Plata Basin Research Articles

Alterations in the sterol signature of detritivorous fish along pollution gradients in the Río de la Plata basin (Argentina): From plant to sewage-based diet

In order to assess the impact of sewage pollution on the diet of the strict detritivorous and migratory South American fish, Prochilodus lineatus, 16 sterol biomarkers were analyzed by gas chromatography-mass spectrometry from fish muscle (n: 144) collected along 1200 km in the Rio de la Plata basin. Sterol concentrations were fairly homogeneous (2.4 ± 1.3 mg g−1 dry weight), but their proportion in lipids was highly variable and inversely related to both body mass and lipid contents, reflecting the more conservative character of sterols compared to the rapid accumulation of fat as fish grows. As expected, the muscle sterol signature was widely dominated by cholesterol (92 ± 4.5% of total sterols), but it exhibited a remarkable diversity with variable proportions of fecal coprostanol (4.0 ± 4.4%) and plant sterols (3.1 ± 1.9%, e.g. sitosterol and campesterol). Muscle sterols exhibited contrasting geographical differences associated with dietary shifts from plant-derived detritus in the northern reaches of the basin (N: Paraná and Uruguay Rivers), to sewage dominated inputs at Buenos Aires (BA). Fish from BA are fattier (lipids: 35 ± 18 vs. 15 ± 9.0% at N), with higher total sterol contents (2.6 ± 1.3 vs. 1.9 ± 1.0 mg g−1), abundant coprostanol (5.3 ± 4.4 vs. 0.46 ± 1.1%) and lower plant sterols (2.6 ± 1.6 vs 4.6 ± 2.0%), reflecting a diet shifted to anthropogenic organic matter as opposed to vegetal detritus in the north. Accordingly, BA fish presented lower phyto/fecal sterol ratios (0.37 ± 0.21 vs. 0.91 ± 0.12 at N) and higher copro/epicoprostanol ratios (0.95 ± 0.082 vs 0.51 ± 0.25 at N), indicating fresh fecal inputs which provide a valuable supply of easily absorbed organic matter at this site. In addition, the sterol signature allowed to distinguish migratory fish from BA collected 900 km north (previously identified by their pollutant fingerprint and biochemical composition). In fact, coprostanol concentrations show a direct relationship with human populations along the basin, highlighting the usefulness of fecal sterol biomarkers as tracers of polluted fish stocks.

RIO DE JANEIRO AND THE SILVER MINING ECONOMY OF POTOSI: TRANS-IMPERIAL, GLOBAL, AND CONTRACTUAL APPROACHES TO SOUTH ATLANTIC MARKETS (18TH CENTURY)

Abstract This paper’s main goal is to advance some considerations on the interrelations between port cities and capital. More specifically, it sheds light on how these interdependencies took place in the eighteenth-century Portuguese and Spanish Atlantic world. This paper thus seeks to draw an urban political economy in transimperial, global, and contractual perspectives. For so doing, particular attention will be put to Rio de Janeiro’s projection far beyond the South Atlantic, and in particular, its interconnections with the Rio de la Plata basin and Potosi markets. Attention will also be paid to the impact of and repercussions that far-flung economic phenomena had for the urban domestic markets.

LISTA DE ESPECIES DE PECES DE LA CUENCA DEL RÍO QUEGUAY, RÍO URUGUAY BAJO

The Queguay river is one of the main tributaries of the lower Uruguay river basin. At the confluencce of its main effluents large wetlands and riparian forest are developed, that according to their biodiversity and ecosystem functions have been included in the National Protected Areas System, under the name “Montes del Queguay”. At a national scale the basin is included in two ecoregions: the Basaltic Slope and the Western Sedimentary Basin. Except for an unsupported listing in scientific collections, there is no documented information about its ichthyofauna. Therefore, the objective of this work was to prepare an updated list of the fish species in the Queguay River basin. Considering all the sources of information, a total of 94 species were registered for the basin, corresponding to 60 genera, 28 families and nine orders. The composition of species found was similar to the largest tributary of the low Uruguay ecoregion, the Rio Negro basin. The main migratory species of the Plata basin stand out, as well as a species of annual fish endemic to the wetlands of the basin, and the presence of an invasive exotic species (Cyprinus carpio).

