Abstract
The growth of Gracilaria gracilis (Stackhouse) Steentoft, Irvine et Farnham was examined by studying the effect of organismic determinants such as thallus length, position along the thallus and branching. Knowledge of these factors is essential in order to increase production from suspended seaweed rafts seeded with vegetative G. gracilis fragments. Seeding netlons with seaweed material freshly collected from subtidal populations provided up to 30% higher relative growth rates than seaweed maintained on the netlons for successive months. Initial seedstock length greatly affected growth rates and yields such that 30-cm thalli fragments resulted in growth rates 14% higher than for 10-cm fragments. This difference is suggested to be due to the higher contribution to overall biomass by growth of lateral branches. Comparisons of the growth of apical and basal fragments suggest that growth takes place over the entire length of the thallus, but that the apex contributes more to overall elongation than does the proximal part. The removal of apical meristems resulted in an enhanced branching frequency with production of four times as many branches as intact fragments. Evidence is also provided for extensive morphological differentiation following long periods of rapid growth. These thalli have very high frequency of branching, are hollow due to the disintegration of medullary cells and are considered to be completely senescent. These factors have implications for the successful cultivation of G. gracilis on commercial mariculture systems.
Similar content being viewed by others
References
Anderson BC, Smit AJ, Bolton JJ (1998) Differential grazing effects by isopods on Gracilaria gracilis and epiphytic Ceramium diaphanum in suspended raft culture. Aquaculture 169: 99–109.
Anderson RJ, Levitt GJ, Keats DW, Simons RH (1993) The role of herbivores in the collapse of the Gracilaria resource at Saldanha Bay, South Africa. Hydrobiologia 260/261: 285–290.
Anderson RJ, Levitt GJ, Share A (1996a) Experimental investigations for the mariculture of Gracilaria in Saldanha Bay, South Africa. J. appl. Phycol. 8: 421–430.
Anderson RJ, Monteiro PMS, Levitt GJ (1996b) The effect of localised eutrophication on competition between Ulva lactuca (Ulvaceae, Chlorophyta) and a commercial resource of Gracilaria verrucosa (Gracilariaceae, Rhodophyta). Hydrobiologia 326/327: 291–296.
Buschmann AH, Westermeier R, Retamales C (1995) Cultivation of Gracilaria on the sea bottom in southern Chile: A review. J. appl. Phycol. 7: 291–301.
Chamberlain AHL, Gorham J, Kane DF, Lewey SA (1978) Laboratory growth studies on Sargassum muticum (Yendo) Fensholt. II. Apical dominance. Bot. mar. 22: 11–19.
Dawes CJ (1993) Phenotypic plasticity in laboratory cultivars and field plants of Gracilaria tikvahiae (Gigartinales, Rhodophyta). Cryptogam. Bot. 3: 345–352.
Dawes CP (1995) Suspended cultivation of Gracilaria in the sea. J. appl. Phycol. 7: 303–313.
Engledow HR, Bolton JJ (1992) Environmental tolerances in culture and agar content of Gracilaria verrucosa (Hudson) Papenfuss (Rhodophyta, Gigartinales) from Saldanha Bay. S. Afr. J. Bot. 58: 263–267.
Fletcher RL (1995) Epiphytism and fouling in Gracilaria cultivation: An overview. J. appl. Phycol. 7: 325–333.
Friedlander M, Levy I (1995) Cultivation of Gracilaria in outdoor tanks and ponds. J. appl. Phycol. 7: 315–324.
Goldstein ME (1973) Regeneration and vegetative propagation of the agarophyte Gracilaria debilis (Forsskål) Børgesen (Rhodophyceae). Bot. mar. 16: 226–228.
Gutierrez LM, Fernández C (1992) Water motion and morphology in Chondrus crispus (Rhodophyta). J. Phycol. 28: 156–162.
Hurtado-Ponce AQ (1990) Vertical rope cultivation of Gracilaria (Rhodophyta) using vegetative fragments. Bot. mar. 33: 477–481.
Isaac WE (1956) The ecology of Gracilaria confervoides (L.) Grev. in South Africa with special reference to its ecology in the Saldanha – Langebaan lagoon. In Braarud T, Sørensen NA (eds), Second International Seaweed Symposium. Pergamon Press, London: 173–185.
Levy I, Friedlander M (1990) Strain selection in Gracilaria spp. I. Growth pigment and carbohydrates characterization of strains of Gracilaria conferta and Gracilaria verrucosa (Rhodophyta, Gigartinales). Bot. mar. 33: 339–345.
Markager S, Sand-Jensen K (1996) Implication of thallus thickness for growth-irradiance relationships of marine macroalgae. Eur. J. Phycol. 31: 79–87.
McLachlan J (1973) Growth media – marine. In Stein JR (ed.), Handbook of Phycological Methods. Cambridge University Press, London: 25–51.
Meneses I (1996) Assessment of populations of Gracilaria chilensis (Gracilariales, Rhodophyta) utilizing RAPDs. J. appl. Phycol. 8: 185–192.
Molloy FJ, Bolton JJ (1995) Distribution, biomass and production of Gracilaria in Lüderitz Bay, Namibia. J. appl. Phycol. 7: 381–392.
Moss B (1965) Apical dominance in Fucus vesiculosus. New Phytol. 64: 387–392.
Moss B (1970) Meristems and growth in Ascophyllum nodosum (L.) Le Jol. New Phytol. 69: 253–260.
Rebello J, Ohno M, Critchley AT, Sawamura M (1996) Growth rates and agar quality of Gracilaria gracilis (Stackhouse) Steentoft from Namibia, Southern Africa. Bot. mar. 39: 273–279.
Rotmann KWG (1990) Saldanha Bay, South Africa: Recovery of Gracilaria verrucosa (Gracilariales, Rhodophyta). Hydrobiologia 204/205: 325–330.
Russell G (1978) Environment and form in the discrimination of taxa in brown algae. In Irvine DEG, Price JH (eds), Modern Approaches to the Taxonomy of Red and Brown Algae. Academic Press, New York: 339–369.
Santelices B, Varela D (1995) Regenerative capacity of Gracilaria fragments: Effects of size, reproductive state and position along the axis. J. appl. Phycol. 7: 501–506.
Simons RH (1977) The algal flora of Saldanha Bay. Transactions of the Royal Society of South Africa 42: 461–482.
Smit AJ (1998) Nitrogen environment, ecophysiology and growth of Gracilaria gracilis in Saldanha Bay, South Africa. Ph.D. thesis, University of Cape Town, 158 pp.
Smit AJ, Robertson BL, du Preez DR (1997) Influence on ammonium-N pulse concentrations and frequency, tank condition and nitrogen starvation on growth rate and biochemical composition of Gracilaria gracilis. J. appl. Phycol. 8: 473–481.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Smit, A.J., Bolton, J.J. Organismic determinants and their effect on growth and regeneration in Gracilaria gracilis. Journal of Applied Phycology 11, 293–299 (1999). https://doi.org/10.1023/A:1008102409472
Issue Date:
DOI: https://doi.org/10.1023/A:1008102409472