Phenology of an agarophyte Gracilaria birdiae Plastino and E.C. Oliveira (Gracilariales, Rhodophyta) in Northeastern Brazil

ABSTRACT

The reproductive phenology and thallus length of Gracilaria birdiae were studied over a period of 12 months in a natural bed in Northeastern Brazil. Fertile specimens of G. birdiae were observed during the entire study period. Tetrasporophytes were the most common with an annual mean of 80.1±5.6 percent, followed by cystocarpic plants (9.3±3.4 percent), male gametophytes (8.3±3.6 percent) and infertile plants (2.2±3.4 percent). Only male gametophytes and infertile plants showed a variation in occurrence frequency during the year (p<0.05). With respect to thallus length, a distinct seasonal variation was observed for all reproductive stages (p<0.05), with the highest values recorded during the rainy season (March to August) and the lowest in the dry season (September to February). The results demonstrate that the size of individuals in this population is significantly affected by the periodic changes in the environment caused by rainfall regimes and hydrodynamism.