The potential added value of Regional Climate Models in South America using a multiresolution approach

This paper aims to identify those regions within the South American continent where the Regional Climate Models (RCMs) have the potential to add value (PAV) compared to their coarser-resolution global forcing. For this, we used a spatial-scale filtering method based on the wavelet theory to distinguish the regional climatic signal present in atmospheric surface fields from observed data (CPC and TRMM) and 6 RCM simulations belonging to the CORDEX Project. The wavelet used for filtering was Haar wavelet, but a comparative analysis with Daubechies 4 wavelet indicated that meteorological fields or regional indices were not very sensitive to the wavelet selected. Once the longer wavelengths were filtered, we focused on analyzing the spatial variability of extreme rainfall and the spatiotemporal variability of maximum and minimum surface air temperature on a daily basis. The results obtained suggest essential differences in the spatial distribution of the small-scale signal of extreme precipitation between TRMM and regional models, together with a large dispersion between models. While TRMM and CPC register a large signal throughout the continent, the RCMs place it over the Andes Cordillera and some over tropical South America. PAV signal for surface air temperature was found over the Andes Cordillera and the Brazilian Highlands, which are regions characterized by complex topography, and also on the coasts of the continent. The signal came specially from the small-scale stationary component. The transient part is much smaller than the stationary one, except over la Plata Basin where they are of the same order of magnitude. Also, the RCMs and CPC showed a large spread between them in representing this transient variability. The results confirm that RCMs have the potential to add value in the representation of extreme precipitation and the mean surface temperature in South America. However, this condition is not applicable throughout the whole continent but is particularly relevant in those terrestrial regions where the surface forcing is strong, such as the Andes Cordillera or the coasts of the continent.

A guerra como instrumento da política imperial brasileira na Bacia do Prata (1852-1858)

How did the war become a political instrument of the Brazilian Empire toreach its objectives in the Plata Basin, contributing to the strengthening of the NationalState? The article is based on research on the cases of the war against Oribe and Rosas(1851-1852) and the political conflict with Paraguay between the years of 1852 and1858, through a theoretical-methodological approach of the critical discourse analysisof documents produced by Brazilian diplomats, among which we highlight Paulino JoseSoares de Souza, Jose Maria da Silva Paranhos and Jose Maria do Amaral. As a result, itis found that segments of the Brazilian elite were responsible for creating a discourse withwhich they legitimized the right to make war, forging an identity and a social reality inwhich the Empire of Brazil resorted to war for the sake of the preservation of civilizationand the maintenance of peace, which in turn, within the discourse, represents a state inwhich Brazilian interests such as territory, free navigation and power are achieved.

Manejo federal de la zona costera Argentina

The Argentine Coastal Zone is a fluvio-maritime continuum of great climatic and biogeographic diversity that extends from the northern end of the Río de la Plata basin to the southern extreme of the Patagonian coast. This paper analyzes the changes related to coastal management in the period 2009-2019 in public policies, regulations, competencies, responsibilities, institutions, instruments, training, capacity building, financial resources, scientific knowledge, environmental information and education, and citizen participation. Among the most significant advances are the determination of the limits of the continental shelf, the more precise regulation in the reformed Civil and Commercial Code, the formulation of a Federal Coastal Management Strategy and several sectoral strategies, the creation of the first marine protected area, the increase of the postgraduate courses related to coastal management, and the expansion of the environmental contents to all levels of the education system. On the other hand, it is worth noting the scarcity of financial resources for institutional strengthening, the low incidence of citizen participation and the persistence of interjurisdictional competition conflicts. It is concluded that the sectoral model of coastal management has consolidated, with a tendency to migrate from a centralized management at the national level to a federal system with greater decision capacity for the provinces.

