ENVIRONMENTAL CHARACTERIZATION OF THE SUBAEREAL SECTOR OF EXPOSED SANDY BEACHES WITH DIFFERENT MORPHODYNAMIC CHARACTERISTICS IN THE CENTER-NORTHERN LITTORAL OF SANTA CATARINA STATE, BRAZIL

Abstract

The characterization and temporal monitoring of environmental variables significant to the structure of beach macrobenthic assemblages were carried out in the subaereal sector of three microtidal and exposed sandy beaches varying from dissipative to reflective conditions in the Center-Northern littoral of Santa Catarina. Monthly samples conducted between March 2000 and March 2001 showed that the environmental characteristics which are important to the development of the beach macrofauna were very distinct among the beaches and were related to their respective modal stages. Few morphological and sedimentary changes occurred along the year in Navegantes beach (dissipative), which was characterized by having wide surf and swash zones. Showing a gentle slope, Navegantes beach profile had homogeneous sediments composed by fine and moderately sorted sands with high moisture contents associated to its superficial water table. On the other hand, Taquaras beach (reflective) showed no surf zone and was dominated by surging/collapsing breakers whose energy dissipated directly on the beach face. Compared to the other beaches, Taquaras revealed the highest spatial and temporal changes in its sedimentary and morphological features and was characterized by a steep slope, narrow swash zone and deep water table. Its sediments were composed by moderately well sorted to well sorted coarse sands with reduced moisture contents. Brava beach (intermediate) was composed by moderately well sorted to well sorted medium sands and showed an intermediate pattern in terms of surf and swash zone extension, water table depth, sediment moisture and intensity of sedimentary and morphological changes. In general, the temporal behavior of the environmental variables was not seasonal along the study period and was specific for each beach, as a consequence of distinct hydrodynamic, sedimentary and morphological features associated to each morphodynamic stage.