oar weed

Oar weed (kelp)

Latin name: Laminaria digitata
Global Distribution: Atlantic coasts of Europe, including Baltic and Black Seas.
UK Distribution: Most British and Irish coasts, scarce along the east coast of England between the Ouse and Thames estuaries.
Size: 2-4m long
Diet: Photosynthetic
Habitat: Exposed shores, attached to bedrock or other suitably hard surfaces. From very low shore to 20m
Sources: http://www.marlin.ac.uk/species/detail/1386

Oarweed is large, brown kelp with a broad body separated into digits (much like finger are digits of a hand). They can be difficult to distinguish from the similar species Laminaria hyperborea, but this species has a circular stalk, compared to the oval shaped stalk in oarweed, which is also stiffer and breaks more easily.

Their habitat can slightly overlap with other seaweeds, such as serrated wrack and dabberlocks (also known as winged kelp). Usually, they are free of any organisms settling and growing on them, but old and damaged individuals may be more susceptible. They are commonly grazed by sea urchins. Reproduction in this species involves going between two different life stages which reproduce through different means. The large kelp stage we often see is the called the sporophyte stage, they release asexual spores that develop into microscopic ‘gametophytes’. They release the egg and sperm cells (gametes) which fuse, develop and grow into large kelps.

Fun facts

  • Compared to other algae L. digitata grows at a very fast pace, with increases in body size of 5.5% per day.
  • This species is traditionally harvested for fertiliser, materials for glass production, iodine extraction and medicine. They are still harvested for the manufacture of alginic acid, an ingredient in some cosmetics.
  • Kelps species, including Oarweed, may also be used as biofuel to avoid growing biofuel crops on land where agriculture for food production could be planted instead.