Seaweed

Seaweed-covered rocks in the UK

For the rock musician, see; Seaweed (musician)

Seaweeds are any of a large number of marine benthic algae. They are macroscopic, multicellular, and macrothallic, in contrast with most other algae ^[1].

Dead Man's Fingers (Codium fragile) off Massachusetts coast

Taxonomy

Seaweeds are classified into brown (Phaeophyta), red (Rhodophyta) and green algae (Chlorophyta) based on their pigment composition.

Seaweeds are often confused with other photosynthetic organisms. Seaweeds are popularly described as plants, but biologists typically do not consider them true Plantae.^{[citation needed]} They should not be confused either with plants, such as seagrasses (which are vascular plants). In addition, a few species of cyanobacteria bear a resemblance to seaweed algae.^{[citation needed]}

Many phycologists prefer the term "marine macroalgae" over "seaweeds". ^{[citation needed]}

History

In the early 19th century seaweeds were treated with disdain by some:

There was a time when a student who, having collected some beautiful algae on the shore, showed the contents of his vasculum to the Professor of Botany, expressing a wish to get some information respecting them. The Professor looked at them, and putting on his spectacles, again looked at them, when, pushing them from him, he exclaimed: "Pooh! a parcel of Seaweeds, Sir; a parcel of Seaweeds!" ^[2]

Structure

The top of a kelp forest in Otago, New Zealand

Seaweeds' appearance somewhat resembles non-arboreal terrestrial plants.

• thallus: the algal body
  • lamina: a flattened structure that is somewhat leaf-like
    • sorus: spore cluster
    • on Fucus, air bladders: float-assist organ (on blade)
    • on kelp, floats: float-assist organ (between lamina and stipe)
  • stipe: a stem-like structure, may be absent
  • holdfast: specialized basal structure providing attachment to a surface, often a rock or another alga.

The stipe and blade are collectively known as fronds.

Ecology

References

Lewis, J.R. 1964. The Ecology of Rocky Shores. The English Universities Press Ltd.

Uses

Food

Packaged seaweed

Seaweeds are extensively used as food by coastal peoples, particularly in Japan and Korea, but also in China, Vietnam, Indonesia, Peru, Taiwan, the Canadian Maritimes, Scandinavia, Ireland, Wales, Philippines, and Scotland, among other places. For example, Porphyra is a red alga used in Wales to make laverbread, and in Japan dried, formed into sheets called nori which is widely used in soups, and for wrapping sushi, boiled rice stuffed with bits of raw fish, sea urchin roe, or other ingredients. Chondrus crispus (commonly known as Irish moss or carrageen moss) is another red alga used in producing various food additives, along with Kappaphycus and various gigartinoid seaweeds.

Seaweeds are also harvested or cultivated for the extraction of alginate, agar and carrageenan, gelatinous substances collectively known as hydrocolloids or phycocolloids. Hydrocolloids have attained commercial significance, especially in food production ^[3]. Agar is used in foods such as confectionary, meats and poultry products, desserts and beverages and moulded foods. Carrageenan is used in preparation of salad dressings and sauces, dietetic foods, and as a preservative in meat and fish products, dairy items and baked goods. Alginates enjoy many of the same uses as carrageenan, but are also used in production of industrial products such as paper coatings, adhesives, dyes, gels, explosives and in processes such as paper sizing, textile printing, hydro-mulching and drilling. The food industry exploits the gelling, water-retention, emulsifying and other physical properties of these hydrocolloids.

Medicine

In the biomedicine and pharmaceutical industries, alginates are used in wound dressings, and production of dental moulds and have a host of other applications. In microbiology research, agar is extensively used as culture medium. Carrageenans, alginates and agaroses (the latter are prepared from agar by purification), together with other lesser-known macroalgal polysaccharides, also have several important biological activities or applications in biomedicine.^{[citation needed]}

A number of research studies have been conducted to investigate claims of seaweed's effects on human health^[4]. It has been asserted that seaweeds may have curative properties for tuberculosis, arthritis, colds and influenza, worm infestations and even tumors^[5].^{(dubious; discuss)}

Other uses

Seaweed washed up on beach

Other seaweeds may be used as seaweed fertiliser.

Knotted wrack, a type of seaweed, on an exposed tidal shore-line

References

1. ^ Smith, G.M. 1944. Marine Algae of the Monterey Peninsula, California. Stanford Univ., 2nd Edition.
2. ^ Landsborough, D. 1857. A Popular History of British Seaweeds
3. ^ Round F.E. 1962 The Biology of the Algae. Edward Arnold Ltd.
4. ^ [1]
5. ^ [2]

External links

• The Seaweed Site, information on all aspects of seaweeds and marine algal biology
• AlgaeBase, a searchable taxonomic, image, and utilization database of freshwater, marine and terrestrial algae, including seaweeds. The database is searched 10,000 times a day.
• SeaweedAfrica, information on seaweed utilisation for the African continent.
• NCBI PubMed Search , allows for search on health research studies, including seaweed
• Seaweed Research Links, Many useful seaweed research links

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