Creating hybrid scientific knowledge and practice: the Jesuit and Guaraní cultivation of yerba mate

ABSTRACTThe drinking of yerba mate tea has become a common symbol of southern South American culture and many studies have explored the economic and social history of yerba mate in Argentina, Paraguay, and southern Brazil. The consumption of yerba mate has its roots in Guaraní culture and practice, and, at the time of European contact, the Guaraní had developed effective practices of harvesting and processing the leaves. The tree is native to different forest types of the Rio de la Plata Basin and its exploitation by the Spanish occurred mainly through natural forest stands from the sixteenth to the twentieth century. Nevertheless, the Jesuit missionaries in colonial Paraguay successfully developed the technology to plant yerba mate in forest stands around the mission towns. This not only stabilized their production but also represented the domination of European scientific knowledge and practice on the untamed wilderness of the Rio de la Plata Basin. This article examines how Jesuit discourse surrounding the invention of this technology masks the very active participation of the Guaraní in developing and testing this scientific practice. The process of cultivation and “civilization” of the wild environment and people of the Americas by the Jesuits was not one sided, but it was rather a hybrid construction of knowledge and technology that actively involved both the Guaraní and the Jesuit Fathers, creating new knowledge and understandings of the forest environment.

Arqueología de los ríos Pilcomayo, Bermejo y Paraguay

Los ríos Paraguay, Pilcomayo y Bermejo son los principales protagonistas del aporte hídrico y sedimentario de la cuenca del Plata y constituyen enclaves estratégicos para comprender el poblamiento y dinámica poblacional de las tierras bajas sudamericanas. Este artículo tiene por objetivo aportar al conocimiento del pasado histórico de estos importantes cursos de agua, desde el momento en que se registran las primeras evidencias de ocupación humana, basadas en el análisis de manifestaciones culturales y biológicas, y de otros rasgos particulares resultantes de la construcción del paisaje en este sector de la cuenca del Plata. Para dar cuenta de la variabilidad arqueológica regional se propone un ordenamiento que articula criterios ecológicos, culturales e históricos. Por ello distinguimos sectores que denominamos Pilcomayo y Bermejo andino pedemontano; Pilcomayo y Bermejo chaqueño y sector Río Paraguay al que hemos diferenciado en superior (nacientes), medio, inferior y confluencia. En estos últimos tramos intervienen los grandes abanicos del Pilcomayo y Bermejo y el área de la confluencia Paraná ? Paraguay, que están culturalmente relacionados. La fuente de información arqueológica utilizada proviene de las investigaciones realizadas por nuestro equipo en la región chaqueña y de la información disponible en la bibliografía, la cual, en un esfuerzo de síntesis, integramos desde la óptica chaqueña y a la luz de las últimas investigaciones regionales. A lo largo de estos tres grandes ríos se destaca la interacción de diversos grupos humanos que capitalizaron el recurso de manera particular. No sólo como elemento vital, sino también por su importancia como proveedor de alimentos, factor de movilidad y comunicación. A lo largo de la sectorización espacial y temporal propuesta daremos cuenta del aprovechamiento de geoformas naturales como los albardones, la producción intencional de elevaciones monticulares y otras obras utilizadas tanto para la protección de desbordes como para almacenar y ¨cosechar¨ agua. Asimismo, las distintas estrategias de movilidad, migración, expansión e intercambio se han articulado de manera compleja dentro del repertorio de resoluciones de estos pueblos a lo largo de su historia. Esto ha cristalizado en el registro arqueológico de organizaciones diferenciales ya sea a través de sociedades pescadoras con movilidad reducida y amplias redes de interacción; otras con énfasis en la caza, pesca y recolección con alta movilidad residencial, o sociedades agropastoriles con marcado grado de sedentarismo que incluyeron el cultivo, en mayor o menor escala, entre sus actividades económicas.

