Economic Importance Of Algae


Algae are useful as food, in industries, in agriculture, as medicine, source of minerals, etc. At the same time production of water blooms, toxicity, etc., are some of their harmful effects.

Useful Activities

The following are some of the important uses of algae.

Benefits of Algae

[I] Algae as food

Algae are rich in carbohydrates, many inorganic and organic compounds, proteins, vitamins, etc. In some of the algae these substances are found in large amounts and are, therefore, used as food.

(1) The following members of Chlorophyceae (green algae) are used as food. Ulva (sea lettuce) is used as a vegetable

after drying and salting. Chlorella has a high percentage of proteins and lipids. Besides this, vitamins A and DD are also found in sufficient amounts. It has a very short life cycle and can be grown quickly. These characteristics make Chlorella a suitable food for future generations. It has also been grown easily in over-head tanks and was considered to be very suitable food for space flights.

(2) Members of Phaeophyceae (brown algae) used as food include Alaria, Laminaria, Sargassum, etc. The food value is due to proteins, fats and carbohydrates. They are rich in iodine and, therefore, goitre does not occur in the countries where these are eaten.

(3) Among Rhodophyceae (red algae) the genera commonly used as food are Chondrus (carrageen or Irish moss), Porphyra, Gigartina, Rhodymenia, etc. In species of Porphyra, vitamins C and B12 are found in sufficient quantities.

(4) A blue-green alga (Cyanophyceae) Nostoc commune is eaten as food in China, Java, etc. Another blue green alga, Spirulina is also used these days being very rich in proteins.

[I] Algae in industry

  1. Agar – Agar. These are obtained from members of Rhodophyceae, collectively called agarophytes e.g., Gelidium, Gracilaria, etc. Agar is a colloidal or jelly-like substance used for culturing bacteria and various other microorganisms. It is also useful in the preparation of medicines. Agar is also used in baking and confectionary
    industry as emulsifying agent and in cosmetics, textile, leather and paper industries. It is also useful as a laxative.
  2. Carrageenin. It is a cell wall derivative of a red alga-Chondrus crispus and is used as an emulsifying and stabilizing agent in ice creams, chocolates, cosmetics, tooth pastes, etc.
  3. Algin. This cell wall derivative of some brown algae like Alaria, Ascophyllum, Fucus, etc., is widely used in preventing formation of crystals in ice-creams. It is also used in the rubber, tyre and paint industry. Besides, it is also used to stop bleeding and in the preparation of. soups, creams, sauces, etc.
  4. Diatomite. It is a deposit of dead frustule styles or cell walls of fossil diatoms (Bacillariophycean The walls of diatoms have a heavy deposit of silicon dioxide (SiO). When the diatoms, which form a major part of planktons, die, the remainder of the cell wall are deposited at the bottom of the water reservoirs. These deposits are called (or kieselguhr). It has diatomaceous earth following uses.

(1) It is used as an insulating agent in boilers, steam pipes, furnaces, etc., where the temperature rises to about 1000° F.

(2) It is used in car polishes, silver polishes and toothpastes.

(3) It is an absorbent for nitroglycerine, hence used in the transport of dynamite.

(4) Diatomite is also useful in oil refineries for the filtration process.

(5) It is useful in the preparation of paint, varnishes, abrasives, glass and porcelain.

[II] Algae as source of minerals

Seaweeds are very rich in minerals and form the commercial source of their extraction. Kelps, the members of Laminariales of Phaeophyceae (Ascophyllum, Ecklonia, Laminaria, etc.) were the chief source of iodine extraction in Europe. Bromine is extracted from members of Rhodophyceae like Polysiphonia, Rhodymenia, etc.

[IV] Algae as manure

In France, Iceland, Scotland and Norway, members of Phaeophyceae (brown algae) like Fucus Macrocystis, Sargassum, etc., are used as manure. Many useful inorganic minerals are obtained from them.

[V] Algae in nitrogen fixation

Blue-green algae (Cyanophyceae), viz., Aulosira, Anabaena, Nostoc, etc., fix elemental nitrogen and thus increase the soil fertility. These algae have special cells called heterocysts which are the sites for nitrogen fixation. P. K. De (1939) was the first to demonstrate N2 fixing ability of blue green algae. Fairly good yield of rice can be obtained over a number of years without addition of any nitrogenous fertilizer because of the presence of nitrogen fixing blue-green algae in the rice fields.

[VI] Algae in reclamation of Usar’ soils

of north India could be Saline Usar reclaimed by growing blue green algae, like Nostoc, Anabaena, Seytonema, etc, The algae increase the mineral content of the soil and thus the crop yield.

[VII] Antibiotic from algae

Chlorella (green alga) yields antibiotiC an chlorellin which is useful against both gram positive and gram negative bacteria. Besides this, Laminaria, Ascophyllum, Rhododmela, etc., also have antibiotic properties.

[VIII] Larvicidal properties of algae

Blue-green algae like Aulosira and Anabaena, and green algae like Chara and Nitella eliminate mosquito larvae from ponds and pools in which they grow.

[IX] Algae in biological research

Algae has always been useful for conducting physiological and genetic experiments since these can be easily grown and manipulated.

(1) Chlorella and Scenedesmus (green algae) have been extensively studying for photosynthesis.

(2) Acetabularia, a green alga, was used to establish the hereditary role of the nucleus.

(3) Halicystis, Valonia, etc., (green algae) are useful in the studies on permeability.

[X] In sewage disposal

The sewage dispOsal is an aerobic process and production of oxygen from algal photosynthesis helps it. Algae like Chlorella, Scenede smus, Pediastrum, Oscillatoria, etc., can grow in these rich organic wastes and provide oxygen to aerobic bacteria. Hence, an oxidation pond is an example of algal bacterial symbiosis.

  1. Harmful Activities

The following are some of the effects of algae causing damage.

[I] Water blooms

Algae grow abundantly in water reservoirs where and (especially nitrates of nutrients and excess sulphates) are available to them. Such an algal growth floats on the water surface and looks like foam or soap lather. It is called water bloom. members of Amongst bloom-forming algae, Anabaena, (e.g Microcystis, Cyanophyceae Oscillatoria, etc.) are common.

Water blooms deplete oxygen of water reservoirs and, therefore, aquatic animals die of deoxygenation. Bloom forming algae also release certain toxins which cause death of aquatic as well as domestic animals.

[II] Parasitism

Cephaleuros virescens, a green alga, is a parasite and causes red rust of tea in some tea growing parts of India, especially Assam. It is known to cause extensive damage to this crop.

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