Digital library

  • Seaweed Resources of the Ocean

    This review of the seaweed resources of the world is part of a continuing programme of evaluating the resources from the sea of food, in a wide sense. These studies of the potential harvest are an important step towards the better planning of the proper use and management of these resources. The area breakdown is that used by FAO in compiling and publishing fishery statistics (see chart at end). 

    Quantitative studies of seaweeds are much rarer than those of fish stocks. The exceptions could be indicated by a few spots on the world map -the southwest coast of Norway,Scotland, Nova Scotia, the Californian kelp beds. The rest of the map is a blank space.This review is a first attempt to fill that space, but is primarily a challenge to field phyoologiBte to produce the data from which a better evaluation of the world's seaweed resources can be made. 

    Since this study concentrates on resource assessment, the potential harvest, and related quantitative studies, less emphasis has been given to studies on relative distribu­tion, seasonal variation, mode of reproduction, etc. except where these are of direct interest to present or future utilization. However, for the areas for which suitable quantitative data are not yet available, ecological and similar information has been used to give an idea of the structure and composition of the flora, and thus provide a first approximation to the potential harvest. 

    Any study of this kind must distinguish between biomass (or standing st)cks) on the one hand and production or potential harvest on the other; further, a distinction needs to be made between the theoretically attainable harvest and that which is feasible in the light of practical and economic constituents. 

    Locally we often see the richest kelp pastures on plumb battered rooks, where no boat can stay in the breakers, or in the surf area, where no diver can find a holdfast. Uninhabited arctic and cold temperate areas may be extrem-ly rich in biomass, but even if collectors could be flown in from distant places, the transport costs for untreated sea­weed or partly processed product put the resource out of all competition. 

    Rockweed of the genera Fucus and Cystoseira are among the richest producers if we estimate the bulk of seaweed in the ocean, but it is not yet solved how to use them. We know that certain laboratories study this problem, but have not yet seen their results being applied on on industrial scale. The same could be said about turtle grass, eel grass and other phanerogams, and mass occurrences of protein-rich Caulerpa green algae. A hind­rance for the utilization of seaweeds in most areas is that they do not occur in single species stands but extremely mixed and entangled, often as epiphytes on each other. 

    Taken as a whole, seaweed resources are not greatly exploited. The potential for increasing the seaweed harvest depends as much on economic factors - the demand for the products and the costs of harvesting and processing - as on the overall biological produc­tion. Assuming no great changes - i.e. considering only the seaweed crops that consist of a sufficiently rich occurrence of a commercially attractive species occurring in areas where they can be really harvested, processed and marketed - the global production of the most important group, the red algae, could be increased by about 50 percent. The biomass of kelp and rockweed beds would permit a twentyfold increase in utilization of brown algae. 

    Several factors could act to support even greater expansion. On the production side seaweed harvesting can be labour-intensive; this could be a great advantage in the numerous developing countries where unemployment, and under-employment, are growing social problems on the marketing side, the continuing growth of world population will produce an increase in demand not only for direct food but also for the various other products in which many seaweeds are rich. The possibilities for expansion may be judged by the temporary boom of seaweed industries in many parts of the world in the early 1940s, when local seaweed production expanded to fill the gap left by the failure of supplies from abroad. changed balance of supply and demand a tenfold increase in present world harvest would not be unrealistic. 

    It is not the aim of this review to deal in detail with the technical and economic aspects of the processing and marketing of seaweeds, which have been discussed extensively Commercial products from seaweeds are encyclopedically treated Levring, Hope and Schmid (1969). Another section of the same handbook takes into separate consideration those species -seaweeds which are of interest as raw material or foodstuff. Further references can be found in "Selected Bibliography on Algae", issued by Nova Scotia Further references This has appeared with 13 Research Foundation, P.O. Box 790, Dartmouth, Nova Scotia. numbers containing references to scientific, technical and popular literature including most valuable sections on cultivation, utilization, economy, industrial methods and patents. 