State formation and identity: Historiographical trends concerning South America's War of the Triple Alliance

AbstractThe War of the Triple Alliance shaped state formation in the Rio De La Plata Basin during the second half of the 19th century. Historians have long debated how emerging countries could have endured such protracted periods of fighting. Recently, however, historiography has moved away from patriotic and military accounts and towards social and political analyses of civilian responses to the bloodbath. These responses had profound consequences for the fragile regional order postindependence. Paraguay, the loser, suffered unspeakable destruction. However, the political systems of the winners, Brazil, Argentina, and Uruguay, were also challenged as initial popular enthusiasm succumbed to the difficult requisites of war. This paper explores how historians have dealt with political, cultural, and demographic changes as war support and resistance waxed and waned over time in the belligerent countries. The war demanded the utmost sacrifices from civilians and soldiers, and their responses created new national identities throughout the Rio de la Plata Basin.

Hidden areas of endemism: Small units in the South-eastern Neotropics

This study aimed to establish if the Lower Río de la Plata Basin (LRPB) wetlands can be considered a biogeographic unit. The species of this area were compiled and segregated according to the habitat, selecting only 87 endemic taxa restricted to the LRPB and linked to wetlands. Distributional data of species obtained from the literature, web databases, biological collections, and field trips were georeferenced. The areas of endemism were established as those areas where the distribution of two or more taxa overlaps in groups of rivers’ sections with geographic continuity and were tested with a cluster analysis. This congruence is due to ecological, geomorphological, and historical factors. Four areas of endemism were found: a broad area that comprises the whole study area (Riverine district), which is divided into three nested smaller areas (Paraguay–Paraná Flooding Valleys, Uruguay Basin, and Paraná Delta subdistricts). Then, we analysed 170 taxa distributions to evaluate the relationship between the study area and the neighbouring biogeographic units. According to the results, the study area belongs to the Paraná biogeographic province. Some areas of endemism are hidden inside broader areas and are hardly detected with the currently used biogeographic grid-methods. We propose to combine the information about ecological requirements of each taxon with its georeferenced records to estimate their areas of distribution as a primary step for searching areas of endemism in intracontinental studies.

Floración excepcional de cianobacterias tóxicas en la costa de Uruguay, verano 2019

Cyanobacterial toxic blooms are a worldwide problem. In Rio de la Plata basin, anthropic eutrophication and dam construction have promoted an increase in cyanobacteria blooms, especially those of the Microcystis aeruginosa complex (CMA). Here, we describe the exceptional blooms observed in the summer of 2019 on the coast of Rio de la Plata and Atlantic coast of Uruguay. We discuss the main driving mechanisms using biological, meteorological and oceanographic sampling data, satellite images and reanalysis. The blooms covered a wide surface (Carmelo to Rocha; 500 km) and were persistent in time (ca. 4 months). Blooms were generated by CMA organisms having similar genetic structure and were associated to quantifiable and high microcystin concentrations. Given the observed oceanographic conditions and the similarity in organisms traits, we hypothesized that blooms had a common origin, probably associated with zones with high nutrient concentrations and high water residence time in the lower Rio de la Plata basin. Extreme precipitations induced high water flows that transported cyanobacteria blooms downstream. In addition, anomalous wind and temperature conditions facilitated their arrival to the Atlantic coast along Rocha, to environments with particular relevance for biodiversity and conservation (e.g. Rocha coastal lagoon).

Human pharmaceuticals in three major fish species from the Uruguay River (South America) with different feeding habits

The accumulation of 17 human pharmaceuticals (HPs) was investigated in the muscle of three fish species characteristic of the “Rio de la Plata Basin” with different feeding habits and of relevance for human consumption: Megaleporinus obtusidens, Salminus brasiliensis, and Prochilodus lineatus. Fish were sampled in fall and spring from 8 localities distributed along 500 Km of the Uruguay River. Atenolol and carbamazepine were the most frequently detected HPs (>50%), but at concentrations always below 1 μg/kg wet weight (w/w). Hydrochlorothiazide, metoprolol, venlafaxine, propranolol, codeine, and the carbamazepine metabolite, 2-hydroxycarbamazepine, were accumulated at higher levels showing maximum concentrations between 1 and 10 μg/kg (w/w), but infrequently (<50%). The other HPs were always below 1 μg/kg (w/w) and at frequencies lower than 50%. Distinctive accumulation patterns were observed among species at different trophic levels. However, biomagnification trends were not identified for any compound. The highest number and concentration of HPs were found in M. obtusidens (omnivorous), followed by P. lineatus (detritivorous), and lastly S. brasiliensis (piscivorous). The most recurrent HPs (i.e. carbamazepine and atenolol) were present in all species, but others exclusively in one. Geographical variations were only found for carbamazepine and atenolol in M. obtusidens and P. lineatus, showing higher concentrations in localities closer to the Rio de la Plata estuary. Differences in the HPs concentrations among seasons were not identified. Acceptable daily intake and predicted no effect concentrations would indicate that measured muscle concentrations in fish from the Uruguay River do not pose a serious risk for human consumption nowadays. Further studies will be necessary for assessing the potential adverse effects on studied fish species.

