Seagrass or eelgrass, is a flowering grass that grows in intertidal and shallow coastal waters on sand or mud. There are 3 species of eelgrass growing in the UK, Zostera marina, Zostera augustifolia and zostera noltii. In Orkney only Zostera marina has been recorded although it is possible the other two species are present but have yet to be recorded. The grass grows in beds, creating an important habitat for young fish and marine invertebrates.
Orkney's beds vary considerably from location to location and each has a different assemblage of animals. In some places a profusion of different seasquirts (shown below) can be found. While species of starfish can be common in certain areas, in other areas, there is an abundance of peacock worms (shown below). Pipefish, sandeels, young pollack and wrasse are among the fish species present. There is also a large variety of molluscs to be seen and discovered.
At a small number of locations eelgrass grows in association with maerl. The beautiful pink maerl contrasts with the green of the seagrass bed, creating an almost tropical appearance. In other places seaweed grows amongst the beds. The largest bed in Scapa Flow is at Widewall Bay with smaller sites including Longhope, Graemsay and the Burray pier.
Eelgrass is a priority habitat within the UK Biodiversity action plan. It is vulnerable to a number of different enviromental threats including pollution, low light levels and damage from boat traffic and anchors. In the 1920's and 1930's a wasting diseased resulted in the widespread loss of previously extensive beds in the UK. In Orkney eelgrass was once used as a thatching material, perhaps this suggests that the range of beds here may have retracted over the last 100 years?