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We examined the taxonomical and functional traits of free-living nematodes, focusing on their density by genus, maturity index (MI), and trophic diversity index (ITD) to determine whether these indices are sensitive to changes in the organic content of the sediment. Samples were collected in autumn and spring from 12 subtidal sampling stations in Rocha Lagoon, distributed between the outer (near the mouth) and the inner sector. We identified 26 genera, with higher abundance in the inner sector, likely due to increased organic matter and biopolymers. In spring, both sectors had sediments rich in fresh organic matter, dominated by deposit-feeding nematodes and showing low trophic diversity (high ITD values). In autumn, the inner sector maintained similar characteristics to spring sampling, while the outer one was dominated by older organic matter, predatory nematodes and higher trophic diversity. The MI showed low variation between sectors, suggesting a disturbed environment. Our findings support the use of ITD to assess other aspects of communities such as the response of trophic groups to the freshness of organic matter, while the MI seems less effective for assessing the ecological status of Rocha Lagoon. Understanding nematode biodiversity and functional traits is crucial for effective ecological quality assessments.

In this paper, we present the results of an experimental study on the characterization of holmium-doped silica fiber. A standard acousto-optic modulator controls the output power of the ytterbium-doped fiber laser operating at 1134.5 nm and serving as a pump source of the holmium-doped fiber under test. This technique allows us to measure the lifetimes of 5I7 and 5I8 energy levels of Ho3+ ions. The effects of the fiber length and the concentration-dependent pair-induced quenching on the accuracy of the fluorescence lifetime measurement are considered. The results of this study are compared with those obtained using the exponential and Förster decay functions used for such types of measurements. It is demonstrated that the knowledge of two fiber parameters, the pump saturation power and the fluorescence saturation power, together with the fiber absorption spectrum, permits one to obtain the absorption cross-sections at the pump and other key wavelengths, the effective concentration of the active ions, and the quantum efficiency of the fluorescence from the laser level. The results of this study are applicable to the reliable characterization of any type of heavily doped gain fibers and to the further numerical modeling and optimization of fiber lasers.

Scientific surveys employing remotely operated vehicles (ROVs) provide valuable imagery for identifying Vulnerable Marine Ecosystems (VMEs). However, there is presently no established framework for distinguishing VMEs from these images. While existing guidelines effectively address certain habitat types, such as scleractinian reefs, dense octocoral gardens, and chemosynthetic ecosystems, achieving consensus becomes more challenging for other habitats. Our investigation centered on two key localized rocky outcrops on the Uruguayan shelf, conducting ROV dives to explore these environments. This study aims to evaluate initial global consensus guidelines for VME identification from imagery and discuss the suitability of these criteria, and report the existence of Hard Bottom Soft Coral Gardens and Sponge associations in the inner Uruguayan shelf. Recognizing these habitats is of utmost importance for the Uruguayan government, which has expressed the intent to safeguard ecologically representative and well-connected systems crucial for marine biodiversity.

Rapana venosa, a gastropod of Asian origin, has become a highly successful invasive species in various coastal-estuarine ecosystems worldwide. It was first recorded in the Río de la Plata (RdlP) in 1999 and has since expanded its range along the Argentine and Uruguayan Atlantic coast, and recently in southern Brazil. This study collected R. venosa samples during spring 2017 in the RdlP (middle/outer) and on the Uruguayan coast of the Argentine-Uruguayan Common Fishing Zone. The study found that 16% of stations surveyed contained R. venosa specimens with a density of 3.88 kg mn-2. Among the 119 specimens analyzed, males predominated, and imposex was observed in two organisms. Most individuals had a high epibiont coverage, and 10% were found consuming native bivalves. Isotopic analysis (d15N and d13C) in 80 individuals revealed no significant differences in location or sex, and the species was classified as secondary consumer with a trophic level (TL) of 2.5. This study provides valuable insights into the population dynamics of R. venosa and its ecological impact on the RdlP, emphasizing its successful invasion and effects on native mollusks. Further research is required to understand the long-term consequences of this invasive species on local and regional ecosystems.