Vascular plant species of the floating vegetation rafts from the Río de la Plata (Argentina)

Abstract In South American rivers, Eichhornia crassipes and other floating plants intertwine and form floating rafts commonly known as "camalotales" which are especially abundant during flooding periods. During extraordinary floods, hectares of floating mats are drifted by the Plata Basin Rivers. In the Río de la Plata several reports suggest that many animal and plant species from subtropical latitudes colonizes the area through these large rafts. These episodes are very important from the economic point of view because they cause several troubles to navigation and other activities. On the other hand, benefits to biodiversity are conspicuous, and many authors consider this process vital to the Río de la Plata wetlands and forests. However, there is scarce knowledge about Eichhornia rafts plant species composition. With the aim of creating an exhaustive list of the flora of the Eichhornia rafts, we visited the Río de la Plata coast during a massive Eichhornia rafts arrival. Thirty-two plant species were recorded in three different plant assemblages: Eichhornia rafts sensu stricto, floating reeds (canutillares) and embalsados. In front of this unexpected we emphasize the need to include this phenomenon in regional biodiversity conservation plans.

Detecting and Quantifying a Massive Invasion of Floating Aquatic Plants in the Río de la Plata Turbid Waters Using High Spatial Resolution Ocean Color Imagery

The massive development of floating plants in floodplain lakes and wetlands in the upper Middle Paraná river in the La Plata basin is environmentally and socioeconomically important. Every year aquatic plant detachments drift downstream arriving in small amounts to the Río de la Plata, but huge temporary invasions have been observed every 10 or 15 years associated to massive floods. From late December 2015, heavy rains driven by a strong El Niño increased river levels, provoking a large temporary invasion of aquatic plants from January to May 2016. This event caused significant disruption of human activities via clogging of drinking water intakes in the estuary, blocking of ports and marinas and introducing dangerous animals from faraway wetlands into the city. In this study, we developed a scheme to map floating vegetation in turbid waters using high-resolution imagery, like Sentinel-2/SMI (MultiSpectral Imager), Landsat-8/OLI (Operational Land Imager), and Aqua/MODIS (MODerate resolution Imager Spectroradiometer)-250 m. A combination of the Floating Algal Index (that make use of the strong signal in the NIR part of the spectrum), plus conditions set on the RED band (to avoid misclassifying highly turbid waters) and on the CIE La*b* color space coordinates (to confirm the visually “green” pixels as floating vegetation) were used. A time-series of multisensor high resolution imagery was analyzed to study the temporal variability, covered area and distribution of the unusual floating macroalgae invasion that started in January 2016 in the Río de la Plata estuary.

