S. Kalimuthu and J. R. Ramalingam,
Mandapam Regional Centre of Central Marine Fisheries Research Institute,
Marine Fisheries, P.O. 623 520, Tamil Nadu, India.
Studies were made on the yield and physical properties of agar from Gracilaria corticata var. corticata, G. corticata var. cylindrica, G. crassa and G. edulis, growing in four localities near Mandapam. The seaweeds were collected from Pudmadam, Pamban, Rameswaram and Thonithurai, respectively. The quality of agar in terms of gel strength was highest in G. edulis, but the yield of agar from this species was slightly less than that of G. corticata var corticata and G. corticata var. cylindrica, which may be due to the repeated commercial harvesting of G. edulis in the study area during recent years. There were no marked variations in the data collected on environmental and hydrological parameters from the four study areas, as all of them are located in the vicinity of Mandapam.
Thirty two species of Gracilaria have already been reported from Indian waters and their occurrence in different parts of the Indian coasts are given. The description and ecology of four species of Gracilaria (G. edulis, G. corticata var. corticata, G. corticata var. cylindrica, and G. crassa) which were investigated as part of the present study are also given. Investigations made on seasonal variations in growth, spore output, agar processing, yield and physical properties of agar on Gracilaria sp., Gelidiella acerosa, Gracilariopsis sjoestedtii by different workers, are reviewed. The work carried out on experimental cultivation of Gracilaria spp. in different environments using various culture techniques are summarised. It is recommended that G. edulis should be selected for commercial scale cultivation in India, because of its high yield and good quality agar.
Among the red seaweeds only some species, belonging to the genera Gelidium, Pterocladia Gelidiella and Gracilaria, are used for commercial production of agar in various countries. However, in many countries of the Asia-Pacific region, the taxonomic status of these species is not properly known. This has often created confusion when comparing information and data provided by different countries on red seaweed production, culture methods, ecological parameters and phycocolloid properties. In addition, several other red seaweeds occurring in this region form an important source of raw material for the extraction of phycocolloids, but little is known about their correct taxonomic status and ecological requirements for culture. In the absence of information on the productivity, biochemical characteristics and chloroplastic genome pattern of the different strains and species, it is difficult to develop a viable culture technology for the lesser known species that would be economically efficient and sustainable. Studies on the Gracilaria spp. of India are currently undertaken to evaluate their agar yielding capacity and study their ecological requirements for commercial farming.
2. ECOLOGY AND TAXONOMY OF GRACILARIA
Boergesen (1933, 1934, 1937 a,b and 1938), reported 11 species and one variety of Gracilaria from different localities in India. Krishnamurthy and Joshi (1970), listed 12 species and two forms of Gracilaria. Umamaheswara Rao (1972), described 17 species and two varieties of Gracilaria. Krishnamurthy and Rajendran (1986) described 4 new species of Gracilaria from Tamil Nadu.
Figure 1: Distribution of Gracilaria spp. in different parts of the Indian coast.
Oza and Tewari (1990), reported G. eucheumoides from the Indian Coast. According to Krishnamurthy (1991), Gracilaria is represented by 32 species in the Indian region, of which 31 are found in different parts of the Bay of Bengal. A list of all species with places of occurrence is given in Table 1 and the places are shown in Figure 1.
Krishnamurthy (1989), gave the criteria for the classification of Gracilaria spp. Thomas (1977), reported the seasonal variations in growth, yield and physical properties of agar in Gracilaria verrucosa. Kaliaperumal et al. (1986) studied the growth, phenology and spore shedding of Gracilaria arcuata var. arcuata and G. corticata var. cylindrica occurring at Kilakkarai. Chennubhotla et al. (1986a) studied the growth, reproduction and spore output of G. foliifera and Gracilariopsis sjoestedtii. Chennubhotla et al. (1986b) studied the changes in growth and phycocolloid content of Gelidiella acerosa and Gracilaria edulis.
For the present study, four species of Gracilaria were collected from different localities near Mandapam every month for a period of five months from May to September 1994. G. edulis was collected from Thonithurai, where the plants grow attached to pebbles and stones at a depth of 0.5 m. G. corticata var. corticata was collected from the intertidal sandy rocks at Pudumadam.
Table 1: Distribution of Gracilaria spp. in different parts of the Indian coast.
