COMPARATIVE STUDY OF POLYCHAETE COMPOSITION FROM ARAÇÁ INTERTIDAL REGION, SÃO SEBASTIÃO (SP,BRAZIL)
Reis, M. de O. 1& Amaral, A. C. Z. 2
1Universidade Estadual Paulista - UNESP - Pós-graduação em Zoologia, Av. 24A, 1515, Rio Claro,SP, 13.506-900, Brazil
2Universidade Estadual de Campinas - IB/Depto. de Zoologia, C.P. 6109, 13083-970, Campinas, SP, Brazil
The Araçá intertidal zone exhibits a very gentle slope and sediment composed by fine and very fine sand, reaching about 200m of amplitude. This study about local polychaete distribution and composition was done from August/95 to August/97 with the purpose of comparison with the results obtained in 1989 after the beginning of a channel openning to instal a submarine emissary concluded and functioning since 1996. The samples were done with an aid of a cylindric corer with 0.01m2 of area and 20cm of height, randomly, in 3 differents levels of the intertidal zone. Some parameters were evaluated simultaneously as salinity, temperature, granulometry and organic matter content. The results from the first sampling (1989) revealed an existence of 47 species and a maximun density of about of 5000 inds./m2, as well as sedimentological and hydrodynamical alterations. Capitella capitata, Heteromastus filiformis and Laeonereis acuta were found as the most frequent and most abundant species. Capitella capitata was the most important in number. Parandalia americana and Glycinde multidens were frequent, with low density. A reduction of species (28) was noticed during this study. The majority was represented by a small number of individuals. Capitella capitata, Heteromastus filiformis and Laeonereis acuta dominated, mainly after 1996. In spite of not being abundant, Glycinde multidens, Parandalia americana and Marphysa sp. were frequent. C. capitata, H. filiformis and L. acuta were located mainly in the superior part of the intertidal region, while Armandia agilis occupied the inferior part of it. Those results show that after the alterations occurred in 1989, the environment has been recovered and the sedimentological and hydrodynamical characteristics were already very similar to the original one. However the recovery of the polychaete community is being delayed due to the emissary functioning since 1996, leading to an environmental complexity, which is allowing and keeping a high density of opportunistic species.