Effect of temperature, salinity and light intensity on the growth of Gracilaria spp. (Gracilariales, Rhodophyta) from Japan, Malaysia and India

Species of Gracilaria Greville were collected from Japan, India and Malaysi a. Growth rate experiments were conducted at different temperatures, salini ties and light intensities. Gracilaria vermiculophylla was found to be the fastest growing species with a growth rate of 22.32%. The growth rates of a il species varied with salinities, but most of them attained their optimum growth rates at a normal seawater salinity 35 parts per thousand. During th e temperature tolerance experiments, it was observed that only G. vermiculo phylla had a high temperature tolerance limit of up to 35 degreesC. The tem perate and the tropical species of Gracilaria were divided into three group s depending upon their optimum growth rates at the optimum temperatures. Gr oup I consisting of G. arcuata and G. textorii from Japan with optimum grow th rates at 20 degreesC. Group II consisting of G. vermiculophylla, G. incu rvata from Japan and G. foliifera, G. corticata from India with optimum gro wth rates at 25 degreesC, while group III consisting of G. edulis from Indi a and G. lichenoides from Malaysia with optimum growth rates at 30 degreesC .