DNA barcode of Parodontidae species from the La Plata river basin - applying new data to clarify taxonomic problems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A new species of the catfish genus Trichomycterus from the La Plata River basin, southern Brazil, with comments on its putative phylogenetic position (Siluriformes: Trichomycteridae)

The genus Trichomycterus is a highly diverse group of Neotropical catfishes that encompass almost 60% of all the currently recognized species of the Trichomycteridae. A new species of this genus, T. perkos, is herein described from tributaries of the Paranapanema and Uruguai River basins, southern Brazil. The new species exhibits a remarkable ontogenetic change in its pigmentation, having a unique color pattern when adult. The adult pigmentation consists of three wide dark brown stripes, located in an inner skin layer of trunk and caudal peduncle, combined with a superficial light brown freckled pattern on the dorsum and caudal peduncle. Small, presumably juvenile specimens lack the superficial freckles but already have the dark stripes, thus resembling the color pattern of a few other congeners. Nevertheless, several unequivocal morphological features distinguish both juveniles and adults of T. perkos from these congeners. In spite of the difficulties in estimating phylogenetic relationships within Trichomycterus, the new species is tentatively proposed as being the sister-taxon of a small group of species composed by T. crassicaudatus, T. igobi, and T. stawiarski.

Supporting land use change modelling with automated monitoring of land use dynamics in the La Plata River Basin.

2008

Sensor TTC - the La Plata River basin application: policy cases, main land use change drivers and case studies.

2008

Niveles de nutrientes y pigmentos fotosintéticos en el Río de la Plata interior (55°-59°W 34°-36°S)

The "Río de la Plata" River is one of the less studied systems of the basin with respect to its biological and ecological aspects. Twenty four and twenty seven surface stations were sample on September 22-23 and November 22-23, 1982, respectively. The section studied is part of the zone called inner "Río de la Plata" River. The discharge was 29.000 m3/s in September and 45.200 m3/s in November. Total phosphorus (PT), total organic nitrogen (NOT), chemical oxygen demad (COT) and total cholrophyll were measured. Dissolved oxygen (DO), turbidity (TURB), pH and electrical conductivity (K20) were also measured at the surface with a HORIBA U7 sensor on November 1982. PT was 72-208 mg/m3 and 66-205 mg/m3 in September and November repectively; the higher values were near the Argentinian coast and the outer zone. NOT was 33-106 µM and 49-117 µM and CHL was 1.4-5.8 mg/m3 and 1.3-9.4 mg/m3. TURB was between 44 and 240 NTU in November; the maximun value were obseved in the central zone. Steep K20 gradients were found near both coast. The reduced organic carbon load into the lower and external part of the "Río de la Plata" River was estimated. (Document contains 40 pages.)

Effects of low-salinity and high-turbidity waters one mpirical ocean colour algorithms: an example for Southwestern Atlantic waters

The spectral reflectance of the sea surface recorded using ocean colour satellite sensors has been used to estimate chlorophyll-a concentrations for decades. However, in bio-optically complex coastal waters, these estimates are compromised by the presence of several other coloured components besides chlorophyll, especially in regions affected by low-salinity waters. The present work aims to (a) describe the influence of the freshwater plume from the La Plata River on the variability of in situ remote sensing reflectance and (b) evaluate the performance of operational ocean colour chlorophyll algorithms applied to Southwestern Atlantic waters, which receive a remarkable seasonal contribution from La Plata River discharges. Data from three oceanographic cruises are used, in addition to a historical regional bio-optical dataset. Deviations found between measured and estimated concentrations of chlorophyll-a are examined in relation to surface water salinity and turbidity gradients to investigate the source of errors in satellite estimates of pigment concentrations. We observed significant seasonal variability in surface reflectance properties that are strongly driven by La Plata River plume dynamics and arise from the presence of high levels of inorganic suspended solids and coloured dissolved materials. As expected, existing operational algorithms overestimate the concentration of chlorophyll-a, especially in waters of low salinity (S<33.5) and high turbidity (Rrs(670)>0.0012 sr−1). Additionally, an updated version of the regional algorithm is presented, which clearly improves the chlorophyll estimation in those types of coastal environment. In general, the techniques presented here allow us to directly distinguish the bio-optical types of waters to be considered in algorithm studies by the ocean colour community.

