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Factors affecting the large-scale production of four species of commercially important marine algae
Aq~acul~ure, 44 (1985) 161-166 Elsevier Science Publishers B.V., Amsterdam -Printed
in The Netherlands
161
Short Communication FACTORS AFFECTING THE LARGE-SCALE PRODUCTION OF FOUR SPECIES OF COMMERCIALLY IMPORTANT MARINE ALGAE
IAN LAX% ~in~~~ of ~ricul~ure, Fisheries and Food, Dire~#ora~e of Fis~e~es Research, Fisheries E~~erirne~~ station, Conwy, ~wy~edd LL32 8UB (Great Britain) (Accepted 3 October 1984)
ABSTRACT Laing, I., 1985. Factors affecting the large-scale production of four species of commercially important marine algae. Aquaculture, 44: 161--166. Semi-continuous cultures of four algal food species were maintained in 80 1 and 200 1 vessels internally illuminated by six 80 W fluorescent lamps. At standard densities Skeietonema costatum produced the greatest average yield, equivalent to 120 1 d-’ for 7-8 weeks. C~ne~oceros calci~rans, Zsochrysis aff. gal&ana (clone T. Iso.) and C~~omonas salina produced 50-60 1 d-’ for 2-4 weeks. Yields for each algal species were similar from 80 1 and 200 1 vessels and lower when four 80 W lamps were used. The harvesting regime to achieve the above yields is evaluated.
INTRODUCTION
The culture of the marine unicellular flagellate TetraseZmis sue&x (Kylin) Butch., and of the diatom Phaeodactylum tricornatum Bohlin in internally illuminated vessels has been described by Laing and Helm (1981) and Helm and Laing (1981). Further work in culture vessels of similar design has determined factors affecting the semi-continuous production of four other algal species valuable in marine aquaculture. The diatoms Ske~etonema costutum (Grev.) Cleve. and Chaetoceros calcitrans (Paulsen) Takano and the unicellular flagellates Isochrysis aff. galbanu Green (widely known as ‘Tahiti’ Isochrysis) and Chroomonas salina Butch. are important food species in the hatchery cultivation of bivalve molluscs (Davis and Guillard, 1958; Tenore and Dunstan, 1973; Walne, 1974). All four species are also fed to copepods which are widely used as foods in fish culture (Kinne, 1977, pp. 761- -798). The nutritional value of Artemia for prawn culture is improved when fed Isochrysis (Wickins, 1972) and larval stages of some prawn species grow well when fed Skeletonema or Chaetoceros (Hudinaga and Kittaka, 1966; Simon, 1978).
162
Preliminary small-scale culture trials were carried out in 250 ml nutrient enriched artificial sea water to determine the optimum silicate enrichment for Skeletonemu and the optimum salinity for all four algal species tested. The aptima determined were used in the subsequent large-scale trials. The growth of Chaetoceros in response to various silica enrichments will be reported elsewhere. In the large-scale trials 30 mg Si 1-l was used. The medium used was as described by Walne (1966), with a supplement of 200 mg 1-l sodium nitrate for C~~oomo~us culture. Semi-continuous cultures of the algal species tested were maint~n~ in continuous illumination at 15-25”C, at a pH of 7.5-7.8, and h~ves~d daily over a 2-8 week period, depending on the species. Several trials were carried out with each species to investigate the effect on yield of culture vessel volume (SO 1 and 200 l), illumination intensity (7.6, 10.9 and 14.0 mW cm-‘) and cell density of the culture after harvesting and topping up with filtered (to 0.45 pm particle size) nutrient enriched sea water medium. Methods were as described by Laing and Helm (1981) for Tetraselmis. RESULTS AND DISCUSSION