|Gulf of kutch||Okha||Dwarka||Gopnath||Bombay||Goa||Darwar||Quilon||Vizhinjam||Kanyakumari||Tiruchendur||Tuticorin||Kilakkarai||Pudumadam||Mandapam||Mahabalipuram||Madras||Visakhapatnam||Lakshadweep||Andamans||Indian Ocean|
|1||Gracilaria arcuata var. arcuata (Zan.) Umamaheswara Rao||+||+||+||+||+|
|2||G. arcuata var. attenuata (Zan.) Umamaheswara Rao||+|
|3||G. armata (C.Ag.) J. Ag.||+|
|4||G. vursa-pastoris (Gmel.) Silva||+|
|5||G. cacalia (J. Ag.) Dawson||+|
|6||G. canalaiculata (Kuetz.) Sonder||+||+|
|7||G. compressa (Agardh) J. Ag.||+|
|8||G. corticata var. corticata J. Ag.||+||+||+||+||+||+||+||+||+||+||+||+||+|
|9||G. corticata var. cylindrica (J. Ag.) Umamaheswara Rao||+|
|10||G. crassa (Harvey) J. Ag.||+||+||+||+|
|11||G. cylindrica Boergersen||+||+|
|12||G. debilis (Forssk.) Boevss.||+|
|13||G. dsticha J. Ag.||+|
|14||G. dura (Ag.) J.Ag.||+|
|15||G. edulis (Gmel.) Silva||+||+||+||+|
|16||G. eucheumoides Harvey||+|
|18||G.foliifera (Forssk.) Boerhesen||+||+||+||+||+||+||+||+|
|19||G.foliifera f. aeruginosa Borgesen||+|
|20||G. foliifera f. granatea Boergesen||+|
|21||G. indica Umamageswara Rao||+|
|22||G. kanyakumariensis Umamaheswara Rao||+||+||+|
|23||G. kilakaraiensis Krishnamurthy and Rajendran||+|
|24||G. marnnarensis Umamahesware Rao||+|
|25||G. millardetii (Montagne) J. Ag.||+|
|26||G. obtusa Grev.||+||+||+||+|
|27||G. opuntia (Svedelius) Durairatnam||+|
|28||G. pudumadamensis Krishnamurthy and Rajendran||+|
|29||G. pygmaea Boergesen||+|
|30||G. textorii (Suringer) J. Ag.||+||+||+||+||+|
|31||G. tuticorinensis Krishnamurthy and Rajendran||+|
|32||G. verrucosa (Hudson) Papenfuss||+||+||+||+||+|
Figure 2: Places of collection of Gracilaria spp. for the present study.
G. corticata var. cylindrica was collected from the intertidal sandy rocks at Pamban. Plants of G. crassa were collected in the intertidal zone attached to the coral stones at Rameswaram. A map showing the collection places is given in Figure 2.
The description and ecology of the four species are given below.
1. Gracilaria edulis (Gmelin) Silva.
Plants erect and grow up to 20 cm or more. Brownish-red or greenish in colour, alternately to irregularly branched, branches slightly constricted at the base. Grows abundantly in seagrass beds in shallow lagoons formed between the shore and fringing coral reefs. It is also attached to small stones and shells in sandy and muddy areas. This agarophyte occurs throughout the year in harvestable quantities.
2. Gracilaria corticata var. corticata J. Agardh.
Plants stand 15 to 20 cm tall; brownish-red in colour, regularly dichotomously branched with thick and cartilagenous fronds, margins entire and rarely proliferous. Grows attached to rocks and stones in the intertidal area. Found throughout the year and occurs in harvestable quantities.
3. Gracilaria corticata var. cylindrica (J. Agardh) Umamaheswara Rao
Plants 6 to 10 cm. tall or more, attached by discs arising from the basal parts of fronds, dark red to yellowish-red in colour often with variegated spots on fronds. Fronds dichotomously, alternately and irregularly branched, flat or compressed at lower parts, subterete to cylindrical and closely branched above with pointed or spinous apices. Grows on rocks protected from wave action in the sub-littoral region and also in rock pools of the intertidal region. This seaweed occurs throughout the year but not in harvestable quantities.
4. Gracilaria crassa (Harvey) J. Agardh.
Plants brownish-red or greenish in colour. Forms dense cushions on the substratum with dichotomously and irregularly branched fronds. Branches are up to 4 mm. in diameter, cylindrical and sometimes constricted at the base forming club shaped segments or oblong articulations. It grows throughout the year on rocks and dead coral pieces as large tufts in the intertidal and subtidal regions. It is available in harvestable quantities.
Environmental data on depth of occurrence, atmospheric temperature, salinity and turbidity were recorded at the collection areas. The plants were examined for their reproductive stages and epiphytes. Other aspects like grazing exposure and maximum and mean values obtained for water depth, atmospheric temperature and salinity of sea water are given in Table. 2.
Table 2: Data collected on environmental and hydrological parameters from the collection localities.
|G. corticata var. corticata||Pudumadam||30||35||31||27.6||29.6||28.3||32.4||35.2||34.16|
|G. corticata var. cylindrica||Pamban||30||35||31.0||37.4||29.6||28.5||30.8||35.6||34.24|
3. PROCESSING OF GRACILARIA SPECIES
During and after the Second World War, attempts were made to extract agar from Indian seaweeds and different techniques were used to purify the agar gel. Bose et al. (1943) leached the whole weed for 18 hours before extraction and the gel was maintained at 60°C to remove suspended impurities. Starch present in the gel was removed by treating with 0.2% acetic acid for 1 hour and then washing the gel in water. Karunakar et al. (1948) employed a bacterial method for gel purification. Chakraborthy (1945) used freezing techniques to remove the suspended material. Mahonty (1956) found that heating under pressure at 230 °F was necessary for the removal of impurities in the gel of G. verrucosa. Thivy (1952;1960), made detailed investigations on extraction of agar from different species of Gracilaria and Gelidiella acerosa and on physical properties of the agar obtained from them. A cottage industry method for the manufacture of pure agar form Gracilaria edulis (=G. lichenoides) was developed in Central Marine Fisheries Research Institute (Thivy 1960). In this method, the impurities are removed from the seaweed before extraction. The leaching process minimised the cost of production and the yield from pulverised weed was also higher than that obtained by the earlier methods. Details of this method is given in Appendix 1. Kappanna and Visweswara Rao (1963) suggested that the quality of agar could be unproved by freezing and thawing. In pilot plant trials, Visweswara Rao et al. (1965) soaked the pulverised weed overnight in fresh water before wet grinding and extracting the agar. Details of this method is given in Appendix 2. To eliminate the cost of freezing, Desai (1967) suggested using 90% industrial alcohol for the flocculation of agar from filtrate.
