Seasonal variations in growth and reproduction of Sargassum orotavicum (Fucales, Phaeophyceae) from the Canary Islands.

Abstract

Phenology and spatial-temporal variation patterns during an annual cycle of Sargassum orotavicum from the Canaries have been studied for the first time. Data on morphological variation of general habit, stipes, primary and secondary branches, primary and secondary blades, vesicles and receptacles are presented. Sargassum orotavicum is a pseudoperennial species showing a significant seasonality in most parameters that have been studied. This species has four phases within the year: (1) regeneration, from perennial stipes and holdfasts in late autumn; (2) growth, with the beginning of the development of thallus structures that renew every year, in winter; (3) reproductive, with a vegetative climax prior to the reproductive, in spring; and (4) senescence and degeneration, with detachment of thallus structures that renew yearly, in summer. Biomass of branches, blades, vesicles and receptacles showed a significant seasonal variation, with maximum values in spring and minimum in late summer and autumn. This warm-temperate species exhibited a phenological behaviour intermediate between tropical and cold-temperate species of Sargassum. Analysis of within- and between-individual stability of eleven continuous traits indicated that the highest variation occurred temporally