SEASONAL VARIATION OF MACROALGAL EPIPHYTISM IN A Sargassum vulgare C. AGARDH (PHAEOPHYCEAE, FUCALES) POPULATION FROM ILHA GRANDE BAY, RIO DE JANEIRO
Keywords:Community structure, epiphytes, Ilha Grande Bay, macroalgae, rocky shores, Sargassum, seasonality.
Epiphytism is an important variable to be considered in studies of marine benthic community structure. The epiphytism of macroalgae enhances stratification in rocky shores, leading to habitat heterogeneity, and increasing species diversity, due to greater diversification of the resources available to the associated fauna. There are records of temporal variations in the number of species and biomass of epiphytic macroalgae, and in some studies these variations were correlated with the degree of vegetative development of he host macroalga. Regarding the populations of Sargassum, the currently available information is insufficient to define relationship patterns between the vegetative development of Sargassum and its epiphytes. The present study aimed: 1) to describe seasonal variations in qualitative and quantitative aspects of the epiphytic macroalgae of a Sargassum vulgare population from the region of Angra dos Reis, Ilha Grande Bay, Rio de Janeiro State, Brazil; and 2) to assess the relationship between degree of epiphytism and vegetative development of the host macroalga. Twenty S. vulgare adult plants were randomly sampled from Gordas Beach in February, May, July and October 2001. Any epiphytic macroalga placed on their thalli were extracted, sorted, identified, classified into morphofunctiontal types, dehydrated and weighted. Apart from calcareous crusts, 46 species of macroalgae (27 Rhodophyta, eight Ochrophyta, and 11 Chlorophyta) were identified. The most numerous groups found were of the order Ceramiales (14 species) and of the filamentous morphofunctional type (17 species). Jania adhaerens and Jania capillacea were the most frequently found epiphytic species in this study. The mean number of species of epiphytic macroalgae found on each Sargassum individual was 7.6. The greatest biomass of epiphytic macroalgae was found during summer, coinciding with the greatest height and wet mass values of S. vulgare. However, we detected no linear relationship between these variables.