Cornish Biodiversity Network  -  Supporting Wildlife Recording

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Cornish Red Data (2009)

The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.

Zostera marina - Eelgrass

Range & Status

Native. Circumpolar Wide-temperate species. Appears to be found all around the coasts particularly between Hampshire and the Isles of Scilly, the Channel Islands, western Scotland and the Orkneys, western Ireland, and scattered elsewhere.

Regional Distribution

Since 1999, rooted Zostera marina has been found in: Mount' s Bay, between St. Michael' s Mount and Newlyn (SW53 to SW42), mostly the western part; in the sub-tidal Helford (SW72); Gerrans Bay (SW83); the western side of St. Austell Bay, between Ropehaven and Duporth (SX05); Looe (SX25); and Cawsand Bay (SX45). It undoubtedly still occurs in the Fal (SW83) and Fowey (SX15) estuaries (last seen in since 1998). Zostera is widespread on the sand-flats on the Isles of Scilly.

Habitat & Ecology

It grows mostly in the sub-tidal zone, rooted in muddy or sandy substrates in the sheltered parts of bays or estuaries on the southern coast of Cornwall or on sandy flats between the main islands of the Isles of Scilly. It often forms dense lawns, important as shelter and breeding grounds for many species of marine fauna. Populations fluctuate markedly, caused by natural changes such as shifts in sediment deposition, and disease, or by destructive man-made changes.


Major threats throughout its range are from dredging, dumping of silt, pollution and mechanical damage from mooring boats, anchors and chains.


Most sites are protected.

Click here to see Aphotoflora images by David Fenwick


I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.

The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.

Cornish Biodiversity Network. 2017.