Benthic foraminifers and thecamoebians from Guaratuba Bay (Paraná, Brazil): Spatial distribution and trophic interactions with carbon sources

Guaratuba Bay is located in the coastal plain of Parana State. It is a small estuarine system with 50 km super(2) of water surface area, maximum depth of 27 m at the mouth, and extensive mangrove and salt marsh ecosystems bordering its northern edge. Foraminiferal and thecamoebian assemblages were studied from eighteen surface sediment samples collected with a van Veen grab, in seven sampling stations located along the east-west axis and two located in the meandering zone of northern edge of the bay in July 2002. Samples (50 cm super(3)) for foraminiferal and thecamoebian analysis were preserved in 4% buffered formaldehyde solution and stained with Bengal Rose. Routine water column oceanographic measurements (temperature, salinity, Secchi disk depth, pH, seston weight, dissolved oxygen), sediment analysis (grain size, total organic carbon, total carbonate content and Chlorophyll a concentration) and microbiological analysis of sediment (total heterotrophic bacteria, bacterial biomass, total coliform bacteria and Escherichia coli) were performed. The results allowed the identification of three distinct zones: marine biofacies characterized by the presence of calcareous species common in the adjacent inner shelf; estuarine biofacies characterized by the presence of euryhaline calcareous foraminifers and dominance of agglutinated foraminifers and thecamoebians, and; riverine biofacies characterized by the absence of both groups, higher coliform (E. coli) densities and sandy sediments with low organic content.