Seaweeds: Distribution, Production and Uses

Seaweeds, otherwise known as marine algae are primitive non-flowering photosynthetic macrophytes occurring in tidal regions of seas and oceans that occupy 71% of the globe and they are natural renewable resources. Green, brown and red seaweeds are generally distributed in the intertidal, tidal and subtidal regions respectively. Seaweed production through aquaculture in the world was 11.66, 16.83 and 19.90 million tons (fresh) in 2002, 2008 and 2010 respectively and in 2012 it was 23.78 million tons (fresh). Kappaphycus alvarezii production in the world was 1,83,000 tons (dry) in 2010 while it was 1, 490 tons (fresh) during the same period in India. Seaweeds formed part of human life from time immemorial and served as food, besides their use as feed, fodder and manure. Some of the edible seaweeds include species of Porphyra, Palmaria, Undaria, Laminaria, Monostroma and Caulerpa and possess desirable quantities of proteins, carbohydrates, fibre, minerals and vitamins, besides having biological compounds to combat diseases. Ascophyllum sp, Macrocystis sp, Laminaria sp, Alaria sp, Palmaria sp and Pelvetia sp are some of seaweeds used as fodder. Seaweeds are the only natural source for hytochemicals viz; agar, algin and carrageenan which have wide applications in various ways in day to day life of human beings. Species of Gelidium, Gracilaria, Pterocladia, Gelidiella, Ahenpeltia and Acanthopeltis are some agarophytes, while those of Laminaria, Macrocystis, Ascophyllum, Durvillea, Ecklonia and Sargassum are some alginophytes. Carrageenophytes include species of Chondrus, Gigartina, Sarcothalia, Eucheuma and Kappaphycus. The alginophytes mentioned here also serve as manure because they contain macronutrients (N, P, K, Ca, Mg, S), micronutrients (Zn, Cu, Mn) and growth regulators (auxins, gibberlins, cytokinins) necessary for plant growth.