SEASONAL-CHANGES IN AGAR CHARACTERISTICS OF 2 POPULATIONS OF PTEROCLADIA-CAPILLACEA IN GRAN-CANARIA, SPAIN

Agar characteristics of Pterocladia capillacea were examined seasonall y at two intertidal populations exposed to different wave energy on th e northern rocky shore of Gran Canaria Island. Plants were collected m onthly from August 1991 to July 1992. Agar yield, gel strength, meltin g and gelling temperature and chemical properties such as sulphate and pyruvate content were measured. Percent epiphytism was determined on both populations, together with the changes in biomass as dry weight. Specimens in the sheltered habitat were larger and more epiphytized th an ones in the exposed area. There was a clear seasonal change in agar characteristics in both populations. Agar yields decreased in late sp ring and early summer, although in the sheltered habitat fluctuations were more erratic. Gel strength increased in winter, reaching a maximu m in December-February. No significant differences were found in agar yield, gel strength or melting and gelling temperatures, but there was a difference between fresh to dry weight ratio. The role of the expos ure degree as a possible environmental factor responsible for this beh avior is discussed. Agars of Pterocladia capillacea from Canary Island s show characteristics for industrial use.