Nursery System in action. Images © Seawilding.

Impact

Data gathered from this project demonstrated that seagrass seeds can be germinated successfully in a simple, low cost, nursery system requiring only pumped, untreated seawater.

Future phases have discontinued the use of closed systems, moving from the nursery to Seawilding HQ’s shore-side location, in order to use the open system exclusively.

“The funding from HIEF allowed us to build and run a small-scale seagrass onshore nursery. This has been essential in fast tracking our project literally years. For example, through our onshore nursery we trialled many different sediments and planting strategies and quickly learnt that some of the methods we had been using in the sea, simply were not effective.”

“It would have taken years in sea trials to come to the same conclusion. Thus, saving us a lot of time and money and making rewilding the sea at a landscape scale much more likely.” 

– Seawilding