Análise da precipitação polínica atual em sedimentos lamosos de um campo salino, município de Quatipuru, Pará, Brasil.

Abstract

The saltmarshes integrate the North Amazônia coastal plain. The salt marshes are made up of herbaceous perennials species that colonize muddy, adapted to the regime of periodic flooding by the salt tide, high topographic gradient and geomorphological features. Salt marshes usually occur at the lower edge of the mangroves, in contact with the continental setting, bordering estuaries. The aim of this present work is to know the pollen spectrum of the salt marshes of Boa Vista, Quatipuru County, sector of the Costa Atlântica do Salgado Paraense and its relationship to the composition of native plant species. The plot method was used in the inventory, consisting of 100 sample squares of Im x Im, over five 20m transects, arranged perpendicular to the gradient saltmarsh/mangrove forest. The standard techniques used to analyze pollen in sediment were applied to eight samples collected from the mudflat surface, along the same transect. Floristic inventory data showed four botanical families, divided into four genera and five species, ali of herbaceous and perennial life cycle. Sporobolus virginicus (L.) Kunth occurs with higher coverage (54.25%), followed by Eleocharis caribea (Rottb.) SFBlake (25.80%) and Sesuvium portulacastrum L. (18.62%). Eleocharis mutata (L.) Roem. Et Schult. (0.87%) and Blutaparon portulacoides (St.Hill) Mears (0.48%) occurred with very low values of coverage. The pollen assemblages revealed 38 taxa, integrating 14 families, 20 genera and 35 species identified. Almost ali species of native herbaceous that integrated salt marsh occurred in pollen assemblages, but the values of relative frequency <7% or absent and the average pollen concentration <0.6 xlO6 grãos/cm3. However, the pollen of E. mutata was absent, Rhizophora mangle L., mangrove forest pecies reached the highest value of frequency (16 to 50.3%) and concentration (2.1 to 5.5 xlO6 grãos/cm3) among the 30 alloctonous pollen taxa, derived from other plant communities. The relatively low frequency of pollen of herbaceous plants, compared with the high values of coverage of these can be explained: 1) differential pollen productivity and 2) dispersai ability, which can be favorable or unfavorable to the deposition and 3) bad conditions preservation of pollen on sedimentation process.