In this paper, we show that a continuous-wave ytterbium-doped fiber laser implemented in the conventional configuration of a Fabry-Perot cavity with two fiber Bragg gratings as selective reflectors and a moderate output power (tens of watts) generates two groups of photons, each of which is characterized by its own statistics. The statistics of the first group are described by the M−fold degenerate Bose-Einstein distribution, where M is the number of independent states of spontaneous emission, which, in turn, depends on the laser linewidth and the radiofrequency band of the recording equipment. This kind of light is classified as narrow-band thermal light. The second group of photons is described by the extreme-value exponential statistics with a probability of encountering extremely large photon events much greater than expected from the Bose-Einstein distribution, which is classified as optical rogue waves. At a low laser power, the first group of photons strongly dominates over the second. As the laser power increases, the fraction of photons of the second group increases monotonically; above a certain threshold, the fraction of this group increases, reaching tens of percent of the total number of laser photons.

Abstract Understand the origin, transport, and character of organic matter entering Antarctic fjords is essential as they are major components of the global carbon cycle and budget. Macromolecular pools of particulate organic matter, bulk organic geochemistry, major and trace elements in surface sediments from Collins Bay were analysed as source indicators. Oceanographic conditions, bathymetry (multibeam) and grain size were considered as environmental controlling factors. Sediment samples were taken with a van Veen grab, during the ANTAR XXV Peruvian expedition (February 2018), onboard the R/V “BAP Carrasco” from the Peruvian Navy. Biopolymeric composition revealed the predominance of fresh marine protein-rich organic matter in the seafloor of Collins Bay, denoting high quality food resource for marine benthic heterotrophs. Based on Igeo values (between 0 and 1) Collins Bay can be considered unpolluted with natural levels of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Distribution of most of these elements with a gradient of decrease from the shallow inner fjord towards the outer deepest fjord, suggest their association with the deposition of detrital material and lithogenic particles supplied by Collins Glacier frontal ablation and runoff. This first comprehensive baseline information would assist in interpreting downcore sedimentary reconstructions and future climate-induce changes.

In this paper, we discuss the effective reflection of a fiber Bragg grating and its dependence on laser power when it is used as an output coupler of an ytterbium-doped fiber laser (here the effective reflection is considered to be a part of intracavity laser power reflected by the grating back to the laser cavity). We propose and discuss an experimental technique based on spectral and power analysis and derive simple formulae that permits one to obtain the intra-cavity power and the grating effective reflection. We show that, due to spectral broadening, the effective reflection dramatically decreases with increasing laser power, the effect precisely fitted using the derived formulae describing this quantity. The experimental part of the present study is based on an analysis of the operational regime of a long-wavelength ytterbium-doped fiber laser.

Reason for addendum: During the preparation of the original manuscript, a scientific work that dealt precisely with Polychaeta as environmental indicators in Patagonia was not considered. This being the first and only work regarding this subject, it was reasonable and necessary to incorporate this information.

La almeja asiática (Corbicula fluminea) es un bivalvo originario del sudeste asiático, introducido en la cuenca del Río de la Plata a fines de la década del sesenta. Desde entonces invadió numerosos cursos de agua en Brasil y la Argentina, hasta llegar a Venezuela y Colombia; actualmente, su distribución en Uruguay es poco conocida. En este trabajo analizamos la distribución espacial y características poblacionales de C. fluminea en las cuencas de las regiones Centro-Sur y Este de Uruguay, en relación con variables abióticas. Se relevó la presencia-ausencia de C. fluminea bimestralmente durante un año y se estimó la abundancia, el crecimiento y la mortalidad en cinco sitios en la cuenca del río Santa Lucía. La incidencia de la almeja asiática en la región fue de 50%. La probabilidad de ocurrencia y abundancia aumentaron con el porcentaje de arena en el sedimento y disminuyeron con el porcentaje de grava. En sedimentos finos (limos y arenas) se observó un crecimiento lento, grandes tamaños corporales y baja mortalidad, mientras que en sedimentos gruesos (gravas), los patrones siguieron una tendencia opuesta. Los parámetros de crecimiento y la mortalidad no se correlacionaron con la densidad, lo que sugiere que esta población estaría regulada primariamente por factores ambientales. C. fluminea podría continuar su expansión en Uruguay invadiendo sectores arenosos de los cursos de agua con bajos porcentajes de grava y limos.