In the small-scale trials lsochrysb grew best in the salinity range 15-30°~oo,with s~nific~tly lower growth at 35%,. Ske~to~ema and Chaetoceros grew s~nific~tly better at 15--20°,/00, compared with 25-,35°1,0. Growth of Chroomonas was similar throughout the salinity range tested (l5-35o/Q,). Growth was assessed as the final cell density reached and total organic weight of cells produced in batch cultures. Skeletonema grew significantly better with a silicate enrichment of 15-30 mg Si 1-l) compared with 5--10 mg l- ‘, and this result was reflected in greater production from the larger vessels (Fig. 1). Figs. 1 and 2 show, for Skeletonema and Isochrysis, how the yield was related to cell density after harvesting and the topping up of the culture volume 24 h previously. Examples are given for culture vessels of different volumes and at different i~umination intensities. Similar relations~ps were obtained for the other algal species investiga~d. In each case it was possible to harvest the culture daily so that after topping up with fresh medium the value of the cell density was that which gave the greatest yield at the next harvest (the ‘optimum catch’, Ketchum et al., 1949). The maximum daily semi-continuous yield of Isochrysis from 200 1 or 80 1 vessels was about 80 1 d-l. A similar result was also obtained with Tetraselmis cultured in both vessels (Helm and Laing, 1981) and was also true for Chaetoceros and Chroomonas in these trials. Skeletonema was not cultured in 80 1 vessels. There are biological and economic advantages in operating 80 1 semicontinuous algal culture vessels when they give the same maximum daily
163
r
180
l%O-
_
140-
ol-_l
’
0
’
’
2 Cell
’
’
4
6
density
(cells
’
’
’
’
8 PI-’
’
10
’ 12
x10-3)
Fig. 1. The calculated daily yield (1 at 6000 cells JAI-‘) from 200 1 ~mi-~ntinuous cultures of Skeletonema after 24 h growth from a range of cell densities in vessels internally with an enrichment of 30 mg Si I-’ ; - - -, with 5 mg illuminated with six lamps (Si 1-l) or four lamps (- - - - -, 30 n& Si 1-l).
0~““““““’ 0
2
4
Cell
density
6
(cells
8
pl-’
10
x
12
14
10b3)
Fig. 2. The calculated daily yield (1 at 10 000 cells &‘) from semi-continuous cultures of Isochrysis after 24 h growth from a range of cell densities in vessels internally illumi200 1 vessels; - - -, 80 1 vessels) or four lamps (- - - - -, 200 nated with six lamps ( -, 1 vessels).
164
yield as 200 1 vessels. When feeding shellfish in sea water recirculation systems, it is desirable to keep the amount of culture medium added with the algae to a minimum. Smaller volumes at a greater cell density are harvested from 80 1 as compared to 200 1 vessels. Smaller vessels are cheaper to construct and have a greater surface area to volume ratio than larger vessels and so may be cooled to the optimum temperature range more efficiently. Also, the cost of preparing and sterilising the culture medium is lower for the 80 1 vessels. The total cost of operating 80 1 vessels, including labour and depreciation on capital items, is about 75% of that for 200 1 vessels. Figs. 1 and 2 show that daily semi-continuous production of ~~elet~~e~a and ~soc~~~s~s increased by 60% when vessels were internally illuminated by six 80 W ‘daylight’ fluorescent lamps (10.9 mW cm-*, 40 000 lx) rather than with four lamps (7.6 mW cm-‘, 28 000 lx). Similar results were obtained with Tetraselmis and Phaeodactylum (Helm and Laing, 1981; Laing and Helm 1981) and with the other algal species tested here. The increase in yield was in the range 40--80%. The total increase in cost of using six lamps rather than four lamps is only about 7%. There was no further increase in yield when eight lamps (14.0 mW cm-*, 51 000 lx) were used. The maximum daily yield of Isochrysis in 80 1 vessels illuminated by six lamps was obtained when cultures were harvested to 9000 cells p1-l (Fig. 2). However, it is more convenient to harvest the vessels three times per TABLE I
Comparisonof yields achieved by harvesting80 I cultures of various algal food species three times per week; all cultures illuminated by six 80 W fluorescent lamps
Alga (standard cell density, cells ~1~’ )
Optimum cell density (cells ~1~’ ) after topping up vessel for next harvest in 2 Days
Skefetonemoa (6000) Phaeodac~luma (10 000) (Helm and Laing, 1981) Tetmsetmis (1000) (Laing and Helm, 1981) Chaetoceros (20 000) Isochrysis (10 000) Chroomonas (1500)
Average yield (1 d-’ at standard density)
Average harvesting period (weeks)
3 Days
1200
600
120
7-8
1400
700
69
7-8
400
200
65
7-8
12 000
6000
63
3-4
3600
1800
62
2-3
600
300
46
2-3
aResults are for 200 1 vessels.
