An irregular patchwork of red and green algae typically covered stretches of the intertidal sand at Studland Bay when I visited in March and April. The density of weed that gets washed up varies from day to day and from one part of the beach to another. This picture was taken on the same afternoon and a few hundred yards apart from the picture at the foot of this posting.
One of the weeds that gets washed up is Eel Grass or Grass Wrack, Zostera marina Linnaeus. It is green and grows in the sea but is not actually a seaweed as we know it but is a flowering plant. Eel Grass grows rooted into the seabed sediments in clear sunlit shallow water at the end of Studland Bay nearest to Old Harry Rocks.
Eel Grass is of great importance at Studland Bay as a habitat for two species of sea horses. The mooring of boats in this part of the bay affects the habitat because the letting down, dragging, and pulling up of anchors uproots the grass. A survey is currently underway to determine the extent of the damage to the Zostera beds. The population of the tiny sea horses is being monitored. Divers are carefully tagging the small creatures to see exactly what is happening to this special population. The results will be used to work out whether activities should be restricted in this area.
The other green weed found in abundance washed up on the beach is a true green alga called Sea Lettuce, Ulva lactuca Linnaeus. Also called Green Laver, this algal species belonging to the Chlorophyceae or green seaweeds is edible just like the Purple Laver Porphyra umbilicalis (Linnaeus) Agardh. It is like a broad flat crumpled green sheet, very thin (only two cells thick), and translucent. It starts off being attached to stones and rocks by a small holdfast but easily becomes detached. It can still live and thrive free-floating in the sea. The colour of green is variable and sometimes it has white edges – which occurs after it has shed its reproductive products into the water.
There are lots of recipes on-line for Sea Lettuce. Its appearance has also inspired creative works like a scarf knitting pattern!