Thomas and Krishnamurthy (1976), studied the yield and quality of agar in the cultivated plants of Gracilaria edulis. It is evident from the results that the best yield of agar was from plants harvested after 3 months growth. Umamaheswara Rao (1978), studied the yield and gel strength of agar extracted from G. corticata from the Visakhapatnam area. Oza (1978), studied the seasonal variations in gel strength, gelling and melting temperature of agar from G. corticata occurring at the Veraval coast. Chennubhotla et al. 1978, studied properties of agar from Gelidiella acerosa, Gracilaria edulis, G. corticata and G. foliifera occurring in the Mandapam area. Kaliaperumal et al. (1990), studied the agar content of Gelidiella acerosa and Gracilaria sp. from the south Tamil Nadu coast.
In the present study, samples were dried and bleached with several washings in fresh water. 20 g of clean sample was immersed in 5% NaOH and heated at 90°C for one hour. The seaweed was washed and acidified with 1 ml HC1. Fresh water was then added (1:30) and the material was boiled at 90°C for one hour. The dissolved seaweed was filtered through a cloth bag with a pressing tool and allowed to set at room temperature. The gel was kept in the freezer for two days. The frozen gel was thawed in tap water and then dried in an oven at 50–55°C to obtain agar-agar.
The present study on the yield of agar, gel strength and melting temperature was carried out on G. edulis initially by collecting samples bi-monthly during the period from June 1992 to April 1993. Later, monthly samples were collected from May to September 1994. Similar studies were made on G. corticata var. corticata, G. corticata var. cylindrica and G. crassa from the samples collected on a monthly basis for 5 months from May to September 1994. The results obtained are given in Table. 3.
Table 3: Data obtained on the yield and quality of agar from Gracilaria spp. in India.
|Seaweed||Locality||Agar Yield (%)||Month of Yield||Salinity (ppt)||Melting Point|
|G. corticata var. corticata||Pudumadam||15.8||30.8||21.5||Sept||Jun||32||45||36||98|
|G. corticata var. cylindrica||Pamban||14.8||25.2||20.8||Aug||Jul||37||66||48||98|
4. SEAWEED CULTURE
In India, seaweeds used as raw material in the seaweed industry have been harvested from natural beds along Tamil Nadu and Gujarat coasts since 1966. There are about 21 agar industries and 25 algin industries in India (Silas and Kalimuthu 1987). As many seaweed processing industries are emerging, there is an increasing demand for materials, particularly agarophytes, which the existing resources cannot meet. Hence, culture of seaweed has been attempted by the Central Marine Fisheries Research Institute, the Central Salt and Marine Chemical Research Institute and the National Institute of Oceanography and other research organisations,In the Central Marine Fisheries Research Institute, Umamaheswara Rao (1973) conducted culture experiments on Gracilaria edulis and G. corticata. Regeneration in both plants was found to be high, the plants growing to harvestable size within 3 to 4 months. Field experiments were conducted in the open-shore environment in the Gulf of Mannar (Umamaheswara Rao, 1974) using two coir nets of 4 x 2 m size. An average yield of 4.4 kg/m2 fresh seaweed was obtained from the seed material of 0.31 kg/m2 area of the coir net after 80 days growth.
Experiments were also carried out for cultivating G. edulis in the inshore waters of Gulf of Mannar, in submerged free floating condition (Chennubhotla et. al. 1978). Culture frames of 2 x 2 m in size with 1.42 kg seed material were tied loosely to the poles fixed in the nearshore waters at lm depth. The fresh weight of the material harvested after 45 days growth was 1.985 kg/m2 against the seed material of 0.355 kg.
Seaweed cultivation in inshore waters is beset with problems such as sedimentation, as well as grazing by fish. To overcome these constraints, cultivation of G. edulis was attempted in slightly deeper water of 3–4 m depth where sedimentation is less. Three plastic rope nets of 5 x 2 m in size were used and the seed material was tied at the mesh intersections using nylon twine. The nets were suspended at different levels with the help of plastic buoys and granite sinkers. Three such nets were introduced with seed material of 0.665 kg/m2 at midwater level in 4 m depth and the yield after 90 days was 1617 gm/m2 (Chennubhotla et al. 1987). Detailed studies were made on the influence of environmental parameters on the culture of G. edulis at Mandpam (Kaliaperumal et al. 1992). Attempts were also made to culture G. edulis at Minicoy Island (Lakshadweep) by transporting the seed material from Mandapam and Kavarattti Island (Laksh adweep). A very encouraging result of a 30 fold increase in biomass was obtained after 60 days growth. G. edulis could be very effectively cultured in the lagoons of Lankshadweep islands during pre-monsoon (March-June) and post-monsoon (October to February ) seasons (Kaliaperumal et. al 1992a and Chennubhotla et. al 1992a and b).
