''Laminaria digitata'' is a large

brown alga Brown algae (: alga) are a large group of multicellular algae comprising the class Phaeophyceae. They include many seaweeds located in colder waters of the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and polar reg ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Laminariaceae Laminariaceae is a Family (biology), family of brown algal seaweeds, many genera of which are popularly called "kelp". The table indicates the genera within this family. Guiry, M.D. & Guiry, G.M. (2006). AlgaeBase version 4.2. World-wide electron ...

, also known by the common name oarweed. It is found in the sublittoral zone of the northern

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

Description

''Laminaria digitata'' is a tough, leathery, dark brown seaweed that grows to long. The holdfast which anchors it to the rock is conical and has a number of spreading root-like protrusions called

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be un ...

s. The stipe or stalk is flexible and oval in cross section and may be over 1 inch in diameter and grow to in length. 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 Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

can be distinguished from the rather similar ''

Laminaria hyperborea ''Laminaria hyperborea'' is a species of large brown alga, a kelp in the family Laminariaceae, also known by the common names of tangle and cuvie. It is found in the sublittoral zone of the northern Atlantic Ocean. A variety, ''Laminaria hyperb ...

'' by being darker in colour and having a shorter stipe that does not easily snap when bent.Laminaria digitata (Hudson) J.V. Lamouroux
The Seaweed Site. Retrieved 2011-09-22.

Reproduction

The life cycle is of the large

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

sporophyte A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...

s and microscopic gametophytes. Spores develop in sori which occur over the central part of the blade.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.

Distribution

''Laminaria digitata'' occurs in the north west Atlantic from

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

south to

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer months. The ...

and in the north east Atlantic from northern

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

and

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

south to

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. It is common round the coasts of the

British Isles The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebr ...

except for much of the east coast of

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

Ecology

''Laminaria 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. It is a known host of the pathogenic fungus '' Phycomelaina laminariae''.Helgi Hallgrímsson & Guðríður Gyða Eyjólfsdóttir (2004)
''Íslenskt sveppatal I - smásveppir'' [Checklist of Icelandic Fungi I - Microfungi
Fjölrit Náttúrufræðistofnunar. Náttúrufræðistofnun Íslands [Icelandic Institute of Natural History]. ISSN 1027-832X

Uses

''Laminaria digitata'' is harvested offshore of France and Morocco for use in manufacturing alginic acid. It is used as an ingredient in some cosmetics. It 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 Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

. Historically, the dried stalks of ''L digitata'', called ''sea-tangle tents'' were used in

traditional medicine Traditional medicine (also known as indigenous medicine or folk medicine) refers to the knowledge, skills, and practices rooted in the cultural beliefs of various societies, especially Indigenous groups, used for maintaining health and treatin ...

as an

abortifacient An abortifacient ("that which will cause a miscarriage" from Latin: '' abortus'' "miscarriage" and '' faciens'' "making") is a substance that induces abortion. This is a nonspecific term which may refer to any number of substances or medications, ...

and for mechanically inducing labour.

References

External links

Laminaria Digitata on AlgaeBase
{{Authority control Laminariaceae Edible algae Edible seaweeds Biota of the Atlantic Ocean Marine biota of Europe Marine biota of North America Flora of Subarctic America Flora of Eastern Canada Flora of the Northeastern United States Flora of France Flora of Northern Europe Flora without expected TNC conservation status