ABSTRACT The present work aimed to evaluate the production of sulfide through the application of different hydraulic retention times (HRT) and different sulfate loading rates in an up-flow anaerobic sludge blanket (UASB) reactor utilizing acetate-butyrate as electron donors and the coupling of the reactor to a crystallizer to remove metals. The sulfidogenic sludge for the UASB was generated from hydrothermal vent sediments and this was operated at room temperature (18-22 ºC). The sulfate reduction process was linked to the precipitation of Cu2+, Zn2+ and Al3+ in a crystallizer coupled to the UASB reactor (two-stage system) to avoid the toxicity of the metals to the sludge. The concentration of dissolved sulfide increased with the HRT up to 312.9 mg HS-/L at 3 d of HRT. As the sulfate loading rate was increasing, the maximum sulfide concentration obtained was of 376.8 mg HS-/L at 500 mg SO4 -2/L/d (1500 mg/L), whereas the concentration of Cu2+, Zn2+ and Al3+ was up to 150, 100, and 100 mg/L, respectively. The removal efficiencies of Cu2+, Zn2+, and Al3+ were higher than 98% when they were fed separately. When a mixture of metals was added, the removal efficiency was close to 80%. Recovery of metals was lower than 57% in all cases. The sulfide production was supported with acetate-butyrate, being the former commonly accumulated because of the oxidation of higher organic compounds; in this case, its utilization sustained sulfate reduction. This process could be controlled by parameters such as HRT and sulfate loading rate to improve the performance of the bioreactor in the treatment of the effluents contaminated with metals in a two-stage system.

RESUMEN El objetivo del presente trabajo fue evaluar la producción de sulfuro mediante la aplicación de diferentes tiempos de retención hidráulica (TRH) y diferentes cargas de sulfato en un reactor de lecho de lodos de flujo ascendente (UASB, por su sigla en inglés) y estudiar su posible aplicación en la precipitación de Cu2+, Zn2+ y Al3+ en un cristalizador acoplado al reactor UASB (proceso de dos etapas). La concentración de sulfuro disuelto aumentó hasta 312.9 mg HS-/L al aumentar el TRH a 3 d. Al aumentar la carga de sulfato, la concentración máxima de sulfuro que se obtuvo fue de 376.8 mg HS-/L a una carga de 500 mg SO4 -2/L/d (1500 mg/L), mientras que la concentración de Cu2+, Zn2+ y Al3+ fue de hasta 150, 100 y 100 mg/L, respectivamente. Las eficiencias de remoción de Cu2+, Zn2+ y Al3+ fueron mayores a 98 % cuando se alimentaron de forma separada. Cuando se alimentó una mezcla de estos elementos, las eficiencias de remoción fueron cercanas al 80 %. La recuperación de todos los metales fue de 57 % en los tres casos. La producción de sulfuro puede ser controlada por parámetros como el TRH y la carga de sulfato para mejorar el desempeño del reactor en el tratamiento de efluentes contaminados con metales.

Abstract This study evaluated the effects of biogenic structures (tree roots and crab burrows) on sediment carbon (C), sulfur (S), and iron (Fe) biogeochemistry during the wet season in the Olaria mangrove forests near the city of Cananéia, São Paulo state, Brazil and the Nobrega mangrove forest approximately 2 km from the city. Anaerobic C oxidation pathways were assessed from sediment profiles and anaerobic incubations and related to the abundance of biogenic structures in the form of pneumatophores and crab burrows. Porewater depth profiles of dissolved inorganic carbon (DIC) and SO42- were less steep in the presence than absence of biogenic structures. While Fe(II) appeared unaffected by biogenic structures, Fe(III) levels were significantly higher in the upper 4 cm of the sediment in the presence than absence of vegetation and bioturbation. Surprisingly, the concentration of Fe(III) in this layer was 2-6 times higher in the Nobrega forest (6-13 µmol cm-3) than in the Olaria forest (1.5-6.5 µmol cm-3). Accordingly, depth integrated sulfate reduction (SR) tended to be highest at Olaria, while iron reduction (FeR) was highest at Nobrega. SR accounted for 54-83% of DIC production, with no diference between forested sites, while FeR accounted for 8-24% of DIC production, with a 2-3 times higher contribution in the Nobrega versus the Olaria forest. The results suggest that mangrove roots and crab burrows in mangrove sediments only promote FeR at the expense of SR in the Nobrega forest. It appears that anthropogenic discharge from Cananéia city may have overridden the impact of biogenic structures on sediment redox conditions at Olaria, thereby diminishing the role of FeR without strong stimulation of overall C oxidation rates.