At the Central Salt and Marine Chemical Research Institute, Raju and Thomas (1971) cultured G. edulis by longline method in a sandy lagoon at Krusadi Island. Three harvests were made at the end of 5, 8 and 10.5 months after planting and the total harvest during the year was about 3.5 kg from a lm length of rope. Krishnamurthy et al. (1975) carried out G. edulis cultivation at Krusadai Island lagoon using coir ropes. In 5 months, the plants attained a length of about 30 cm and the average weight of the plant was about 300 g. The harvest was made by clipping the plants close to the rope and the remnants were left on the rope for further growth. Two more harvests were made at intervals of 10 weeks, thus giving three harvests in a period of 10 months.
Attempts were made to culture Gracilaria spp. from spores. Krishnamurthy et al. (1969) raised the germlings of Gracilaria edulis and G. corticata on a nylon fabric from carpospores under laboratory conditions. They were then transferred to the sea. After 4 months, the young plants appeared and took another 4 months to attain maturity and develop reproductive structures. G edulis was cultivated successfully also by Reeta Jayasankar and Kaliaperumal (1991) and Reeta Jayasankar (1992) using tetraspores and carpospores. The spores from mature plants were liberated and settled on circular cement blocks, coir ropes, nylon ropes, plastic strip and coral stones and cultured to germlings in the laboratory for 17 days in Conway & Walne's medium at a temperature of 23–25 °C, light intensity of 1000 lux and a photoperiod of 16:8 LD cycle. Thereafter they were transferred to the sea. The young plants grew from the germlings after one month of transplantation and they took another 4 to 5 months to reach harvestable sized plants.
5. DISCUSSION AND CONCLUSIONS
There are no marked variations in the data collected with respect to environmental and hydrological parameters from the four study areas as all of them are located near to each other in the vicinity of Mandapam. The present study made on the yield and physical properties of agar from Gracilaria corticata var. corticata, G. corticata var. cylindrica, G. crassa and G. edulis from the Mandapam area indicates that the quality of agar (gel strength) obtained from G. edulis is higher than the other three species, although the yield of agar is slightly less than that in G. corticata var. corticata and G. corticata var. cylindrica (Table 3). The slightly low yield of agar obtained from G. edulis may be due to the vegetation being subject to repeated commercial harvesting from the study areas during recent years.
Table 4: Yield and physical properties of agar of Gracilaria spp. from the Indian Coast.
|Melting temp (°C)||Reference|
|1.5% sol.||1.5% so1||1.5% sol.|
|G. arcuata var. arcuata||Kilakarai||52.2||67||47–50||89–99||Kaliaperumal et al. 1992b|
|G. corticata var. corticata||Mandapam||38||20||44||68||Thivy, 1952|
|Pudumadam||42.8||22||40–49||49–60||Chennubholta et al. 1979|
|Tiruchendur||44||19||33||51||Subba Rao et al. 1977|
|Tiruchendur||27.2||9||33||70||Kaliaperumal et al. 1990|
|Manapad||21.5||9||36||72||Kaliaperumal et al. 1990|
|Visakhapatna||44.6||134||Umamaheswara Rao, 1978|
|G. corticata var. cylindrica||Kilakkarai||48.6||67||45–52||90–99||Kaliaperumal et al. 1992b|
|Idinthakarai||37.9||15||45||74||Kaliaperumal et al. 1990|
|G. crassa||Mandapam||23||140||48||84||Thivy, 1952|
|Karaichalli Is.||18||11||13||86||Kaliaperumal et al. 1990|
|G. edulis||Mandapam||43||120||45||84||Thivy, 1952|
|Mandapam||55||63||48||65||Chennubhotla et al. 1977|
|Rameswaram||49.2||111||41–57||46–69||Chennubhotla et al. 1979|
|Krusadils.||45||139||44–50||61–78||Chennubhotla et al. 1979|
|Hare Is. (Tuticorin)||43.8||9||39||64||Kaliaperumal et al. 1990|
|G. fergusonii||Tiruchendur||35||19||22||38||Subba Rao et al. 1977|
|Rameswaram||50.4||55||35–51||48–70||Chennubhotla et al.. 1979|
|Tiruchendur||25||31||41||68||Subba Rao et at. 1977|
|Idinthakarai||27.5||15||37||84||Kaliaperumal et al. 1990|
|Kovalam (Kanyakumari)||26.8||11||36||78||Kaliaperumal et al. 1990|
|G. indica||Tiruchendur||28.1||13||47||97||Kaliaperumal et al. 1990|
|Manapad||28.5||23||48||92||Kaliaperumal et al. 1990|
|Kovalam (Kanyakumari)||48.3||46||42||98||Kaliaperumal et al. 1990|
|G. obtusa||Idinthakarai||43.7||11||42||63||Kaliaperumal et al. 1990|
|G. verrucosa||Mandapam||23||41||40||55||Chennubhotla et al. 1977|
In general, the present observations agree with the earlier findings on the yield and physical properties of commonly occurring Gracilaria spp in the Mandapam region and other parts of the Indian coast (Table 4).