165
week, for example on Mondays, Wednesdays and Fridays, than every day. The part of the culture required for feeding on the intermediate days is maintained by aeration in a suitable container. This method reduces the maximum potential yield but it also greatly reduces the amount of medium preparation and filtration and time spent servicing the vessels. For maximum production efficiency with this method, cultures are harvested to reduce cell density to about 40% (Monday, Wednesday) or 20% (Friday) of the value calculated for daily semi-continuous harvesting. The average yields achieved with this method are shown in Table I. The average yields for the different algal species cultured are comp~able, as they have been calculated to a standard cell density which represents an equal biomass (organic weight) of cells. S~e~etonem~ was the most productive of the species tested, followed by Tetraselmis and Pkaeodactylum, which gave similar yields and harvesting periods. Chroomonas, Chaetoceros and Isochrysis were the least reliable in mass culture. Yield and harvesting period of Isochrysis and Chroomonas are improved by using continuous culture t.echniques, but semi-continuous culture is better for diatoms (Laing and Jones, 1983). It was also noticed that productivity of SkeZetonema was not affected when sea water that had only been filtered to 2 pm particle size, as opposed to the usual 0.45 pm particle size, was used. This gives a considerable saving in cost of filtration but the culture could only be operated for 5- ~6 weeks with 2 p:m filtered water, compared with 7-8 weeks with 0.45 pm filtered water. CONCLUSION
The productivity of a number of species of algae can be improved, with considerable economic advantage, by using 80 1 as opposed to 200 1 culture vessels, and by a simple adjustment of nutrient mixtures and husbandry techniques.
REFERENCES Davis, H.C. and Guillard, R.R.L., 1958. Relative value of ten genera of microorganisms as foods for oyster and clam larvae. Fishery Bull., Fish Wildl. Serv. U.S., 136: 293-304. Helm, MM. and Laing, I., 1981. Cost effective culture of marine unicellular algae. In: F. Vogt (Editor), Energy Conservation and Use of Renewable Energies in the Bioindustries. Pergamon Press, Oxford, pp. 247-259. Hudinaga, M. and Kittaka, J., 1966. Studies on food and growth of larval stages of a prawn, Penoeus japonicus, with reference to the application to practical mass culture. Inf. Bull. Planktol., Japan, 13: 83-34. Ketehum, B.H., Lillick, L. and Redfield, AX., 1949. The growth and optimum yields of unicellular algae in mass culture. J. Cell. Comp. Physiol., 33: 267-280. Kinne, O., 1977. Cultivation of animals - research cultivation. In: 0. Kinne (Editor), Marine Ecology, Vol. III, Part 2. John Wiley and Sons, Chichester, pp. 579-1293.
166 Laing, I. and Helm, MM., 1981. Factors affecting the semi-continuous production of Tetraselmis suecica (Kylin) Butch. in 200-l vessels. Aquaculture, 22: 137--148. Laing, I. and Jones, E., 1983. Large-scale turbidostat culture of marine microalgae. Aquacult. Engng., 2: 203-212. Simon, C.M., X978. The culture of the diatom Chaetoceros gmcilis and its use as a food for penaeid protozoeal larvae. Aquaculture, 14: 105-113. Tenore, K.R. and Dunstan, W.M., 1973. Comparison of rates of feeding and biodeposition of the American oyster, Crassostrea virginica Gmelin, fed different species of phytoplankton. J. Exp. Mar. Biol. Ecol., 12: 19-26. Wahre, P.R., 1966. Experiments in the large-scale culture of the larvae of Ostrea edulis L. Fish. Invest., Lond., Ser. 2, 25 (4): 53 pp. Walne, P.R., 1974. Culture of Bivalve Molluscs - 50 Years Experience at Conwy. Fishing News (Books) Ltd., West Byfleet, 173 pp. Wickins, J.F., 1972. The food value of brine shrimp Artemia salina L. to larvae of the prawn Palaemon serratus Pennant. J. Exp. Mar. Biol. Ecol., 10: 151-170.
