The Namibian seaweed industry: Present and potential

Bioresource Technology 38 (1991) 137-143

The Namibian Seaweed Industry: Present and Potential* A. T. Critchley Botany Department, University of the Witwatersrand, PO Wits, 2050, Johannesburg, Republic of South Africa

K. W. G. Rotmann Taurus Chemicals Namibia (Pty) Ltd, PO Box 68327, Bryanston 2021, Republic of South Africa

& F. J. Molloy Directorate of Sea Fisheries, PO Box 394, Lfideritz, 9000, Namibia

Abstract

The new country of Namibia has a seaweed industry which centres upon the natural harbour of Lgideritzbucht, one of the few inlets and rocky outcrops of" the entire coastline. Algal utilisation is presently based on collection of natural casts of the agarophvte Gracilaria verrucosa. Storms and persistent winds result in large quantities of the alga being washed ashore (c. 15 000 tonnes fresh weight per annum) at various beaches around Lffderitzbucht for most of the year. Other algae of commercial importance include Suhria vittata (agarophyte) and the kelp Laminaria schinzii. Since 1981, the collection of Gracilaria has been coordinated by Taurus Chemicals Namibia, resulting in a significant source of employment to an otherwise depressed labour force. Cast Gracilaria is sorted into various grades for export or direct consumption in a recently installed agar factoo~. The process of agar extraction is outlined here. 'Natural' harvesting of cast Gracilaria only results in an unpredictable and variable yield of raw material, which in turn influences export and local consumption strategies. In order to stabilise local agar production, the amount of raw material

available must be increased. Direct harvesting from the Gracilaria beds is ruled out, thus production can only be increased by aquaculture. Cultivation of seaweeds in ponds and various forms of outplanting are being investigated. Key words: Namibian seaweeds, Gracilaria verrucosa, agarophytes, agar production. INTRODUCTION The Namibian coastline extends for 1500 km between the Kunene River, bordering Angola and the Orange River forming the border with South Africa (Fig. 1). The coast is predominantly sandy (some 78% of the total), with few indentations. Li.ideritzbucht (15 ° longitude; 27 ° latitude; Figs 1 and 2) is a natural harbour also comprising the only major area of rocky shore. The average annual seawater temperature range for Ltideritzbucht is 12-14-8°C (Sea Fisheries, Namibia; Taurus Internal Reports), which is the lowest for the entire Namibian coastline. This is due to the effects of the cold, northflowing Benguela Current and the influence of a strong up-welling cell, bringing cold, nutrient-rich, Antarctic water to the surface (Fig. 1). The cold waters are very productive and contribute to the temperate marine climate of the area. Seawater temperature increases both northerly and

*Paper presented at: The 5th International Conference of the Society of Applied Algology:Recent Advances in Algal Biotechnology,Tiberius, Israel 28 January-2 February 1990. 137 Bioresource Technology 0960-8524/91/S03.50 © 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain

138

A. T. Critchley, K. W. G. Rotmann, F. J. Molloy

COLD CURRENTS

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• L[

...... i iii

1

.~a

i .....................

,,.' ,"""

Fig. 1. The position of Liidcritz,Namibiaand the influence of the North-flowingBenguelaCurrent causingup-welling.

• • m i n g o1 Flamin"goIsland

Beach

SealIsland~'~//// Agate~ PenguinIsland~//// [ AngraPequena AngraPoint @AngraF 'lJl~'xm SharkIsland _/ Diaz~o~t ( ) '~ ~AeroplaneBay (" "~ ShearwaterBay/ \ )/

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......... ............

