Seaweed
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Seaweed-covered rocks in the UK |
Biologists, specifically
phycologists, consider
seaweed to be any of a large number of
marine benthic algae that are
multicellular, macrothallic, and thus differentiated from most algae that tend to be
microscopic in size
[ Smith, G.M. 1944. Marine Algae of the Monterey Peninsula, California. Stanford Univ., 2nd Edition.]. Many phycologists prefer the term "
marine macroalgae" over "seaweeds". Seaweeds are classified into
brown (
Phaeophyta),
red (
Rhodophyta) and
green algae (
Chlorophyta) based on their pigment composition. There are a few species of
cyanobacteria however, that may also be categorized as seaweeds. Seaweeds are not to be confused either with plants like
seagrasses (which are
vascular plants), or actual weeds in the sense of nuisance blooms or accumulations of unwanted species — certainly, seaweeds are natural components of pristine marine ecosystems. (The best definition of "weed" is "A plant in the wrong place").
There was a time when a book on the study of seaweeds would have been the reverse of popular. In the early 19th Century they were treated with distain by some:- There was a time when a student who, having collected some beautiful algae on the shore, showed the contants 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!" (Landsborough, D. 1857.
A Popular History of British Seaweeds...)
Seaweeds may have an appearance that 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 (in 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
frond.
References
Lewis, J.R. 1964.
The Ecology of Rocky Shores. The English Universities Press Ltd.
Seaweeds are extensively used as food by coastal peoples, particularly in
Japan and
Korea, but also in
China,
Vietnam,
Indonesia,
Peru, 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) is another red alga used in producing various food additives.
Seaweeds are also harvested or cultivated for the extraction of
Alginate,
Agar and
Carrageenan, collectively known as
hydrocolloids or phycocolloids. Hydrocolloids have attained commercial significance because they are used in various industries, the most common being food production
[Round F.E. 1962 The Biology of the Algae. Edward Arnold Ltd.]. Agar is found 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. Alginate enjoy many of the same uses as carrageenan, but is 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. 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 less-know macroalgal polysaccharides, also have several important biological activities or applications in biomedicine. For instance, it has been demonstrated in laboratory studies that seaweeds may have curative properties for
tuberculosis,
arthritis, colds and
influenza, and worm infestations. [
1]
A number of research studies have been conducted to investigate claims of seaweed's effects on human health. [
2]
Other seaweeds may be used as
seaweed fertiliser.
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The Seaweed Site, information on all aspects of seaweeds and marine algal biology
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AlgaeBase, a taxonomic database of algae
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SeaweedAfrica, information on seaweed utilisation
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NCBI PubMed Search , allows for search on health research studies, including seaweed
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Seaweed Research Links, Many useful seaweed research links
