HR: 10:50h
AN: OS22A-03    [Abstracts]
TI: Foraminifera and Thecamoebians as hydrodynamic indicators for Amazon estuarine system
AU: Laut, L L
EM: laut@igeo.uff.br
AF: Dept. of Geology, Lagemar - UFF, Av. Litoranea, sn, Niteroi, RJ 24210-340, Brazil
AU: * Figueiredo, A G
EM: alberto@igeo.uff.br
AF: Instituto de Pesquisas Cientificas e Tecnologicas do Amapa - IEPA, Rod. JK, km 10, s n Fazendinha , Macapa, AP 6890.-656, Brazil
AU: Santos, V F
EM: valdenira.ferreira@iepa.ap.go.br
AF: Dept. of Geology, UFPA, Tv. Mariz e Barros 2765, apto. 303, Belem, PA 66093-090, Brazil
AU: Souza-Vieira, S
EM: suzane@ufpa.br
AF: Dept. of Geology, UFPA, Tv. Mariz e Barros 2765, apto. 303, Belem, PA 66093-090, Brazil
AB: The Amazon mangrove forest in Brazilian territory is one of the most extended in the world. It goes from Ponta do Tubarao (4S e 43W) to Cape Orange (5N e 51W) along 2,250 km of coast line. Because the Amazon River System influence, it can be divided into two regions; one with river influence toward north and the other without river influence. In order to characterize the mangrove environment hydrodynamic on both sides of the Amazon River System, foraminifera and thecamoebians assemblages were investigated in the sediment of two estuaries; Araguari to the North (1 15S - 50 30W) and Caete to the South (0 50S - 46 30W). For both estuaries forams and thecamoebians species distribution are atypical relative to other world regions. In both, there are only few calcareous forams and almost all are small and possible of being transported in suspension. Typical estuarine species were not identified. The typical mangrove forams which are agglutinated species were dominant in both estuaries. However, the Caete estuary has a large number of forams species (29), indicating better efficiency in mixing fresh and salt water in comparison to the Araguari. On the other hand, the Araguari has big richness of thecamoebians species (15) indicating fresh water prevalence. The fresh water predominance is due to the Amazon water plume being diverted to the Amapa coast where the Araguari estuary is located. The foraminifera species was also used to determine the salt water penetration in the estuary. In the Caete estuary, salt water penetrates to about 40 km while in the Araguari it does coincide with the limit of the bore tide wave "pororoca" penetration, 45 km. Based on the species succession (forams to thecamoebians species) the Araguary estuary can be divided into three regions controlled by turbidity: the outer, middle and inner estuary. The Caete species succession is not that clear and only could be divided based on salinity into outer and inner estuary. In both estuaries forams and thecamoebians assemblages are efficient tools to distinguish hydrodynamic patterns. The Amazon water plume flowing toward North interferes in salt water penetration in the Araguari estuary, which inhibits forams development but favoring the thecamoebians. On the Amazon south side, the macrotidal regime and smaller volume of fresh water in the estuaries contribute to fresh and salt water mixing and thus resulting in homogeneity of forams and thecamoebians species distribution.
DE: 4235 Estuarine processes (0442)
DE: 4558 Sediment transport (1862)
DE: 4840 Microbiology and microbial ecology (0465)
DE: 4950 Paleoecology
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly