MACOI - Portuguese Seaweeds Website

Class:

Phaeophyceae

Genus:

Laminaria J.V. Lamouroux

Species:

Laminaria digitata

Authority:

(Hudson) J.V. Lamouroux

Description:

A large conspicuous kelp growing up to 2 m in length commonly found at low water during spring tides on rocky shores. The frond is broad and digitate, glossy and dark brown in color and lacks a midrib. The stipe is oval in cross section, smooth and flexible and is usually free of epiphytes, although old stipes which has become slightly roughened may support a few epiphytes, notably Palmaria palmata. The kelp is attached by freely branched haptera, which spread out to form a shallow dome-shaped holdfast. Laminaria digitata may be confused with young Laminaria hyperborea plants. However, the stipe of Laminaria hyperborea is circular in cross section, is stiff and snaps easily when bent (although you won't see that in younger plants).

Original publication: Lamouroux, J.V.F. (1813). Essai sur les genres de la famille des thalassiophytes non articulées. Annales du Muséum d'Histoire Naturelle, Paris 20: 21-47, 115-139, 267-293, Plates 7-13.

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Laminaria digitata is a large, tough, glossy kelp, which can grow from 1 to 3 meters in size, and up to 4 meters in optimum conditions. Its color ranges from dark brown to golden brown to olive brown to olive green. The broad frond or blade is large, lacks a midrib, and is shaped like the palm of a hand with a number of more or less regular finger-like segments (hence the Latin name for this seaweed). The number of frond digits extend almost to the base of the frond, and vary with amount of exposure. In shelter these are few and short, but with increasing exposure, they are more numerous (up to 10 or 12). The length of the frond varies with season, age of plant and location, and can reach lengths of 1 to 1.5 meters in suitable conditions. The smooth and flexible stipe (stem, or stalk) is oval in cross-section, can be 3 to 4 centimeters in diameter, smooth, flexible, non-sticky, and is usually free of epiphytes, although old stipes which have become slightly roughened may support a few epiphytes, particularly Palmaria palmata. Laminaria digitata attaches to anchor stones and rocky substrates by freely branched haptera, which spread out to form a shallow dome-shaped, claw-like holdfast. The spreading root-like protrusions are called rhizoids.

This perennial species lives for 3 to 6 years, and in some cases reached 10 years. Laminaria digitata grows more slowly from late summer to January, and then experiences rapid growth from February through July. It is one of the more deeper growing edible seaweeds, and may only accessible a few days out of every month on the lowest new and full moon tides. Laminaria digitata is found in rock pools and attached to rocks, bedrock or other suitable hard substrata in the lower intertidal and subtidal or sublittoral fringe, down to a maximum depth of 20 meters in clear waters. It can be found higher up on the shore in areas of intense wave action. Laminaria digitata clings to the rocks as the full force of the ocean flows through its fingers in heavy waves, swells, and surf, and flourishes in moderately exposed areas or at sites with strong water currents. With its flexible stipe and deeply divided blade, it is well adapted to fast, turbulent water flow and multidirectional forces. In the upper sublittoral, Laminaria digitata grows in masses and forms extended uniform kelp beds or meadows. When it does become occasionally exposed at extreme low tide, it lies flat on the seabed with the uppermost blades covering the lower ones, protecting them against desiccation from wind and sun. The extension of Laminaria digitata beds into greater depths of the mid-sublittoral zone is restricted by the occurrence of Laminaria hyperborea, thus Laminaria digitata can often be found as a belt above Laminaria hyperborea. Its distribution is also limited by salinity, wave exposure, temperature, desiccation and general stress. Laminaria digitata may be confused with young Laminaria hyperborea plants. Laminaria digitata is darker, its stipe is oval in cross-section and is very flexible, whereas Laminaria hyperborea is lighter in color, and its stipe is circular, longer, and thicker.

