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Abstract

Sixteen isolates of the red alga, Bostrychia tenuissima King et Puttock, from New South Wales, Victoria and South Australia were cultured in the laboratory and analysed for low molecular weight carbohydrates using C-13-NMR and HPLC techniques. All populations south of 34 degrees S contain D-sorbitol in combination with the heteroside digeneaside. The isolates north of 34 degrees S lack digeneaside, but contain D-sorbitol and, in addition, an isomeric form D-dulcitol. Moreover, the C-13-NMR spectra showed an unknown metabolite which was only measured in combination with digeneaside. While in the strains south of 34 degrees S digeneaside and the unknown compound occur in small quantities and remained unchanged with increasing salinities (5-60 ppt), the relatively high D-sorbitol contents strongly increased under hypersaline conditions. In the populations north of 34 degrees S both the concentrations of D-sorbitol and D-dulcitol increased with increasing salinity. These data demonstrate the important role of polyols in the osmotic acclimation of B. tenuissima. The ecological and/or biological factors controlling this geographical pattern of metabolite content are not known. However, the different carbohydrate patterns within B. tenuissima are considered as indicators of the development of physiological ecotypes.