/J/ '//lilly" \G,,,th3 /

L°°ritz

GRACILARIABEDS Fig. 2. L/ideritzbucht, to illustrate the position of Gracilaria beds and the number of beaches upon which material is cast.

southerly from Lfideritzbucht (Agenbag & Shannon, 1988). One of the major problems facing development of the Namibian seaweed industry is poor access to the coast. Liideritz has a single road and rail connection to the Namibian interior and there are few roads through the coastal Namib Desert (Molloy, 1990). Access to the coast is further

confounded by restrictions imposed by the diamond-mining operation in the area. Namibia does not have a tradition of seaweed utilisation. Indeed, the resource is poorly studied, with few published reports of the marine flora (Penrith & Kensley, 1970a, b; 1980; Wynne, 1986; Lawson et al., 1990; Molloy, 1990). Seaweeds of commercial importance have been collected sporadically since 1950 (Isaac, 1964; Anderson et al., 1989). Only since 1975 have seaweed collections been organised, leading to a significant demand for locally collected seaweeds, principally for export and processing overseas (Rotmann, 1987). In 1980, the then South West African/Namibian Government called for tenders for the concession to utilise seaweeds on the coast. Since 1981, an intense effort has been made to develop the Namibian seaweed industry by Taurus Chemicals, Namibia, including the relocation of an agar extraction plant to Liideritz in 1986. The industry and infrastructure so formed around seaweed utilisation created employment for over 250 people in an otherwise depressed job market. Of the local seaweeds, Gracilaria verrucosa is the most important resource, around which the agar extraction facility has developed. However, the agarophyte, Suhria vittata and the kelp, Laminaria schinzii have also been collected for export.

ALGAL UTILISATION IN NAMIB1A Laminaria schinzii is a digitate kelp occurring from low water to a depth of 16 m in the Lfideritzbucht area. Approximately 300 tonnes of Larninaria blades are available for utilisation annually. Blades are cut manually, during spring tides, 2 cm above the intercalary meristem. Regrowth of the laminae occurs after 3-4 months (Molloy, 1990). Cut blades are returned to a processing area and hung out to dry. Lfideritz has an ideal desert climate for rapid drying with persistent winds, high air temperatures (13-25°C) and little rainfall. The Larninaria blades, once dried, are manually sorted to discard damaged or epiphytised portions, flattened and then packaged. During the period July 1987-May 1989 a total of 150 tonnes (fresh weight) Laminaria were harvested for export to Taiwan as kombu. Collection has presently ceased due to the market requiring a more tender blade for consumption. Suhria vittata is an agarophyte which grows

7he Namibian seaweed indust~': present and potential

epiphytically on the stipes of kelp, beneath the frond canopy; the agar quality of the alga is low (gel strength 4 0 0 - 6 0 0 g/cm 2) but a consignment of 10 tonnes was supplied to Japan, where the alga was found to be very acceptable for the production of 'square' agar (bars). Export of Suhria is limited by its availability. The natural habitat of the alga indicates that it would be a suitable candidate for domestication in terms of rope cultivation (Anderson & Bolton, 1985). Gracilaria verrucosa is central to all algal utilisation in Namibia. The alga occurs in a number of beds, within sheltered areas of Liideritzbucht (Fig. 2). Surprisingly, in spite of the tremendous value of the material, the extent, production and condition of the beds is little known. Gracilaria populations in the area comprise a vegetative assemblage of plants which lie loose or within a sandy substratum; fronds are fragmented by frequent Atlantic storms. Surges and swells through the bay are sufficient to bring large quantities of Gracilaria onto shore (Fig. 3; c. 15 000 lonnes per annum).

139

remove salt which acts as a preservative in transit. Dehydration of the seaweed must be sufficient to ensure preservation, otherwise anaerobic fermentation may occur, causing high temperatures and even carbonisation (McHugh, 1987). The product excels in colour, purity and moisture content; it is exported to Japan, Korea and Chile and used to improve their agar quality (specifically gel strength). Such is the quality of the product that Namibia is now the second largest Gracilaria supplier to Japan (after Chile). The strict selection and grading of Gracilaria resulted in significant amounts of waste, which did not meet international requirements. Traditionally this material was discarded, but due to the large quantities and the quality of the agar therein an agar extraction factory was relocated to Li,ideritz in mid-1986. Presently the factory has a targeted output of c. 100 tonnes of agar powder per annum, which is exported to Europe (Germany, Italy and Britain), South Africa and Mauritius. AGAR EXTRACTION AT LISDERITZ