Link for Seaweeds Industry Association

Name History

Adjective (Latin), digitate, with leaflets radiating from tip of leaf-stalk

Biogeography

Laminaria digitata is a North Atlantic Arctic-cold-temperate species which does not occur in the North Pacific. It is found along both coasts of the English Channel; the southernmost occurrence of this species in European waters is on the southern coasts of Brittany. Laminaria digitata grows along most coasts of Britain and Ireland, and along the North Sea coasts of Scandinavia. Its northerly range includes into the Barents Sea and the western shores of Novaya Zemlya, and has been reported to occur in the Svarlbard Archipelago. Laminaria digitata also grows in Iceland, the Faeroes, southern Greenland and the eastern coasts of North America, as far south as Cape Cod.

Uses and compounds

Animal aquaculture - animal feed

Direct use as food - additive, ground whole tissue; food, consumed whole; Contains: ascorbic acid (vitamin C); calcium; carbohydrates; iodine; iron; laminarins/laminarans; lipids; magnesium; manganese; mannitol; niacin (vitamin B3); protein; riboflavin (vitamin B2); sodium; thiamin (vitamin B1).

Health, cosmetics, thalasotherapy, wellness & folk medicine - used as additive in cosmeticas; mineral supplement; Contains: ascorbic acid (vitamin C); iodine

Provide biological, medical and pharmacological activity - antimicrobial; treatment of goitre

Source of hydrocolloids - source of agar; Contains: alginates/alginic acids; source of laminaran; source of porphyran

Source of organic chemicals - source of polyols; Contains: mannitol

Terrestrial plant and animal production - animal feed (additive); Contains: ash; carbohydrates; fibre; lipids; protein; water; fertiliser - contains: ash; copper; iron; manganese; nitrogen; organic matter; phosphates; strontium; water; zinc.

Other uses: Laminaria digitata plants contain minerals, vitamins and trace elements. These include iodine, calcium, potassium, iron, carotene, alginic acid, laminaran, mannitol, protein, carotene, niacin, phosphorus, the B complex vitamins, vitamin C and many other trace elements. This species stores flavor-enhancing glutamic acid, or sodium glutamate, which imparts a mellow, silky taste to dishes. The slight sweet background is mannitol, a natural sugar. In terms of relatives, Laminaria digitata is closely related to the five species (Saccharina latissima, Saccharina japonica, Laminaria angustata, Laminaria longissima and Laminaria ochotensis) typically harvested as 'kombu' in Japan, and is frequently harvested and sold as kombu in North America. Many recipes calling for kombu could be made with this form of kelp.

Laminaria digitata, both harvested and collected from the shore, was traditionally used as an agricultural fertilizer. In the 18th century it was burned to extract the potash it contained for use in the glass industry. In the 19th and 20th centuries it was used for the extraction of iodine. It is still used as an organic fertiliser but more recently Laminaria digitata is commercially harvested in Brittany for alginate production. Its use is expanding to thalassotherapy and balneotherapy and other specialty products. The extraction of alginic acid contributes to applications such as the manufacture of toothpastes and cosmetics, and in the food industry for binding, thickening and moulding. With increased demand, harvesting became mechanised in order to be effective. In Europe, the other kelp species exploited by the hydrocolloid industry is Laminaria hyperborea. They are also utilised by the cosmetic and agrochemical industries and for biotechnological applications. Laminaria digitata is imported in Japan and China for making dashi, a soup stock, and for other culinary purposes, such as accelerating the cooking time of vegetables such as beans and lentils.

Over 40 companies from the UK, Ireland, Iceland, France, Italy, Germany, United States, Canada, and Australia are selling more than 100 different products which include Laminaria digitata as an ingredient. Some examples are listed below.
Personal care products:

body wraps, cleansing muds, and bath soak products
facial masks and toners, body scrubs and soaps
shampoos and conditioners
makeup removers, and cleansing milks, gels, and creams
body lotions, shaving lotion, and indoor tanning lotion
eye contour serum, rejeuvenating eye cream, day creams, night creams, hand creams, and repair creams
slenderizing gels and anti-cellulite drainage serums and treatments
skin rejeuvenators, hydrators, and moisturizers, including collagen stimulators for increasing skin elasticity and firming which helps diminish fine lines and wrinkles over time
Laminaria digitata is known to revitalize tired looking skin and is an effective anti-oxidant helping repair damage caused by free radicals and improving dull complexions

