ReMEDIES Seagrass Survey on Scilly, 2022

Over the summer, partners in the LIFE Recreation ReMEDIES project took advantage of good weather to survey seagrass beds along the south coast of England. The second week of August saw the annual seagrass survey in the Isles of Scilly. This is part of the longest annual seagrass survey in the world (1996-present), and it also meets the UK's legal requirement to assess this species in the Isles of Scilly Special Area of Conservation.

In addition to being part of ReMEDIES, the survey also contributes to work for Project Seagrass. A team of seven volunteer divers and snorkellers from Swansea University, Natural England and the Marine Conservation Society visited five sites across Scilly to collect data about the condition of the seagrass beds there. The focus of this survey was the species called common eelgrass (Zostera marina) which occurs on sandy seabeds in shallow, sheltered waters and was funded this year by Natural England.

Each survey follows a strict protocol to avoid potential bias when collecting data.

Previous studies have indicated the overall extent of seagrass in Scilly (and more broadly in the UK) has declined, so there is clear need for greater understanding about the status and function of this important habitat. Over 92% of seagrass beds have been lost from the UK coastline over the last century, mostly through human disturbance. The habitat itself is important because it supports large densities of invertebrates, provides habitat for threatened and protected species (including stalked jellyfish), nursery-grounds for commercially valuable fish, protects the coastline from erosion and of increasing interest acts as a repository for ‘blue carbon’ (organic carbon that is stored within marine habitats). Seagrasses are pretty amazing; they are the only flowering plant that can photosynthesise and pollinate whilst underwater.

Other epiphytic animals found regularly in the seagrass were stalked jellyfish (Calvadosia campanulata)

The trip was coordinated by Jim Bull and Emma Kenyon of Swansea University and under their careful organisation, it ran very smoothly. We stayed in Hugh Town on St Mary’s. Our host Lisa, at The Bylet B&B, is by now very used to (and tolerant) of our unusual activities (like measuring thousands of seagrass fronds, sometimes in the rain) and clutter of diving equipment. Having the Swansea University rib (which we shipped over with us on the RMV Scillonian) meant we could get to the sites easily when weather and tides permitted; this made planning of surveys relatively easy.

In contrast to last year, when windy weather meant we were a little pushed to complete the work, calm weather in the first few days allowed us to survey the five sites - Broad Ledges (Tresco), Old Grimsby Harbour (Tresco), West Broad Ledges, Higher Town Bay (St Martin’s) and Little Arthur (Eastern Isles) - ahead of time. This meant we could spend a day exploring some of the other islands and I spent a lovely day walking round Bryher and Tresco.

The five sites we visited have each been surveyed every year since 1996 – that’s a pretty impressive time-series!  We collected data about the density and length of shoots, how much of the leaves are covered by other organisms (epiphytes) and the prevalence of a wasting disease that affects seagrass. The data will be worked up in due course in a report to Natural England and will contribute to the overall objectives of the ReMEDIES project.

Inquisitive common prawns (Palaemon serratus) come to check out the surveyors.

AUTHOR

Dr Angus Jackson
Seasearch Data Officer

Angus joined the Marine Conservation Society in 2018 as the data officer for Seasearch. Much of his working week is spent delving around the large project databases containing records of species and habitats on the seabed around the British Isles.