COLLECTION AND DRYING OF G R A CILA R I A Washups occur throughout the year, with varying frequency. The coast is inspected daily and fourwheel drive vehicles are dispatched to collect cast material. It is important that the Gracilaria is removed from the strand-line as quickly as possible, in order to prevent decay. Wet weed is taken from the beach manually, with pitch forks (Fig. 3) and transported to a nearby drying area in the desert. Material is off-loaded and spread into thin mats on the sand (Fig. 4). Summer south-westerly winds prevent rain from falling for most of the year; this coupled to hot desert conditions ensures that the Gracilaria dries rapidly (within 2-3 days), to give a rich maroon material, preferred by FarEast buyers. If bleached Gracilaria is specifically requested then the material must lie in the desert for 4-6 weeks on either side. Once the Gracilaria is dried it is transported to a bailing factory to be graded and cleaned. The alga is sorted into a number of grades (based on thallus colour, diameter, length of axes, amount of bleaching and lack of epiphytes). Material is cleaned by hand and shaken to remove excess salt/sand and bailed into 100 kg bags (Fig. 5). The Gracilaria so prepared is then ready for export; the material is not washed since this would

Gracilaria arrives at the agar factory in 100 kg (dry weight) bales; 500 kg are loaded into 10 m -~ stainless steel vessels (Fig. 6). Within the vessels, the seaweed is washed in fresh water to remove impurities (8500 litres of water per washing). Washing may be repeated up to four times. The Gracilaria is then treated with 6% caustic soda for 2 h, which breaks down cellulose, hemicellulose and algal pigments; strong alkali treatment also increases agar gel strength by reducing the amounts of agaropectin present (McHugh, 1987). The seaweed is then washed and neutralised in fresh water. Bleaching is carried out with sodium hyperchloride; the material is cooked for 2 h at 100°C (Fig. 6; pH adjusted to 7), bringing the agar into solution. The liquid is then passed through a filter press (Fig. 7) which results in a hot, clear liquid solution of agar. The operation is difficult and requires high temperatures (90-100°C) because of the extract's viscosity and high gelling power. Pure agar solution drains from the filter press into a heated holding tank (80°C), to keep it in liquid form. Hot agar is pumped from the holding tank, via a heat exchanger, onto a rotating, chilled, stainless-steel conveyor belt (Fig. 8). The conveyor is 20 m long; in the first 3-4 m the agar solidifies into a watery jelly. At the end of the belt, the agar passes through a comb chopping it into strands,

140

A. T. Critchley, K. W. G. Rotmann, F. J. Molloy

Fig. 3. Cast Gracilaria is removed from the beaches around L/ideritzbucht manually.

k

Fig. 4.

£

Collected Gracilaria is spread thinly in the desert to

dry.

Fig. 6. Dried Gracilaria is loaded into stainless steel vessels for treatment.

which then fall into a trough. The jelly is transferred into sterile, muslin, pressing 'nappies' which are folded and stacked into a press. In the first instance, concrete blocks are placed onto the nappies, increasing pressure from 0.5 t/m 2 to 4 t/m 2 (Fig. 9), to remove as much water as possible. Finally, the nappies are placed in a hydraulic press (20-25 t/m 2) for 1-2.5 h. Once removed, the nappies are opened and sheets of 'rubbery' (90% moisture content) agar are taken out (Fig. 10), fed into a mincer and dried in a fluid-bed drier at 80°C. Once removed from the drier, the agar flakes are further processed mechanically into a powder form. The final agar powder has a moisture content of 10-16%; specifications for the agar powder are given in Table 1. The agar plant is in operation for 24 h per day. The agar content of Gracilaria verrucosa from Ltideritzbucht is good, ranging from 16-30% of dry weight. Monthly yields of agar powder have been 5"3 t/month (1988/89); 7 t/month (1989/ 90); 12 t/month are planned for 1990/91.