Food and nutrition products:

as a sea vegetable: snacks, soup mixes, flavoring and seasoning; slaw
flakes, powder, and whole
nutritional supplements and energy drinks

Commercial applications:

agricultural and gardening fertilizers, and animal feeds
alginic acid for the hydrocolloid industry
biodegradable surface cleaners for use in home, garden, and commercial and industrial settings

Harvesting: Large scale, mechanical harvesting of Laminaria digitata takes place in Brittany, France and Iceland. Smaller scale harvesting by hand takes place in Ireland, the UK, Canada, and the United States.

France has a long history of seaweed harvesting. Kelps were traditionally harvested by hand and transported from the shore by horses. Today, there are certain ports along the coast of Brittany where the boats land their harvest. In the ports the raw material is loaded onto trucks. Each loaded truck has to drive over a balance to register the weight of the biomass harvested by the particular boats, before transporting the raw material to the processing companies. The prices for the Laminaria digitata are negotiated by the fishermen and the industry before the start of the harvesting season and are valid throughout the season. Prices are adjusted for each boat at the dockside to take into account the actual quality in terms of purity of the crop (for example, the proportion of Saccharina polyschides within the Laminaria digitata harvest, and the amount of stones pulled up with the crop). In France, about 60,000 tonnes of Laminaria digitata are harvested annually, primarily in Brittany, for the French hydrocolloid industry. Laminaria digitata was previously an important source for the Norwegian alginate industry. This was harvested in Norway by hand from the lower eulittoral, but with the advent of mechanical harvesting of Laminaria hyperborea and Ascophyllum nodosum, the use of Laminaria digitata has essentially ceased there.

Because kelp species are long-lived and are of major importance as constituents of the benthic lower intertidal and subtidal ecosystems, specific management schemes have been developed to ensure sustainable harvesting. In France, seaweed harvesting is regulated by the French Government and the National Syndicate of Marine Algae, which is a group drawn from the kelp industry (comprised of two companies), fishermen and scientific advisers. Several dozen boats are licensed for harvesting of Laminaria digitata. Landings of raw material per boat are restricted to 1,000 to 1,500 tons per year, and harvesting quotas are bound to the harvesting vessel. Only a portion of the biomass of a kelp forest is harvested. Regulations of harvesting times are imposed to make allowance for growth, reproduction and regeneration of kelp beds. These measures are thought to be sufficient to ensure sustainable harvesting. Thus, because of a relatively short regeneration time, there are no official regulations on fallow periods. Only in certain areas supporting only a small number of fishing boats, fishermen have introduced fallow periods in self-management.

Harvesting Techniques: In Iceland, the company Thorverk mechanically harvests Laminaria digitata in late autumn and winter by a coaster equipped with a dredge. In Brittany, a specialised mechanical kelp harvesting device mounted on small boats called a "scoubidou" is used. This was a further development of a tool used in the 1950s. The scoubidou is a 2 to 4 meter long steel bar with a spiral curved iron hook or sickle at the end which is suspended from a hydraulic arm mounted on the boat. This is lowered into the thickest part of the Laminaria digitata forests and then rotated or twisted, gathering up the stipes like twisting spaghetti on a fork. The hook is then winched inboard using the hydraulic arm, and whole plants of Laminaria digitata are ripped from the substratum, including blades, stipes and some holdfasts. The scoubidou can pull up about 10 kg per extraction, which takes about 30 seconds. By employing the scoubidou method, kelp plants smaller than 60 centimeters (plants younger than 2 years) are thought to be too small to be caught by the hook and remain to develop into the crop for the following year. Using this method harvests averaged 1.5 to 2 tons wet weight per boat per day. The scoubidou is operated from an 8 to 12 meter long boat manned by one or two harvesters and have a loading capacity of 10 to 20 tons raw material. The larger boats can carry two scoubidous. The scoubidou boats operate in the Laminaria digitata beds from May to October, and during the winter are used to collect scallops. Depending on the size of the boat and the equipment (one or two scoubidous), the boats are allowed to land between 12 to 18 tons of Laminaria digitata per day and 1,000 to 1,500 tons per year.