El Río de la Plata (RdlP) presenta significativas variaciones naturales (hidro- dinámicas y oceanográficas) asociadas a diferentes condiciones climáticas. El propósito de este trabajo es inferir los cambios de aportes continentales de sedimentos y su relación con las variaciones hidrológicas del Río de la Plata, a través del análisis de proxies sedimentológicos y geoquímicos en testigos de sedimentos de la plataforma interna uruguaya que registran los últimos 100 años, aproximadamente. A partir de la datación por 210Pb de dos testigos de sedimentos (GeoB 13813-4 y BAR1) se reconstruyó la geocronología del ambiente, y se relacionó con datos de las forzantes climáticas Pacific decadal oscillation, El Niño/La Niña southern oscillation, Atlantic Multidecadal oscillation, y las anomalías hidrológicas de los ríos Paraná y Uruguay. Los valores más positivos y estables del southern oscillation index, los cuales corresponden a fases La Niña, se observan en el periodo correspondiente entre 1910-1970, respecto al resto de la serie, donde se aprecia una mayor variabilidad y una tendencia hacia valores más negativos (eventos El Niño). Se hicieron dendrogramas (clustering) jerárquicos para ambos testigos. Para el testigo GeoB 13813-4, se utilizó la relación Ca/Ti y la granulometría, mientras que para BAR1 se recurrió a variables granulométricas y la tasa de sedimentación. El mayor aporte continental hacia la región de la plataforma adyacente al Río de la Plata registrado a partir del año 1970, podría ser el factor principal de los agrupamientos observados en los clusters para ambos testigos. Las agrupaciones mostraron una diferenciación en la década de 1970, lo que estaría asociado al aumento de los caudales de los ríos Paraná y Uruguay, durante las últimas tres décadas del siglo XX. Por otra parte se observa que la granulometría del testigo BAR1 presentó un mayor tamaño de grano y más variabilidad que en el caso del testigo GeoB 13813-4. También se determinó una mayor acumulación de sedimentos a través del tiempo en el cinturón de barro del Río de la Plata (plataforma continental adyacente), comparado con aquel registrado en la Barra del Indio (límite entre zona intermedia y externa del estuario). Estas diferencias podrían estar relacionadas con la influencia del Río de la Plata, el cual genera un ambiente altamente dinámico sobre la Barra del Indio y un ambiente más estable sobre el cinturón de barro en la plataforma continental.

Los poliquetos (Annelida) son organismos en íntimo contacto con el sedimento donde viven y el agua sobrenadante. El estrés ambiental genera rápidas respuestas en estos organismos que se refleja en los individuos y sus poblaciones, por lo que se utilizan como indicadores biológicos de disturbios y de calidad ambiental. Los poliquetos han sido ampliamente utilizados en monitoreo ambiental y en bioensayos, y muchos estudios ecotoxicológicos se realizan con poliquetos. En casi todos los hábitats bentónicos estos organismos juegan un papel muy importante en la organización y estructura de las comunidades bentónicas y redes tróficas. Son un ítem fundamental en la alimentación de otros invertebrados y de aves migratorias y peces. Los poliquetos también tienen importancia económica para la industria farmacéutica, y de alimentos concentrados para especies marinas de cultivo (peces y crustáceos), en el campo médico y en la bioingeniería, además de la recreativa (acuarofilia, carnada) y por supuesto para el consumo humano. Varios de los índices de impacto ambiental y calidad ambiental existentes se basan en las características de tolerancia/sensibilidad de los organismos bentónicos, y muchos de ellos son poliquetos. Existen unos pocos trabajos de revisión de estos organismos como indicadores, pero todos en idioma inglés. Este trabajo muestra una actualización de los datos referidos a Latinoamérica y el Caribe, e incluye una amplia revisión bibliográfica.

