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Algae: (A) Uses:

The algae are useful for human beings as follows:

(1) Algae as Food:

Carbohydrates, organic compounds and vitamins are abundantly found in algae. Vitamin A, C, and D, E are mostly found in algae. In Japan, Porphyra of the class phycophyceae is eaten. Chiefly P. umblicus and P. perfbrarata are used as food in many countries. In Japan and nearly countries, Alaria, Ulva, Sargassum, Laminaria, etc. are used as salad (vegetable).

Iodine is manufactured from Laminaria. Ulva is commonly known as sea lettuce. In India, pepole of sea shore states take marine algae as favourite food. In China Nostoc commune is used as food. In Scotland, Rodomenia palmata is chewed as tobacco.

Now a days, various scientists are doing research to obtain foods from Chlorella as it contains proteins and vitamins A and D in abundant quantity. Some algae, e.g. Gelidium, Gracilaria etc., produce agar- agar, a jelly like substance employed in the manufacture of ice-cream.

Sargassum and Macrocystis are used as food for marine as well as domestic animals. Some algae are commercially cultivated in fish culture ponds and are used as their food.

(2) Algae in Industry:

Diatoms develop into diatomaceous earth which is employed as :

(i) filter for microorganisms in sugar industry.

(ii) in manufacture of glass and porcelin.

(iii) insulator in boiler and blast furnace.

(iv) abrasive for manufacture of metal paints, varnish, polish, tooth paste.

(v) absorbent of liquid nitroglycerine.

Algin is derived from an marine algae and is used in vulcanisation, typewriter roller and in the manufacture of inflammable films. It is also found in manufacture of artificial fibres and to control blood flow during surgery. In Japan Sargassum is used in manufacture of artificial wool. A mucilaginous substance, the caroganin obtained from the alga Charadrus is used in the manufacture of cosmetics, boot-polish and shampoo.

Agar-Agar is also used for conducting tissue- culture experiments in the laboratory and it is also used as heat and sound proof. This substance is also used in manufacture of artificial fibres, leather, sauce etc. Various algae e.g. Laminaria, Fucus etc., are used in the manufacture of iodine, bromine, acetone etc.

(3) Algae in Agriculture nitrogen fixation:

Myxophycean plants, e.g. Nostoc, Anabaena, etc. convert atmospheric (elemental) nitrogen into nitrogen compounds which are absorbed by higher plants. This process is known as nitrogen fixation. Bacteria also take part in this process. By this action, fertility of soil is increased.

Some algae are used as fertilizer and some blue- green algae are capable of converting clay soil into cultivable land.

(4) Medicinal Use of Algae:

An antibiotic chlorellin is extracted from Chlorella. It is crystalline and is active at 120°C. It antagonises effect of gram- negative bacteria and Nitella causes death of mosquitoes in ponds hence it is used in control of malaria.

(5) Algae in Biological Research:

Recent knowledge about the photosynthetic processes is based on the research carried out in Chlorella. Acetabularia and Valonia are used in research to study nucleocytoplasmic relations.

(B) Harmful effects of Algae:

In addition to useful effects of some alage such as Microcystis, Chrococcus, Oscillatoria, Anabaena etc. cause water blooms in water reservoirs and on death and decay emit bad smell. Water gets contaminated with such things which make it unfit for’drinking by animals and fishes as they die upon drinking such water. Sometimes marine algae grow more and more and retard speed of ships. Cephaleuros species are parasitic on leaves of tea and causes harm to tea industry.