in The Netherlands
161
Short Communication FACTORS AFFECTING THE LARGE-SCALE PRODUCTION OF FOUR SPECIES OF COMMERCIALLY IMPORTANT MARINE ALGAE
IAN LAX% ~in~~~ of ~ricul~ure, Fisheries and Food, Dire~#ora~e of Fis~e~es Research, Fisheries E~~erirne~~ station, Conwy, ~wy~edd LL32 8UB (Great Britain) (Accepted 3 October 1984)
ABSTRACT Laing, I., 1985. Factors affecting the large-scale production of four species of commercially important marine algae. Aquaculture, 44: 161--166. Semi-continuous cultures of four algal food species were maintained in 80 1 and 200 1 vessels internally illuminated by six 80 W fluorescent lamps. At standard densities Skeietonema costatum produced the greatest average yield, equivalent to 120 1 d-’ for 7-8 weeks. C~ne~oceros calci~rans, Zsochrysis aff. gal&ana (clone T. Iso.) and C~~omonas salina produced 50-60 1 d-’ for 2-4 weeks. Yields for each algal species were similar from 80 1 and 200 1 vessels and lower when four 80 W lamps were used. The harvesting regime to achieve the above yields is evaluated.
INTRODUCTION
The culture of the marine unicellular flagellate TetraseZmis sue&x (Kylin) Butch., and of the diatom Phaeodactylum tricornatum Bohlin in internally illuminated vessels has been described by Laing and Helm (1981) and Helm and Laing (1981). Further work in culture vessels of similar design has determined factors affecting the semi-continuous production of four other algal species valuable in marine aquaculture. The diatoms Ske~etonema costutum (Grev.) Cleve. and Chaetoceros calcitrans (Paulsen) Takano and the unicellular flagellates Isochrysis aff. galbanu Green (widely known as ‘Tahiti’ Isochrysis) and Chroomonas salina Butch. are important food species in the hatchery cultivation of bivalve molluscs (Davis and Guillard, 1958; Tenore and Dunstan, 1973; Walne, 1974). All four species are also fed to copepods which are widely used as foods in fish culture (Kinne, 1977, pp. 761- -798). The nutritional value of Artemia for prawn culture is improved when fed Isochrysis (Wickins, 1972) and larval stages of some prawn species grow well when fed Skeletonema or Chaetoceros (Hudinaga and Kittaka, 1966; Simon, 1978).
162
Preliminary small-scale culture trials were carried out in 250 ml nutrient enriched artificial sea water to determine the optimum silicate enrichment for Skeletonemu and the optimum salinity for all four algal species tested. The aptima determined were used in the subsequent large-scale trials. The growth of Chaetoceros in response to various silica enrichments will be reported elsewhere. In the large-scale trials 30 mg Si 1-l was used. The medium used was as described by Walne (1966), with a supplement of 200 mg 1-l sodium nitrate for C~~oomo~us culture. Semi-continuous cultures of the algal species tested were maint~n~ in continuous illumination at 15-25”C, at a pH of 7.5-7.8, and h~ves~d daily over a 2-8 week period, depending on the species. Several trials were carried out with each species to investigate the effect on yield of culture vessel volume (SO 1 and 200 l), illumination intensity (7.6, 10.9 and 14.0 mW cm-‘) and cell density of the culture after harvesting and topping up with filtered (to 0.45 pm particle size) nutrient enriched sea water medium. Methods were as described by Laing and Helm (1981) for Tetraselmis. RESULTS AND DISCUSSION
In the small-scale trials lsochrysb grew best in the salinity range 15-30°~oo,with s~nific~tly lower growth at 35%,. Ske~to~ema and Chaetoceros grew s~nific~tly better at 15--20°,/00, compared with 25-,35°1,0. Growth of Chroomonas was similar throughout the salinity range tested (l5-35o/Q,). Growth was assessed as the final cell density reached and total organic weight of cells produced in batch cultures. Skeletonema grew significantly better with a silicate enrichment of 15-30 mg Si 1-l) compared with 5--10 mg l- ‘, and this result was reflected in greater production from the larger vessels (Fig. 1). Figs. 1 and 2 show, for