Influence of Spartina alterniflora and tide level on the structure of polychaete associations in an euryhallne salt marsh in cananéia lagoon estuarine region (SE Brazil)

Abstract

Polychaete species composition, abundance and seasonal variation were analyzed in relation to Spartina alterniflora cover and tide level at Ponta do Arrozal, Cananéia, during 1989/1990. Two intertidal stations were located on the S. alterniflora bellt, one ca mean high water of neap tides (MHWN) and the other ca mean high water of spring tides (MHWS). Two other stations were established at corresponding tide levels at an adjacent site devoid of vegetation. A total of 17 species were collected. Each station was sampled twice seasonally with a 20 cm of diameter corer. Capitella capitata, Isolda pulchella, Nereis oligohalina and Lumbrineris sp were the most abundant species. Statistically significant differences bettween the vegetated and bare sites considered were observed for the number of species, density, diversity and evenness, with their values being higher at the vegetated site. Multivariate analysis showed spatial variations of the fauna according to vegetation cover and tide level. In relation to vegetation cover, polychaetes assemblages were distinguishable mainly by individual species densities of the more common species, since the most abundant species were present at the vegetated and bare sites. In relation to tide level, the faunal densities and number of species at the MHWN station were significantly higher than those at the MHWS station mainly at the bare site.