Seaweed Mariculture: Scope and Potential

In India

Prepared by: Venkatesh R Thakur, Bhakti Peje

Introduction

The marine ecosystem is one of the richest ecosystems among all. Marine algae, commonly known as seaweeds are one of the major potential living as well renewable resources of the oceans. Seaweed resources available around the world include more than 1000 species, from which only a hundred species are being commercially used. Seaweeds are mainly utilized in phycocolloid industries, but many edible types of seaweed are rich in proteins, vitamins, minerals and trace metals. In the past few decades, the research in the marine areas has yielded vast knowledge on seaweed utilization. The major utilization of the seaweeds is in phycocolloid industries, for extraction of agar (Gelidiella, Gracilaria), alginate (kelps, Sargassum), and carrageenan (Eucheuma, Chondrus, Hypnea). Apart from this, other uses such as fertilizer, non-conventional source of energy, bioactive compounds, etc.

The increasing demand of the raw material required for phycocolloid production such as agar, alginate and carrageenans leads to only one direction and that is large scale cultivation of these species. In many places, so far the natural harvest used to be the source. The cultivation of seaweeds involving several protocols such as seeding, site selection, laying out nets in the field etc.

Seaweeds are an untapped source of income from the seas, which has been ignored. In India, with the advent of Kappaphycus cultivation along the Tamilnadu coast, some awareness has been created. However, the local communities, though little importance is known traditionally, remain oblivious to this treasure in their vicinity.

• Creating the awareness among the locals regarding the importance of seaweeds towards economical and ecological importance.

• The harvesting of seaweeds will be additional income for poor artisan.

Global seaweed production and trade

Currently there are 42 countries in the world with reports of commercial seaweed activity. China holds first rank in seaweed production, with Laminaria sp. accounting for most of its production, followed by North Korea, South Korea, Japan, Philippines, Chile, Norway, Indonesia, USA and India. These top ten countries contribute about 95% of the world's commercial seaweed volume. About 90% seaweed production comes from culture based practices. The most cultivated seaweed is the kelp Laminaria japonica, which alone accounts for over 60% of the total cultured seaweed production while Porphyra, Kappaphycus, Undaria, Eucheuma and Gracilaria make up most of the rest to a total of 99%. The most valuable crop is the red alga Nori (Porphyra species, mainly Porphyra yezzoensis), used as food in Japan, China and Pacific.

According to FAO, between 1981 and 2000, world production of aquatic plants increased from 3.2 million tons to nearly 10.1 million tons (wet weight), upholding US $6 billion world trade in 2000, compared to US $ 250 million trade in 1990. The contribution of cultured seaweeds is 15% of total global aquaculture volume (45,715,559 tons) or nearly 5% of total volume of world fisheries production (141,798,778 tons) for 2000. The seaweeds that are most exploited for culture are 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). East and South-East Asian countries contribute almost 99% cultured production, with half of the production (3 million tons) supplied by China. Most output is used domestically for food, but there is a growing international trade. The Porphyra cultivation in Japan is the biggest seaweed industry, with a turnover of more than US $1.8 billion per annum.

Total EU imports of seaweed in 2001 amounted to 61,000 metric tons with the Philippines, Chile and Indonesia as the biggest suppliers. Significant quantities of Eucheuma are exported by the Philippines, Tanzania and Indonesia to USA, Denmark and Japan. The Seaweeds are macrophytic algae, a primitive type 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 seaweed, 4000 red species and 1500 brown species found in nature1. The greatest variety of red seaweeds is found in subtropical and tropical waters, while brown seaweeds are more common in cooler, temperate waters.

Economic importance

Some 221 species of seaweed are utilized commercially. Of these, about 145 species are used for food and 110 species for phycocolloid production (eg. agar). Seaweed has been a staple food in Japan and China for a very long time. The green seaweeds Enteromorpha, Ulva, Caulerpa and Codium are utilized exclusively as a source of food. These are often eaten as fresh salads or cooked as vegetables along with rice. Porphyra (Nori), Laminaria (Kombu) and Undaria (Wakame) are used for making fish and meat dishes as well as soups and accompaniments. Agar-agar, agarose and carrageenan are commercially valuable substances

extracted from red seaweeds and find extensive use in many industries.

The greatest use of agar is in association with food preparation and in the pharmaceutical industry as a laxative or as an outer cover of capsules. With the advent of modern molecular biology and genetic engineering, agar gums producing an 'agarose' factor are used extensively in electrophoresis in most laboratories around the world.

Philippines accounts for nearly 80% of the world's total Eucheuma cottonii production of 1,300,000 tons, roughly 35% of which is traded in dried form. It supply 14% of the world's total raw seaweed production and holds first rank as producers of semi-refined carrageenan, contributing close to 60% of the world market.