    The economic and commercial aspects of seaweed utilization have been subject to remarkably few published investigations as compared to ecological and biochemical aspects. Haken (1958) gave a brief account of the major seaweed product industries in the mid-1950; a more recent review of the major seaweed products and their origin with data on industries and value was prepared by Silverthorne and Sorensen (1971). 

    Information on seaweed trade, prices, market trends and technical literature is iTU, regularly reported by International Seaweed Exchange, 24 Southwark Street, London, SEl in a market information bulletin, mainly intended for sellers and buyers transacting through the Exchange. 

    The Department of fisheries of FAO is presently undertaking a comprehensive review of the economic and commercial potential of the world's algaic resources, to be published as the study will examine trends in the production of sea­one of its Commodity Study series; weeds and seaweed products, their utilization, trade and consumption. In progenting per­spectives of likely future demand for such products it will try to indicate possible opportunities, particularly in the developing countries, for achieving higher levels of production and utilization.

    A revision and updating of figures and statements in this paper is foreseen. are invited to send any comments and proposals to Aquatic Resources Survey and Evaluation Service, Fishery Resources and Environment Division, FAO, Rome, Italy, or directly to the author.

     

    Author(s): Obran Michanek

  • Seaweed resources of the Tuticorin-Tiruchendur coast, Tamil Nadu, India

    The southern coast of Tamil Nadu (Mandapam to Kanyakumari) supports luxuriant growth of economic seaweeds. The entire indigenous phycocoUoid industry of the country gets the raw material from this region and during the last two decades, due to indiscriminate harvesting, there has been over-exploitation of the resource. The present paper deals with survey conducted in the first sector from Tuticorin to Tiruchendur during December 1986—March 1987. In this study 58 species of marine algae were recorded of which 7 belong to Chlorophyta, 12 to Phaeophyta and 39 to Rhodophyta besides 3 species of seagrasses namely Cymodocea seiriilata, Halophila ovalis and //. ovata within 650 sq. km area surveyed. The total standing crop of the seaweeds was estimated at 9,100 tonnes (wt.). The estimates for the dominant species are Dictyota maxima 530 t, Sargassum tenerrium 640 t, D. bartayresiana 8601, Selieria rebusta 2,0901 and Hypnea valemiae 2,4301. The seaweed potential for commercial exploitation has been briefly discussed.

    Author(s): Chennubhotla, V S Krishnamurthy, Kaliaperumal, N, Kalimuthu, S, Ramalingam, J R, Subbaramaiah, K, Rao, K Rama, Rao, P V Subba

  • Seaweed resources off Tamil Nadu coast - Kattapadu- Tiruchendure

    The southern coast of Tamil Nadu from Mandapam to Kanyakumari supports luxuriant growth of economically important seaweeds and the total standing crop was estimated at 22,000 tonnes (wet). All the seaweed based industries in India mostly depend on the raw material available from this area. The seaweeds exploited from this region, particularly the agarophytes Gelidiella acerosa and Gracilaria edulis are insuiBcient to meet the raw material requirement of the industries.

    Author(s): Chennubhotla, V S Krishnamurthy, Kaliaperumal, N, Kalimuthu, S, Ramalingam, J R, Pillai, S Krishna, Subrahmanyan, M, Rao, K Rama, Rao, P V Subba

  • Seaweed resources off Tamil nadu coast, Sector - IV Kilakkarai - Rameswaram island (Dhanushkodi

