Vertical distribution of planktonic foraminifera in the southwestern Atlantic

Abstrac

Paleoproductivity changes during the Late Quaternary in the southeastern Brazilian upper continental margin of the Southwestern Atlantic

Changes in the Brazilian continental margins oceanic productivity and circulation over the last 27,000 years were reconstructed based on sedimentological and microfaunal analyses. Our results suggest that oceanic paleoproductivity and the supply of terrigenous sediments to the Brazilian continental margin were higher during the Last Glacial Maximum (LGM) than during the Holocene. These changes may have been primarily influenced by significant sea level fluctuations that have occurred since the late Pleistocene. During the LGM, the lower sea level, higher productivity and lower sea-surface paleotemperatures may have been the result of the offshore displacement of the main flow of the Brazil Current. However, during the Holocene, the warm waters of the Brazil Current were displaced toward the coast. This displacement contributed to the increase in water temperature and prevented an increase in oceanic productivity. The decrease in terrigenous supply since the LGM could be related to the increase of the extension of the continental shelf and/or drier climatic conditions.Mudanças na produtividade e circulação oceânica da margem continental Brasileira foram reconstituídas a partir de análises sedimentológicas e microfaunísticas realizadas em sedimentos de um testemunho representativo dos últimos 27 000 anos. Nossos dados sugerem maior produtividade oceânica e suprimento de sedimento terrígeno na área de estudo no Último Máximo Glacial (UMG) do que no Holoceno. Estas mudanças foram principalmente influenciadas por flutuações do nível relativo do mar. Durante o UMG, num cenário de nível relativo do mar mais baixo, a maior produtividade oceânica e menor temperatura da superfície do mar, podem ter sido produtos do deslocamento para o largo da Corrente do Brasil. No Holoceno, o deslocamento para a costa das águas quentes da Corrente do Brasil contribuiu para o aumento na temperatura da água e menor produtividade oceânica. A diminuição do aporte de sedimentos terrígenos desde o UMG pode estar relacionado ao aumento da extensão da plataforma continental e/ou a condições climáticas mais secas no continente.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Estudio de foraminífiros bentónicos en escala mensual en una bahía subtropical moderadamente afectada por efluentes urbanos

Benthic foraminifera were sampled monthly during a one-year period in order to examine their biological response to the environmental factors in the Ubatuba Bay (northern coast of São Paulo State, Brazil). The area is a popular tourist destination with a population that varies during the year, as does the untreated sewage carried into the bay by the rivers. Four sites were analysed. Each station is near one of the rivers that discharge into the bay. Biological data were analysed with multivariate and univariate techniques. The influence of the abiotic parameters on the foraminiferal fauna was inferred through statistical methods and time correlation functions. Geochemical and populational parameter differences allowed the sites to be separated into two groups according to their stress conditions. One group was dominated by Ammonia tepida—a herbivore species—and showed higher densities indicating a more productive and less contaminated location. The other one was dominated by Buliminella elegantissima—a detritivore species. Species diversity did not seem to be a good indicator of environmental health in this area due to the low densities and the high dominance of few species. Nevertheless, density and richness were used as evidence of local productivity and environmental conditions. Quasi-azoic moments related to the high degree of contamination were observed. Anthropogenic effects were stronger in the austral summer period, when sewage input through the rivers increases due to mass tourism.Fueron analizados foraminíferos bentónicos en cuatro estaciones muestreadas mensualmente con la intención de investigar la respuesta biológica a los factores ambientales en la Ensenada de Ubatuba (costa noreste de São Paulo, Brasil). El área es un importante local turístico cuya población fluctúa a través del año y recibe efluentes no tratados a través de los ríos que en ella desembocan. Fueron analizados cuatro locales. Cada estación se encuentra localizada próxima a uno de los cuatro ríos que desembocan en la bahía. Los datos biológicos fueron analizados con técnicas uni y multivariadas. La influencia de los parámetros abióticos sobre la fauna de foraminíferos fue inferida a través de métodos estadísticos y de funciones de correlación temporal. Parámetros geoquímicas y poblacionales permitieron distinguir dos grupos de estaciones que reflejan las condiciones de estrés local. Uno de los grupos estuvo dominado por Ammonia tepida –especie herbívora– y se mostró más productivo y menos contaminado. El otro local estuvo dominado por Buliminella elegantísima –especie detritívora. La diversidad especifica no se mostró un buen indicador de la salud ambiental en esta región debido a las bajas densidades y a la alta dominancia de unas pocas especies. Sin embargo, la densidad y riqueza pudieron ser utilizadas como evidencias de la productividad local y condiciones ambientales. Fueron observados momentos casi azoicos relacionados con el alto grado de contaminación. Los efectos antropogénicos fueron mayores durante el período de verano austral, cuando la entrada de deshechos domésticos a través de los ríos aumenta como consecuencia del incremento del turismo

Response of Benthic Foraminifera to Environmental Variability: Importance of Benthic Foraminifera in Monitoring Studies

