Laminaria digitata

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Laminaria digitata
Scientific classification
(unranked): SAR
Superphylum: Heterokonta
Class: Phaeophyceae
Order: Laminariales
Family: Laminariaceae
Genus: Laminaria
Species: L. digitata
Binomial name
Laminaria digitata
(Huds.) Lamouroux, 1813

Laminaria digitata is a large brown alga in the family Laminariaceae, also known by the common name Oarweed. It is found in the sublittoral zone of the northern Atlantic Ocean.


Laminaria digitata

L. digitata is a tough, leathery, dark brown seaweed that grows to two or three metres. The holdfast which anchors it to the rock is conical and has a number of spreading root-like protrusions called rhizoids. The stipe or stalk is flexible and oval in cross section and may be over 1 inch in diameter and grow to 5 feet in length.[1] The blade is large and shaped like the palm of a hand with a number of more or less regular finger-like segments. This seaweed can be distinguished from the rather similar Laminaria hyperborea by being darker in colour and having a shorter stipe that does not easily snap when bent.[2]


The life cycle is of the large diploid sporophytes and microscopic gametophytes. Spores develop in sori which occur over the central part of the blade.[3]


L digitata occurs in the north west Atlantic from Greenland south to Cape Cod and in the north east Atlantic from northern Russia and Iceland south to France. It is common round the coasts of the British Isles except for much of the east coast of England.[2]


L digitata is found mostly on exposed sites on shores in the lower littoral where it may form extensive meadows and can be the dominant algal species. It has a fairly high intrinsic growth rate compared to other algae, 5.5% per day, and a carrying capacity of about 40 kg wet weight per square meter. It may reach lengths of about 4 m. It overlaps to a small degree in distribution with Fucus serratus and Alaria esculenta. It is highly susceptible to grazing by sea urchins, among other species. It has low and high light limitation values of about 5 and 70 W per square meter respectively. Its distribution is also limited by salinity, wave exposure, temperature, desiccation and general stress. These and other attributes of the alga are summarized in the publications listed below.[4][5][6]


L digitata was traditionally used as a fertiliser and spread on the land. In the 18th century it was burnt to extract the potash it contained for use in the glass industry. In the 19th century it was used for the extraction of iodine. Both these uses died out when cheaper sources for these products became available. It is still used as an organic fertiliser but also for the extraction of alginic acid, the manufacture of toothpastes and cosmetics, and in the food industry for binding, thickening and moulding.[7] It is used in Japan and China for making dashi, a soup stock, and for other culinary purposes.[7]

Historically, the dried stalks of L digitata, called sea-tangle tents were used as an abortifacient[8] and for inducing labour.[9]


  1. ^ Dickinson, C.I. 1963 British Seaweeds. The Kew Series,
  2. ^ a b Laminaria digitata (Hudson) J.V. Lamouroux The Seaweed Site. Retrieved 2011-09-22.
  3. ^ Bunker, F.StP.D., Maggs, C.A., Brodie, J.A. and Bunker A.R. 2017, Seaweeds of Britain and Ireland. Second Edition. Wild Nature Press, Plymouth, UK. ISBN 978-0-9955673-3-7
  4. ^ Lewis, J.R.year=1964. The Ecology of Rocky Shores. English Universities Press, London. 
  5. ^ Seip, K.L. 1980. A mathematical model of competition and colonization in a community of marine benthic algae. Ecological modelling 10:77-104
  6. ^ Seip, K.L. Mathematical models of rocky shore ecosystems. In Jørgensen, SE and Mitch, WJ (Eds) Application of ecological modelling in environmental management, Part B, Chap 13, pp 341-433
  7. ^ a b Irish seaweeds[permanent dead link] Retrieved 2011-09-22.
  8. ^ Brookes, Barbara. "Isabel Annie Aves". Dictionary of New Zealand Biography. Ministry for Culture and Heritage. Retrieved 23 April 2017. 
  9. ^ Lawrence, Ghislaine. The Lancet360. 9331 (Aug 10, 2002): 497.

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