Remarks on the morphology and distribution of some rare centric diatoms in southern Brazilian continental shelf and slope waters

This paper provides information on the morphology and occurrence of extant diatoms of the family Asterolampraceae and Azpeitia species of the southernmost Brazilian continental shelf and slope waters in the Southwestern Atlantic Ocean (28 - 34°S), under the influence of Tropical, Subtropical, Subantarctic Waters, terrestrial discharges from La Plata River and Lagoa dos Patos lagoon. Plankton was sampled (20 µm net; vertical hauls) at the same 27 stations in winter 2005 and summer 2007. Among Asterolampraceae, Asteromphalus flabellatus was the most frequent species (57% of samples) observed mainly in winter samples (92%) in Subtropical Shelf Water but also under the influence of La Plata River plume (salinity <35). Lower frequencies were observed for Asterolampra marylandica, Asteromphalus elegans, Asteromphalus heptactis and Spatangidium arachne. Four species of Azpeitia were observed: A. barronii and A. neocrenulata for the first time in the South Atlantic Ocean while A. africana and A. nodulifer had already been registered in equatorial and southern areas of Brazil. All Azpeitia species were rare (19%) in offshore samples (100-200 m depth. Remarks on the morphology based on light and scanning electron microcopy observations are provided along with their distribution in the study area.

Identification guide to some Diaptomid species (Crustacea, Copepoda, Calanoida, Diaptomidae) of "de la Plata" River Basin (South America)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A note on a mineralogical analysis of the sediments associated with the Plata River and Patos Lagoon outflows

Riverine waters bring to seas a variety of suspended materials, which are ultimately deposited on the shelf or exported to the deep ocean. Investigation of the mineralogical contents of these continental-borne constituents on seafloors may reveal valuable information about the environmental conditions in the drainage basin. In this note we report results of X-ray diffraction and other analysis of sediments in bottom samples collected on the continental shelf under influence of the Plata River and the Patos Lagoon, in South America. The analysis reveals that non-clay materials are mostly concentrated south of 33 degrees S, while clay sediments are relatively more abundant further north. We propose that such distributions are controlled by the circulation pattern and water mass distribution of the lower and upper layers, respectively. (C) 2008 Elsevier Ltd. All rights reserved.

Trabajos de marcación de peces en el Río de la Plata

Sampling sites were located at: 1) a coastal area on Buenos Aires harbour where high concentrations of "sábalo" occur year round and which on account of its importance merits a specific program itself; 2) a coastal fringe from Buenos Aires harbour to Quilmes (34° 10' - 58° 10') and 3) different stations within the inner zone of the river, which were covered through a tagging campaign performed as part of an agreement among INIDEP-Argentina, CARP-Argentina, Uruguay, INAPE-Uruguay. At present (Winter 1989) recaptures from the first seven species have been obtained, with a total recovery of 3.81 o/o the highest percentages corresponding to patí, boga, armado and sábalo. (Document contains 25 pages.)

Phylogeography and Pleistocene demographic history of the endangered marsh deer (Blastocerus dichotomus) from the Rio de la Plata Basin

The marsh deer is the largest neotropical cervid with morphological and ecological adaptations to wetlands and riparian habitats. Historically, this now endangered species occupied habitats along the major river basins in South America, ranging from southern Amazonia into northern Argentina to the Parana river delta. This particularly close association with wetlands makes marsh deer an excellent species for studying the effects of Pleistocene climatic changes on their demographic and phylogeographic patterns. We examined mitochondrial DNA variation in 127 marsh deer from 4 areas distributed throughout the Rio de]a Plata basin. We found 17 haplotypes in marsh deer from Brazil, Bolivia and Argentina that differed by 1-8 substitutions in a 601 bp fragment of mitochondrial control region sequence, and 486 bp of cytochrome b revealed only 3 variable sites that defined 4 haplotypes. Phylogeny and distribution of control region haplotypes suggest that populations close to the Pantanal area in central Brazil underwent a rapid population expansion and that this occurred approximately 28,000-25,000 years BP. Paleoclimatic data from this period suggests that there was a dramatic increase for precipitation in the medium latitudes in South America and these conditions may have fostered marsh deer's population growth.

