Biotic (Foraminifera and Thecamoebians) and Abiotic Parameters as Proxies for Identification of the Environmental Heterogeneity in Caeté River Estuary, Amazon Coast, Brazil

Abstract

Foraminifera and thecamoebians assemblages were analyzed at Caeté River Estuary in order to identify saline gradients and intensity of human impacts. In the study area, 29 species of foraminifera typically from intertidal environments and 11 species of thecamoebians were identified. The microfaunal assemblages were characterized by low diversity, averaging 1.9 at the mouth and 0.5 near Bragança City. These values are common in transitional coastal environments along de Brazilian Coast. Statistical analysis, based on the relative abundance of species, did not reveal the presence of an estuarine gradient, which was corroborated by the physical and chemical parameters measured in the field. An increasing of sedimentary fine fraction and organic matter occurs in the intermediate region of the estuary, indicating attenuation of the stream influence. The calcareous foraminifera species were associated with high salinity, temperature and pH values. The agglutinated species were associated with muddy sediment, total organic matter and lower salinity. Four environmental compartments were identified based on biotic and abiotic analysis, but they do not represent the classic estuarine gradient, instead, they represent the differences in the freshwater supply and mangrove distance.

Benthic Foraminiferal Response to Trace Elements in a Tropical Mesotidal Brazilian Estuary

“…The dominant agglutinated species in the CRE, P. clossi, is reported in other regions of the Brazilian coast normally associated with mangroves (Disaró 2006;Laut et al 2012Laut et al , 2016cLaut et al , 2021a, but often in lower relative abundances than in the present study. In the PCA, P. clossi is related to lower marine influence and in the opposite relation to DO.…”

Registro das Oscilações Climáticas do Holoceno Tardio no Estuário do Rio Piraquê-Açu (ES - Brasil)

“…Nos estuários recentes do Brasil, a região estuarina inferior geralmente é caracterizada pela presença de foraminíferos bentônicos calcários marinhos e mixohalinos que vão gradativamente sendo substituídos pelos mixoalinos no estuário intermediário e por espécies aglutinantes no estuário superior (Duleba et al, 2005;Laut et al, 2007). As espécies de foraminíferos dominantes (A. tepida, A. parkisoniana e C. excavatum) ao longo da sequência sedimentar dos testemunhos analisados são consideradas cosmopolitas e dominantes em regiões estuarinas (Muñoz et al, 1995;Ruiz et al, 2005;Laut et al, 2007Laut et al, , 2010Laut et al, , 2012aLaut et al, , 2012bLaut et al, , 2015Laut et al, , 2016aLaut et al, , 2016bLaut et al, , 2016c. Espécies de testa aglutinante não foram encontradas nos testemunhos, o que pode indicar que nenhum intervalo analisado corresponde ao compartimento do estuário superior.…”

“…As quatro associações de foraminíferos, definidas pela análise de agrupamento em Modo R, são compostas por organismos com afinidades ecológicas. A associação A foi composta somente pelas espécies dominantes que são comuns em regiões estuarinas; a Associação B agrupou espécies comumente encontradas em regiões de mistura de águas estuarinas com grande influência marinha (Muñoz et al, 1995;Ruiz et al, 2005;Laut et al, 2007Laut et al, , 2010Laut et al, , 2012aLaut et al, , 2015Laut et al, , 2016aLaut et al, , 2016bLaut et al, , 2016c; e nas Associações C e D foram dominantes as espécies que ocorrem na plataforma continental, que geralmente são encontradas na região de estuário inferior e comumente são transportadas em suspensão (Clemente et al, 2015;.…”

Benthic Foraminifera and Thecamoebians of Godineau River Estuary, Gulf of Paria, Trinidad Island

“…This sector integrates predominantly the Assemblage C which is composed typically by estuarine species (Laut et al, 2007(Laut et al, , 2014(Laut et al, , 2016a(Laut et al, , 2016bSouza et al, 2010, Clemente et al, 2014. The third sector (stations of Group IV) represents the outer part of the estuary with the strongest marine influence as pointed out by the Assemblage D. This assemblage is characterized by foraminiferal taxa characteristic of marine settings and the absence of thecamoebians (Todd & Brönnimann, 1957) transported from the Gulf of Paria to the estuary mouth by tidal currents.…”