MACOI - Portuguese Seaweeds Website

Class:

Phaeophyceae

Genus:

Ascophyllum Stackhouse

Species:

Ascophyllum nodosum

Authority:

(Linnaeus) Le Jolis

Description:

Common large brown seaweed, dominant on sheltered rocky shores. The species has long strap like fronds with large eggshaped air bladders at regular intervals. The fronds of Ascophyllum nodosum are typically between 0.5 and 2 m in length.

This is a brown seaweed that is closely related to Fucus. It forms a single bladders centrally in long, flattened strap-like fronds. The fronds hang downwards, draping sheltered intertidal rocks. Many fronds grow from the base and the plant generally regenerates new fronds from the base when one of the larger fronds are damaged. There is evidence that clumps can be over 400 years old and may be even older. Ascophyllum is currently confined to the North Atlantic basin, but plants have been found growing in San Francisco Bay, but the species does not persist there. The plants are used as packing for shellfish from the North Atlantic and when discarded may take hold.

Link for (Pereira, 2010) Handbook Guide

Original publication: Le Jolis, A. (1863). Liste des algues marines de Cherbourg. Mémoires de la Société Impériale des Sciences Naturelles de Cherbourg 10: 5-168, pls I-IV.

Download PDF from Algaebase

Original description: Download PDF from Algaebase

Ascophyllum nodosum is a perennial brown intertidal seaweed species most abundant on sheltered rocky shores in the mid-intertidal zone of the North Atlantic. Olive green in colour, Ascophyllum nodosum generally grows upward in the water column anchoring to hard substrates using a disc-shaped holdfast. A single specimen resembles an intertwined mass of shoots and branches. Incoming tides gradually refloat vast stands of Ascophyllum nodosum, until it becomes an expansive swaying undersea forest. Its thallus can measure from 30 to 60 centimeters, and is flexible to decrease breakage that may result from strong wave action. Its long, thick, leathery, branching strap-like fronds are typically between 0.5 and 2 meters in length, and have large egg-shaped air bladders ("pneumatocysts") at regular intervals along their length which keep the plant floating upright when submerged at high tide, and hang downwards, draping over intertidal rocks in a thick, tangled, and glistening mat at low tide. The large air bladders take it towards the light for maximum photosynthesis. The fronds have no midrib.

It is present and grows all year round, and has no resting period. The species grows slowly and can live to be several decades old in wave-sheltered locations of temperate waters, and it has the capability to survive low temperatures. It can eventually grow to three and four meters; individual fronds can become up to 15 years old before breakage. The holdfasts of Ascophyllum nodosum are thought to persist for several decades from which new fronds regenerate. Another interesting attribute of Ascophyllum nodosum is that it repeatedly sloughs its entire outer epidermis, a phenomenon not exhibited by other related seaweeds.

Ascophyllum nodosum attaches to rocks and boulders on the middle shore in a range of habitats, from estuaries to relatively exposed coasts. These site can have low, moderate and high wave action across low-, mid- and upper tidal heights, although some subtidal populations have been reported. The upper limits of Ascophyllum nodosum distribution are controlled by its ability to resist desiccation and high temperatures.

Link for Seaweed Industry Association

Name History

Adjective (Latin), knotted, knobbly (Stearn 1973).

Biogeography

Distribution is confined to the North Atlantic basin, found in the Arctic Ocean, Baltic Sea, Belt Sea, Northern Europe, Gulf of Maine, North Sea, and Northwest Atlantic. Its northern limits are northern Norway and the White Sea in the east, and Baffin Island in the west. Southern distributions extend to northern Portugal and New Jersey.

Life Cycle

Link for lifecycle of Ascophyllum nodosum

Uses and compounds

Direct use as food - additive, ground whole tissue;

Health, cosmetics, thalasotherapy, wellness & folk medicine - appetite stimulant, mineral supplement, treatment of rheumatism and unspecified health food;

Source of hydrocolloids - source of alginate and fucoidan;

Terrestrial plant and animal production - animal feed (additive), foliar spray and soil improver.

Ascophyllum nodosum is very effective at accumulating nutrients and minerals from the surrounding seawater, and this is what makes them a valuable resource for human enterprise. This species is harvested for use in items such as food, fertilizer, soil conditioners, animal feed, skin and hair care products, cleaners, degreasers, equestrian products, and nutritional supplements. It is also popular in cosmetology and thalassotherapy. Seaweed Industry Association has identified more than 200 product types from over 100 companies which include Ascophyllum nodosum as an ingredient.

Harvesting

The species is harvested commercially in Canada, the United States, Scotland, France, Norway, Iceland and Ireland.

Harvesting Techniques

Various harvesting practices are used for Ascophyllum nodosum, however the species is predominantly hand-harvested using sickles, knives and various cutting and raking tools. Harvesting is done both from the shore and by boat. It can be cut from rocks while the plants are suspended using small boats and cutting rakes to minimize the disturbance of the plants. One recommendation is to cut at a height of 15 to 25 centimeters above the holdfast so that a portion of the plant remains attached to the rock for further growth.

Mechanical means for harvesting Ascophyllum nodosum are being used in some areas of Iceland and Norway. At one time, floating material was encircled by a seine net and loaded by hand or conveyor belt on a vessel. A different mechanical method involved use of a "cutter rake" consisting of a rake with widely spaced tines and triangular cutting edges between the tines. These rakes permitted harvesting and loading in one operation.

References

Baardseth, E. (1970). Synopsis of biological data on knobbed wrack Ascophyllum nodosum (Linnaeus) Le Jolis. FAO Fisheries Synopsis 38(Rev. 1): various.

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.

Cho, G.Y, Rousseau, F., Reviers, B. de & Boo, S.M. (2006). Phylogenetic relationships within the Fucales (Phaeophyceae) assessed by the photosystem I coding psaA sequences. Phycologia 45: 512-519.

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.

Habitat:

Marine species

Common names:

English: Knotted wrack, Asco, Sea Whistle, Bladderwrack, Egg wrack.

Other names: Alga nodosa, alga nudosa, algue noueuse, an fheamainn bhuí, asco, ascophylle, ascophylle noueuse, ascophylle noueux, egg wrack, favach, feamainn bhuí, fheamuinn bhuide bhuilgíneach, goémon noir, knobbed wrack, Knotentang, Knotswier, knotted kelp, knotted wrack, Norwegian kelp, robert, rockweed, sea whistle, yellow tang.

Type information:

Basionym: Fucus nodosus Linnaeus

Type locality: Atlantic Ocean (Silva, Basson & Moe 1996: 895). Type: LINN “Hallands Väderösund” (Athanasiadis 1996: 217).