Magnetic fingerprint of the late Holocene inception of the Río de la Plataplume onto the southeast Brazilian shelf.

Measurement of changes in the assembly ofmagnetic particles in sediment records is useful both for paleoclimatic and paleoceanographic reconstructions and for assessing provenance and pathways of sediment transport. In this study we provide detailed rockmagnetic analysis along with scanning electron microscopy (SEM), Ti/Ca ratio and particle size distribution of the decarbonated fraction of sediments to trace terrigenous source changes during the last 6 cal kyr BP in core 7610 collected on the SE Brazilian continental shelf. Magnetic mineralogy data indicate a gradual shift between two distinct sources of sediments: (1) dust fromsouthern South America (Patagonia, central western Argentina and Puna-Altiplano plateau) and (2) sediments eroded fromtheweathered volcanics of Paraná Basin. Thesematerials reached the continental margin off Argentina and Uruguay by different pathways andwere transported northward by the Brazilian Coastal Current (BCC). The chronology of events related to the environmental record of core 7610 indicates that between 6 and 4.7 cal kyr BP dry conditions over continental South America resulted in enhanced eastward eolian transport of the Argentinean loess and a limited discharge of the RdlP river load into the Atlantic Ocean. At this time, the sedimentary magnetic fraction that reached the SE Brazilian shelf reflect predominantly loessic sources transported from the Pampean terraces to the Argentinean and Uruguay shelves and then distributed northward by the shelf current system. From 4.7 to 2 cal kyr BP the climate became gradually wetter over the continent and the contribution of oxidized phases from the weathered Paraná Basin (mainly from the basaltic and acidic volcanics) started to become important. This change in climate overlaps in time awith the late Holocene sea level fall recorded along the SE South American coast. Later, from2 up to 0.9 cal kyr BP even wetter conditions were prevalent in S and SE South America, and the RdlP sedimentary load became themain source of sediments transported to the SE Brazilian shelf by the BCC. The magnetic record of core 7610 reported here together with other paleoenvironmental tracers (palynology, geochemistry and stable isotopes) thus indicates that the inception of the RdlP plume onto the SE Brazilian shelf started as early as 4.7 cal kyr BP and has been strengthened since then mostly due to changes in precipitation over South America and to a smaller extent by sea-level changes

The Southwestern Atlantic Ocean: present and past marine sedimentation

Marine Geology is one of the most recently developed branches of the geological sciences, which began to actively evolve after the mid XX century when the “modern” research techniques for obtaining really trustworthy data from the ocean floor and subbottom appeared, such as high resolution bathymetry, seismic, sea-bottom profilers, submarine photography and sea-floor sampling. In the Southwestern Atlantic continental margin the first great impulse occurred in the 1950´s and 1960´s by the agreement achieved between the Lamont-Doherty Earth Observatory (LDEO) of the Columbia University (USA) and the Argentina Hydrographic Survey (SHN). It was a pioneering work at a global scale as it represented a leading case for developing marine seismic technologies at sea useful for understanding the major oceanic sedimentary processes and the subbottom structure (e.g., Ahrens et al., 1971). Also in the 1960’s, another major agreement between CONICET (Argentina) and Woods Hole Oceanographic Institution (USA) allowed the acquisition by the Argentine government of the former research vessel Atlantis (later named, under Argentine flag, as “El Austral” and presently “Dr. Bernardo Houssay”), which was the first ship specifically built for oceanographic research and one of the most famous and internationally recognized because of its contribution to the knowledge of the ocean floors between 1939 and the latest 1950´s, including the findings that initially supported the continental drift´s theory. Following that, several national initiatives helped to advance in the development of marine geological sciences in the region. Among the most important we can mention: the REMAC Project in Brazil in the 1960’s and 1970’s -that allowed the participation of several Brazilian universities as well as North American research institutions-, the agreement between the SHN and the Uruguayan Oceanographic, Hydrographic and Meteorological Survey (SOHMA) in the 1970 ´s and 1980´s under the framework of the Administrative Commission for the Río de la Plata (CARP), the agreement between SOHMA and the Rio Grande do Sul University (URGS, Brazil) in the 1980´s and 1990´s, and the Projects MARGEN in Argentina and REVIZEE in Brazil - that began in the 1980´s-. The highly significant results that arose from those agreements and national projects impulsed the Argentina-Brazil-Uruguay geological communities to focus on the importance of deeply studying the ocean environments in the region and the needs to organize working teams aimed at developing research programs on the subject

The effect of age on the acquisition and selection of cancer driver mutations in sun-exposed normal skin

BACKGROUND: The accumulation of somatic mutations contributes to ageing and cancer. Sunlight is the principal aetiological factor associated with skin cancer development. However, genetic and phenotypic factors also contribute to skin cancer risk. This study aimed at exploring the role of photoaging, as well as other well-known epidemiological risk factors, in the accumulation of somatic mutations in cancer-free human epidermis. MATERIAL AND METHODS: We deeply sequenced 46 genes in normal skin biopsies from 127 healthy donors, from which phenotypic data (including age, pigmentation-related genotype and phenotype) and sun exposure habits were collected. We determined the somatic mutational burden, mutational signatures, clonal selection and frequency of driver mutations in all samples. RESULTS: Our results reveal an exponential accumulation of UV-related somatic mutations with age, matching skin cancer incidence. The increase of mutational burden is in turn modified by an individual's skin phototype. Somatic mutations preferentially accumulated in cutaneous squamous cell carcinoma (cSCC) cancer genes and clonally expanded with age, with distinct mutational processes underpinning different age groups. Our results suggest loss of fidelity in transcription-coupled repair later in life. CONCLUSION: Our findings reveal that aging is not only associated with an exponential increase in the number of somatic mutations accumulated in normal epidermis, but also with selection and expansion of cancer-associated mutations. Aged, sun-exposed normal skin is thus an extended mosaic of multiple clones with driver mutations, poised for the acquisition of transforming events