The Guiana Shield rainforests—overlooked guardians of South American climate

Tropical forests are global climate regulators through their interaction with hydrological and biogeochemical cycles. Despite extensive research on deforestation in South America and its global impact, the role of the largely intact Guiana Shield forests, north of the Amazon, has not yet been considered as part of this climate system. We use a regional climate model with a realistic deforestation scenario to test the impact of deforestation in the Guiana Shield on climate throughout South America. We show that replacing ~28% of the current Guiana Shield rainforest with savannah leads to multi-scale impacts across South America, through vegetation-land-atmosphere interactions that disrupt the initial phase of two major ‘atmospheric rivers’: the Caribbean low-level Jet and the South American low-level jet (SALLJ). Our climate simulations suggest that following deforestation, locally, precipitation and runoff would more than double in lowland forests, whilst mean annual temperatures would increase by up to 2.2 °C in savannahs. Regionally, significant wetting is simulated in northern South America (April−September) and the western Amazon (October–March), while temperatures increase up to 2 °C in central and eastern Amazon, causing more dry months in up to 64% of the Amazon basin. Reduction of moisture transfer by the SALLJ of 2.2% of total annual flow causes noticeable and highly diverse spatial changes in simulated monthly rainfall in la plata basin (LPB). These results highlight the potential consequences of land cover change in a sensitive hot-spot with hydro-climatic impacts 1000 km west and 4000 km south. Such multi-scale perturbations can severely impact biodiversity and ecosystem services across South America, including agriculture in LPB. Recognition of the far field effects of localised deforestation in key areas is urgently needed to improve development plans for a sustainable future.Significance statementThe Guiana Shield, at the northern boundary of Amazonia, is located at the start of two atmospheric rivers which carry moisture across South America. We show that deforesting less than a third of the Guiana Shield, in areas currently under threat from mining, logging and agricultural activities, could result in significant changes in the water cycle across the continent. This includes large variations in temperature and precipitation affecting areas 4000 km away, impacting ecosystems and economies, with consequences for society. The study demonstrates how land-use change, even if small in spatial scale, but occurring in particularly sensitive hot-spots, can alter the flow of atmospheric rivers, with large consequences. This pan-continental cascade must be considered when designing trans-national management plans for a sustainable future.

Spatial segregation and connectivity in young and adult stages of Megaleporinus obtusidens inferred from otolith elemental signatures: Implications for management

Boga Megaleporinus obtusidens is a teleost fish of economical and sport importance from Río de la Plata Basin (South America). Otolith core and edge elemental ratios (Ba:Ca, Cu:Ca, Li:Ca, Mg:Ca, Mn:Ca, Pb:Ca, Rb:Ca and Sr:Ca) were compared among three sampling areas from the Río de la Plata Basin (Paraná and Uruguay Rivers and Río de la Plata Estuary) to evaluate the applicability of the fingerprint to study segregation and connectivity in young and adult stages. Several ratios were significantly different among sites for otolith core and edge (p < 0.05). PERMANOVA (p < 0.05) and quadratic discriminant function analysis (classification rates: 86.8% and 82.5% for otolith core and edge, respectively) were found to be highly effective in detecting differences in otolith core and edge fingerprints between sampling sites suggesting the existence of spatial segregation in young and adult life stages, respectively. The presence of relatively isolated groups may require the need to manage the stocks separately.

Silversides (Odontesthes bonariensis) reside within freshwater and estuarine habitats, not marine environments

Otolith core-to-edge Sr:Ca ratio was determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze the salinity-habitat migration history of the silverside, Odontesthes bonariensis, within the Uruguay River (freshwater) and Río de la Plata Estuary (estuarine water) (Plata Basin, South America). Regular core-to-edge oscillations in Sr:Ca suggest that the silverside makes annual migrations between freshwater (<1 PSU) and brackish (>1 PSU) habitats, with no evidence of marine incursion or non-migratory individuals. Empirical equations that represent the relationship between conductivity/salinity and otolith Sr:Ca ratio were used to identify where in an otolith an individual transitioned between freshwater and brackish habitats. In most specimens, the first migration between habitats likely occurred within the first year of life. Average numbers of changes between stable Sr:Ca signatures (sites with different salinities) determined by Change-Point analysis were similar from Uruguay River (8.9 ± 3.7) and Río de la Plata Estuary (7.5 ± 2.5) for comparable age fish (p < 0.05), suggesting that habitat use is similar in both collection sites.

