ENDOLITHIC POLYCHAETES FROM THE GUARAJUBA REEFS, BAHIA, BRAZIL
Santa-Isabel, L. M¹ ² & Leão, Z.M. A.²
Departamento de Zoologia do Instituto de Biologia - UFBA. Campus Universitário de Ondina, Salvador, Bahia, Brazil. 401170-290. E-mail: ledama@ufba.br
Laboratório de Estudos Costeiros - Centro de Pesquisa em Geofísica e Geologia IGEO-UFBA. Rua Caetano Moura, 123, Federação, Salvador, Bahia, Brazil. 40210-340
The composition and distribution of the polychaete fauna from the coral reefs of Guarajuba beach (eastern Brazil) and their relation with the physical parameters were examined. The functional feeding groups were used to investigate their distribution patterns. The organisms were randomly sampled in three zones. The first in the intertidal region, on the top of the emergent reef, facing the continent to the west (Internal exposed reef - IER). The second zone, in the same region, facing the ocean to the east (External exposed reef - EER), and the third one on the top of submerged reefs, at depths of five to six meters (Submerged reef - SR). Fifteen blocks with volumes ranging from 350 to 1050 cm³ were collected from each zone, twice a year, making a total number of ninety samples. The polychaetes were removed by means of careful fragmentation of the blocks using geologic hammers and chisels. The specimens were anesthetized in 7,5% magnesium chloride solution, fixed in 4% formaline and stored in 70% ethanol. A total of 1754 individuals and 40 species were registered from the three zone samples. The IER samples contained a total of 405 individuals represented by 17 species. Perinereis nigropunctata (58%) dominated the polychaete fauna in this area. The EER samples presented a total of 1184 specimens and Eunice wasinensis (73%) was the most abundant of the 30 species recorded. The SR samples contained a total of 165 individuals represented by 22 species. Lysidice ninetta (52%) was the dominant species. Subsurface-deposit feeders were dominant in the Guarajuba reefs (IER=86%, EER=92% and SR=73%) , while carnivores, filter-feeders, surface-deposit feeders and omnivores veried between 0,3 and 11%. The dominance by subsurface-deposit feeders in this area probably indicates that changes occur in the structure and function of the polychaete fauna as reefs change from a condition of growth to one of decay and erosion. Most of the decomposed organic matter is buried, and it is available only to the subsurface-deposit feeders. These results suggest a apparently correlation between the density and distribution of the endolithic polychaetes with physical parameters, such as sedimentation reef exposure, depth, salinity, and temperature of the water.