Salinity and light effects on growth, photosynthesis, and respiration of Grateloupia filicina (Rhodophyta)

Effects of salinity and irradiance on growth, photosynthesis, and respiration of the commercially important red alga Grateloupia filicina (Lamouroux) C. Agardh were examined in laboratory cultures. G. filicina thalli showed various degrees of growth over a broad range of experimental conditions, with a maximum growth rate of 13% d (- 1) observed at 20 parts per thousand and 100 mu mol photons m (- 2) s (- 1). Salinity also altered parameters of the photosynthesis-irradiance relationship. Maximum photosynthetic capacity (P-max) reached a high value of 109.2 mu mol O-2 g fw (- 1) h (- 1) at 20 parts per thousand but decreased to much lower values toward 0 parts per thousand and 40 parts per thousand. P-max at 0 parts per thousand was only 15.3 mu mol O-2 g fw (- 1) h (- 1). The respiration rate ranged between 3.0 and 9.6 mu mol O-2 g fw (- 1) h (- 1). The respiration-to-P-max ratio (R/P-max ratio) showed an inverse relationship with the growth rate and had a minimum value of 0.07 at 20 parts per thousand. These results suggest that salinity and irradiance need to be carefully controlled during mass cultivation of G. filicina in order to maximize growth and yield. (C) 2000 Elsevier Science B.V. All rights reserved.