The response of benthic foraminifera to pollution and environmental stress in Ria de Aveiro (N Portugal)

This work evaluates the quality of the sediment in Ria de Aveiro, a coastal lagoon located at N of Portugal that is under strong anthropic influence, and the effects of the contamination on benthic foraminifera. The initial approach for measuring pollution was done through the load pollution index (LPI), based on As, Cd, Cr, Cu, Ni, Pb and Zn concentrations, and determined by total digestion of the sediments (TDS). This information was complemented by conducting a metal fractionation technique (sequential chemical extraction - SCE) in some of the most contaminated samples in order to define the relevance of different metal bearing- phases (exchangeable cations adsorbed by clay and co-precipitated with carbonates, absorbed by organic matter and retained in the mineralogical phase) and to evaluate the toxic heavy metal availability. Multivariable statistical analyses were carried out taking into consideration the geochemical results, as well as the biotic (percentage of species/groups of species; foraminifer abundance and diversity) and abiotic variables, such as sediment content in mud, total organic carbon (TOC) and Eh. SCE results show that most of the element concentration in the sediments is retained in the resistant mineralogical phase. However, the higher bioavailability of some toxic elements, such as As, Cd, Cu, Hg, Ni, Pb and Zn, found in Laranjo Bay, Aveiro City, Aveiro Harbours and Espinheiro Channel, have a generic negative impact on benthic foraminifera of the Aveiro lagoon. Differential sensitivity of benthic foraminifera to high concentrations of heavy metals may exist. quinqueloculina seminulum, for instance, seems to be more tolerant to higher bioavailable concentrations of Pb and Cu than Ammonia tepida or Haynesina germanica. Both species were previously considered to be the most heavy metal-tolerant foraminifer species. This study confirmed the use of benthic foraminifera as an important tool for the evaluation of the environmental quality of an ecosystem and for monitoring and restoring it.FCT (Portugal) [POCTI/ECM/59958/2004]; Geobiotec Research Centre, of Aveiro Universit

An extensive reef system at the Amazon River mouth

Large rivers create major gaps in reef distribution along tropical shelves. The Amazon River represents 20% of the global riverine discharge to the ocean, generating up to a 1.3 x 10(6)-km(2) plume, and extensive muddy bottoms in the equatorial margin of South America. As a result, a wide area of the tropical North Atlantic is heavily affected in terms of salinity, pH, light penetration, and sedimentation. Such unfavorable conditions were thought to imprint a major gap in Western Atlantic reefs. We present an extensive carbonate system off the Amazon mouth, underneath the river plume. Significant carbonate sedimentation occurred during lowstand sea level, and still occurs in the outer shelf, resulting in complex hard-bottom topography. A permanent near-bottom wedge of ocean water, together with the seasonal nature of the plume's eastward retroflection, conditions the existence of this extensive (similar to 9500 km(2)) hard-bottom mosaic. The Amazon reefs transition from accretive to erosional structures and encompass extensive rhodolith beds. Carbonate structures function as a connectivity corridor for wide depth-ranging reef-associated species, being heavily colonized by large sponges and other structure-forming filter feeders that dwell under low light and high levels of particulates. The oxycline between the plume and subplume is associated with chemoautotrophic and anaerobic microbial metabolisms. The system described here provides several insights about the responses of tropical reefs to suboptimal and marginal reef-building conditions, which are accelerating worldwide due to global changes.Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Coordenadoria de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERS)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)BrasoilMCTIBrazilian NavyU.S. NSFGordon and Betty Moore Foundation (GBMF)Univ Fed Rio de Janeiro UFRJ, Inst Biol, BR-21941599 Rio De Janeiro, RJ, BrazilUniv Fed Rio de Janeiro, COPPE, Inst Alberto Luiz Coimbra Posgrad & Pesquisa Engn, Lab Sistemas Avancados Gestao Prod, BR-21941972 Rio de Janeiro, RJ, BrazilInst Pesquisas Jardim Bot Rio de Janeiro, BR-22460030 Rio De Janeiro, RJ, BrazilUniv Sao Paulo, Inst Oceanog, BR-05508120 Sao Paulo, SP, BrazilUniv Fed Espirito Santo, Dept Oceanog, BR-29199970 Vitoria, ES, BrazilUniv Estadual Norte Fluminense, Lab Ciencias Ambientais, Ctr Biociencias & Biotecnol, BR-28013602 Campos Dos Goytacazes, RJ, BrazilUniv Fed Fluminense, Inst Geociencias, BR-24210346 Niteroi, RJ, BrazilUniv Fed Fluminense, Inst Biol, BR-24210130 Niteroi, RJ, BrazilUniv Fed Rio de Janeiro, Museo Nacl, BR-20940040 Rio De Janeiro, RJ, BrazilFed Univ Para, Inst Estudos Costeiros, BR-68600000 Braganca, PA, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, BR-11070100 Santos, SP, BrazilUniv Fed Pernambuco, Dept Oceanog, BR-50670901 Recife, PE, BrazilUniv Georgia, Dept Marine Sci, Athens, GA 30602 USAUniv Fed Paraiba, BR-58297000 Rio Tinto, PB, BrazilUniv Estadual Santa Cruz, Dept Ciencias Biol, BR-45650000 Ilheus, BA, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, BR-11070100 Santos, SP, BrazilU.S. NSF: OCE-0934095GBMF: 2293GBMF: 2928Web of Scienc