Variations in the yield and quality of agar within a species may be due to its geographic location (Figures 1 and 2) and seasonal variation in the growth and size of the plants at the time of collection. It is concluded that G. edulis should be selected for commercial scale culture because of the high yield and quality of agar obtained from it.
All of the Indian agar industry currently uses G. edulis as a raw material for the production of food grade agar while Gelidiella acerosa is used for the manufacture of bacteriological grade agar. Since 1980, many agar industries have developed in India and there is paucity of raw materials of G. acerosa and G. edulis for the production of agar. As a result, some agar industries have tried G. crassa and G. foliifera for producing agar whenever plants of G. edulis were not available in harvestable quantity. However, due to the poor yield and quality of agar from these two species most have stopped using them (Kalimuthu et al. 1990). Annually 318 to 982 tonnes (dry wt) of G. edulis are commercially exploited from natural seaweed beds on the Tamil Nadu coast. This amount is not sufficient to meet the raw material requirements of the agar industry. The whole requirement of raw materials for the Indian agar industry is met only by the seaweeds harvested from the natural beds of the Tamil Nadu coast.
In order to augment production and have a continuous supply of raw materials for the agar industry, large scale cultivation of G. edulis had to be undertaken by preserving the natural beds as a source of seed material. Studies made on the growth behaviour of different species of Gracilaria in nature and experimental culture showed that G. edulis is a fast growing species and suitable for culture conditions. The technology developed for commercial scale cultivation of G. edulis by the Central Marine Fisheries Research Institute (Chennubhotla and Kaliaperumal, 1983) using coir rope net methods may be adopted for large scale cultivation in India. The yield and quality of seaweed could be improved by selecting fast growing and high agar yielding strains and by adopting breeding and other modern scientific techniques of crop improvement.
At present, cultivation of seaweeds such as Gracilaria, Gelidiella, Hypnea and Acanthophora (red algae) Sargassum, Turbinaria, Cystoseira and Hormophysa (brown algae) Ulva, Enteromorpha and Caulerpa (green algae) is carried out only on an experimental scale by the Central Marine Fisheries Research Institute, the Central Salt Marine Chemical Research Institute and other research organisations at different field environments using various culture techniques. No attempt was made at commercial scale cultivation of any of these species. The seaweed suppliers and users should come forward first to undertake large-scale cultivation of seaweeds availing the financial assistance provided by banks and other funding agencies connected with rural development programmes. Once they demonstrate successful harvests, fish farmers and private entrepreneurs will automatically come forward to take up seaweed culture on a large scale. Seaweed cultivation on a commercial scale would not only augment a continuous supply of raw material to the seaweed industry, but will also improve the economic status of people living in the coastal areas.
Detailed studies on the ecology, growth and agar content of all other Gracilaria spp. growing in Indian waters have to be undertaken with a view to identifying the higher agar yielding species among them. Experimental cultivation of those species by vegetative propagation and spore method must be attempted in different field environments using various culture techniques in order to develop suitable technologies for commercial scale cultivation. This will lead to the increased production of Gracilaria spp. in the country and help to meet the needs of the Indian agar industry.
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CMFRI COTTAGE INDUSTRY METHOD FOR THE EXTRACTION OF AGAR FROM
METHOD FOR AGAR EXTRACTION ON A COMMERCIAL SCALE
(VISWESWARA RAO et al. 1965).
Suci Antoro, National Seafarming Development Centre, PO Box 74, Telukbetung, Indonesia
Sutimantoro, Laboratory and Fish Processing Development, Directorate General of Fisheries, Jl. Harsono RM No. 3 Ragunan, Jakarta 12550, Indonesia.
Five species of Gracilaria, namely: G. edulis; G. lemaneiformis; G. salicornia; G. eucheumoides; and Gracilaria sp., were studied. G. edulis and G. lemaneiformis occurred most commonly and also give good agar yields (8–17%) with good agar quality (gel strength: 565–880 g/cm2). Most species had a low gelling temperature, which is an important characteristic of agar to be used as a microbiological medium. The study recommends G. edulis and G. lemaneiformis, which have robust thallus and high biomass production (estimated on a per square metre basis), for culture in both pond and field areas.
Indonesia has a very long coastline (81,000 km) and occupies a 5,000 km band of ocean between the Pacific and Indian oceans. This area is the heart of the Indo-west Pacific biogeographic region which has the world's most diverse biota. Briggs cited by Frankenberg (1986), said that the diversity of the Indo-West Pacific shelf fauna and flora far exceeded that of other tropical regions. The Siboga Expedition (1888–1889), reported not less than 555 seaweed species as part of its findings (Weber van Bosse as cited by Soegiarto et al., 1978). Among Indonesia's algal flora, 55 species have been utilised by coastal people mostly as food and sometimes for medicinal treatments (Zeneveld cited by Soegiarto and Sulistijo, 1986). Presently, most of Indonesia's seaweed production serves as raw material for the manufacture of industrial products, such as agar and carrageenan. In 1993, Indonesia exported 14,367 tonnes of dried seaweed valued at US $ 7,429,000 (Indonesia Fisheries Statistics, 1994).