Abstract This paper aims to test the suitability of some biotic indices for their application in Southeast Caspian Sea. For this purpose, the ecological quality of the Gomishan lagoon was assessed using three biotic indices (AMBI, BENTIX, BOPA) during summer and autumn 2010. The results from the application of the biotic indices do not highlight a clear distinction between the stations. The results show that two of the indices (AMBI and BENTIX) are very close in terms of diagnosis (good and high) and seem to generally perform better than BOPA. In addition, Principal Component Analysis (PCA) based on abiotic parameters showed clear spatial and temporal differences in environmental variables. However, at this shallow sites with low human pressure and high water residence times, such benthic community composition can be associated with physical stress due to salinity increase and to changes in environmental characteristics, triggered by conventional seasonal variations. Natural variability of transitional waters is a crucial factor for a correct evaluation of the ecological condition of macroinvertebrate communities across the lagoonal system.

AbstractSituated opposite the Freshwater Front, Montevideo city with its more than 1.5 million inhabitants encircles Montevideo Bay, where one of the most active and polluted harbors in South America is located. Faecal sterols, trace metals, organochlorine compounds and petroleum derivatives in the sediments of Montevideo Harbor were evaluated and their spatial distribution inside the harbor as well as in the input of two main tributary streams analyzed. Specifically for the harbor sites, a temporal comparison of metal and hydrocarbons was made with previous measurements taken 12 years ago. Clear changes were observed at these sites. The concentration of metals such as Pb, Cr and Zn have diminished, while aliphatic hydrocarbons have increased their values at almost all of the stations studied. Differences were observed between summer and winter suggesting sedimentation, input or hydrodynamic changes in the area. These results help one to understand the present situation and develop the management measures needed to improve the environmental quality of the harbor and bay.

AbstractThe knowledge of the extent of DNA damage in aquatic organisms in polluted areas is an important issue because contamination may alter their health at sublethal levels. Although molluscs have been widely used to monitor water pollution, there are no records of in vivo genotoxicity studies. Heleobia cf. australis, is distributed in almost all Uruguayan coastal ecosystems, including highly polluted sites. The comet assay is a damage genetic biomarker based on the migration of negatively charged DNA fragments produced by mutagenic agents in individual cells. Live individuals were collected in the Montevideo Bay (impacted area) and Laguna Garzón (control) to analyze the presence of mutagenic agents in the former site through comet assay. Cells from organisms of the impacted area showed significantly higher levels of genetic damage than those obtained in the control population, measured by percentage of DNA in the tail. Although preliminary, this approach supports the idea that H. cf. australis could be used as a sentinel to evaluate the presence of mutagenic agents in estuarine environments, alerting to the impact of contamination in its early stages.

Analysis of macrofauna from 91 quantitative soft-bottom samples (from five surveys) obtained in the São Sebastião Channel at depths ranging from 2 to 45 m yielded 431 species from a total of 38,630 individuals. The present contribution gives a list of the species found in the area and their depth distribution and sedimentary preferences (granulometric characteristics of the sites where they occurred). This is the first complete inventory of the subtidal invertebrate soft-bottom fauna of the São Sebastião Channel, a peculiar marine area under crescent human impact.

Diversity and community organization of the benthic macrofauna were investigated along the São Sebastião Channel, northern coast of São Paulo State, Brazil, and related to sedimentary variables and organic load. These important outstanding soft bottom benthic habitats are characterized by their close proximity to sources of human impact. Sampling was undertaken seasonally, using a Van Veen grab (0.1 m²) in 15 oceanographic stations, from November 1993 to August 1994. A total of 392 species were recorded and polychaetes completed nearly 50% of the fauna. Twenty three species were most numerous and frequent and comprised the baseline pool for the area. Sites were classified with respect to sediments in three site-groupings according to Arasaki et al. (2004). The finest-sediment site-group had significantly fewer species than coarser site-groups. The stations locate at the south opening and in the axis of the channel presented sediments with organic matter predominantly of marine origin, indicating the flow of open sea waters across the channel. These places showed also higher values of diversity and species richness. The site-group located along the insular side and in the channel north mouth, stood out for the significantly higher density. Although its relative small area the channel presented species richness similar to that found in the adjacent inner continental shelf. Comparisons between channel and adjacent shelf habitats are addressed in the light of ecological data.

