Responses of Porphyra linearis (Rhodophyta) to environmental factors under controlled culture conditions

The effect of environmental parameters on the growth of Porphyra linearis gametophytes was examined under controlled conditions, and related to the multilinear regression growth model recently developed for this seaweed under coastal conditions in the eastern Mediterranean. Growth chambers, a gradient table, special culture devices and analytical methods were combined for this culture study. The major factors significantly controlling the growth rate of the P. linearis gametophyte in glass dishes were: photoperiod, temperature, age in culture, photosynthetic photon flux (PPF), salinity and water dynamics. Maximal growth occurred under daylength of 12 h, medium temperature (15-20 degreesC), low PPF (70-140 mu mol photon m(-2) s(-1)), ambient salinity (30-40 ppt), 1-3 h of daily air exposure, and water velocity of 4 cm s(-1). Photosynthesis and respiration rates were dominantly affected by daylength and temperature, while the concentration of pigments was dominantly affected by PPF and temperature. These conditions correspond well to the optimal natural growth environment of this local species and are in agreement with the optimum estimated through the recently developed outdoor mathematical growth model.