Sea weeds, a rich source of agar and algin form the basis of confectionery, pharmaceutical and other industries. After the second world war great interest has been developed on Indian sea weeds and its industries.
The anchored sea weeds are found in the photic zone, all around the sea coast in gravelly and rocky sea bottom, where their holdfast can grip the substrata. They belong to Spermatophyta, while most of the marine algae without true roots, stems and leaves come under Thallophyta. They grow attached to rocks or other plants as epiphytes. They are broadly classified into four classes as follows:-
i. Chlorophyceae - Green algae - Ex - Ulva, Enteromorpha
ii. Pheophyceae - Brown algae - Ex- Padina, Sargassumiii. Rhodophyceae - Red algae - Ex - Gelidiella, Gracillaria
iv.Myxophyceae - Blue green algae
Nutritive value of the weeds:
When sea weeds are dried, dehydrated, products containing about 10-20 percent water are obtained. The main components of those products are carbohydrates such as saccharides and cellulose, proteins and minerals. Besides these components, they contain about one percent lipids and vitamins.
Sea weed products and utilisation:
Besides being only and rich source of agar and algin, it is directly used as human food, fertilizer, cattle fooder. Valuable chemicals like iodine (inorganic) agar, agaroids, algin (organic) can be derived from sea weeds. Pharmaceutical and confectionery industries also depend on them.
Agar:
A colloidal carbohydrate present in the cell wall of red algae, made up of two polysaccharides, agarose and agaropectin. Agar is a gel forming substance soluble in hot water and require 1% solution to set as a gel on cooling. The following are important agarophytes of India.
i) Gelidiella acerosa
ii) Gracillaria lichinoidesiii) G.crassa
iv) G.verucosa
v) G.corticata
vi) G.folliifera
Agaroids:
Jelly like extracts from red sea weeds like Chondrus, Gigartia containing higher organic sulphate content having a different chemical nature from agar. Pure solution of agaroids do not form gel on cooling as in case of agar.
Algin or Aginic acid:
It is the main polysaccharides occurring in the cell walls of pheophyceae. It contains higher proportion of sodium, potassium and magnesium salts, which make it soluble in water to form viscous solution and does not form gel, Sargassam, Cystophyllum, Dictyota and Padina are principal sources of alginic acid in Indian waters.
Algal protein:
Some green and red sea weeds like Ulva, Porphyra, Acanthophora, etc. contain 16-30% of protein in the form of many essential amino acids, combined with iodine. This can supplement the protein deficiency of human beings.
Sea weed as food:
Fresh and dried sea weeds are utilised as human food due to the mineral, trace element, protein and vitamins content in them. In Japan Prophyra form the basis of human food in the form of salad.
Most of the Chlorophyceae and Rodophyceae could be used as human food. Porphyra has been reported from Tamil Nadu, Vishakapatnam and Cap Comorin in East Coast and Colachel in West Coast. In India at present Gracilaria lichinoides is being used for preparation of `Kanji’ in Tamil Nadu coastal areas.
Sea weed meal:
Thivy (1960) has given a simple method for preparation of sea weed meal from G.Lichineides to supplement the ration of cattle and poultry.
Sea weed mature:
Sea weeds are being used in coastal areas as manures for long time with good result for coconut growth. Thivy (1958 & 1960) has given a method of composting sea weeds with cow dung for increasing manuring quality.
Medicinal uses of sea weeds:
Hypnea musciformes is used as vermifugeAspergiopsis taxiformis and Sarconema sp are very rich in iodine and is used to cure goitre.
Distribution of sea weeds.
The sea weeds prefer a rocky coral line or gravelly substrata for their proper growth and establishment. The planktonic` spores require a solid substratum to stick and develop a hard fibrous stipe, which bears at its distal end young frond or leafy portion. These young sea seeds take 3-4 months to develop into large luxuriant adult with frond measuring upto 20 feet or more (Porphyra) Besides nature of substratum, other factors like salinity, water currents, tital action are some of the other important factors which limit distribution of sea weeds.
Natural population of sea weeds occur in Gujarat, Tamil Nadu (Pulicat lake), Maharashtra (Bombay, Karwar, Ratnagiri), Goa, Kerala, Andhra (Vishakapatnam),Orissa (Chilka lake), Laccadive archipelago and Andaman Nicobar islands.
Sea weeds resources and commercial exploitation.
Our knowledge of production of sea weeds along Indian coasts is very limited, however surveys have been made for some area and the figures are given below:
|
S N |
Locality | Dry weeds | |
|
|
Agarophytes |
Alginophytes |
1 |
Chilka lake(1946) |
4-5 |
|
2 |
Cape comorin to Colachel (1948) |
10 |
|
3 |
Calimere to Cape comorin (1958) |
6,000 |
60,000 |
4 |
Tamil Nadu(1960) |
7.1 |
|
Commercial exploitation in India started in 1966 off Tamil Nadu coast. The export of dry sea weed (Mostly agarophytes Gellidiella accrosa) from Gujarat and Tamil Nadu from 1966-1968 are given below: -
1966-162 tonnes amounting to Rs. 4,17,677.00
1967-198 tonnes amounting to Rs. 7,40,542.00
1968-92 tonnes amounting to Rs. 2,13,732.00Government of India had brought in some restrictions on the export of sea weeds, particularly because of the iodine extraction possibilities and developing our own iodine extraction Industries.
Methodical cultivation of sea weeds or kelp by Japanese may serve as a guide to develop culture of Indian sea weeds. Experiments made in Pore-Bander and Mandapam indicated that the regenerating capacities of Indian sea weeds have been proved extremely rapid for Chlorophyceae, Pheophyceae and Rhodophyceae.
Ag.
Technologies
(Fisheries)