Abstract Deep-sea sediments comprise one of the largest habitats on Earth. The archaeal groups contribute to a large fraction of the deep-sea benthic biomass, playing a key role in biogeochemical cycles. However, their diversity in deep-sea benthic ecosystems remains poorly understood, mostly because only recently novel taxa have been proposed, thus remodeling the phylogenetic tree. Despite the dificulty in obtaining cultivated representatives, the metabolic capabilities of archaea have lately been described through metagenomic data, indicating that archaeal taxa are highly versatile. Here, we aimed to reveal the diversity of archaeal communities in surface (0 to 15 cm depth) and subsurface (200 cm depth) sediments from a carbonate-rich region in the Southwestern Atlantic upper slope. We performed 16S rRNA gene sequencing, and found that the archaeal composition in surface sediments was mainly dominated by ammonia-oxidizing archaea within Nitrososphaeria class. The distribution of Nitrososphaeria ASVs (amplicon sequence variants) indicates the presence of several species or ecotypes. Contrastingly, the subsurface sediment was dominated by uncultivated anaerobic and poorly known archaea, including representatives of all supergroups (Asgard, TACK, DPANN and Euryarchaeota). These archaea have been described as having potentially diverse metabolic capabilities, including autotrophic and heterotrophic pathways, such as acetogenesis, methylotrophy, and degradation of labile and recalcitrant organic compounds. This indicates an important role in the remineralization of organic matter in the SW (Southwest) Atlantic slope. They are likely enriched due to the transport and mixing of sediments by the IWBC (Intermediate Western Boundary Current) along the continental slope. However, further studies are needed to reveal the geochemical and oceanographic drivers of the archaeal distribution. This study provides the first description of the archaeal communities in carbonate-rich sediments in the SW Atlantic slope, and adds new biodiversity insights to this geological feature, which is considered a vulnerable marine ecosystem, thus helping for future conservation strategies.

Abstract: Acid sulfate soils (ASS) are naturally occurring soils or sediments formed under reducing conditions that either contain sulfuric acid or have the potentail to form it, in an amount that can have adverse imapcts on the environment. The negative impacts of ASS are associated with the release of acidity produced and the release of toxic metals and metaloids from solubulised soil matricies into the environment. It has been shown recently that addition to ASS of dead plant material as organic matter creates microenvironments for soil microbes to ameliorate sulfuric soil and prevent sulfidic soil oxidation. Initial breakdown of the organic matter results in an oxygen demand that generates anaerobic conditions conducive to the reduction of sulfate to sulfides by sulfate reducing bacteria using the residual organic material as a carbon source and causing the pH to rise. There is also evidence that live plants increase acidification, potentially by aerating the soil. In nature, plants shed dead material as they grow, so that both live and dead organic matter co-exist. It is not known what happens to ASS chemistry, particularly pH, under such natural conditions. In this study, Phragmites australis was used to examine the combined effect of growing plants and incorporated organic matter on ASS chemistry (pH, redox potential and sulfate content) under aerobic and anaerobic conditions. In almost all cases, live plants enhanced sulfuric soil acidity and sulfidic soil oxidation. The mechanism for these changes on ASS chemistry appears to be the facilitation of oxygen penetration into the soil via aerenchymatous tissues in the plant roots.

The procedures to implement a chromatographic method for the quantification of linear alkyl benzene sulfonate (LAS) in the influent, effluent and sludge of a wastewater treatment plant (WWTP), and in river water and sediment, are described and evaluated. The columns octylsilane (C8) and octadecylsilane (C18) for high performance liquid chromatography were evaluated for separation of LAS homologues. The results showed that both columns separated the four homologues, but C18 was better for separation of the isomers of each homologue. This enabled to qualitatively evaluate the degradation of homologues in the WWTP, according to their respective isomers. Samples pre-treatment by solid phase extraction (SPE) columns, strong anionic exchange (SAX) and C18, was also evaluated. SPE was necessary for water river samples, either to concentrate LAS or to remove interference in the matrix; however, for WWTP samples, SPE showed unnecessary. The recovery of LAS homologues, after the procedures for sample preparation, was 90 to 110% with an accuracy of 1 to 5%. The WWTP was efficient in LAS removal from domestic sewage; however, the concentrations in water and sediments of the receiving body were higher than the limits established by legislation due to illegal discharges of untreated sewage.

Resumen:Las bacterias sulfatorreductoras (BSR) y las arqueas metanogénicas (AM) comparten nichos comunes en los sedimentos costeros durante las fases terminales de la mineralización anaerobia de la materia orgánica. El objetivo del presente estudio fue analizar la variación espacio-temporal de las BSR y AM en los sedimentos de una laguna costera tropical con una boca efímera (La Mancha, Veracruz, Golfo de México) y su relación con los cambios ambientales. Un total de 24 muestras de sedimentos fueron recolectadas en las temporadas de secas (abril, mayo), lluvias (julio, septiembre) y nortes (noviembre, febrero) en el periodo 2013 - 2014. Los análisis microbiológicos incluyeron la cuantificación de las BSR y AM viables con diferentes sustratos, así como experimentos de mineralización para determinar el efecto de los sulfatos en la oxidación del acetato. Las variables ambientales analizadas en los sedimentos incluyeron la temperatura, pH, Eh, salinidad, sulfatos, H2S, sólidos volátiles, carbohidratos y las características granulométricas. Los principales cambios se presentaron entre las estaciones de secas y lluvias. En la temporada de secas la abundancia sulfatorreductora fue significativamente superior con lactato (8.3x105 - 1.2x107 células / g) y propionato (1.8x105 - 6.6x106 células / g) como sustratos, mientras que las AM que emplean metanol dominaron (4.2x105 - 9.1x106 células / g). Por el contrario, en la época de lluvias aumentaron significativamente las AM hidrogenofílicas (2.6x105-8.3x106 células / g) y acetoclásticas (5.4x105-6.4x106 células / g), disminuyendo las BSR con los sustratos analizados. Se determinó una competencia aparente por el acetato. Su oxidación fue mayor en los medios con presencia de sulfatos en las temporadas de secas (0.06 mM acetato / g sedimento / día), mientras que aumentó en los medios sin sulfatos en la época de lluvias (0.02 mM acetato / g sedimento / día). Las BSR y las AM estuvieron presentes a lo largo de la columna sedimentaria; sin embargo, las BSR dominaron en los primeros centímetros del sedimento y las AM abundaron a mayor profundidad. En conclusión las BSR y AM participaron de manera conjunta en la mineralización de la materia orgánica en los sedimentos de la laguna de La Mancha, dominando la sulfatorreducción en la temporada de secas (boca cerrada) y la metanogénesis en la época de lluvias (boca abierta). Los cambios en el aporte fluvial y la precipitación en esta laguna afectaron significativamente la salinidad y el contenido de sulfatos, siendo los principales factores que regularon la dinámica de las BSR y AM en los sedimentos.

Abstract:Sulfate-reducing bacteria (SRB) and methanogenic archaea (MA) share common niches in coastal sediments during the terminal phases of the anaerobic mineralization of organic matter. The purpose of this study was to analyze the spatial - temporal variation of SRB and MA in the sediments of a tropical coastal lagoon with ephemeral inlet (La Mancha, Veracruz, Gulf of Mexico) and its relationship with environmental changes. A total of 24 sediment samples were collected during the dry (April, May), rainy (July, September) and Northern (November, February) seasons in the period 2013-2014. Microbiological analyses included the quantification of the viable SRB and MA with different substrates, as well as mineralization experiments to determine the effect of sulfate on acetate oxidation. The analyzed environmental variables in the sediments included: temperature, pH, Eh, salinity, sulfates, H2S, volatile solids, carbohydrates, and granulometric characteristics. Major changes occurred between the dry and rainy seasons. During the dry season, sulfate-reducing abundance was significantly greater with lactate (8.3x105 - 1.2x107 cells / g) and propionate (1.8x105 - 6.6x106 cells / g) as substrates, while the MA that use methanol were dominant (4.2x105 - 9.1x106 cells / g). In contrast, during the rainy season, hydrogenophylic (2.6x105 - 8.3x106 cells/g) and acetoclastic (5.4x105-6.4x106 cells / g) MA increased significantly and SRB decreased in the analyzed substrates. An apparent competition for acetate was observed, with a greater oxidation in the media with sulfates in the dry season (0.06 mM acetate / g sediment / day), and a greater oxidation in the media without sulfates in the rainy season (0.02 mM acetate / g sediment / day). SRB and MA were present throughout the sediment column, however SRB dominated in the first centimeters of the sediment while MA were abundant in deeper layers. In conclusion, SRB and MA together played a role in the mineralization of organic matter in the sediments of La Mancha lagoon, with sulfate-reduction dominating in the dry season (closed inlet) and methanogenesis during the rainy season (open inlet). Changes in rainfall and river input in this lagoon significantly affect salinity and sulfate content, the main factors that regulate the dynamics of SRB and MA in the sediments. Rev. Biol. Trop. 64 (4): 1759-1770. Epub 2016 December 01.

La Bahía de Pertigalete está bordeada de una extensa zona de manglares y se encuentra afectada por un intenso tráfico náutico, el vertido de aguas servidas procedente de poblaciones aledañas y los efluentes de la empresa Cementos de Venezuela. Este trabajo tuvo como objetivo determinar la actividad microbiana en sedimentos superficiales y el posible impacto antropogénico en zonas de manglar de la Bahía de Pertigalete durante los períodos de surgencia y transición. La biomasa microbiana, expresada en carbono de masa microbiana (Cmic), respiración basal (RB), actividad de las deshidrogenasas (DHS), hidrólisis del diacetato de fluoresceína (HDAF) y el cociente metabólico (qCO2) fueron empleados en la determinación de la actividad microbiana. En tres zonas de la bahía se establecieron tres transectos de 30 m de longitud, con una separación de 10 m. En cada transecto se situaron tres puntos de muestreo tomándose por triplicado muestras de sedimento superficial. Los resultados mostraron que durante el período de surgencia existe una mayor Cmic en las tres zonas seleccionadas: 851,01; 539,87; y 533,66 mg Cmic kg-1 sedimento en las zonas I, II y III respectivamente. La DHS indicó que existe un predominio de poblaciones heterotróficas anaeróbicas durante éste período. La HDAF confirmó que ocurre una mayor actividad heterotrófica durante la surgencia y el qCO2 reflejó mayor eficiencia en la utilización del carbono. Los resultados reflejan que la predominancia de la flora microbiana y su actividad en los sedimentos está determinada principalmente por las temporadas de surgencia y transición, especialmente en la zona I, la cual está menos expuesta a la acción antrópica.

