Macro marine algae, the humble seaweed, is today considered one of the best sources of food, fodder, fertiliser, medicine and chemicals. Seaweed extract is widely used in toothpaste, ice cream, tomato ketchup, textile printing, teeth filling, cosmetics, tissue culture, plywood, packaging and many other industries. Recently, it has been proposed that large scale seaweed cultivation may be used for carbon dioxide sequestration to combat global warming.
China, Japan, Korea and Philippines together produce more than 24 million tonnes of wet seaweed worth hundreds of millions of dollars annually. The seaweed industry is a fast growing multi-billion dollar business worldwide. In India, there is a tremendous opportunity for development of new business and enterprise in this area. Sea farming through large scale seaweed cultivation can be developed as an alternate and additional means of livelihood for the people inhabiting the country’s vast coastal areas.
In recent years, fishing for a livelihood is becoming increasingly stressed. Daily earnings of the indigenous communities engaged in fishing are meagre and to supplement it many illegally mine coral, engage in unscientific fishing activities to maximise harvests, or practice indiscriminate seaweed harvesting – harmful for the marine ecosystem. Poverty, disease, malnutrition, lack of job opportunities and a host of other problems force many to migrate to nearby towns. Thus, there is an urgent need to enhance the earning capabilities of the coastal people to empower them economically. Seaweed cultivation and utilisation is one such alternative that can create earning opportunities, especially for women as the men leave for fishing during the day.
Presently, despite the increased demand for seaweed in the Indian industry, supply levels remain low. India does not have a well organised seaweed cultivation programme and the exploitation from wild sources is damaging the marine ecosystems to a great extent. A programme initiated by the Marine Biotechnology Laboratory, Department of Botany, University of Delhi, and supported by Science for Equity, Empowerment and Development (SEED), Division of Department of Science and Technology, Government of India, New Delhi, is working towards the goal of providing a replicable model of sustainable seaweed cultivation that could fill the demand-supply gap. The implementation, training and coordination between a number of institutes, universities and non government organisations (NGOs) has been undertaken for four economically important seaweeds – Gracilaria verrucosa, Sargassum sp., Porphyra sp., and Kappaphycus alvarezii for large scale cultivation in different parts of the Indian coast. The four species have been selected considering their demand both in the domestic and international market.
Sea Farming | Cultivating Gracilaria
The article discusses Gracilaria cultivation, which has nearly 150 species distributed all over the world. Gracilaria verrucosa, chosen due to its wide distribution, adapts easily and is a good source of agar. The seaweed grows in a wide range of salinity ranging from 5-34 parts per thousand (ppt) – and easily adapts to brackish water, mangrove swamps and the sea. There are two distinct morphotypes of Gracilaria verrucosa – the attached and the floating type as found in Chilika Lake, Orissa.
Before venturing into large scale cultivation, it was important to determine the daily growth rate (DGR) of the plant and create a seedling bank. A test plant in a small area, about half an acre, in two or three locations usually serves as the future ‘seedling bank’. The selection of the cultivation site was based on two main criteria – protection from strong winds and away from fresh/polluted water source. Various ecological conditions like temperature, light and pH (7.5 – 8.0) were also checked for compatibility.
Gracilaria cultivation does not require any sophisticated machinery or large investments. Easily available and inexpensive material such as bamboo, nylon ropes, torn fishing nets, hammer etc., are enough. The cultivation does not require any fertiliser or chemical treatment. Gracilaria grows naturally, once it is cultured.
The seaweed Gracilaria is harvested manually or by simple hand made tools available locally. After harvesting, the plants are cleaned and sun dried for 2-3 days on raised platforms and not on the sand. Care should be taken not to clean the seaweed in fresh water as it damages the quality of agar. The seaweed is then packed in jute or plastic bags when it is fully dried. Semi-dried seaweed should not be stored as it is prone to fungal and bacterial infection. The bags are then stored in a dry place away from moisture.
Seaweed cultivation and NREGA
Following the successful completion of the cultivation cycle, seaweed farmers can sign an agreement with the concerned industries to sell their harvest at a pre-determined price. Alternatively, the seaweed farmers can form their own village co-operative to sell the seaweeds. It has been estimated that a person can earn between Rs 7,000–15,000 per month through seaweed cultivation from one acre of water area. Thus, seaweed cultivation can be an ideal programme for the Mahatma Gandhi National Rural Employment Guarantee Act (NREGA).
Nutritional value of seaweeds
1 kg fresh vegetables = 100 g of seaweed
100 g of seaweed provides:
- 30 – 40 g Proteins
- Vitamin – A
- Vitamin – B2
- Vitamin – B12
- Vitamin – C (67 per cent)
- Vitamin – E and Sodium (Na), Potassium (K), Magnesium (Mg)