Auto- and heterotrophic nanoplankton and filamentous bacteria of Guanabara Bay (RJ, Brazil): estimates of cell/filament numbers versus carbon content

Variações do nanoplâncton (2-20µm) e bactérias filamentosas (diâmetro: 0.5-2.0 µm) da Baía de Guanabara (RJ, Brasil) são apresentadas, considerando densidade celular e biomassa de autótrofos e heterótrofos. A meta deste trabalho é contribuir para uma futura modelagem da dinâmica trófica neste sistema. Amostras subsuperficiais de água foram coletadas semanalmente durante um ano em dois pontos: Urca (próximo à entrada, mais salino, eutrófico) e Ramos (no interior, menos salino, hipertrófico). Foi feita análise por microscopia de epifluorescência, com densidade celular convertida para biomassa através do biovolume celular. A concentração do nanoplâncton total foi alta (10(8)cel.l-1) na maioria das amostras (>;57%) e das bactérias filamentosas variou de 10(5) a 10(8)fil.l-1. A densidade de autótrofos em Ramos foi uma ordem de grandeza superior tanto para o nanoplâncton (Md: 10(8)cel.l-1 em Ramos e 10(7)cel.l-1 na Urca) quanto para as bactérias filamentosas (Md: 10(6)fil.l-1 em Ramos e 10(5)fil.l-1 na Urca). A biomassa autotrófica do nanoplâncton (Md: 10³µgC.l-1 em Ramos e 10¹µgC.l-1 na Urca) e das bactérias filamentosas (Md: 28µgC.l-1 em Ramos e 1,4µgC.l-1 na Urca) seguiu o mesmo padrão. A contribuição relativa de autótrofos aumentou após a conversão para biomassa. Uma tendência temporal foi evidenciada para as bactérias filamentosas em ambos os pontos e, para o nanoplâncton autotrófico, em Ramos, com valores máximos no período chuvoso (primavera-verão).Variations of nanoplankton (2-20 µm) and filamentous bacteria (diameter: 0.5-2.0 µm) of Guanabara Bay (RJ, Brazil) are presented, considering cell density and carbon content of auto- and heterotrophs. Our goal is to contribute to future modeling of local trophic dynamics. Subsurface water samples were taken weekly during the year 2000 at two sites: Urca (close to the entrance, more saline, eutrophic) and Ramos (inner area, less saline, hypertrophic). Microscopic analysis was done by epifluorescence and cell density was converted to biomass through cell biovolume. Total nanoplankton was about 10(8) cells.l-1 in most samples (>;57%), and total filamentous bacteria densities varied from 10(5) to 10(8) fil.l-1. Autotroph density was one order of magnitude higher at Ramos, both for nanoplankton (Md: 10(8)cells.l-1 at Ramos and 10(7)cells.l-1 at Urca) and for filamentous bacteria (Md: 10(6) fil.l-1 at Ramos and 10(5) fil.l-1 at Urca). The same was observed for autotrophic biomass (Md: 10³µgC.l-1 at Ramos and 10¹µgC.l-1 at Urca for nanoplankton; Md: 28µgC.l-1 at Ramos and 1.4µgC.l-1 at Urca for filamentous bacteria). The relative contribution of autotrophs increased after conversion to biomass. Seasonal variation was conspicuous for filamentous bacteria at both sites and for nanoplankton only at Ramos, with maximum autotrophic abundances during the rainy period (spring-summer)

ANÁLISE DE ABUNDÂNCIA BACTERIANA NO ESTUDO DA ECOLOGIA MICROBIANA DE SEDIMENTOS MARINHOS

Deep-sea ecosystems cover about 65% of the Earth's surface and play an important part in biomass production and biogeochemical cycles on a global scale. These processes are largely mediated by benthic prokaryotes which use organic detritus for biomass production and respiration. Therefore marine sediments are configured as important biological matrix and play a prominent role in the ecology of the system of the deep sea. Events that occur in this compartment as organic matter degradation profoundly affect the chemical composition of the ocean and atmosphere in geological time. Due to its importance and complexity, the system of deep sea and its associated microorganisms have been the object of numerous studies in the last 50 years, especially in the last decade. Bacterial abundance, biomass and metabolic activity are the parameters most commonly measured in the sediments. Several methodologies can be used in microbial activity analysis of sediments, including the amino acids labeled with 14C or ³H incorporation and the measurement of bacterial respiration. The biomass analysis often requires previous determination of bacterial abundance making it imperative that the quantification of sediment microorganisms is performed correctly. The separation of cells from sediment particles and their proper detachment are necessary for epifluorescence microscopy applications and flow cytometry analysis. The optimal use of extraction and analysis techniques and combined evaluation with other microbial parameters enable a greater understanding of the role played by prokaryotic organisms in world oceans.Los ecosistemas de mar profundo representan cerca de 65% de la superficie del planeta y desempeñan un papel importante en la producción de biomasa y en los ciclos biogeoquímicos en una escala global. Estos procesos son ampliamente mediados por procariotes bentónicos, los cuales utilizan detritos orgánicos para la producción de biomasa y respiración. Por este motivo, los sedimentos marinos se configuran como una importante matriz biológica y tienen gran relevancia en la ecología del sistema de mar profundo. Los eventos que ocurren en tiempo geológico, como la degradación de materia orgánica, afectan profundamente la composición química del océano y de la atmosfera. Debido a la importancia y complejidad, el sistema de mar profundo y la microbiota asociada ha sido objeto de diversos estudios a lo largo de los últimos 50 anos, especialmente en la última década. Los parámetros más comúnmente analizados en los sedimentos son: abundancia bacteriana, biomasa y actividad metabólica. Diversas metodologías pueden ser utilizadas en el análisis de la actividad microbiana en sedimentos, entre ellas la incorporación de aminoácidos marcados con 14C  o ³H y la medida de la respiración bacteriana. El análisis de biomasa frecuentemente exige la determinación previa de la abundancia bacteriana, tornando imprescindible que la cuantificación de la microbiota del sedimento sea realizada de forma correcta. La separación de las células de las partículas de sedimento y su apropiada desagregación son necesarias para aplicaciones de microscopia de epifluorescencia y para el análisis por citometria de flujo. El uso optimizado de las técnicas de extracción el análisis y su evaluación de modo combinado con otros parámetros microbianos posibilitará un mayor entendimiento del papel desarrollado por los organismos procariotes en los océanos del mundo.Os ecossistemas de mar profundo representam cerca de 65% da superfície do planeta e desempenham um papel importante na produção de biomassa e nos ciclos biogeoquímicos em uma escala global. Estes processos são amplamente mediados por procariotos bentônicos, os quais utilizam detritos orgânicos para a produção de biomassa e respiração. Por este motivo, os sedimentos marinhos se configuram como importante matriz biológica e tem grande relevância na ecologia do sistema de mar profundo. No tempo geológico, eventos que ocorrem neste compartimento, como a degradação de matéria orgânica, afetam profundamente a composição química do oceano e da atmosfera. Devido à sua importância e complexidade, o sistema de mar profundo e a sua microbiota associada têm sido objeto de inúmeros estudos ao longo dos últimos 50 anos, especialmente na última década. Os parâmetros mais comumente analisados nos sedimentos são abundância bacteriana, biomassa e atividade metabólica. Diversas metodologias podem ser utilizadas na análise da atividade microbiana em sedimentos, entre elas a incorporação de aminoácidos marcados com 14C ou ³H e a medida da respiração bacteriana. A análise de biomassa frequentemente exige a determinação prévia da abundância bacteriana, tornando imprescindível que a quantificação da microbiota do sedimento seja realizada de forma correta. A separação das células das partículas de sedimento e sua apropriada desagregação são necessárias para aplicações de microscopia de epifluorescência e para a análise por citometria em fluxo. O uso otimizado das técnicas de extração e análise e sua avaliação de modo combinado com outros parâmetros microbianos possibilitará um maior entendimento do papel desenvolvido pelos organismos procariotos nos oceanos do mundo

Influencia de la dinámica de estuarios sobre la variabilidad espacial de macrobentos a lo largo de la plataforma continental del sudeste de Brasil

Along the southeast continental shelf of Brazil, the Paraíba do Sul River (PSR) plays a fundamental role in sediment and nutrient transport. This study focuses on the contribution of the PSR and its effect on the benthic macrofauna. Physical and chemical analyses of the sediment were conducted, and the macrofauna were identified and counted. Multivariate analyses were used to compare the distribution patterns of the benthic assemblages related to the depth gradient over two sampling periods. The principal component analysis showed that shallow waters assemblages are mostly influenced by the environmental descriptors temperature, salinity and chlorophyll a, whereas pheophytin, degree of sediment sorting, total carbonate and organic carbon were correlated with benthic assemblages at greater depths. The high organic enrichment reflected an increase in surface and sub-surface deposit feeders such as the polychaetes Spiophanes sp. and Prionospio cristata and the crustacean Phtisica marinain the deeper stations, with a corresponding decrease in other trophic groups. This study provides evidence of differences in organic matter sources, from primary production in shallow waters to detritus in deep waters. These sources provide different niches for the corresponding macrofaunal assemblages along the continental shelf adjacent to the PSR, with species richness and abundance of benthic populations related to the river output.A lo largo de la plataforma continental del sudeste de Brasil, el río Paraíba do Sul (RPS) juega un papel fundamental en el transporte de sedimento y nutrientes. Este estudio se enfoca en la contribución del RPS y sus efectos sobre la macrofauna bentónica. Se condujeron análisis físicos y químicos del sedimento, y la macrofauna fue identificada y contada. Se realizaron análisis multivariados para comparar los patrones de distribución de los ensamblajes bentónicos relacionados al gradiente de profundidad en dos periodos de muestreo. El análisis de componentes principales (ACP) mostró que los ensamblajes de aguas poco profundas son influenciados principalmente por los descriptores ambientales de temperatura, salinidad, y clorofila a, mientras que la feofitina, grado de clasificación de sedimentos, carbonato total y el carbón orgánico estaban correlacionados a los ensamblajes bentónicos a mayores profundidades. El alto enriquecimiento orgánico se refleja en un incremento de detritívoros superficiales y sub-superficiales como los poliquetos Spiophanes sp. y Prionospio cristata y el crustáceo Phtisica marinaen las estaciones más profundas, con el decrecimiento correspondiente en otros grupos tróficos. Este estudio provee evidencia de diferencias entre fuentes de materia orgánica, desde la producción primaria en aguas poco profundas hasta detrito en aguas profundas, que proveen distintos nichos a los ensamblajes macrofaunales correspondientes a lo largo de la plataforma continental adyacente al RPS, con la riqueza de especies y abundancia de las poblaciones bentónicas relativas al flujo del rio

Temporal patterns of picoplankton abundance and metabolism on the western coast of the equatorial Atlantic Ocean

Picoplankton are central global carbon (C) cycling players and often dominate the ocean plankton communities, especially in low latitudes. Therefore, evaluating picoplankton temporal dynamics is critical to understanding microbial stocks and C fluxes in tropical oceans. However, the lack of studies on low-latitude picoplankton communities translates into a common conception that there is an absence of seasonality. Herein, we studied the temporal variation in abundance (measured by flow cytometry), and carbon flux (taking bacterial production and respiration as proxies) of the picoplanktonic community for the first time, as well as their environmental drivers in a low-latitude (05° 59’ 20.7″S 035° 05’ 14.6″W) Atlantic coastal station. We performed monthly samplings between February 2013 and August 2016 in a novel microbial observatory – hereafter called the Equatorial Atlantic Microbial Observatory – established on the northeastern Brazilian Atlantic coast. Our results revealed stability in temporal dynamics of picoplankton, despite a considerable inter-annual variation, with some related to the El Niño (ENSO) event in 2015. However, weak environmental relationships found were not enough to explain the variation in picoplankton’s abundance, which suggests that other factors such as biological interactions may lead to picoplankton abundance variation over time. Heterotrophic bacteria dominated picoplankton during the entire study period and between photosynthetic counterparts, and Synechococcus showed greater relative importance than picoeukaryotes. These results bring a novel perspective that picoplankton may exhibit more pronounced fluctuations in the tropical region when considering inter-annual intervals, and is increasing prokaryotic contribution to carbon cycling towards the equator.Fil: Menezes, Maiara. Universidade Federal do Rio Grande do Norte; BrasilFil: Junger, Pedro C.. Universidade Federal do São Carlos; BrasilFil: Kavagutti, Vinicius S.. Universidade Federal do São Carlos; BrasilFil: Wanderley, Bruno. Universidade Federal do Rio Grande do Norte; BrasilFil: Cabral, Anderson de Souza. Universidade Federal do Rio de Janeiro; BrasilFil: Paranhos, Rodolfo. Universidade Federal do Rio de Janeiro; BrasilFil: Unrein, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de San Martin. Instituto Tecnologico de Chascomus. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - la Plata. Instituto Tecnologico de Chascomus.; ArgentinaFil: Amado, André M.. Universidade Federal do Rio Grande do Norte; Brasil. Universidade Federal de Juiz de Fora; BrasilFil: Sarmento, Hugo. Universidade Federal do São Carlos; Brasi