Juan Baltasar Maziel y su contribución a la enseñanza de la filosofía en el Río de la Plata

Se intenta una contribución al conocimiento de la enseñanza de la filosofía en el Colegio de San Carlos de Buenos Aires hacia fines del siglo XVIII. Para ello se examinan las propuestas de Juan Baltasar Maziel (1727-1788) para dicho Colegio en materia de Filosofía, Teología y Derecho. Esta información se complementa con la exposición de otras ideas jurídico-políticas de Maziel, en el contexto de su actividad eclesiástica.

Forjando la frontera. Políticas públicas y estrategias privadas en el Río de la Plata, 1780-1860

Este trabajo trata sobre el rol que tuvo la frontera en la instauración del capitalismo agrario en el Río de la Plata. Mediante un enfoque socio-demográfico, económico y comparativo, se analizan distintas estrategias e itinerarios individuales y familiares llevados a cabo por diversos sectores de la sociedad rural, especialmente los pequeños-medianos productores/propietarios, en el marco de la expansión territorial del norte al sur de la campaña bonaerense desde fines del siglo XVIII a mediados del siguiente. Este proceso fue uno de los factores que coadyuvó al gran crecimiento económico que tuvo la región durante el lapso abordado, sólo comparable al de algunos otros países del continente americano

Las inundaciones en la ciudad de La Plata. Su análisis en relación con las precipitaciones durante las últimas décadas del siglo XX

En la cuenca del Plata, durante las últimas dos décadas del siglo XX, se desarrollaron importantes inundaciones producto de los cambios ocurridos en el sistema climático global y, como el área del Gran La Plata (partidos de Berisso, Ensenada y La Plata) no escapa a este problema, se ha tomado como caso para nuestra investigación. Se analiza la distribución temporal de las precipitaciones en la ciudad de La Plata (provincia de Buenos Aires, Argentina), para el período comprendido entre las últimas décadas del siglo XX y la actualidad. En el Gran La Plata el problema de las inundaciones es resultado de la confluencia de tres factores: las precipitaciones (sobre todo cuando se producen con gran intensidad), las napas freáticas que han aumentado su presión hacia arriba por haberse elevado y la sudestada que provoca la crecida de los ríos. El estudio se realizó considerando los valores diarios de precipitación disponibles para la localidad, brindados por estación meteorológica La Plata Aero, dependiente del Servicio Meteorológico Nacional, y los datos de inundaciones obtenidos del diario "El Día", de circulación local. La variación temporal se estudió a escala anual y mensual, detectándose cambios en monto e intensidad que, además de responder al incremento de las precipitaciones acaecido en la pradera pampeana en las últimas décadas, son una llamada de atención para la planificación de futuros emprendimientos en la ciudad y toma de decisiones en el caso de eventos hidrológicos extremos, como es el caso de las inundaciones. En los resultados de este análisis se observó que las inundaciones en la década 1971 - 1980 fueron 25, y que se incrementaron a 78 en la última década estudiada (1991-2000).

Identidades y alteridades en el Río de la Plata : Una visión histórica desde la banda oriental del "río mar"

Desde un recorrido histórico de "larga duración", en el texto se estudian los itinerarios y factores que han incidido con mayor gravitación en la construcción de la identidad nacional uruguaya, con la referencia de su particular dialéctica con sus alteridades regionales. Se hace especial hincapié en las raíces y en los efectos del signo "antiporteñista" (devenido a menudo en "antiargentinismo") del nacionalismo uruguayo más clásico. En esa perspectiva, se analiza la influencia en estos asuntos de tópicos como el de los cambios producidos en los ejes geopolíticos de la Cuenca platense, en las trayectorias polémicas de los relatos de nación predominantes en la historia uruguaya, en sus perfiles cosmopolitas y en sus alteridades regionales, en la interconexión del tema con los retos de la construcción del "Uruguay internacional". El texto culmina con una reflexión que procura contribuir al señalamiento de algunas raíces históricas de la agenda de contenciosos contemporáneos entre Argentina y Uruguay