Foraminifera are eukaryotic unicellular microorganisms inhabiting all marine environments. The study of these protists has huge potential implications and benefits. They are good indicators of global change and are also promising indicators of the environmental health of marine ecosystems. Nevertheless, much remains to be learned about foraminiferal ecology. The goals of this chapter are (1) to provide a few examples from foraminifera studies, presenting possible use of foraminifera as bioindicators for the monitoring of transitional and marine ecosystems and (2) to highlight the importance of applying these organisms in environmental monitoring studies. A semienclosed coastal lagoon (Aveiro Lagoon; Portugal), an estuarine system (São Sebastião Channel; SE Brazil), a continental shelf sector (Campos Basin; SE Brazil), and a segment of continental slope (Campos Basin; SE Brazil) are used as examples

Mid-lower bathyal benthic foraminifera of the Campos Basin, southeastern Brazilian margin: biotopes and controlling ecological factors

Abstrac

The Southern Brazilian shelf: general characteristics, quaternary evolution and sediment distribution

Extending from latitude 34ºS to 22ºS the Southern Brazilian shelf constitutes the only part of the Brazilian shelf with a subtropical to temperate environment. The studies on the different geological aspects of the area began in the 1960's and have recently been reassessed after studies related to the determination of the Economic Exclusive Zone. In terms of morphology, the Southern Brazilian shelf may be divided into three sectors, the São Paulo Bight, the Florianópolis-Mostardas Sector and the Rio Grande Cone, characterized by conspicuous differences in terms of geological determining factors, bathymetry, declivities and the presence of canyons and channels. Despite the existence of hundreds of radiocarbon datings the sea level changes curve of southern Brazil during the Last Glacial Cycle is still a matter of debate. A recent controversy on the Middle and late Holocene sea level changes curve raised the question of the amplitude of the oscillations which occurred in the period. Also, a few but relatively consistent radiocarbon datings suggest the occurrence of a high sea level during Isotope Stage 3. In terms of sedimentary cover the Southern Brazilian shelf exhibits a very strong hydrodynamic control, both latitudinal and bathymetrical. The sector southward from 25ºS is characterized by the influence of the plume of water carrying sediments originating from the Río de La Plata. Actually its presence is conspicuous up to 28ºS, with the area between this latitude and 25ºS constituting a transitional zone. In terms of bathymetry the outer shelf is marked by the "floor-polisher" effect of the Brazil Current, which is responsible for the maintenance of a relict facies in areas deeper than 100 meters.Estendendo-se entre as latitudes 34ºS e 22ºS, a plataforma continental sul-brasileira constitui o único setor que corresponde a um ambiente subtropical a temperado. Os estudos dos diferentes aspectos geológicos da área iniciaram-se na década de 1960 e foram recentemente retomados após os trabalhos relativos à delimitação da Zona Econômica Exclusiva. Em termos de morfologia, pode ser dividida em três setores: Embaiamento de São Paulo, Setor Florianópolis-Mostardas e o Cone do Rio Grande, cada qual definido com base em diferenças geológicas relativas a batimetria, declividade e a presença de cânions e canais. A despeito da existência de centenas de datações ao radiocarbono, a curva de variações relativas do nível do mar no Último Ciclo Glacial é ainda tema de debate. Controvérsia recente sobre as curvas de variação do nível do mar sobre as durante o Holoceno Médio e Tardio trouxe à tona a questão da amplitude das oscilações do nível do mar. Adicionalmente, poucas mas consistentes datações sugerem a ocorrência de um nível do mar elevado durante o Estágio Isotópico 3. Em termos de processos sedimentares atuais, a plataforma continental sul-brasileira exibe um controle hidrodinâmico muito forte, tanto latitudinal quanto batimétrico. O setor ao sul de 25ºS é caracterizado pela influência da pluma de água que carreia sedimentos originários do Rio da Prata, cuja presença é conspícua até 28ºS, havendo uma zona de transição entre essas duas latitudes. A plataforma externa é marcada pelo "efeito enceradeira" da Corrente do Brasil, relíquia responsável pela manutenção de uma fácies em áreas além da isóbata de 100 metros.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)(CNPq) Conselho de Desenvolvimento Científico e Tecnológic

A high-resolution Holocene record on the Southern Brazilian shelf: 1 paleoenvironmental implications 2 3

ABSTRACT 22 A high resolution multi-proxy record has been used to determine environmental changes during the Holocene on 23 the southern Brazilian shelf. Present oceanographic conditions reveal wind and freshwater input as determinants 24 of short-term productivity changes in the study area. Thus, magnetic susceptibility and grain size parameter 25 variations, together with proxies of productivity (organic carbon, carbon accumulation rate, Ba, Sr and Ca 26 content, Ba/Al, Ba/Ti and Al/Ti ratios) were analyzed and compared with proxies of redox condition (V/T

Nd and Pb isotope signatures on the Southeastern South American Upper Margin: Implications for sediment transport and source rocks

ABSTRACT Neodymium and lead isotope values in sediment samples were used to interpret sediment transport and source rocks on the Southeastern South American upper margin