Farm lands across the world are losing their fertility and food production levels are hitting a plateau; against this background sea weeds are fast emerging as a viable alternative for ensuring food and nutritional security. With their excellent nutrient value and production potential, sea weeds are seen by many countries as capable of meeting both domestic and international demands. With adequate investment, India too could emerge as a top producer of seaweed-based products, with export potential as well as multiple benefits for coastal communities.
What are seaweeds? They are large algae - a primitive group of plants lacking true roots, stems and leaves. Most seaweeds belong to one of three divisions - the Chlorophyta (green algae), the Phaeophyta (brown algae) and the Rhodophyta (red algae). There are about 900 species of green seaweeds including 4000 red species and 1500 brown species found in nature. Red seaweeds are found mostly in subtropical and tropical waters, while brown seaweeds are more common in cooler, temperate waters.
Around 221 species of seaweed are being harvested commercially. Of these, 145 species are used for food and 110 for phycocolloid production (eg. agar). Agar-agar, agarose and carrageenan are commercially valuable substances extracted from red seaweeds. Agar is used extensively in food preparation and in the pharmaceutical industry as a laxative or as an outer cover of capsules. Carrageenans are generally employed for their physical functions in gelation (in foods like ice cream), viscous behaviour and stabilization. They are also used in lipsticks, soaps, film, paint, varnish and buttons. According to the Journal of Chemical Technology and Biotechnology, seaweeds can help in cleansing lands contaminated with DDT. Researchers have found that sprinkling the right amount of powdered seaweed on contaminated soil can accelerate the breakdown of the deadly insecticide.
According to the Food and Agriculture Organisation, between 1981 and 2000, global production of aquatic plants rose from 3.2 million tons to nearly 10.1 million tons (wet weight). While the trade in seaweeds raked in US $250 million in 1990, the year 2000 saw seaweed trade rise to a whopping US $6 billion. The contribution of cultured seaweeds in 2000 was 15% of total global aquaculture volume (45,715,559 tons) or nearly 5% of total volume of world fisheries production (141,798,778 tons). Seaweeds most exploited for culture include the brown algae with 4,906,280 tons (71 % of total production) followed by the red algae (1,927,917 tons) and a small amount of green algae (33,700 tons). China holds the first rank in production followed by North and South Korea, Japan, Philippines, Chile, Norway, Indonesia, USA and India.
The nutritional value of seaweeds is undisputed. They are rich in minerals, vitamins, trace elements and bioactive substances. In fact, seaweeds have been aptly called the medical food of 21st century. Digenea (Rhodophyta) produces an effective vermifuge (kainic acid). Laminaria and Sargassum species have been used in China for the treatment of cancer. Anti-viral compounds from Undaria have been found to inhibit the Herpes simplex virus, which are now sold in capsule form. Research is being carried out into using Undaria extract to treat breast cancer and HIV AIDS. Calcareous species of Corallina have been used in bone-replacement therapy. Asparagopsis taxiformes and Sarconema sp. are used to control and cure goiter while heparin, a seaweed extract, is used in cardiovascular surgery.
The Indian scenario
Seaweeds grow abundantly along the Tamilnadu and Gujarat coasts and around Lakshadweep and Andaman and Nicobar islands. Rich seaweed beds are found around Mumbai, Ratnagiri, Goa, Karwar, Varkala, Vizhinjam and Pulicat in Tamilnadu and Chilka in Orissa. Surveys carried out by the Central Salt and Marine and Chemical Research Institute (CSMCRI), Central Marine Fisheries Research Institute (CMFRI) and other research organisations have revealed vast seaweed resources along the coastal belts of South India. On the West Coast, especially in the state of Gujarat, abundant seaweed resources are present on the intertidal and subtidal regions. These resources translate into great potential for the development of seaweed-based industries in India.
Out of approximately 700 species of marine algae found in the Indian coast, 60 species are commercially important. Agar-yielding red seaweeds such as Gelidiella acerosa and Gracilaria sp. are collected throughout the year while algin-yielding brown algae such as Sargassum and Turbinaria are collected seasonally from August to January off the southern coast.
Barriers to growth
The seaweed industry in India is mainly a cottage industry based only on the natural stock of agar-yielding red seaweeds, such as Gelidiella acerosa, Gracilaria edulis, and algin-yielding brown seaweeds species such as Sargassum and Tubineria. The production of seaweeds (all categories) in India in 2000 was approximately 600,000 tons (wet weight). India produces 110-132 tons of dry agar annually utilizing about 880-1100 tons of dry agarophytes. Annual algin production is 360 to 540 tons from 3,600 to 5,400 tons dry alginophytes.
The industry is yet to overcome many obstacles including over-exploitation of certain species leading to scarcity of raw material, poor quality of raw materials, labour shortages during the paddy harvesting and transplanting seasons, lack of technology to improve processed product quality, and lack of information on new and alternative sources of raw materials. Despite the great number of sheltered bays and lagoons suitable for mariculture, large-scale attempts to grow seaweed have not been made so far. More effort is needed to increase production through improved harvesting techniques, elimination of competing species, creation of artificial habitats and seeding of cleared areas.
With regard to pharmaceutical substances, heparin analogues (heparinoids) that are inhibitory to thrombin activities have been reported from Chlorophyta of Indian coast. But the extraction of bioactive compounds needed for production of important pharmaceutical products needs extensive technology infusion, and the full potential of Indian production is hampered without this.
Seaweeds have also proved to be excellent fertilisers. In Gujarat, powder derived from dried brown black seaweed (saragassam wighti) harvested from the Gulf of Kutch is being used as a fertiliser. The ratio for use is nearly 1 tonne per 15 hectares. The Madurai based Srinivasa Marine Chemicals is manufacturing many seaweed-based products including seaweed granules, fertiliser, Sodium Alginate and Alginic Acid.
Pepsi Foods, India, has announced a tie up with CSMCRI to produce an plant growth enhancer from seaweeds. This technology according to CSMCRI can enhance plant growth by 20-30 percent. The company had come out with plans in April this year to collaborate with several self-help groups (SHGs) in Tamilnadu whereby it would provide assured buyback of seaweeds from the groups.
Low input requirements, high returns on investment, and excellent employment potential make seaweed culture a lucrative enterprise for coastal communities. The financial and labour capital invested in seaweed cultivation and its utilization through product and process development could help meet the food and nutritional security of Indian population as well as augment the value of total fisheries export. The need of the hour is to train, encourage and support coastal fishermen. This can be achieved through the combined efforts of State Governments, research institutes, seaweed industry, Marine Products Export Development Authority and local NGOs. This partnership can ensure adequate investment in terms of finance and technology and in providing marketing channels for selling the harvest.