A study on sediment surface diatom composition in relation to both protein/carbohydrate content and salinity was carried out in Montevideo Bay and the adjacent coastal zone. Samples were seasonally taken during one year along a human impact gradient, and the trophic conditions were assessed from the biochemical composition of the surface sediment organic matter. The co-occurrence of the marine-brackish (Actinocyclus curvatulus, Actinocyclus gallicus, Coscinodiscus excentricus, Coscinodiscus radiatus, Hyalodiscus subtilis, Paralia sulcata) and freshwater diatom flora (Aulacoseira granulata, Aulacoseira italica, Aulacoseira muzzanensis, Actinocyclus normanii, Amphora copulata, Cyclotella meneghiniana, Nitzschia linearis), suggests myxohaline estuarine conditions in the study area. The sampling stations located within the bay, close to several contamination sources, exhibited hypertrophic conditions as indicated by the highest levels of protein content, but also by the high relative abundances of Actinocyclus normanii and Cyclotella meneghiniana, as both diatom species are very well established cosmopolitan proxies of aquatic degradation. The levels of both protein and carbohydrate content, but also photosynthetic pigments, recorded in the adjacent coastal zone suggest meso-eutrophic conditions as contamination levels from the inner bay might become diluted off shore. Multivariate diatom species-environmental data relationships, indicate that the trophic gradient is hierarchically more important than salinity in explaining the diatom distribution. The present data imply an improvement in our ability of assessing organic contamination in the study area, since both biological and biopolymer variables were introduced for the first time as a tool for assessing the benthic health/degradation in one of the most populated regions of the Río de la Plata.Foi realizado um estudo da salinidade e da composição das diatomáceas presentes no sedimento superficial em relação ao conteúdo de proteínas/carboidratos na Baía de Montevidéu e região costeira adjacente. Foram obtidas amostras sazonalmente durante um ano ao longo de um gradiente de impacto ambiental humano, e as condições tróficas foram determinadas através da análise da composição bioquímica da matéria orgânica do sedimento superficial. A coocorrência de espécies de diatomáceas marinhas-salobras, (Actinocyclus curvatulus, Actinocyclus gallicus, Coscinodiscus excentricus, Coscinodiscus radiatus, Hyalodiscus subtilis, Paralia sulcata) e diatomáceas indicadoras de águas doces (Aulacoseira granulata, Aulacoseira italica, Aulacoseira muzzanensis, Actinocyclus normanii, Amphora copulata, Cyclotella meneghiniana, Nitzschia linearis) sugerem condições mixohalinas estuarinas na área de estudo. As estações amostradas dentro da baía, próximas às fontes contaminadoras, apresentam condições hipertróficas apontadas pelos maiores valores de proteínas e pela alta abundância relativa de Actinocyclus normanii e Cyclotella meneghiniana, sendo que ambas espécies são consideradas cosmopolitas e indicadoras de degradação aquática. As concentrações de proteínas e carboidratos, bem como os pigmentos fotossintéticos registrados na região costeira adjacente sugerem condições meso-eutróficas e uma diluição dos níveis de contaminação do interior da baía rumo à região externa. A análise multivariada entre espécies de diatomáceas e parâmetros ambientais indica que o gradiente trófico possui hierarquicamente maior peso que a salinidade na explicação da distribuição das diatomáceas. Os resultados obtidos demonstram um aperfeiçoamento na habilidade de determinar a contaminação orgânica dentro da área de estudo, já que pela primeira vez tanto as variáveis orgânicas quanto os biopolímeros foram introduzidos como ferramenta para a determinação da relação degradação/saúde de uma das mais populosas regiões do Río de la Plata.

