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From small seeds, big eelgrass meadows grow

Logo: Alderney Wildlife Trust

By Dr Mel Broadhurst-Allen

Alderney Wildlife Trust and their work on discovering and conserving one of their most important marine habitats!

An up-close photograph of a patch of common eelgrass (Z. marina) spotted during a walk during a low spring tide at Longis Bay, Alderney (©Mel Broadhurst-Allen, Alderney Wildlife Trust)
An up-close photograph of a patch of common eelgrass (Z. marina) spotted during a walk during a low spring tide at Longis Bay, Alderney (©Mel Broadhurst-Allen, Alderney Wildlife Trust)

Eelgrass is a fascinating, truly wondrous, yet, bizarre set of species (aka Zostera species or seagrasses). Despite growing in the shallows of our seas, taxonomically, they are terrestrial plants. As the name suggests, eelgrass appears as long, green blades of grass, poking out of sandy substrates, primarily in sheltered bays and inlets. Eelgrass can grow in small patches in the intertidal zone, but given the right conditions, can become large, dense beds or meadows in waters down to 5m of depth. Underneath the sands, eelgrasses have complex root systems, comprising of networks of rhizomes bound to the sand. In UK waters, there are approximately two species of eelgrass; dwarf eelgrass (Zostera noltei) and common eelgrass (Z. marina).

In terms of their conservation importance, eelgrass are a habitat forming species, providing shelter and food for a vast number of wildfowl and marine species, such as Brent geese, widgeon, fish, molluscs, invertebrates (including stalked jellyfish!) and algae. This includes a number of interesting cryptic, juvenile and endemic species, as well as well-known charismatic ones, such as seahorses. Eelgrass beds support a number of food chains, including detritivores from the decomposition of eelgrass leaves. Its root system also provides valuable air pockets and space for burrowing worms and molluscs. Aside from high biological diversity within the eelgrass beds themselves, scientific evidence suggests adjacent habitats also benefit significantly; with increased numbers of individuals and species.

The presence of common eelgrass (Z. marina) identified within Alderney’s waters, taken from past records to help inform the Bailiwick Eelgrass Exploration Project (©Mel Broadhurst-Allen, Alderney Wildlife Trust)
The presence of common eelgrass (Z. marina) identified within Alderney’s waters, taken from past records to help inform the Bailiwick Eelgrass Exploration Project (©Mel Broadhurst-Allen, Alderney Wildlife Trust)

Eelgrass beds can also be considered a good ‘all-rounder’ within the marine environment, as a whole. The root system stabilises the sandy substrates, whilst the leaves slow down strong tidal currents and wave action upon the adjacent shores; reducing the potential for coastal erosion. More recently, eelgrass beds have been recognised as important sites for ‘blue carbon’; whereby they ‘store’ organic carbon within the sediments below. In essence, eelgrass is a pretty big deal in our seas.

The presence of eelgrass within the waters of the channel island of Alderney is of considerable interest. Alderney is a small lump of a rock, surrounded by two extreme high velocity tidal streams, strong wave action and variable weather conditions. Hidden, snug and sheltered within a small number of bays, common eelgrass (Z. marina) exists in patches, with a particularly large bed located at the East end of Alderney, known as Longis Bay.

Training new citizen scientists on how to identify and help record eelgrass presence and location across the Channel Islands, for the Bailiwick Eelgrass Exploration Project (©Mel Broadhurst-Allen, Alderney Wildlife Trust)
Training new citizen scientists on how to identify and help record eelgrass presence and location across the Channel Islands, for the Bailiwick Eelgrass Exploration Project (©Mel Broadhurst-Allen, Alderney Wildlife Trust)

Over the last decade, the Alderney Wildlife Trust has worked with other NGOs, stakeholders and research students to identify eelgrass presence around Alderney. This work developed into the Bailiwick Eelgrass Exploration Project. The aim of this project is to record the presence of eelgrass across the Bailiwick (islands of Alderney, Guernsey, Herm and Sark) through citizen science. It entails engaging with the public on what eelgrass is and how to record it during their recreational snorkelling and diving activities. The project has been a huge success, with numerous new eelgrass sightings recorded by the public across the islands. In part, this is why in 2019, Alderney Wildlife Trust volunteers (and others) were tasked by Project Seagrass to harvest eelgrass (Z. marina) seeds from the Longis Bay bed. This was to help create a new two-hectare eelgrass bed in Dale, Wales. Over 750,000 seeds harvested from eelgrass beds across the UK including the Channel Islands were grown in labs over the winter. In a herculean task by volunteers, the seedlings were finally sown at the site earlier this year. By all accounts, the new eelgrass bed is growing well, and a large proportion of the newly planted seedlings have survived - which is fantastic news. If it continues to grow and colonise new areas nearby, then it could very well form the blue print for restoring this important habitat across all our seas, not only in UK seas, but across the world on a grand scale.

The presence of common eelgrass (Z. marina) identified within Guernsey’s waters, taken from past records to help inform the Bailiwick Eelgrass Exploration Project (©Mel Broadhurst-Allen, Alderney Wildlife Trust)
The presence of common eelgrass (Z. marina) identified within Guernsey’s waters, taken from past records to help inform the Bailiwick Eelgrass Exploration Project (©Mel Broadhurst-Allen, Alderney Wildlife Trust)

To learn more about the wonderful marine conservation work The Wildlife Trusts movement are involved in across the UK, then visit wildilfetrust.org and join us in celebrating National Marine Week this summer from 25th July.

Further information and links

Alderney Wildlife Trust is one of 46 independent environmental charities which collectively are known as The Wildlife Trusts which has more than 850,000 members and 38,000 volunteers across the UK all working together for Nature’s recovery and a Wilder Future.

Project seagrass is a conservation collaboration involving Swansea and Cardiff Universities, Sky Ocean Rescue and WWF

Bailiwick Eelgrass Exploration Project was founded by Alderney Wildlife Trust alongside the Guernsey Biological Records Centre, Guernsey’s Biodiversity Partnership, La Société Guernesiaise and Seasearch.

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