Early diagenetic alterations of sterol biomarkers during particle settling and burial in polluted and pristine areas of the Rio de la Plata Basin

Sources and diagenetic alterations of sterol markers were studied in settling material and sediments near the Buenos Aires main sewer (BA), and at a relatively non-polluted northern site at the Uruguay River (N). Vertical particle fluxes were 7-times higher at BA relative to N (34 ± 24 vs 4.6 ± 3.6 mg/cm2/day; mean ± standard deviation), increasing during rainy months. Total sterol contents were consistently higher at BA, both in settling material (7140 ± 7905 vs 41 ± 47 μg/g at N) and sediments (708 ± 454 vs 1.9 ± 0.18 μg/g). This difference was further amplified in the vertical flux of sterols (116 ± 168 vs 0.070 ± 0.13 mg/cm2/year). At BA, sterol composition of settling material and sediments was dominated by fecal sterols (75–77%), with extreme coprostanol concentrations (3.6 ± 4.8 vs 0.35 ± 0.28 mg/g at N) which are similar to sewage sludge. In contrast, at N the sterol profile was dominated by plant sterols (57–64%), mainly sitosterol, stigmasterol and campesterol. At BA the discharge of fresh sewage was confirmed by the high coprostanol/(coprostanol + epicoprostanol) ratio. At N, the overwhelming dominance of plant sterols over herbivore fecal sterols was reflected by the high sitosterol/(sitosterol + 24-ethylcoprostanol) ratio and the low coprostanol/(coprostanol + 24-ethylcoprostanol) ratio. The coprostanol/(coprostanol + epicoprostanol) and cholesterol/(cholesterol + cholestanol) ratios were lower in sediments than in settling material, reflecting the sterol degradation at the sediment surface. The accumulation efficiencies, calculated as the difference between trap fluxes and sediment inventories, were 2–7 times higher at BA reflecting strong vertical fluxes and enhanced preservation under anoxic conditions. During diagenetic processes, epicoprostanol (partially produced in situ), cholestanol and plant sterols were the best-preserved sterols, while cholesterol was the most labile during burial.

Speculative petroleum systems of the Punta del Este Basin (offshore Uruguay)

ABSTRACT: The Uruguayan continental margin was generated as the result of the breakup of Gondwana and, later, the opening of the South Atlantic Ocean, which began in the Jurassic. Three major areas of Meso-Cenozoic sedimentation are located in the Uruguayan offshore: the Punta del Este Basin, the southernmost sector of the Pelotas Basin and the Oriental del Plata Basin. These basins share the classical stages of tectono-sedimentary evolution of the other Atlantic basins, including the prerift (Paleozoic), rift (Jurassic-Early Cretaceous), transition (Barremian-Aptian) and postrift (Aptian-present) phases. Based on the analysis of basin evolution through seismic sections and well data as well as on the establishment of analogies with productive Atlantic basins, four speculative petroleum systems are proposed for the Punta del Este Basin: 1) Marine petroleum system of the prerift stage: Devonian/Permian-Devonian/Permian(?), 2) Lacustrine petroleum system of the synrift stage: Neocomian-Neocomian(?), 3) Marine petroleum system of the Cretaceous postrift: Aptian-Late Cretaceous(?), 4) Marine petroleum system of the Cenozoic postrift: Paleocene-Paleogene/Neogene(?).

DNA barcoding of odonates from the Upper Plata basin: Database creation and genetic diversity estimation.

We present a DNA barcoding study of Neotropical odonates from the Upper Plata basin, Brazil. A total of 38 species were collected in a transition region of “Cerrado” and Atlantic Forest, both regarded as biological hotspots, and 130 cytochrome c oxidase subunit I (COI) barcodes were generated for the collected specimens. The distinct gap between intraspecific (0–2%) and interspecific variation (15% and above) in COI, and resulting separation of Barcode Index Numbers (BIN), allowed for successful identification of specimens in 94% of cases. The 6% fail rate was due to a shared BIN between two separate nominal species. DNA barcoding, based on COI, thus seems to be a reliable and efficient tool for identifying Neotropical odonate specimens down to the species level. These results underscore the utility of DNA barcoding to aid specimen identification in diverse biological hotspots, areas that require urgent action regarding taxonomic surveys and biodiversity conservation.