Journal of Applied Phycology 2: 281-287, 1990. © 1990 Kluwer Academic Publishers. Printed in Belgium. 281 Effects of environmental parameters on net photosynthesis of a free-living brown seaweed, Cystoseira barbata forma repens: determination of optimal photosynthetic culture conditions D. Baghdadli 1 3, G. Tremblin ',* M. Pellegrini 2 & A. Coudret 3 lLaboratoire de Biologie et Physiologie Vigetales, Faculte des Sciences, UniversitJ du Maine, route de Laval, F-72017 Le Mans Cedex, France (* author for correspondence); 2 Laboratoire de Biologie marine fondamentale et applique, Facultg des Sciences de Luminy (Case 901), 163 Avenue de Luminy, F-13288 Marseille Cedex 09, France; 3 Laboratoire de Physiologie Vgdtale, UniversitJ de Clermont II, 4, rue Ledru, F-63000 Clermont-Ferrand, France Received 7 March 1990; revised 26 July 1990, accepted 30 July 1990 Key words: Cystoseira barbata, photosynthesis, light, temperature, salinity Abstract The net photosynthesis of the Mediterranean brown seaweed Cystoseira barbata f. repens is measured according to irradiance, temperature and salinity. There is not only, a good utilization of low light intensities (light-shade adaptation), but also a specific ability to use a broad range of irradiance, which corresponds in the photosynthesis-irradiance curves to a high initial slope and an extended light saturation level from 300 to 1500 /mol photon m-2 s - '; only very high irradiances induce photoinhibition. Maxi- mum net photosynthesis occurred at temperatures ranging from 20 C to 30 OC. The alga tolerates not only a low level of salinity, but also a slight increase in salinity; however, at more than 47.5 g 1 - NaCl, oxygen exchange is significantly reduced. Light, temperature and salinity requirements are discussed, taking into account ecological con- siderations. Yields and quality of alginic acid are presented according to the irradiance and yearly evolution in situ in order to aid future cultivation of this species. Introduction a detailed knowledge of the physiology of the species selected. Among the brown seaweeds, the When considering the diversity of recent indus- genus Cystoseira, abundantly represented in the trial applications of phycolloids, and the practical Mediterranean, may provide an original and inter- limits for harvesting and cultivating along the esting subject, in so far as the phytochemical chai- French Mediterranean coast, culture away from acteristics of several species of this genus have the sea appears to be a likely future solution. The been studied recently (Pellegrini, 1971; Pellegrini economic value of any such culture is, however, & Pellegrini, 1971 a, 1971 b, 1972; Gilven & closely linked to a judicious choice of alga and to Bergisadi, 1973; Glombitza et al., 1975; Gtlven Correspondence address: G. Tremblin, Laboratoire de Biologie et Physiologie vegetales, Facult6 des Sciences, Universit6 du Maine, route de Laval, F-72017 Le Mans Cedex, France.