POTENTIAL D E V E L O P M E N T S IN T H E NAMIBIAN SEAWEED I N D U S T R Y

Fig. 5. Dried Gracilaria is sorted, by hand, into a number of grades, based on thallus colour, diameter, bleaching, length of axes and epiphytisation.

Since Gracilaria is obtained only from beach washups, the quantities are very variable. Furthermore, there are variations in the quality of the seaweed (i.e. length of axes, bleaching in the desert, epiphytisation, etc.) thus affecting amounts which are either exported or used locally. Variations within and between the quantities of export and locally consumed Gracilaria can be tremendous

The Namibian seaweed industry: present and potential

141

Fig. 9. Agar jelly is collected in muslin 'nappies' and excess water is removed from the agar with the application of concrete weights (0'5-4 t/m2). Fig. 7. A hot liquid solution of agar is passed through a filter press to remove seaweed debris.

Fig. 8. Hot agar solution is pumped onto a rotating, chilled, stainless-steel conveyor belt. The agar solidifies within the first 3-4 m.

(see Table 2 for p r o d u c t i o n data), d u e to the reliance u p o n n a t u r a l events to bring the s e a w e e d o n t o shore. T h e s e f l u c t u a t i o n s i m p o s e difficulties in m a i n t a i n i n g a p e r m a n e n t , full c o m p l i m e n t of

Fig. 10. Following compression in a hydraulic press the "nappies' are removed. Agar is taken out as rubbery sheets for further drying.

labour, resulting in t r a n s f o r m a t i o n to p a r t - t i m e w o r k i n g , or a d e c r e a s e in viability of the o p e r a t i o n if a p e r m a n e n t w o r k f o r c e w e r e to r e m a i n idle. T h e r e is a t e m p t a t i o n to h a r v e s t Gracilaria directly f r o m the n a t u r a l beds, in times of low

142

A.T. Critchley, K. W. G. Rotmann, F. J. Molloy

Table 1. Specifications of agar powder produced at LiJderitz Product name Product Colour Uniformity Gels strength (kobe) Moisture pH Viscosity Clarity (gel solution) Transparency (gel) Total ash Acid insoluble ash Melting point Gelling point

Keigel Agar-agar powder Light coloured Average mesh 80 #m 800-900 g/cm2 14% maximum 5-7.5 12 cp 70 mm 40 mm 3% maximum 0"3-0"5% 98°C 36-38°C

Table 2. Production of 'export' and 'local' grades of Gracilaria verrucosa at Liideritzbucht, Namibia, March 1986-February 1990 Tonnes dry weight Gracilaria

Month

Jan. Feb. Mar. Apr. May June July Aug. Sep. Oct. Nov. l, Dec.

1986

1987

1988

1989

1990

E" k E L E L E L

----101-0 -72-0 --

78.6 30'5 90.0 6"0 121"0 9'0 63"0 65-0

54.0 2.0 36.0 10.0 102'0 27'8 52-4 52'4

63-2 30.8 64.0 17.0 93'6 1"8 100-4 22"8

30"6 32'0 40'4 42-4

E L E L E L E L E L E L E L E L

101-0 -142"0 -88'0 -36'0 -57.0 -53-0 -56-4 12.1 70-0 21.7

77.0 42'0 68-0 15"0 87-9 9'0 61'0 1-0 33.0 1.0 32.0 1.0 26.0 10-0 44.0 17.0

82'8 35"4 161"6 135"8 169"0 40'0 75'4 17"0 115.0 2.6 124.8 2.6 65-6 4.6 183.0 88-0