Skeletonema and Isochrysis, how the yield was related to cell density after harvesting and the topping up of the culture volume 24 h previously. Examples are given for culture vessels of different volumes and at different i~umination intensities. Similar relations~ps were obtained for the other algal species investiga~d. In each case it was possible to harvest the culture daily so that after topping up with fresh medium the value of the cell density was that which gave the greatest yield at the next harvest (the ‘optimum catch’, Ketchum et al., 1949). The maximum daily semi-continuous yield of Isochrysis from 200 1 or 80 1 vessels was about 80 1 d-l. A similar result was also obtained with Tetraselmis cultured in both vessels (Helm and Laing, 1981) and was also true for Chaetoceros and Chroomonas in these trials. Skeletonema was not cultured in 80 1 vessels. There are biological and economic advantages in operating 80 1 semicontinuous algal culture vessels when they give the same maximum daily
163
r
180
l%O-
_
140-
ol-_l
’
0
’
’
2 Cell
’
’
4
6
density
(cells
’
’
’
’
8 PI-’
’
10
’ 12
x10-3)
Fig. 1. The calculated daily yield (1 at 6000 cells JAI-‘) from 200 1 ~mi-~ntinuous cultures of Skeletonema after 24 h growth from a range of cell densities in vessels internally with an enrichment of 30 mg Si I-’ ; - - -, with 5 mg illuminated with six lamps (Si 1-l) or four lamps (- - - - -, 30 n& Si 1-l).
0~““““““’ 0
2
4
Cell
density
6
(cells
8
pl-’
10
x
12
14
10b3)
Fig. 2. The calculated daily yield (1 at 10 000 cells &‘) from semi-continuous cultures of Isochrysis after 24 h growth from a range of cell densities in vessels internally illumi200 1 vessels; - - -, 80 1 vessels) or four lamps (- - - - -, 200 nated with six lamps ( -, 1 vessels).
164
yield as 200 1 vessels. When feeding shellfish in sea water recirculation systems, it is desirable to keep the amount of culture medium added with the algae to a minimum. Smaller volumes at a greater cell density are harvested from 80 1 as compared to 200 1 vessels. Smaller vessels are cheaper to construct and have a greater surface area to volume ratio than larger vessels and so may be cooled to the optimum temperature range more efficiently. Also, the cost of preparing and sterilising the culture medium is lower for the 80 1 vessels. The total cost of operating 80 1 vessels, including labour and depreciation on capital items, is about 75% of that for 200 1 vessels. Figs. 1 and 2 show that daily semi-continuous production of ~~elet~~e~a and ~soc~~~s~s increased by 60% when vessels were internally illuminated by six 80 W ‘daylight’ fluorescent lamps (10.9 mW cm-*, 40 000 lx) rather than with four lamps (7.6 mW cm-‘, 28 000 lx). Similar results were obtained with Tetraselmis and Phaeodactylum (Helm and Laing, 1981; Laing and Helm 1981) and with the other algal species tested here. The increase in yield was in the range 40--80%. The total increase in cost of using six lamps rather than four lamps is only about 7%. There was no further increase in yield when eight lamps (14.0 mW cm-*, 51 000 lx) were used. The maximum daily yield of Isochrysis in 80 1 vessels illuminated by six lamps was obtained when cultures were harvested to 9000 cells p1-l (Fig. 2). However, it is more convenient to harvest the vessels three times per TABLE I
Comparisonof yields achieved by harvesting80 I cultures of various algal food species three times per week; all cultures illuminated by six 80 W fluorescent lamps
Alga (standard cell density, cells ~1~’ )
Optimum cell density (cells ~1~’ ) after topping up vessel for next harvest in 2 Days
Skefetonemoa (6000) Phaeodac~luma (10 000) (Helm and Laing, 1981) Tetmsetmis (1000) (Laing and Helm, 1981) Chaetoceros (20 000) Isochrysis (10 000) Chroomonas (1500)
Average yield (1 d-’ at standard density)
Average harvesting period (weeks)
3 Days
1200
600
120
7-8
1400
700
69
7-8
400
200
65
7-8
12 000
6000
63
3-4
3600
1800
62
2-3
600
300
46
2-3
aResults are for 200 1 vessels.