The world-wide increasing demand for seaweed and seaweed products has been the main factor which has encouraged the development of production technologies of economic species of seaweed. The production of carrageenophyte in Indonesia comes mainly from artificial cultivation, but the greater part of agarophyte production comes from direct harvest of natural stocks. The agarophytes which are harvested are mainly from the genera Gracilaria, Gelidium and Hypnea. At present, pond culture of Gracilaria is still being attempted.
The major constraint to Gracilaria cultivation in Indonesia is that there is no complete database available about the taxonomy, ecology and agar content on each species of the genus. Trono (1990) recommended that the species targeted for culture should have the following properties:
It must be a fast growing species which can be propagated using vegetative propagules (cuttings) or spores and can produce large amount of biomass within relatively short cropping periods.
It must have a high content of good quality of agar.
Taking these restrictions into consideration, the available species can be screened and comparative studies on their productivity may be conducted to determine the best species to select. As the properties of agar differ among species, it is very important that the correct name be applied. Thus the taxonomy of the species Gracilaria should be clarified to stimulate the culture of Gracilaria in Indonesia.
2. TAXONOMY AND ECOLOGY OF GRACILARIA
Earliest taxonomic and ecological data of Gracilaria spp. dates from the Siboga Expedition (1888–1889). Of the 31 sheet herbarium specimens belonging to the Gracilariaceae, six species were identified, namely: Polycavernosa fastigiata, P. vanbossae, P. urvillei, Gracilaria arcuata, G. arcuata var. snackeyi and G. blodgettii (Abbott, 1988). Soerjodinoto (1962), based on Valerie May and Zeneveld descriptions, reported three species from Indonesia: Gracilaria confervoides, G. lichenoides and G. taenioides.
Presently, studies on the taxonomy, ecology and processing (agar yield and quality) of Gracilaria spp. in Indonesia are conducted under the seaweed development programme, one of the projects under the large regional aquaculture development and environment programme of NACA. This study focuses on two provinces, Lampung and West Java (Figure 1).
Figure 1: Map of sampling site.
A: Grupuk; B: Cukuh Balak; C: Bojonegara; D: Pameungpeuk.
2.1 Materials and methods
For the purposes of this study, fresh materials were examined from four locations namely Cukuh Balak and Grupuk in Lampung Province, and Bojonegara and Pameungpeuk in West Java Province. Nine herbarium specimens were collected and marked as SW 01, SW 02 from Grupuk, SW 03, SW 04, SW 05, SW 06 from Cukuh Balak, SW 08, SW 09 from Pameungpeuk and SW10 from Bojonegara. Liquid specimens were preserved with 5% formalin in seawater and examined. Ecological parameters such as salinity, temperature, transparency, substratum and season, were also recorded. Sections were cut by hand, stained with 1% aniline blue, mounted in 25% glucose syrup and examined under a light microscope.
Among the nine specimens collected, five species were identified: Gracilaria edulis, G. lemaneiformis. G. salicornia, G. eucheumoides, and Gracilaria sp.
2.3 Species descriptions
1. Gracilaria edulis (Gmelin) Silva (Figure 2).
Thallus growing from a disk-like holdfast with prostrate rhizome forming a tuft or cluster of 8–25 cm tall, dark green to yellowish in colour, branching di- or tri-chotomous, main axis 1–1.5 mm, branches 0.5–1.0 mm in diameter with wide angle furcation. Lower branch intervals much longer than the last two orders, branch cylindrical, lower branch about 1 mm in thickness and getting thinner to 0.5 mm for terminal segments with attenuate apices. Fronds in transverse section consisting of roundish thin walled medulla cells, 100–250 um in diameter, 1–2 rows of small cortical cells, transition from medulla to cortex, abrupt. Cystocarp globose 0.5–1.0 mm in diameter with rostrate tips and constriction at the base.
Grows on rocks or muddy surfaces in sandy-mud areas, sheltered or not sheltered, intertidal zone, clear water and not exposed to air during low tide. Distributed around Grupuk and Cukuh Balak Lampung and Bojonegara West Java along the Java sea coast.
2. Gracilaria lemaneiformis (Bory) Weber-van Bosse (Figure 3).
Thallus solitary or caespitose, dark green to brownish in colour, up to 40 cm tall with few to several long branches. Branches 0.5–1.5 mm in diameter, branching irregular, mostly from lower portion, branches simple, 2–5 branchlets frequently occur from a single branch apex. Fronds in transverse section of medulla of large thin walled cells, 130–260 um in diameter, two layers of cortex, transition of cell from medulla to cortex, abrupt. Cystocarp spherical 0.7–1 mm, slightly or non rostrate, constriction at the base.
Grows on sand or in muddy areas, intertidal zone, clear water, sheltered area, not exposed to air during low tide. Found in the Grupuk, Lampung area.
3. Gracilaria eucheumoides Harvey (Figure 4A).
Thallus cartilaginous, greenish-brown to purple in colour when fresh, forming prostrate clumps and attached to the substratum by hapters originating from the ventral side of the flattened branches. The branching pattern is very irregular and the branches are compressed measuring 2.5–7 mm across, provided with coarse teeth along their margins, attached by discoid holdfast.
