Sedimentary and environmental characterization of the potengi river estuary and its proximal shelf
Estuary, Shelf, Potengi, Foraminifera
The objective of this work is the characterization of bottom's sediment of the Potengi River Estuary and its inner shelf and to evaluate the environmental quality through the use of foraminifera species present in these environments, correlating these data with environmental parameters. To accomplish this objective, physical and chemical data collection of the water column via CTD and background sediment sampling were carried out using Van-Veen grab. The foraminifera were manually separated from the sediment using the optical microscope and glued at numbered plates according to species similarities. With data from CTD and abundance of foraminifera, univariate and multivariate statistical graphs (PCA, MDS and CLUSTER) were elaborated in PRIMER software. The results showed that the organic matter contents were higher in the shelf when compared to the contents in the estuary the same was verified for the carbonate contents and for the abundance of foraminifera. In the estuary predominate fine siliciclastic sands to many fine ones, occurring average siliciclastic sands in isolated points. In the shelf there are siliciclastic sands medium to thick in the west and south, bioclastic sediments also occur from medium to thick in the central portion and east of the shelf studied. The Cluster, MDS and PCA analyzes compartmentalized the area in three regions, the first one located in the estuary, dominated by fine siliciclastic sedimentation and with little variation in the foraminifera assemblies, the second and third are located in the shelf and are dominated respectively by a carbonic and siliciclastic sedimentation. The abundant presence of the cosmopolitan and opportunistic species Ammonia tepida supports the hypothesis of an environment exposed to high levels of pollution and environmental stress in the Rio estuary