Structure of intertidal and subtidal benthic macrofauna in the northeastern region of Todos os Santos Bay (TSB), northeast Brazil, was investigated during a period of two years. Relationships with environmental parameters were studied through uni-and multivariate statistical analyses, and the main distributional patterns shown to be especially related to sediment type and content of organic fractions (Carbon, Nitrogen, Phosphorus), on both temporal and spatial scales. Polychaete annelids accounted for more than 70% of the total fauna and showed low densities, species richness and diversity, except for the area situated on the reef banks. These banks constitute a peculiar environment in relation to the rest of the region by having coarse sediments poor in organic matter and rich in biodetritic carbonates besides an abundant and diverse fauna. The intertidal region and the shallower area nearer to the oil refinery RLAM, with sediments composed mainly of fine sand, seem to constitute an unstable system with few highly dominant species, such as Armandia polyophthalma and Laeonereis acuta. In the other regions of TSB, where muddy bottoms predominated, densities and diversity were low, especially in the stations near the refinery. Here the lowest values of the biological indicators occurred together with the highest organic compound content. In addition, the nearest sites (stations 4 and 7) were sometimes azoic. The adjacent Caboto, considered as a control area at first, presented low density but intermediate values of species diversity, which indicates a less disturbed environment in relation to the pelitic infralittoral in front of the refinery. The results of the ordination analyses evidenced five homogeneous groups of stations (intertidal; reef banks; pelitic infralittoral; mixed sediments; Caboto) with different specific patterns, a fact which seems to be mainly related to granulometry and chemical sediment characteristics.A estrutura da macrofauna bêntica das regiões entre marés e infralitoral raso na porção nordeste da Baia de Todos os Santos (BTS), nordeste do Brasil, foi investigada durante um período de dois anos. Sua relação com os parâmetros ambientais mensurados foi estudada através de análises estatísticas uni -e multivariadas, sendo os principais padrões de distribuição espacial e temporal relacionados principalmente ao tipo de sedimento e ao conteúdo de três indicadores da matéria orgânica sedimentar (Carbono, Nitrogênio e Fósforo). A macrofauna, composta majoritariamente por anelídeos poliqueta (cerca de 70% do total), apresentou baixa densidade, riqueza de espécies e diversidade, exceto nas estações amostradas nos bancos recifais. Estes se destacam como ambiente peculiar, formado por sedimentos grosseiros, pobres em matéria orgânica e ricos em carbonatos, apresentando fauna abundante e diversificada. A região entre marés e os locais rasos adjacentes à refinaria RLAM são formados por sedimentos compostos principalmente por areia fina e baixo conteúdo orgânico e constituem ambiente instável, com poucas espécies altamente dominantes, como Armandia polyophthalma e Laeonereis acuta. Em outras regiões da BTS, onde dominam os sedimentos pelíticos, densidade e diversidade foram muito baixas, especialmente nas proximidades da refinaria. Aqui, os indicadores biológicos apresentaram seus mais baixos valores, sendo as estações mais próximas (4 e 7) algumas vezes azóicas. A região adjacente de Caboto, inicialmente considerada como controle, apresentou baixa densidade, porém valores médios para diversidade, o que indica ser este ambiente relativamente menos perturbado. Foi possível identificar a existência de 5 grupos com padrões estruturais próprios (entremarés; bancos recifais; infralittoral pelitico; sedimentos mistos; Caboto), que parecem estar relacionados principalmente às características físicas e químicas do sedimento.

