SUBTIDAL PHYTOBENTHUS COMPOSITION AND STRUCTURE OF THE ARVOREDO MARINE BIOLOGICAL RESERVE, SANTA CATARINA, BRAZIL -- IMPLICATIONS TO THE CONSERVATION.

Abstract

Benthic organisms of the subtidal region are usually studied from dredged samples, what is an inefficient approach for community structure studies. Only a few community studies in Brazil made use of scuba diving. The present study describes the phytobenthic community structure of the Arvoredo Marine Biological Reserve on the south part of Brazil. Sampling was done through scuba diving close to three islands that are part of the Reserve. The sampling sites were selected based on their degree of shelter or exposition to wave action and currents. A hundred and twenty seven species of organisms were identified. Some of species found were unprecedented to the south part of Brazil, and a potentially new species of the genus Callophyllis was found. Sargassum vulgare was the dominant species for all the sampled sites, composing 41.5% of the total biomass. There was a rhodolith bed present in a sheltered area. Shannon diversity index was 0 and 1.73 to Arvoredo and Gales islands, respectively, and the richness index was 6.6 sp.sample-1 for the Rhodolith bed nutriand 20.8 sp.sample-1 for Deserta Island. We think the studied region is a transition area of seaweed flora, for presenting organisms that are typical of both tropical and temperate regions. We suggest the main factors structuring the phytobenthic communities near the islands to be substrate heterogeneity, hydrodynamics, organic effluents and grazing pressure. Minding that this is the only protected area of the category in the south part of Brazil, we stress the importance of protecting other areas of the Brazilian coast, to ensure the protection of seaweed diversity and associated organisms to future generations.