Foraminíferos e atividade bacteriana aplicados no diagnóstico ambiental do estuário do rio Itacorubí, Florianópolis, SC

Abstract

The relationship between foraminifera distribution and bacterial respiratory activity (BRA) in sediment is applied for environmental diagnose in the Itacorubi estuary, Santa Catarina State. Seven sediment samples were analyzed for foraminifera content, BRA (fermentation, desnitrification and sulphate reduction), sediment grain-size, organic matter and bacterial carbon. Bottom water samples were taken for inorganic nutrients analysis. BRA showed similar values in all stations. Sulphate reduction was more important in the inner mangrove area. Twenty-eight species of foraminifera were identified, with dominance of A. beccarii f. tepida and A. mexicana. Correlation analyses using Spearman coefficient indicated that A. mexicana was related positively with organic enrichment, hypoxic and the presence of sulphate reduction bacteria. The opposite occurred with calcareous species mainly A. becarii f. tepida. Correlation matrix followed by MDS analysis identified three group of sampling points (stations), in Itacorubi estuary, probably related to level of confinement and environmental stress: A – marine conditions; B – transitional conditions with abundance but no dominancy of species in the outer estuary; C – typical estuarine conditions, in the inner estuary. These results suggest that Itacorubí estuary shows estuarine conditions, despite station IT 05 being next to the eutrophicated landfill area, which indicates a recovering gradient downstream.