Analyses of organic matter content, organic carbon, nitrogen, sulfur and granulometric variables were performed on 101 surface sediment samples from Ubatuba Bay in order to investigate the spatial distribution of organic matter, its origin and the relationships among its components. The samples were obtained with a manual corer, from water depths between 1 and 15m during 5 cruises of the R/V "Veliger II'', two months apart. Pearson correlation, regression and Principal Component Analysis (PCA) statistical methods were used to analyze the data. Strong correlations between organic matter and fine sediment fractions were obtained. The PCA revealed at least two main sample groups that reflect the different environmental conditions prevalent in the bay. There is a simple linear relationship between organic carbon content and the organic matter content determined by the calcination technique. Taking into account that the analysis of organic matter content is less expensive and less time consuming than the analysis of organic carbon, the present method of estimation can be useful when fast evaluation of the organic carbon content is needed for samples from similar environments.Foram realizadas análises de matéria orgânica, carbono orgânico, nitrogênio, enxofre e granulometria utilizando-se 101 amostras de sedimentos superficiais na Enseada de Ubatuba, SP, com a finalidade de investigar a origem e distribuição espacial da matéria orgânica, sua origem e as relações existentes entre seus componentes químicos. O material foi coletado com amostrador tipo "corer'', em profundidades compreendidas entre 1 e 15m, a bordo do B/Pq "Veliger II'', em 5 coletas a cada dois meses. As amostras foram analisadas estatisticamente através de correlação linear de Pearson, regressão e análise de componentes principais (PCA). Foram obtidas boas correlações entre a matéria orgânica e as frações finas do sedimento. O PCA revelou a existência de duas regiões principais dentro da enseada, que refletem diretamente as condições hidrodinâmicas locais. Foi estabelecida uma equação linear simples para obtenção de boas estimativas de carbono orgânico, a partir de dados de matéria orgânica obtida por técnicas de calcinação. Considerando-se a rapidez e o baixo custo das análises de matéria orgânica quando comparadas às de carbono orgânico, o presente método mostrou-se útil em análises de rotina ou quando se fazem necessárias avaliações imediatas do conteúdo de matéria orgânica em ambientes impactados.

Abstract Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships.

El Río de la Plata (RdlP) presenta significativas variaciones naturales (hidrodinámicas y oceanográficas) asociadas a diferentes condiciones climáticas. El propósito de este trabajo es inferir los cambios de aportes continentales de sedimentos y su relación con las variaciones hidrológicas del Río de la Plata, a través del análisis de proxies sedimentológicos y geoquímicos en testigos de sedimentos de la plataforma interna uruguaya que registran los últimos 100 años, aproximadamente. A partir de la datación por 210Pb de dos testigos de sedimentos (GeoB 13813-4 y BAR1) se reconstruyó la geocronología del ambiente, y se relacionó con datos de las forzantes climáticas Pacific Decadal Oscillation, El Niño/La Niña Southern Oscillation, Atlantic Multidecadal Oscillation, y las anomalías hidrológicas de los ríos Paraná y Uruguay. Los valores más positivos y estables del Southern Oscillation Index, los cuales corresponden a fases La Niña, se observan en el periodo correspondiente entre 1910-1970, respecto al resto de la serie, donde se aprecia una mayor variabilidad y una tendencia hacia valores más negativos (eventos El Niño). Se hicieron dendrogramas (clustering) jerárquicos para ambos testigos. Para el testigo GeoB 13813-4, se utilizó la relación Ca/Ti y la granulometría, mientras que para BAR1 se recurrió a variables granulométricas y la tasa de sedimentación. El mayor aporte continental hacia la región de la plataforma adyacente al Río de la Plata registrado a partir del año 1970, podría ser el factor principal de los agrupamientos observados en los clusters para ambos testigos. Las agrupaciones mostraron una diferenciación en la década de 1970, lo que estaría asociado al aumento de los caudales de los ríos Paraná y Uruguay, durante las últimas tres décadas del siglo XX. Por otra parte se observa que la granulometría del testigo BAR1 presentó un mayor tamaño de grano y más variabilidad que en el caso del testigo GeoB 13813-4. También se determinó una mayor acumulación de sedimentos a través del tiempo en el cinturón de barro del Río de la Plata (plataforma continental adyacente), comparado con aquel registrado en la Barra del Indio (límite entre zona intermedia y externa del estuario). Estas diferencias podrían estar relacionadas con la influencia del Río de la Plata, el cual genera un ambiente altamente dinámico sobre la Barra del Indio y un ambiente más estable sobre el cinturón de barro en la plataforma continental.