THE INTERTIDAL RED ALGA BOSTRYCHIA-SIMPLICIUSCULA HARVEY EX J-AGARDH FROM A MANGROVE SWAMP IN SINGAPORE - ACCLIMATION TO LIGHT AND SALINITY

The growth of the mangrove red alga Bostrychia simpliciuscula Harvey e x J. Agardh was studied in relation to a gradient of salinities (5-70 ppt) and photon fluences rates (2.5-60 mumol m-2 s-1). The photosynthe sis-irradiance (PI) curve and the effect of salinity on the intracellu lar D-sorbitol and D-dulcitol concentrations were also examined. Bostr ychia simpliciuscula grew under all salinities tested with a preferenc e for brackish water conditions. The growth versus light pattern and t he PI curve indicate an adaptation to shaded habitats. This alga synth esised and accumulated D-sorbitol in parallel with increasing saliniti es over the whole range of 5-60 ppt, while D-dulcitol was only involve d in the osmotic acclimation between 15 and 45 ppt. The abundance of B . simpliciuscula under the extreme environmental conditions predominan t in mangrove swamps of southeast Asia can be explained by these physi ological properties.