Meiofauna in the soft-bottom habitats of the Patos Lagoon estuary (south Brazil)

ROSA¹, L.C. & BEMVENUTI², C.E.

Laboratório de Ecologia de Invertebrados Bentônicos - Departamento de Oceanografia, Fundação

Universidade Federal do Rio Grande (FURG), Caixa Postal 474, CEP 96201-900 Rio Grande, RS, Brasil.

¹ cielcr@furg.br; ² docbemve@furg.br

 ABSTRACT: This study aims to compare the composition and the density of the meiofauna among three soft-bottom habitats over an emersion gradient during a prolonged tidal exposure period (summer 2000). The selected habitats were (1) a Spartina alterniflora-marsh, (2) an intertidal mudflat (both exposed at ca. 25 days), and (3) a subtidal bottom. The meiofauna composition was similar among habitats, where nematodes, ostracods and harpacticoid copepods were the organisms numerically dominant. Mean meiofaunal density ranged from 2,908 to 896 individuals 10cm^-2. The higher densities values were achieved at subtidal bottom and significantly decrease in salt marsh direction. The meiofauna density was negatively correlated with increase of fine fractions and organic matter content as well as decrease of grain size, sorting and pH values of sediment. The presence of marsh roots and the prolonged tidal exposure time also contributed for observed differences.

Key-words: meiofauna, soft-bottom, salt-marsh, controlling factors, Patos Lagoon Estuary.