The Pertigalete Bay is bordered by an extensive mangrove zone and it is affected by an intense boating and sailing traffic, the pouring of the waste water coming from the nearing population and effluent from the company Cements of Venezuela. The objective of this research was to determinate the microbial activity and the possible anthropogenic impact in surface sediments of mangrove zones in the Pertigalete Bay during the up welling and transition periods. The microbial biomass (Cmic), the basal respiration (RB), dehydrogenases activity (DHS), fluorescein diacetate hydrolysis (HDAF) and the metabolic quotient (qCO2) were used in the determination of the microbial activity. In three zones of the bay three transects of 30 m of length were established with a separation of 10 m among them. In each transect, three sampling points were placed and triplicate samples of the surface sediments were taken from each. The results showed that during the up welling period there is a higher Cmic in the three selected zones: 851.01; 539.87 and 533.66 mg Cmic kg-1 sediment in zones I, II and III, respectively. The DHS indicated that there is a predominance of the anaerobic heterotrophic population during this period. The HDAF confirmed that there is a higher heterotrophic activity during the up welling and the qCO2 indicated a greater efficiency in the use of carbon by the microorganism present in the sediments. The results showed that the predominance of the microbial flora and its activity in the sediments is mainly determined by the up welling and transition periods, especially in the zone I, which is less exposed to the anthropogenic action.

Resumo: Objetivo Este estudo teve como objetivo quantificar as taxas de emissão de gases resultante da decomposição anaeróbia de diferentes recursos vegetais em condições usualmente encontradas em sedimentos de sistemas aquáticos tropicais e solos orgânicos drenados. Métodos As incubações foram preparadas com folhas verdes, cascas, galhos, serapilhera, talos e folhas de cana-de-açúcar, folhas de soja, gramíneas, folhas de foresta e uma macrófita aquática (Typha domingensis). Durante 10 meses, o volume diário de gás liberado pela decomposição foi medido e um modelo cinético foi utilizado para descrever a mineralização anaeróbia. Os modelos consideraram a heterogeneidade dos recursos vegetais. Resultados A variação temporal das taxas de gases indicou que a mineralização das frações lábeis dos detritos variaram, em uma base de carbono, de 16,2 (cascas) a 100% (amostras compostas de folhas, gramíneas e talo de cana-de-açúcar). Foi observada uma elevada emissão de gás durante a mineralização das gramíneas, talo de cana de açúcar, amostra compostas de folhas e serapilhera, enquanto que baixos volumes de gases foram medidos durante a mineralização de cascas, galhos, amostra composta de folhas da floresta e T. domingensis que representam os detritos mais fibrosos e recalcitrantes (teor de carbono: 83,8, 78,2, 64,8 e 53,4%, respectivamente). A mineralização do carbono lábil apresentou valores de meia-vida que variaram de 41 (galhos) a 295 dias (gramíneas). Conclusões Considerando a quantidade elevada de detritos refratários remanescentes, a decomposição anaeróbica desses recursos vegetais indicou grande tendência ao acúmulo de matéria orgânica nos solos encharcados, apesar das temperaturas mais elevadas encontradas no ambiente tropical, esses ambientes representam um sumidouro de detrito particulado devido à sua decomposição lenta.

Abstract: Aim The aim of this study was to quantify the emission rates of gases resulting from the anaerobic decomposition of different plant resources under conditions usually found in sediments of tropical aquatic systems and drained organic soils. Methods Incubations were prepared with green leaves, bark, twigs, plant litter, sugarcane stalks and leaves, soybean leaves, grasses, forest leaves and an aquatic macrophyte (Typha domingensis). Over 10 months, the daily volume of gas evolved from decay was measured and a kinetic model was used to describe the anaerobic mineralization. Results Using the mathematical model, it can be observed that the composition of the plant resources is heterogeneous. The temporal variation of the gas rates indicated that the mineralization of the labile fractions of detritus varied, on a carbon basis, from 16.2 (bark) to 100% (samples composed of leaves, grasses and sugar cane stalks). High gas emissions were observed during the mineralization of grasses, sugar cane stalks, leaves and plant litter, while low volumes of gases were measured during the mineralization of bark, twigs, forest leaves and T. domingensis, which are the most fibrous and recalcitrant resources (carbon content: 83.8, 78.2, 64.8 and 53.4%, respectively). The mineralization of labile carbon presented half-life values, which varied from 41 (twigs) to 295 days (grasses). Conclusions Considering the high amount of remaining recalcitrant fraction, the anaerobic decomposition of these plant resources showed a strong trend towards accumulating organic matter in flooded soils. Despite the higher temperatures found in the tropical environment, these environments represent a sink of particulate detritus due to its slow decomposition.