Manual harvesting is sometimes done with a small boat at low tide, and may involve stepping out of the boat in a wetsuit to cut the Laminaria digitata with a knife. In certain locations with higher tidal range, it may be possible to harvest it without a boat. Regardless of method, juvenile plants should remain uncut.

Provide biological, medical and pharmacological activity - Sixteen species of British marine algae were screened, of which four species, i.e. Laminaria digitata, L. hyperborea, L. saccharina and Fucus spiralis showed potent anticoagulant activity (Deacon-Smith et al., 1985).

References

Braune, W. (2008). Meeresalgen. Ein Farbbildführer zu den verbreiteten benthischen Grün- Braun- und Rotalgen der Weltmeere. pp. [1]-596, 266 pls. Ruggell: A.R.G. Gantner Verlag.

Connan, S., Delisle, F., Deslandes, E. & Gall, E.A. (2006). Intra-thallus phlorotannin content and antioxidant activity in Phaeophyceae of temperate waters. Botanica Marina 49: 39-46.

Dieck, I. tom & Oliveira Filho, E.C. de (1993). The section Digitatae of the genus Laminaria (Phaeophyta) in the northern and southern Atlantic: crossing experiments and temperature response. Marine Biology, Berlin 115: 151-160.

Lane, C.E. & Saunders, G.W. (2005). Molecular investigation reveals epi/endophytic extrageneric kelp (Laminariales, Phaeophyceae) gametophytes colonizing Lessoniopsis littoralis thalli. Botanica Marina 48: 426-436.

Lane, C.E., Mayes, C., Druehl, L.D. & Saunders, G.W. (2006). A multi-gene molecular investigation of the kelp (Laminariales, Phaeophyceae) supports substantial taxonomic re-organization. Journal of Phycology 42: 493-512.

Loiseaux-de Goër, S. & Noailles, M.-C. (2008). Algues de Roscoff. pp. [1]-215, col. figs. Roscoff: Editions de la Station Biologique de Roscoff.

McHugh, D.J. (2003). A guide to the seaweed industry. FAO Fisheries Technical Paper 441: x + 105, 64 figs.

Roeder, V., Collén, J., Rousvoal, S., Corre, E., Leblanc, C. & Boyen, C. (2005). Identification of stress gene transcripts in Laminaria digitata (Phaeophyceae) protoplast cultures by expressed sequence tag analysis. Journal of Phycology 41: 1227-1235.

Deacon-Smith, R. A., Lee-Potter, J. P. and Rogers, D. J., Bot. Mar., 1985, 28, 333–338.

Habitat:

Marine species

Common names:

Oarweed (Eng); tangle (Eng); red-ware (Eng); sea-girdles (Eng); seastaff (Eng); sea-wand (Eng); sea-ware (Eng); seaweed (Eng)

Other names: an choirleach, anguillier, Atlantic kombu, bezhin bleuñv, bezhin siliou, bezhin sklej, bezhin stonn, bezhin warle, Braggair, cholgorn, coirleach, coirrleach, common kelp, cupóga, feamannach dubh, fingered tangle, Fingertang, Fingertäng, Fingertare, foetoù-traezh, fouet de sorcière, gladgesteeld, vingerwier, goazle, goémon de coupe, grac'hle, gwaskle, gwrac’hle, horsetail kelp, kaol, kaolenn, kelp, kombu, Kombu Breton, konbu, korle, laminaire digitée, laminaire flexible, learach, leath, leathach fada, leathrach, liadhaig, melkern, oarweed, oarweed kelp, ouarle, red ware, red wrack, salkorn, sea girdle, sea girdles, sea tangle, sea wand, sea-girdles, silketare, taangel, tali, tali du, tali gwrac'hle, tali laezh, tali moan, tali warle, taly, tangle, Thöngull, vingerwier, warle

Type information:

Type species: This is the type species (lectotype) of the genus Laminaria

Basionym: Fucus digitatus Hudson

Type information: Type locality: England (Silva, Basson & Moe 1996: 904).