Latin name: Zostera marina
Global Distribution: North Atlantic and North Pacific, Arctic region, only seagrass known from Iceland
UK Distribution: Wide but patchy distribution in southwest of England, the Solent and Isle of Wight on the south coast, Wales, western Ireland, western and eastern Scotland including Orkney and the Shetland Islands
Size: up to 1m in length
Diet: Buoyant leaves shoot from a mat of seagrass roots and these leaves draw energy from the sun by photosynthesis
Habitat: Sands and fine gravels in shallow and often sheltered subtidal waters up to 8 metres deep on spring tides.
Seagrass ecosystems as a globally significant carbon stock, Nature Geoscience (2012) 20 May 2012

Seagrass is a vascular plant that has roots, stems and leaves and should not be confused with algae or seaweed. Seagrasses can store up to twice as much carbon per square kilometre as a land-based forest. By trapping sediments, seagrass meadows are now increasingly recognised as natural hot-spots for carbon sequestration. Sea grass meadows have been recorded in coastal waters around the south of Arran and off Pirnmill to the North West of the island.

There are two types, one short and hardy – Zostera noltii – and the longer Zostera marina, which looks much like a tangled thicket of grass and grows in deeper parts of the seabed. They stabilise sandy sediments and provide habitat and nursery grounds for commercially important species of fish and crustaceans. Unfortunately, seagrass meadows are in decline due to pollution, dredging, and other marine activities which damage the seabed. It is estimated that 29% of historic seagrass meadows have been lost globally and will continue to shrink by 1.5% annually. The science which has now linked seagrass meadows with carbon storage will only further strengthen the case for their protection in years to come as government and industry seek to reduce greenhouse gas emissions.

Fun facts

  • Even when the seagrass dies and/or is detached from the seabed, the washed up remains can still build ecosystems inhabited by insects and other invertebrates.
  • Humans use this particular species for various purposes, such as roof thatching, fertiliser (especially in Norway) and as stuffing for mattresses and furniture.