    Survey of the deep water area from Kilakkarai (Appa Tivu to Rameswaram Island (Dhanushkodi) was undertaken from December 1990 to January 1991 in the IV Sector survey of Deep water Seaweed Resources off Tamil Nadu coast, which formed the last phase of the survey from Rameswaram to Kanyakumari carried out during 1986-91. An area of 417.5 sq.km. was surveyed yielding a total biomass of 18,162.5 tons (wet) seaweeds. Out of 167 stations surveyed in 13 transects, vegetation occurred only in 12 stations. Of the 29 species of marine algae recorded 8 belonged to Chlorophyta, 8 to Phaeophyta, 12 to Rhodophyta, and I to Cyanophyta, One species of seagrass Cymodocea serrulata was also recorded. Twenty species were found in estimable quantities, of which the following 8 species were abundant: Halimeda macroloba, Spatoglossum asperum, Zonaria crenata, Sargassum ilicijolium, Amphiroa fragilissima, Hypnea musciformis, Botryocladia leptopoda and Lyngbya majuscula with a biomass of 1325, 9775, 650, 1550, 1925,300,862.5 and 1012.5 tons (wet) respectively. The species of Hypnea and Sargassum could be exploited for the manufacture of phytochemicals.

    Author(s): Rao, K Rama, Rao, P V Subba, Thomas, P C, Zaidi, S H, Subbaramaiah, K, Kaliaperumal, N, Kalimuthu, S, Muniyandi, K, Ramalingam, J R, Najmuddin, N, Chennubhotla, V S Krishnamurthy

  • Seaweed resources off Tamil Nadu coast: Sector II. Alanthali - Manapad and Vembar – Nallathanni Thivu

    The seaweeds are used for the production of polysaccharides such as agar, algin, carragennan and they are harvested from intertidal regions along the southeast shores of India. The resource potential from intertidal regions was estimated (Anon 1978)

    Author(s): Rao, P V Subba, Rao, K Rama, Mal , T K, Subbaramaiah, K, Kaliaperumal, N, Kalimuthu, S, Muniyandi, K, Ramalingam, J R, Chennubhotla, V S Krishnamurthy

  • Seaweed resources off Tamil Nadu coast: Sector III. Valinokkam - Kilakkarai

    Survey of seaweed resources in deep water was carried out in the area between Valinokkam and Kilakkarai during January 1989 and March,l990 respectively. In the survey from Valinokkam to Kilakkarai 33 species of marine algae were recorded of which 8 species belong to Chlorophyta, 8 to Phaeophyta and 17 to Rhodophyta. Only one species of seagrass Halophila ovalis was recorded. Among the 200 sq Icm area surveyed, vegetation occurred only in 27.5 sq.km with a total standing crop of 2962.5 tonnes (wet wt).

    Author(s): Kaliaperumal, N, Kalimuthu, S, Muniyandi, K, Ramalingam, J R, Chennubhotla, V S Krishnamurthy, Rao, K Rama, Rao, P V Subba, Thomas, P C, Zaidi, S H, Subbaramaiah, K

  • Seaweed resources, products and utilization

    India has extensive seaweed resources and these have been surveyed by several workers. In India, more attention is being bestowed on increasing the production of economically important seaweeds by different culture techniques. The growth rate and production of Gelidiella acerosa, Gracilaria edulis, Hypnea musciformis, Acanthophora spicfera and Sargassum spp. in different culture methods have been studied. Considerable data are also available on the commercial exploitation of Indian seaweeds. The important commercial products from seaweeds are agar-agar, algin, mannitol and proteins. The algae are also found to bear bioactive substances such as toxins and antibiotics. Attempts have been made to develop antiviral, antifungal and antimicrobial substance from seaweeds.

    Author(s): Silas, E G, Chennubhotla, V S Krishnamurthy, Kaliaperumal, N

  • Seaweed salt from Ulva: A novel first step in a cascading biorefinery model

    We compared post-harvest processing of two species of Ulva (chlorophyta) using 36 washing time-by-temperature combinations. We quantified the yield of crystallized salt after evaporation of the washing water as a target product and characterized the composition of salts and processed biomass, with the additional aim of improving the composition of the processed biomass for production of fertilizer, feed or fuel. Washing of biomass of Ulva ohnoi and Ulva tepida effectively reduced its mineral content with concomitant production of crystalline salts with Na:K ratios of 1.1-2.2 and a maximum of 19% soluble fiber (ulvan). The maximum yield of salt was 29% of the biomass for U. ohnoi and 36% for U. tepida. Salts from both species have potential for human health applications and functional foods. Washing increased the energy content of the biomass from both species by 20-50% to a maximum of 18 MJ kg-1 and protein contents by 11-24% to a maximum of 27.4%. The production of seaweed salt is therefore a novel first step in a cascading biorefinery model for the utilization of macroalgal biomass which simultaneously improves the quality of the processed biomass for production of fertilizer, feed or fuel.

