Everything about Seaweed totally explained
Seaweeds are any of a large number of
marine plants and
protists in the category of
benthic algae. They are macroscopic and
multicellular, in contrast with most other algae. Seaweeds are often found in the seashore
biome.
Taxonomy
Seaweeds consist of several groups of multicellular
algae: the
red algae,
green algae, and
brown algae. As these three groups are not thought to have a common multicellular ancestor, the seaweeds are a
paraphyletic group. In addition, tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered as seaweeds.
Seaweeds are popularly described as plants, but only red and green algae belong to the
kingdom Plantae. They shouldn't be confused with
aquatic plants such as
seagrasses (which are
vascular plants).
Structure
Seaweeds' appearance somewhat resembles non-
arboreal terrestrial
plants.
- thallus: the algal body
- lamina: a flattened structure that's somewhat leaf-like
- stipe: a stem-like structure, may be absent
- holdfast: specialized basal structure providing attachment to a surface, often a rock or another alga.
- haptera: finger-like extensions of holdfast anchoring to benthic substrate
The stipe and blade are collectively known as fronds.
Ecology
The ecology of seaweeds is dominated by two specific environmental requirements. These are the presence of sea-water (or at least
brackish water) and the presence of light sufficient to drive
photosynthesis. A very common requirement is also to have a firm point of attachment. As a result, seaweeds are most commonly found in the
littoral zone and within that zone more frequently on rocky shores than on sand or shingle. The ecological niches utilised by seaweeds are wide ranging. At the highest level are those that inhabit the zone that's only wetted by the tops of sea spray, the deepest living are those that are attached to the sea-bed under several meters of water. In some parts of the world, the area colonized by littoral seaweeds can extend for several miles away from the shore. The limiting factor in such cases is the availability of sufficient sun-light to support photosynthesis. The deepest living sea-weeds are the various
kelps.
In addition to the familiar sea-shore seaweeds, a number of species have adapted to a fully planktonic niche and are free-floating, often with the assistance of gas filled sacs.
Sargassum is one of the better known examples of this type of seaweed.
A number of species have adapted to the specialised environment of tidal rock pools. In this niche seaweeds are able to withstand rapidly changing temperature and salinity and even occasional drying.
Uses
Food
Seaweeds are extensively used as food by coastal peoples, particularly in East Asia, for example
Japan,
China,
Korea,
Taiwan, and
Vietnam, but also in
Indonesia,
Peru, the
Canadian Maritimes,
Scandinavia,
Ireland,
Wales,
Philippines, and
Scotland, among other places.
Tiwi,
Albay residents discovered a new pansit or
noodles made from seaweed, which has health benefits. It is rich in
calcium and
magnesium and the seaweed noodles can be cooked into pansit canton, pansit luglug,
spaghetti or
carbonara.
In Asia,
gim (in Korea) and
nori (in Japan) are sheets of dried
Porphyra used in soups or to wrap
sushi.
Chondrus crispus (commonly known as
Irish moss or
carrageenan moss) is another red alga used in producing various food additives, along with
Kappaphycus and various gigartinoid seaweeds.
Porphyra is a red alga used in Wales to make
laver and
laverbread, made from oats and the laver, is a popular dish in Wales.
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 as food additives. The food industry exploits the gelling, water-retention, emulsifying and other physical properties of these hydrocolloids. Agar is used in foods such as confectionery, 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.
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.
Seaweed is also a known source of
iodine, an element necessary for
thyroid function with deficiencies leading to
goitre.
It has been asserted that seaweeds may have curative properties for
tuberculosis,
arthritis, colds and
influenza, worm infestations and even
tumors.
(External Link
) A number of research studies have been conducted to investigate these claims and other effects of seaweed on human health.
See also
Fucoidan
Other uses
Other seaweeds may be used as
seaweed fertilizer.
Further Information
Get more info on 'Seaweed'.
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