143-6 22"6 195'2 1-6 176.3 55-2 64"9 13"8 17.8 0.4 30.3 2-6 50.6 21.6 51-2 2.8

~E ='export' grade dried material; L='local' grade material for agar production in Liideritz. bLiideritz agar plant on-line. material availability. This must be resisted at all costs since perturbations of natural beds are often followed by drastic reductions in the Gracilaria populations, as in Chile, A r g e n t i n a and South Africa (Santelices & Doty, 1989; R o t m a n n ,

1990). T h u s all efforts must be directed to increase Gracilaria p r o d u c t i o n via one or several forms of aquaculture. L a b o r a t o r y studies indicate that the natural populations of Gracilaria are growing at suboptimal t e m p e r a t u r e conditions. T h e o p t i m u m t e m p e r a t u r e range for growth of G. verrucosa f r o m Liideritzbucht is 18-20°C (Critchley & Baines, unpublished), yet the m e a n range within Liideritzbucht is s o m e 12-14"8°C. O n s h o r e p o n d cultivation (Rotmann, 1987) has shown that seawater t e m p e r a t u r e can be elevated to a m e a n range of 18.3-22.3°C, providing a potential productivity of 24 t (dry weight) Gracilaria per hectare per year. T h e introduction of polyculture of Gracilaria, together with shellfish of commercial value (e.g. Pacific oyster, Crassostrea gigas; black mussel, Chorornytilus meridonalis and prawns, Penaeus penicillatus), remains a possibility (Safriel & Bruton, 1984). Various forms of outplanting of Gracilaria are being investigated (Santelices & Doty, 1989) but it seems that G. verrucosa is sensitive to sand abrasion and direct planting into s a n d / m u d d y substrata m a y not be appropriate; G. chilensis is better suited to such conditions (Santelices unpublished). R o p e cultivation of Gracilaria is providing a promising alternative. T h e o p t i m u m depth for the cultivation of Gracilaria on ropes, in Liideritzbucht, is 0.5-2.0 m below water surface level. T h e increase in length is up to 1 cm per day with a 4.6-fold increase in mass per w e e k (Molloy, unpublished). T h e quality and quantity of agar p r o d u c e d by Gracilaria at different depths is being assessed. However, the axes of G. verrucosa are not sturdy and rope cultivation would be m o r e successful with a plant with thicker axes (cf. E u c h e u m a (Doty & Alvarez, 1973; L i m & Porse, 1981; A d n a n & Porse, 1987)). To this end, interspecific hybridisation via protoplast fusion was investigated, using G. verrucosa f r o m Lfideritz and G. aculeata f r o m the east coast of South Africa. Results using the digestive enzymes of the sea urchin Stornponeustres variolaris for protoplast release are encouraging (Nelson & Critchley, unpublished). Whilst an interspecific hybrid has not, as yet, b e e n regenerated, the research continues. CONCLUSIONS T h e 'natural' harvesting of cast Gracilaria verrucosa remains the b a c k b o n e of the Namibian

l h e Narnibian seaweed industry: present and potential

seaweed industry. The alga produces high levels of good-quality agar, which is sought on the international market. Unpredictability of this resource leads to difficulties in management strategies for both collection, export of dried material and local production of agar powder. The problems of seasonal fluctuations in the natural (;racilaria crop is to be addressed by supplementation of stock by various forms of aquaculture (ponds, outplanting and rope cultivation). Lfideritzbucht is ideally placed for such developments, with an embayment protected from the worst storms of the Atlantic Ocean and a plentiful supply of nutrient-rich water due to a large upwelling cell, which forms part of the Benguda Current. In this way, the indigenous seaweed industry provides a significant source of employment in this remote location and can contribute to the developing economy of a new country. ACKNOWLEDGEMENT ATC would like to acknowledge the continued financial support of the Foundation for Research Development (FRD) and the University Research Fund. We are grateful to Mrs S. Taylor for typing the manuscript. REFERENCES Adnan, H, & Porse, H. ( 19871. Culture of Eucheuma eottonii and l'2Hchetona spinosum in Indonesia. Hydrobiologia,

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