    Author(s): Marie Magnusson, Christina Carl, Leonardo Mata, Rocky de Nys, Nicholas A. Paul

  • Seaweed structure shapes trophic interactions: A case study using a mid- T trophic level fish species

    Biogenic habitat structure, such as that created by foundation macrophytes, shapes the interactions of higher trophic level organisms by creating three-dimensional refuge spaces. In recent decades, many kelp habitats have transformed into turf-dominated communities. This represents a fundamental change in the overall habitat structure in these communities, with an unknown impact on upper trophic level organisms. We investigated how macroalgae morphology affects a common residential mid-trophic level wrasse, Tautogolabrus adspersus (cunner), which utilizes macroalgae for both refuge and foraging. Three studies were conducted: in situ behavioral video observations, a refuge choice experiment, and a foraging efficiency experiment. Video observations revealed that in kelp-dominated and mixed habitat types cunner use macroalgae more often for refuge than for foraging, but in turf-dominated habitats refuge and foraging events were equal. In these habitats, refuge-seeking was more often associated with a tall, morphologically simple kelp. The refuge choice experiment supported our video ob- servations with cunner preferentially seeking refuge beneath taller but less morphologically complex algae in- stead of shorter filamentous forms. In predation trials, macroalgae complexity did not significantly affect the number of prey the fish captured. Our results provide evidence that the refuge-seeking behavior of this re- sidential mid-trophic level fish may be impacted by the ongoing shifts in macroalgae dominance in the Gulf of Maine. Loss of its preferred refuge (tall, canopy-forming kelps) may force it to use the less-preferred introduced turf algae instead. However, whether turf provides sufficient protection for this species remains unclear. With the ongoing loss of kelp in temperate coastal ecosystems worldwide, it is important to understand the potential indirect effects that changes in habitat structure will have on the trophic interactions of upper level organisms.

    Author(s): Brandon S. O'Brien, Kristen Mello, Amber Litterer, Jennifer A. Dijkstra

  • Seaweed Supplements Normalise Metabolic, Cardiovascular and Liver Responses in High-Carbohydrate, High-Fat Fed Rats

    Increased seaweed consumption may be linked to the lower incidence of metabolic syndrome in eastern Asia. This study investigated the responses to two tropical green seaweeds, Ulva ohnoi (UO) and Derbesia tenuissima (DT), in a rat model of human metabolic syndrome. Male Wistar rats (330–340 g) were fed either a corn starch-rich diet or a high-carbohydrate, high-fat diet with 25% fructose in drinking water, for 16 weeks. High-carbohydrate, high-fat diet-fed rats showed the signs of metabolic syndrome leading to abdominal obesity, cardiovascular remodelling and non-alcoholic fatty liver disease. Food was supplemented with 5% dried UO or DT for the final 8 weeks only. UO lowered total final body fat mass by 24%, systolic blood pressure by 29 mmHg, and improved glucose utilisation and insulin sensitivity. In contrast, DT did not change total body fat mass but decreased plasma triglycerides by 38% and total cholesterol by 17%. UO contained 18.1% soluble fibre as part of 40.9% total fibre, and increased magnesium, while DT contained 23.4% total fibre, essentially as insoluble fibre. UO was more effective in reducing metabolic syndrome than DT, possibly due to the increased intake of soluble fibre and magnesium. 

    Author(s): Senthil Arun Kumar, Marie Magnusson, Leigh C. Ward, Nicholas A. Paul, Lindsay Brown

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