Figure 2: Gracilaria edulis (Gmelin) Silva.
|B. External view of cystocarp.||C. Cross-section of main axis|
Figure 3: Gracilaria lemaneiformis (Bory) Weber-van Bosse.
|B. External view of cystocarp||C. Cross section of main axis|
Grows on rocks in the intertidal zone, in clear water exposed to moderate to strong wave and currents during low tide not exposed to air. Found in Cukuh Balak, Lampung and along the coast of Semangka Bay.
4. Gracilaria salicornia (C. Agardh) Dawson (Figure 4.B).
Thallus grow creeping or erect from a disc on subtidal shell, or rock, 5–15 cm in length, 3–8 cm broad, cylindrical throughout, very brittle when fresh, light orange to yellow-green in colour; main axes absent or distinct in lower portion. Branches irregular, some strongly constricted throughout, branches at nodes, dichotomously or some trichotomous and some without regular constriction. The basal portion of some thalli are less consciously constricted than those in the upper portion, some branches from root-like discs on the apices of ramuli or on margins, by which fronds attach to the substratum.
Grows on rocks, shell or sand surface in the intertidal zone, clear water, exposed area. During low tide partially exposed to air. Found at Cukug Balak, Lampung and Pameungpeuk West Java, along the coast of the Indian ocean.
5. Gracilaria sp. (Figure 5).
Thallus rigid, 4–12 cm tall, compressed, with many orders of short densely branched intervals; branching pattern dichotomy, 0.5–1 mm in diameters, dark red to brownish in colour. Fronds in transverse section consist of large thin walled medulla, 100–250 um in diameter, 1–2 layers of small cortical cells; transition from cortex to medulla abrupt.
Grows on rocks or shell in clear water in the intertidal zone, exposed to wave and currents, during low tide not exposed to air. Found in Cukuh Balak, Lampung and Pameungpeuk West Java along the coast of the Indian ocean.
3. PROCESSING (AGAR YIELD AND QUALITY) OF GRACILARIA
As described above, the species targeted for culture must have a high content of good quality agar. Unfortunately, no complete information exists on the agar content of various seaweeds and their properties in Indonesia. There are, however, three publications covering this subject. Harlim (1986), extracted agar from G. crassa and G. eucheumoides which were collected from the coast of 10 islands of the Spermonde (Table 1).
Table 1: Agar quantity of Gracilaria collected from the coast of Spermonde.
|Locations||Gracilaria crassa||G. eucheumoides|
|Lae-Lae and Gusung Islands||15%||27%|
|Kodemgareng Keke Island||22%||32%|
Soegiarto and Soelistijo (1986), reported the organic compositions of Gracilaria sp. and G. confervoides and the nutritional value of G. gigas from Bali Island (Table 2). Finally, Anggadireja (1990) studied the quality of Gracilaria spp. from 31 locations (Table 3). In this study, agar yield and quality was analysed from 5 species, namely: Gracilaria edulis, G. lemaneiformis, G. salicornia, G. eucheumoides and Gracilaria sp.
Figure 4A: Gracilaria eucheumoides Harvey.
Figure 4B: Gracilaria salicornia (C. Agardh) Dawson.
Figure 5: Gracilaria sp. (A, B, C show main thalli; D shows a cross section of the main axis.
Table 2: Organic composition of Gracilaria sp., G. confervoides and G. gigas.
|Locations||Gracilaria spp.||G. confervoides||G. gigas|
|Protein (6.25 N)||4.17||3.14||7.30|
|Thiamin (mg/100 g)||-||-||0.02|
|Riboflavin (mg/100 g)||-||-||4.00|
|Vitamin C (mg/100 g)||-||-||12.00|
|Minerals, Ca (ppm)||-||-||29.920|
Table 3: Variation in the quality of some Indonesian Gracilaria.
|Location||Yield (%)||Gel strength (g/cm2)||Gelling/Melting Temp.(°C)||Dried Product (tonne/yr)||Harvest Season|
|Teroa, Bali||8.7||170||25/96||8.0||Aug - Jan|
|Geger, Bali||9.4||210||29/76||9.5||Aug - Jan|
|Paciran, East Java||18.7||880||41/88||80.0||(FA)|
|Sekotong, Lombok||19.2||890||40/92||60.0||Jul - Feb|
|Lembar, Lombok||17.3||825||39/90||50.0||Jul - Feb|
|Lbn. Haji, Lombok||15.4||770||36/87||40.0||Sept - Feb|
|Tg. Gontor, Sumbawa||18.2||900||39/91||60.0||Sept - Mar|
|Lbn. Lalar, Sumbawa||18.2||920||41/91||120.0||Sept - Feb|
|Sumbawa Besar||16.6||740||35/87||40.0||Jun - Feb|
|Dompu, Sumbaw||20.6||720||36/88||50.0||Sept - Jun|
|Plb.Ratu, West Java||16.9||570||36/88||30.0||Jul - Dec|
|Lb. Batten, W. Java||17.1||710||34/83||35.0||Aug - Dec|
|Malimping, W. Java||16.7||770||41/87||40.0||Aug - Dec|
|Pameungpeuk, W. Java||15.4||480||33/81||35.0||Oct-Mar|
|Baron, Yogyakarta||14.9||390||32/81||25.0||Nov - Apr|
|Pacitan, East Jaba||15.8||440||33/83||15.0||Jun - Dec|
|Warambadi, Sumba||18.2||660||37/87||25.0||Apr - Nov|
|P. Besar, Flores||12.3||310||31/82||15.0||Sept - Jan|
|Tongga, P. Rote||17.4||720||36/89||40.0||Jul - Jan|
|Tg. Pila, P. Rote||13.3||290||32/86||10.0||Aug - Jan|
|Tg. Bunga, Sulawesi||18.1||710||39/89||35.0||(FA)|
|Maros, Sulawesi||14.4||510||35/87||20.0||Jul - Dec|
|Takalar, Sulawesi||18.7||1090||40/92||60.0||(FA, WS)|
|Bone, Sulawesi||17.1||790||40/88||50.0||(FA, WS)|
Notes: Moisture content of all samples less than 20%
FA= farming area;
WS = wild stock;
4.1 Materials and methods
Dried material of seaweeds from fresh specimens were collected from the same 4 locations as the specimens for taxonomic and ecological study. Not less than 1 kg (wet weight) of each species was collected for analysis. The sequence of processes involved in the extraction of agar from seaweed was adopted from Chandrkrachang (1992), meanwhile methods for analysis of agar yield and quality were adopted from Laboratory Methods for Qualification of Red Seaweed and their Polysaccharides (Anon, 1992). Nine properties of seaweeds and seaweed products were recorded from 5 species, namely: wet weight (g), dry weight (g), clean anhydrous weight (CAW), moisture content (%), ash content (%), agar yield (%), gel strength, sulphate content (%) and gelling and melting temperature (°C).