Seaweed resources of India

Seaweeds grow abundantly along the Tamil Nadu and Gujarat coasts and around Lakshadweep and Andaman and Nicobar islands. There are also rich seaweed beds around Mumbai, Ratnagiri, Goa, Karwar, Varkala, Vizhinjam and Pulicat in Tamil Nadu and Chilka in Orissa. Out of approximately 700 species of marine algae found in both inter-tidal and deep water regions of the Indian coast, nearly 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 anuary on Southern coast.

A standing crop of 16,000 tons of Sargassum and Turbinaria has been reported from Indian waters. The surveys carried out by Central Salt and Marine and Chemical Research Institute (CSMCRI), Central Marine Fisheries Research Institute (CMFRI) and other research organizations 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 resourceshave great potential for the development of seaweed-based industries in India.

Seaweed mariculture

Large-scale seaweed mariculture is carried out only in Asia, where there is a high demand for seaweed products and burgeoning populations to create market growth. Cultivation of seaweeds in Asia is a relatively low-technology business in that the whole, attached plants are placed in the sea and there is a high labor content in the operation. Except for the large kelp harvesters of Southern California and Baja California or in Philippines and Taiwan Province of China, most seaweed are grown or harvested from wild stocks using manual techniques. The demand from the phycocolloid industry of India is great but the present production from natural habitats is very low and insufficient to cater to the needs of the local industry.

This gap between the demand and supply can be bridged through mariculture practices for seaweeds by cultivating the useful species on a commercial scale. Continuous supply, improved yield and quality as well as conservation of natural seaweeds beds are some of the important advantages of seaweed mariculture. Laminaria Brown Japan Kombu China Hai Dai Japan Nori / Amanori / Hoshinori China Zicai Korea Kim Porphyra Red UK (Wales) Purple laver / Laver bread Undaria stipes Japan Wakame Undaria pinnatifida Brown China Quindai cai Scotland Dulse Ireland Dillisk Rhodymenia palmate Palmaria palmate Red Iceland Sol Chondrus crispus Red Europe Irish Moss / Carraghean Asparogopsis taxiformis Red Hawaii Limu kohu Misc. sp. - Hawaii Limu.

Problems and Prospects

1. The major problems in the seaweed industry include overexploitation leading to a scarcity of raw material, poor quality raw material, labor shortages during the paddy harvesting and transplanting season, lack of technology to improve processed product quality, and a lack of information on new and alternative sources of raw materials.

2. Despite the great number of sheltered bays and lagoons suitable for mariculture, no large-scale attempts to grow seaweed have been made in India so far.

3. Efforts are needed to increase production through improving harvesting techniques, removal of competing species, creation of artificial habitats and seeding of cleared areas. As the technology for reliable methods for the cultivation of different commercially important seedstocks and their improvement has either already been developed or presently being in research, it needs to be disseminated effectively to the target community.

4. Extensive surveys need to be conducted to identify suitable sites for large-scale seaweed culture. There is great potential for the agarophyte cultivation because of its low availability from the wild stock due to over-exploitation.

5. Many edible seaweed species are available on the Indian coast; attempts should be made to develop products suitable for the Indian palate and to popularize the same amongst the public.

6. With regard to pharmaceutical substances, heparin analogues (heparinoids) that are inhibitory to thrombin activities have been reported from Chlorophyta of Indian coasts; this and many other important types of seaweed are available on Indian coast that can be utilized for production of many important pharmaceutical products through extraction of bioactive compounds.

7. Attention should also be given towards developing hybrid species with superior growth and nutritional characteristics, as the same has been proved successful in countries like Japan.

8. Rather opting for high-volume, low-value seaweeds, culture of highvalue seaweeds should be aimed for, as part of integrated coastal and national development programmes.

9. Seaweed polyculture in association with molluscs and fishes seems to have good prospects to increase harvest and profits.

10. Pond and canal culture of seaweeds (e.g. Gracilaria) in shrimp farming areas can help to treat effluent water.

11. The problem of eutrophication of culture ponds due to overfeeding and excreta released by fish/shrimp can be tackled by culturing seaweeds in such ponds. Out of estimated around US $3 billion global phycocolloid and biochemical business, India's share is meager.

12. We can surely grab a bigger part in this lucrative business with sincere efforts towards large-scale cultivation of commercially important species and processing.

13. To facilitate this, more technologically sophisticated extraction plants with easy access to markets and marketing.

References:

• Dawes C. J. (1981) Marine Botany. John Wiley & Sons, New York.

• Chapman V. J. (1970) Seaweed and their uses. Second edition, Methuen & Co. Ltd., London.

• FAO (2002) Status of world fisheries and aquaculture. Food and Agricultural Organization of United Nations, Rome, Italy.

• Kaliaperumal N. (1992) Seaweed culture. In:

• Handbook of Aquafarming.