El alquilbenceno sulfonato lineal (LAS) es el tensoactivo sintético más usado en todo el mundo en los produtos de limpeza domestica e industrial y puede llegar a las masas de agua a través de la descarga de aguas residuales sin tratamiento o con un tratamiento ineficaz. El objetivo del estudio consistió en evaluar la capacidad de la microbiota presente en el sedimento del río Tietê en la degradación del tensoactivo anionico - LAS. El experimento se llevó a cabo en un bioreactor de lotes secuenciales en condiciones de desnitrificación con ciclos de 24 horas, agitación de 150rpm, usando 430mL de sedimento y 1 070mL de sustrato sintético constituido por extracto de levadura, almidón soluble, bicarbonato de sodio y sacarosa. El LAS fue añadido a diferentes concentraciones de 15mg/L y 30mg/L. El funcionamiento del bioreactor se dividió en la adaptación de la biomasa con sustrato sintético sin LAS y tres condiciones experimentales: A) adición de 15mg/L de LAS; B) 15mg/L de LAS y reducción del 50% de la concentración del co-sustrato y C) 30mg/L de LAS y la concentración de 100% de co-substrato. Los resultados obtenidos muestran que la eficiencia en la degradación del LAS está directamente relacionada con la población de bacterias desnitrificadoras y que el sedimento del río Tietê se puede utilizar como inóculo en el tratamiento de LAS en condiciones desnitrificadoras. La población de bacterias fue capaz de degradar el LAS independiente de la fuente de carbón adicionada. La remoción de LAS y de nitrato se puede lograr simultáneamente en aguas residuales con una baja carga orgánica. La reducción de la concentración del co-sustrato fue influenciado directamente por la población de bacterias desnitrificantes (2.2x10(13) a 1.0x10(8)MNP/gTVS) y por lo tanto la degradación de LAS (60.1-55.4%). Los microorganismos en el sedimento del río Tietê se pueden usar como inóculo alternativo para el tratamiento de efluentes contaminados con nitrato y LAS.

Linear alkylbenzene sulfonate (LAS) is widely used in the formulation of domestic and industrial cleaning products, the most synthetic surfactants used worldwide. These products can reach water bodies through the discharge of untreated sewage or non-effective treatments. This study evaluates the ability of the microorganisms found in the Tietê river sediment to degrade this synthetic surfactant. The experiment was conducted in a bioreactor, operated in batch sequences under denitrifying conditions, with cycles of 24 hours and stirring at 150rpm, using 430mL of sediments and 1 070mL of a synthetic substrate consisting of yeast extract, soluble starch, sodium bicarbonate and sucrose. LAS was added at different concentrations of 15mg/L and 30mg/L. The reactor operation was divided into the biomass adaptation to the synthetic substrate without LAS and three experimental conditions: a) addition of 15mg/L of LAS; b) 50% reduction the co-substrate concentration and 15mg/L of LAS, and c) addition of 30mg/L of LAS and 100% co-substrate concentration. The results showed that the degradation efficiency of LAS was directly related to the addition of co-substrates and the population of denitrifying bacteria. The removal of LAS and nitrate can be achieved simultaneously in wastewater with low organic loads. The reduction in the co-substrates concentration was directly influenced by the number of denitrifying bacteria (2.2x10(13) to 1.0x10(8)MPN/gTVS), and consequently, LAS degradation (60.1 to 55.4%). The sediment microorganisms in the Tietê river can be used as an alternative inoculum in the treatment of wastewater with nitrate and LAS contamination.

Conventional denitrification and anaerobic ammonium oxidation (anammox) contributes to nitrogen loss in oxygen-deficient systems, thereby influencing many aspects of ecosystem function and global biogeochemistry. Mejillones Bay, northern Chile, presents ideal conditions to study nitrogen removal processes, because it is inserted in a coastal upwelling system, its sediments have anoxia and hypoxia conditions and under the influence of the Oxygen Minimum Zone (OMZ), unknown processes that occur there and what are the microbial communities responsible for their removal. Microbial communities associated with coastal sediments of Mejillones Bay were studied by denaturing gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH), by incubation experiments with 15N isotope tracers were studied nitrogen loss processes operating in these sediments. DGGE analysis showed high bacterial diversity, certain redundant phylotypes and differences in community structure given by the depth; this reflects the microbial community adaptations to environmental conditions. A large fraction (up to 70%) of DAPI-stained cells hybridized with the bacterial probes. Nearly 52-90% of the cell could be further identified to know phyla. Members of the Cytophaga-Flavobacterium cluster were most abundant in the sediments (13-26%), followed by Proteobacteria. Isotopic tracer experiments for the sediments studied indicated that nitrogen loss processes that predominated were performed by denitrifying communities (43.31-111.20 µM d-1) was not possible to detect anammox in the area and not anammox bacteria were detected.

La desnitrificación convencional y la oxidación anaeróbica del amonio (anammox), son procesos que contribuyen a la pérdida de N en los sistemas deficientes de oxígeno, determinando en muchos aspectos el funcionamiento de los ecosistemas y su biogeoquímica global. Bahía Mejillones, norte de Chile, presenta condiciones ideales para estudiar los procesos de remoción del nitrógeno, debido a que está inserta en un sistema de surgencia costera y sus sedimentos presentan condiciones de anoxia e hipoxia generadas por la influencia de la Zona Mínima de Oxigeno (ZMO), desconociéndose los procesos que regulan la pérdida de nitrógeno y cuáles son las comunidades microbianas responsables de su remoción. Las comunidades microbianas asociadas a los sedimentos costeros de bahía Mejillones se estudiaron por electroforesis en geles de gradiente denaturante (DGGE) y por hibridación in situ fluorescente (FISH), mientras que los procesos de remoción de N se estudiaron mediante experimentos de incubación con trazadores isotópicos 15N. El análisis por DGGE indicó una alta diversidad bacteriana, ciertos filotipos redundantes y la existencia de diferencias en la estructura comunitaria dada por la profundidad y la estacionalidad, lo que refleja adaptaciones de la comunidad microbiana frente a las condiciones ambientales imperantes. Los análisis realizados mediante FISH revelaron que sobre el 70% de las bacterias teñidas con DAPI hibridaron con las sondas específicas, cerca del 52 al 90% de estas fueron asignadas a phyla conocidos. Miembros del cluster Cytophaga-Flavobacterium fueron los más abundantes (13-26%), seguido por Proteobacteria (9-21%). Los experimentos con trazadores isotópicos indicaron para los sedimentos estudiados que los procesos de remoción de nitrógeno que predominaron fueron realizados por comunidades desnitrificantes (43,31-111,20 µM d-1) no detectándose anammox ni las bacterias responsables de dicho proceso.