Metagenomics in Polluted Aquatic Environments

Metagenomics is defined as the culture-independent genomic analysis of biological assemblages providing access to the whole set of genes and genomes from a sample. It encompasses a variety of techniques that are based on (i) total DNA extraction from samples followed by PCR amplification of specific genes, (ii) library construction or amplification and sequencing of the whole genetic material. These methodologies have successfully been applied in studies of composition, dynamics, and functions of microbial communities in a variety of ecosystems including those subjected to anthropogenic modifications (Gilbert & Dupont, 2011). Culture independent methods allow the analysis of a set of metabolic genes from microbial communities, which can be used to determine how environmental conditions such as pollution can shape community composition and the diversity of genes associated with biogeochemical cycles such as those of carbon, nitrogen, and phosphorus (Singh et al., 2009). This approach is also useful for the discovery of novel environmental microorganisms and genes, with important applications for biotechnology, medicine, and bioremediation (Cardoso et al., 2011). This applicability has resulted in a recent sharp increase in studies focusing in the metagenomic analysis of polluted sites. Their aim is to characterize microbial communities from a diverse set of environments such as freshwater, marine sediments, open ocean, pelagic ecosystems, soil, and host-associated communities. An example of these initiatives is the Global Ocean Sampling Expedition (GOS), which assessed the genetic diversity of marine microbial communities around the Earth. Since 2003, an enormous amount of data has been generated by GOS helping scientists to reveal the microbial diversity and also allowing them to better understand microbial phylogeny and ecology (Gilbert & Dupont, 2011)

Trophic and Microbial Patterns in the Ross Sea Area (Antarctica): Spatial Variability during the Summer Season

In open regions of the Ross Sea, the role of the microbial community in the turnover of organic matter has scarcely been investigated; indeed, very little is known on how microbial distribution and functional diversity respond to environmental conditions and hydrographic structures. During the austral summer of 2017, two pelagic areas of the Ross Sea [the Drygalski Ice Tongue and the nearby Terra Nova Bay polynya (A area), and the continental Shelf Break area near Cape Adare (C area)] were studied at selected depths [surface, Deep Chlorophyll Maximum (DCM), Circumpolar Deep Water (CDW), deep waters]. Trophic properties [nutrient concentrations, particulate (POC), dissolved organic carbon (DOC) and its optically significant fraction (CDOM) were measured, together with the main hydrological variables. Microbial community abundance [total prokaryotes, living, dead, and actively respiring fraction, high- and low nucleic acid cells (HNA and LNA), picoand nano-eukaryotes, culturable heterotrophic bacteria], composition, and metabolism (as whole community and as isolated bacteria) were also assessed. Through a multidisciplinary dataset, this study highlighted the variable response of microbial abundance, diversity, and metabolism of the microbial community to the changing local environmental conditions of the Ross Sea. Different forces, such as organic matter inputs (mostly of detrital nature) released from the Drygalski glacier in the A area, and a coastal-to-offshore gradient in the C area, coexisted within this extreme ecosystem. This resulted in a significant spatial segregation of the edaphic parameters, and of the microbial community distribution and metabolic activity patterns