ABSTRACT
This paper aim evaluate the composition, abundance and richness of diatoms and to relate theses attributes to actual hydrodynamic processes evidenced by sedimentary texture on surface sediments located on intertidal zone of Itupanema Beach, situated on estuarine continental sector of the Pará State, Amazon. The 10 samples were collected in perpendicular transects within 5 m intervals on coordinates 01º31'03''S and 48º43'28''W in 2006, March and were applied diatoms analysis following standard techniques. The results showed 58 species, being 82,75% benthic/epiphytic and 17,25% planktonic species, occurring commonly in fresh to oligo-mesohaline waters, the more abundant and frequent species in decrescent order were Staurosirella pinnata, Aulacoseira granulata, Thalassiosira sp, Staurosira obtusa, Encyonemasilesiacum, Gomphonema parvulum, Planothidium lanceolatum, Thalassiosira eccentrica, Cyclotella meneghiniana, Encyonema minutum, Nitzschia amphibia and Frustulia sp. The data also revealed that the sedimentary ratio sand/clay was influenced by actual hydrodynamic processes, probably determining the local prevalence of planktonic species groups or benthic species groups on the intertidal zone, in terms of the composition and the abundance of diatoms species. The aquatic herbaceous vegetation had a possible role on the reduction the both energy waves and tidal current velocities, and the retention of muddy sediments, with the reduction of abrasion processes in the intertidal zone and consequently preserving planktonic taxa.
Key words:
diatoms; hydrodynamic; estuary