The quantity and quality of agar varied according to species and the locations of the collected sample, as shown in Table 4.
Table 4: Analytical results of agar quantity and quality.
|Agar yield and properties||Species Code|
|SW 01||SW 02||SW 03||SW 04||SW 05||SW 06||SW 08||SW 09||SW 10|
|Biomass production (kg/m2)*||0.41||0.65||0.60||0.37||0.36||0.08||0.15||0.12||0.52|
|Wet weight (kg)||4.82||5.12||9.75||12.6||22||2.5||4.15||4.5||5.1|
|Dry weight (kg)||0.635||0.65||1.27||1.5||2.88||0.3150||0.6||0.7||0.82|
|Agar Yield (%)||8.13||9.96||13.61||8.18||5.47||16.99||11.07||12.12||15.77|
|Gel strength (g/cm2)||610||880||840||780||580||850||625||550||575|
|Melting temperature (°C)||68||85||90||86||75||82||72||89||79|
|Gelling temperature (°C)||36||34||39||28||32||29||31||28||32|
|SW 01, 03 & 10:||Gracilaria edulis|
|SW 02:||G. lemaneiformis|
|SW 04, 09:||Gracilaria sp.|
|SW 05, 08:||G. salicornia|
|SW 06:||G. eucheumoides|
|* wet weight|
|CB:||Cukuh Balak, Lampung|
|P:||Pameungpeuk, West Java|
|B:||Bojonegara, West Java|
5. DISCUSSION AND CONCLUSIONS
In addition to determining species, other factors which should be considered in the selection of species for culture include: production of biomass per square meter (Table 4), ecological parameters, and the quantity and quality of agar content. The taxonomic and ecological data recorded, indicated that Gracilaria edulis and G. lemaneiformis have robust thalli and the highest production of biomass. G. edulis is widely distributed in various areas from shallow areas in Grupuk and Bojonegara with sandy-muddy substrates, to unprotected area in Cukuh Balak with coral or rock substrates. G. lemaneiformis is only found in Grupuk with sandy-muddy substrates. Other species, have lower biomass production and are only found in unprotected areas with coral or rock substrates.
As shown in Table 4, the quantity and quality of agar from the 5 species collected, varied according to species and the locations of sample collection. Two species had higher agar contents than the other species, G. eucheumoides from Cukuh Balak (16.99%), and G. edulis from Bojonegara (15.77%) and Cukuh Balak (13.61%). Results of the analyses of agar properties, indicated that G. lemaneiformis from Grupuk had the highest gel strength (880 g/cm2), followed by G. eucheumoides from Cukuh Balak (850 g/cm2 ) and then G. edulis from Cukuh Balak (840 g/ cm2). Gel strength is one of the factors mat is used to determine agar quality (Dawes, 1981).
The utilisation of highly productive species or strains with high quality and quantity of agar is essential for the successful farming of Gracilaria. On the basis of the results of this study and Trono's description of the factors that should be considered in the selection of species for culture, the species selected must:
have a large amount of biomass (indicated by large and robust thalli);
have a high content of good quality agar; and
be found in areas characterised by calm water, high nutrient levels and shallow areas with sandy-muddy substrates;
This study concluded that G. edulis and G. lemaneiformis from Grupuk Lampung Province had good potential for artificial cultivation in pond or field areas, compared with the other species examined.
Bearing in mind that Gracilaria spp. are economically important seaweeds, the following recommendations are made:
Gracilaria edulis and Gracilaria lemaneiformis showed greatest potential for artificial cultivation in both pond or field areas, compared with the other species studied.
A follow-up study should be held on the taxonomy, ecology and processing of seaweeds, especially Gracilaria spp., by the Indonesian Government around Indonesian territories to gather complete and accurate data as a basis for planning and establishing seaweed farms and the seaweed processing industry.
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