Sedimentation and accumulation of autochthonous and allochthonous organic detritus in marine sediments stimulate microbial activity, consume dissolved oxygen and decrease redox potential. In anaerobic conditions, other electron acceptors are utilized in organic matter oxidation process. Nitrate reduction is an important pathway which is related with nitrogen cycling and oxidation. The purpose of this study was to assess the nitrate reduction activity in sediments of Encerrada Bay, which is under a strong anthropogenic influence from Ushuaia city. Sediment samples were taken in September 2007 with a Van-Veen dredge and stored in darkness. Nitrate reduction activity was estimated in vitro using continuous flow-through system. Nitrate uptake rate followed a Michaelis-Menten kinetic where Km and Vmax values were equal to 1028 mM and 2.7 µmol g-1 h-1, respectively. We concluded that nitrate is used principally as terminal electron acceptor during the oxidation of organic compounds in sediment of Encerrada Bay.

La sedimentación y acumulación de detritos orgánicos autóctonos y alóctonos en el sedimento marino, favorece la actividad microbiana, consume el oxígeno disuelto y disminuye el potencial de óxido-reducción. En condiciones anaeróbicas otros aceptores de electrones son utilizados en los procesos de oxidación de la materia orgánica. La reducción de nitrato es un proceso importante que está relacionado con el ciclo del nitrógeno y la oxidación. El objetivo de este estudio fue estimar la actividad nitrato reductora en sedimentos de la Bahía Encerrada, la cual se encuentra sometida a una fuerte influencia antropogénica desde la ciudad de Ushuaia. Las muestras de sedimento fueron tomadas en septiembre de 2007 con draga Van-Veen y almacenadas en oscuridad. La actividad nitrato reductora fue estimada in vitro mediante un sistema de flujo continuo. La tasa de incorporación de nitrato se aproximó a una cinética del tipo Michaelis-Menten donde los valores de Km y Vmax fueron 1028 mM y 2,7 µmol g-1 h-1, respectivamente. Se concluye que el nitrato es utilizado preponderantemente como aceptor final de electrones durante la oxidación de compuestos orgánicos en el sedimento de Bahía Encerrada.

Acidification of dredged sediments which have been disposed on land is highly dependent on redox shifts. The aim of the present work was to assess changes in sulphur, metal speciation (Zn, Fe, Cr y Cu) and acidity caused by a polluted sediment oxidation event. Sediments were dessicated under controlled conditions and sulphide compounds (acid volatile sulphides-AVS- and sulphate), pH and neutralization potential were measured through time during 36 days. Zinc, Cu, Cr and Fe speciation (BCR metal sequential extraction procedure) were measured at the beginning of the experiment and at day 22. An acid-base equilibrium method based on the BCR procedure was employed to assess the sediment acidification risk. Some of the re-suspension experiments were inoculated with an Acidithiobacillus ferrooxidans strain to assess biological catalysis on sulphide oxidation. Acid-base equilibrium results indicated the sediment sample had a significant acidification potential. Oxidation increased sulphate levels (56 to 2300 mg S kg-¹ in the desiccation experiment with a temporal evolution adjusted by a logistic model, and a 2100 to 3000 mg SO4 -² L-¹ increase for the resuspension experiments). Sulphide oxidation rates varied between 0 to 3.1.10-9 mg O2 kg-¹ s-¹ for the drying sediment. Zinc changes could be explained partially by ZnS conversion to ZnSO4 during oxidation. Iron reduction could be attributed to an increase in Fe oxides crystallinity. Acid-base equilibrium for the sample indicated it was a potentially acid-generating material. Zinc increased its bioavailability during drying and was the only metal that appeared in significant amounts in solution during re-suspension. Land-filling with dredged sediments could present increased metals bioavailability problems despite having an important and effective neutralization potential.