165
week, for example on Mondays, Wednesdays and Fridays, than every day. The part of the culture required for feeding on the intermediate days is maintained by aeration in a suitable container. This method reduces the maximum potential yield but it also greatly reduces the amount of medium preparation and filtration and time spent servicing the vessels. For maximum production efficiency with this method, cultures are harvested to reduce cell density to about 40% (Monday, Wednesday) or 20% (Friday) of the value calculated for daily semi-continuous harvesting. The average yields achieved with this method are shown in Table I. The average yields for the different algal species cultured are comp~able, as they have been calculated to a standard cell density which represents an equal biomass (organic weight) of cells. S~e~etonem~ was the most productive of the species tested, followed by Tetraselmis and Pkaeodactylum, which gave similar yields and harvesting periods. Chroomonas, Chaetoceros and Isochrysis were the least reliable in mass culture. Yield and harvesting period of Isochrysis and Chroomonas are improved by using continuous culture t.echniques, but semi-continuous culture is better for diatoms (Laing and Jones, 1983). It was also noticed that productivity of SkeZetonema was not affected when sea water that had only been filtered to 2 pm particle size, as opposed to the usual 0.45 pm particle size, was used. This gives a considerable saving in cost of filtration but the culture could only be operated for 5- ~6 weeks with 2 p:m filtered water, compared with 7-8 weeks with 0.45 pm filtered water. CONCLUSION
The productivity of a number of species of algae can be improved, with considerable economic advantage, by using 80 1 as opposed to 200 1 culture vessels, and by a simple adjustment of nutrient mixtures and husbandry techniques.
REFERENCES Davis, H.C. and Guillard, R.R.L., 1958. Relative value of ten genera of microorganisms as foods for oyster and clam larvae. Fishery Bull., Fish Wildl. Serv. U.S., 136: 293-304. Helm, MM. and Laing, I., 1981. Cost effective culture of marine unicellular algae. In: F. Vogt (Editor), Energy Conservation and Use of Renewable Energies in the Bioindustries. Pergamon Press, Oxford, pp. 247-259. Hudinaga, M. and Kittaka, J., 1966. Studies on food and growth of larval stages of a prawn, Penoeus japonicus, with reference to the application to practical mass culture. Inf. Bull. Planktol., Japan, 13: 83-34. Ketehum, B.H., Lillick, L. and Redfield, AX., 1949. The growth and optimum yields of unicellular algae in mass culture. J. Cell. Comp. Physiol., 33: 267-280. Kinne, O., 1977. Cultivation of animals - research cultivation. In: 0. Kinne (Editor), Marine Ecology, Vol. III, Part 2. John Wiley and Sons, Chichester, pp. 579-1293.
166 Laing, I. and Helm, MM., 1981. Factors affecting the semi-continuous production of Tetraselmis suecica (Kylin) Butch. in 200-l vessels. Aquaculture, 22: 137--148. Laing, I. and Jones, E., 1983. Large-scale turbidostat culture of marine microalgae. Aquacult. Engng., 2: 203-212. Simon, C.M., X978. The culture of the diatom Chaetoceros gmcilis and its use as a food for penaeid protozoeal larvae. Aquaculture, 14: 105-113. Tenore, K.R. and Dunstan, W.M., 1973. Comparison of rates of feeding and biodeposition of the American oyster, Crassostrea virginica Gmelin, fed different species of phytoplankton. J. Exp. Mar. Biol. Ecol., 12: 19-26. Wahre, P.R., 1966. Experiments in the large-scale culture of the larvae of Ostrea edulis L. Fish. Invest., Lond., Ser. 2, 25 (4): 53 pp. Walne, P.R., 1974. Culture of Bivalve Molluscs - 50 Years Experience at Conwy. Fishing News (Books) Ltd., West Byfleet, 173 pp. Wickins, J.F., 1972. The food value of brine shrimp Artemia salina L. to larvae of the prawn Palaemon serratus Pennant. J. Exp. Mar. Biol. Ecol., 10: 151-170.