La evaluación de los riesgos de acidificación por deposición de sedimentos dragados en superficie es muy dependiente de los cambios generados por potencial redox. El objetivo del presente trabajo fue el de evaluar cambios en las formas de azufre, metales (Zn, Fe, Cr y Cu) y aumento de acidez generado por la oxidación de sedimentos contaminados durante un proceso de oxidación controlado. Se midió, sobre sedimentos en proceso de desecación y durante 36 días, sulfuros, sulfuros volátiles, sulfatos, pH y potencial de neutralización. A partir del día 22 se aplicó un procedimiento de extracción sequencial de Zn, Cu, Cr y Fe para evaluar el riesgo de acidificación del sedimento, incluyendo entre los tratamientos la inoculación con una cepa de Acidithiobacillus ferrooxidans como catalizador de la oxidación de los sulfuros. La oxidación de sulfatos aumentó de 56 a 2300 mg S kg-¹ con una evolución temporal que ajustó a un modelo logístico. Hubo un aumento de 2100 a 3000 mg SO4 -² L-¹ de sulfatos en el experimento de resuspensión. La oxidación de los sulfuros osciló entre 0 y 3,1.10-9 mg O2 kg-¹ s-¹. Los cambios en el comportamiento del Zn pueden ser explicados parcialmente por la conversión de ZnS a ZnSO4 durante el proceso de oxidación. La reducción del hierro podría ser atribuida a un aumento en la cristalinidad de los óxidos de Fe. El balance ácido-base señala que la muestra es un material con capacidad generadora de acidez. El Zn aumentó su biodisponibilidad durante el proceso de secado y es el único metal que se encuentra presente en cantidad significativa durante el proceso de resuspensión. La disposición en tierra firme de sedimentos dragados puede generar aumento de biodisponibilidad de metales más allá de su impacto en el potencial efectivo de neutralización.

Trinta amostras de sedimento foram coletadas na Baía de Guanabara em agosto, novembro e dezembro de 2005. Foram analisados matéria orgânica, coliformes totais e fecais, bactéria heterotrófica, atividade respiratória bacteriana, atividade de esterase e do sistema transportador de elétrons. A matéria orgânica no sedimento superficial variou entre 4 e 6%. O maior nível de coliformes totais e fecais foi 1.7 x 10(5) MPN/g e 1.1 x 10³ MPN/g, respectivamente. Bactérias heterótrofas mostraram o maior valor na estação 7 (4.1 x 10(6) CFU/g) e o menor na estação 3 (7 x 10(4) CFU/g) (nordeste da Baía de Guanabara). A enzima esterase mostrou atividade em todos os sedimentos das 30 estações. A atividade do sistema transportador de elétrons variou entre 0.047 miL O2/h/g e 0.366 miL O2/h/g em seis estações. A cadeia microbiana bêntica é anaeróbia. Os processos como fermentação, desnitrificação e sulfato redução são responsáveis pelos ciclos biogeoquímicos no sedimento da Baía de Guanabara. O despejo de esgoto não tratado no Canal do Mangue da Baía de Guanabara tem favorecido o aumento da carga orgânica e a manutenção de coliformes totais e fecais no sedimento. Os coliformes fecais são bons indicadores de poluição e contaminação orgânica na coluna de água, mas os coliformes totais também poderão ser um grupo candidato para testes de qualidade de sedimento.

Thirty sediment samples were collected in Guanabara Bay in August, November and December 2005. The material was analyzed for organic matter, total and faecal coliforms, heterotrophic bacteria, bacterial respiratory activity, esterase activity and electron transport system activity. The organic matter in the superficial sediments (2 cm) ranged from 4 to 6%. The highest level of total coliforms and faecal coliforms were 1.7 x 10(5) MPN/g and 1.1 x 10³ MPN/g, respectively. Heterotrophic bacteria presented the highest values at station 7 (4.1 x 10(6) CFU/g) and the lowest values at station 3 (7 x 10(4) CFU/g) (northwestern part of Guanabara Bay). Esterase enzyme activity showed activity in the sediment of all 30 stations. Electron transport system activity ranged between 0.047 muL O2/h/g and 0.366 muL O2/h/g at six stations. The benthic microbial foodweb is anaerobic. Anaerobic processes such as fermentation, denitrification and sulphate-reduction are responsible for the biogeochemical cycles in the sediment of Guanabara Bay. The input of untreated sewage in the Mangue Channel outflow in Guanabara Bay has favored the increase of the organic load, and the maintenance of the total coliforms and faecal coliforms in the sediment. Faecal coliforms have been reported to be a good indicator of aquatic pollution and organic contamination in the water column, but total coliforms may be an ideal candidate group for sediment quality tests as well.

During December 2003, sediment samples were collected at 20 stations along the northwest coast of Baja California (Mexico). Analyses of DDT were performed by gas chromatography, percentage of particles <63 μm in diameter, organic carbon, and sulphate-reducing bacteria. A bacterium from station 49, which showed the highest concentration of DDT and its metabolites DDE and DDD, was isolated and identified biochemically and molecularly to belong to the genus Vibrio. In the laboratory this bacterium was tested in minimal salts medium plus DDT and incubated at 28°C under aerobic and anaerobic conditions for 90 days. In general, the sediments showed low concentrations of DDT, ranging from undetected to 4.78 ng g-1, and the highest concentrations occurred at the deepest stations containing higher percentages of particles <63 μm and organic carbon concentrations. The isolated Vibrio strain showed an ability to biotransform DDT under aerobic and anaerobic conditions, presenting the o,p'-DDE and o,p'-DDD metabolites after 60 and 90 days of incubation in both conditions.

Durante diciembre de 2003 se colectaron muestras de sedimento superficial en 20 estaciones de la costa noroccidental de Baja California (México). Se realizaron análisis de DDT por cromatografía de gases, porcentaje de partículas <63 μm de diámetro, carbono orgánico y bacterias reductoras de sulfato. De la estación 49, la cual mostró la mayor concentración de DDT y sus metabolitos DDE y DDD, se aisló una bacteria identificada bioquímica y molecularmente como del género Vibrio, misma que fue sometida a un bioensayo en el laboratorio, en medio de sales mínimas más DDT, e incubada a 28°C bajo condiciones aerobias y anaerobias durante 90 días. En general, los sedimentos mostraron bajas concentraciones de DDT, desde indetectables hasta 4.78 ng g-1, con tendencia a aumentar en las estaciones más profundas, las cuales contienen mayor porcentaje de partículas <63 μm y concentración de carbono orgánico. La cepa aislada mostró en el laboratorio la capacidad de biotransformar el DDT, detectándose la presencia de los metabolitos o,p'-DDE y o,p'-DDD a los 60 y 90 días de incubación en ambas condiciones.

Las fluctuaciones en el número, biomasa y composición de la comunidad bacteriana heterotrófica fueron estudiadas con respecto a la profundidad y a los cambios de profundidad, pH, Eh, O2 y concentración de carbono orgánico, durante un período corto de tiempo (diarias durante 2 días), en una zona del canal que comunica la laguna de Coyuca de Benítez (Guerrero, México) con las aguas costeras. Durante los tres momentos del día (6 am, 2 pm y 10 pm) estudiados, las concentraciones de oxígeno en el agua sobrenadante y en la película superficial del sedimento se encontraron próximas a la de saturación del aire durante los muestreos diurnos (582 µM a las 6 am y de 665 µM a las 2 pm) y de subsaturación durante la noche (158 µM). En los sedimentos, los modelos de distribución vertical del Eh y del carbono orgánico fueron muy irregulares debido a la bioperturbación causada por la meio- y macrofauna béntica, ya que su actividad excavadora per-mite que del carbono orgánico superficial pase a las capas más profundas del sedimento. La distribución vertical de la comunidad bacteriana heterotrófica viable parece estar ligada a la hidrodinámica del canal de comunicación y a la heterogeneidad de los sedimentos. En la columna de sedimento, el número total de bacterias heterótrofas variaron entre 6.8 y 20.3 x 10(8) cel cm-3. Los valores más altos de biomasa bacteriana heterótrofa se registraron en los muestreos realizados de día (39.2 µgC.l-1 a las 6 am y 33.4 µgC.l-1 a las 2 pm) y los menores durante la noche (9.7µgC. l-1). Las fluctuaciones del número de bacterias viables con diferentes metabolismos respiratorio (aeróbicos, microaerofílicos y anaeróbicos), se pueden explicar por la existencia de micronichos subóxicos que se forman debido a la resuspensión de partículas sedimentarias por la circulación del agua y por acción de las actividades de excavación de los organismos bentónicos que a través de sus galerías permiten que el oxígeno del agua sobrenadante penetre a las zonas más profundas del sedimento. El análisis estadístico (Modelo de regresión lineal múltiple r²≥ 0.5) señaló que no hubo una relación directa entre los parámetros hidrológicos y la abundancia de las poblaciones bacterianas (r²≤ 0.5). Sin embargo, las variaciones de la comunidad bacteriana heterotrófica observada durante los dos días de muestreo, pareció estar gobernada por los flujos irregulares de materia orgánica biodisponible y por la porosidad del sedimento (F-valores de 0.6 a 0.9)

The fluctuations of the number, biomass and composition of the heterotrophic community were studied daily for two days, according to depth, pH, Eh, O2 and organic carbon concentration within a zone of the canal between the Coyuca de Benítez lagoon (Guerrero, Mexico) and the coastal waters. At the three moments of the day studied (6 am, 2 pm and 10 pm), the oxygen concentrations in the overlying water and in the superficial sediment layer were near air-saturation in the diurnal samplings (582 µM at 6 am and 665 µM at 2 pm), and sub-satured during the night (158 µM). In the sediments, the models of vertical distribution of Eh and organic carbon distributions were very irregular due to the bio-perturbation of the benthic, meio- and macrofauna, whose activity allows the superficial organic carbon to migrate towards sediment deeper layers. Vertical distribution of the different viable bacteria populations seems to be related to the hydrodynamic patterns of the communicating canal and sediments heterogeneity. In the sediment column, the heterotrophic bacteria total number varied from 6.8 to 20.3 x 108 cells cm-3. The highest heterotrophic bacterial biomass values were encountered during the diurnal samplings (39.2 µgC.l-1 at 6 am and 34.4 µgC.l-1 at 2 pm) and the lowest during the night (9.7 µgC.l-1). The fluctuations of viable heterotrophic bacteria populations with different respiratory metabolisms (aerobic, microaerophilic and anaerobic) can be explained by the existence of suboxic microniches that appear when particles of sediment are resuspended due to the water circulation and the benthic infauna excavating activity, that allows the supernatant water oxygen to penetrate through its galleries towards deeper sediment zones. The statistical analysis (Multiple lineal regression model r²≥ 0.5) showed that the on the whole, the hydrological parameters are not influence over the bacterial number and bacterial biomass distribution (r²≤ 0.5), Nevertheless, the variations of the heterotrophic bacteria community observed in the two days sampling, seem to be governed (with F-values of 0.6 to 0.9) by the irregular flows of bio-available organic material and the sediment porosity. Rev. Biol. Trop. 55 (1): 157-169. Epub 2007 March. 31.