Prevendo mudanças climáticas: resposta da meiofauna a mudanças na distribuição espacial de espécies-chave

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Geologia do depósito de ouro de C1-Santaluz no greenstone belt do rio Itapicuru, Brasil

Pós-graduação em Geociências e Meio Ambiente - IGCE

Sistemas petrolíferos especulativos da bacia de Pelotas (offshore do Uruguai)

Pós-graduação em Geociências e Meio Ambiente - IGCE

Laminitos microbiais no membro Crato (Neoaptiano), bacia do Araripe, nordeste do Brasil

Pós-graduação em Geociências e Meio Ambiente - IGCE

Estratigrafia do Andar Alagoas na sub-bacia do Tucano Norte, Bahia

Pós-graduação em Geociências e Meio Ambiente - IGCE

Oscilações climáticas Plio-Pleistocênicas e sua influência na prospecção de ouro na área do garimpo do Manelão (PA)

No garimpo do Manelão, o ouro está associado a veios de quartzo encaixados na seqüência metavulcano-sedimentar São Manoel. No período Plio-Pleistoceno, sob um clima úmido, desenvolveu-se sobre a seqüência São Manoel uma cobertura laterítica autóctone e imatura. Essa cobertura residual contém partículas de ouro com elevada pureza, sugerindo processos de lixiviação da liga Au-Ag ou de remobilização e redeposição do Au em ambiente laterítico. Durante o Pleistoceno, o clima tornou-se árido a semi-árido, favorecendo a erosão parcial da cobertura laterítica, através dos processos coluviais associados a enxurradas periódicas. Esse depósito coluvial recobre o perfíl laterítico, destruindo um possível padrão de dispersão geoquímica do ouro supergênico e prejudicando a prospecção geoquímica de superfície. No final do Pleistoceno e início do Holoceno, o clima úmido retorna, juntamente com os processos de intemperismo, formando stone line e latossolos. As coberturas laterítica e coluvial serviram de área-fonte para os aluviões atuais a subatuais do igarapé São Manoel, onde o ouro ocorre livre nos estratos sedimentares mais basais, formando concentrações da ordem de 10 g/ton.

A New Species of Myxidium (Myxosporea: Myxidiidae), from the Western Chorus Frog, Pseudacris triseriata triseriata, and Blanchard's Cricket Frog, Acris crepitans blanchardi (Hylidae), from Eastern Nebraska: Morphology, Phylogeny, and Critical Comments on Amphibian Myxidium Taxonomy

During March 2001-April 2004, 164 adult anurans of 6 species (47 Rana blairi, 35 Rana catesbeiana, 31 Hyla chrysoscelis, 31 Pseudacris triseriata triseriata, 11 Bufo woodhousii, and 9 Acris crepitans blanchardi) from Pawnee Lake, Lancaster County, Nebraska, were surveyed for myxozoan parasites. Of these, 20 of 31 (65%) P. triseriata triseriata and 1 of 9 (11%) A. crepitans blanchardi were infected with a new species of Myxidium. Myxidium melleni n. sp. (Myxosporea) is described from the gallbladder of the western chorus frog, P. triseriata triseriata (Hylidae). This is the second species of Myxidium described from North American amphibians. Mature plasmodia are disc-shaped or elliptical 691 (400-1,375) × 499 (230-1,200) × 23 (16-35) μm, polysporic, producing many disporic pansporoblasts. The mature spores, 12.3 (12.0-13.5) × 7.6 (7.0-9.0) × 6.6 (6.0-8.0) μm, containing a single binucleated sporoplasm, are broadly elliptical, with 2-5 transverse grooves on each valve, and contain two equal polar capsules 5.2 (4.8-5.5) × 4.2 (3.8-4.5) μm positioned at opposite ends of the spore. Myxidium melleni n. sp. is morphologically consistent with other members of Myxidium. However, M. melleni n. sp. was phylogenetically distinct from other Myxidium species for which DNA sequences are available. Only with improved morphological analyses, accompanied by molecular data, and the deposit of type specimens, can the ambiguous nature of Myxidium be resolved. Guidelines for descriptions of new species of Myxidium are provided.

RP97-362 File It Easy, Find It Fast: A Home Filing System

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Late Pleistocene and Holocene Paleolimnology of Two Mountain Lakes in Western Tasmania

The analysis of diatoms from two lake-sediment cores from southwestern Tasmania that span the Pleistocene-Holocene boundary provides insight about paleolimnological and paleoclimatic change in this region. Both Lake Vera (550 m elevation), in west-central Tasmania, and Eagle Tarn (1,033 m elevation), in south-central Tasmania, have lacustrine records that begin about 12,000 years ago. Despite significant differences in location, elevation, and geologic terrane, both lakes have, had similar, as well as synchronous, limnological histories. Each appears to have been larger and more alkaline 12,000 years ago than at present, and both became shallower through time. Fossil diatom assemblages about 11,500 years old indicate shallow-water environments that fluctuated in pH between acidic and alkaline, and between dilute and possibly slightly saline hydrochemical conditions ( The synchroneity and similar character of the paleolimnological changes at these separate and distinctive sites suggests a regional paleoclimatic cause rather than local environmental effects. Latest Pleistocene climates were apparently more continental and drier than Holocene climates in southwestern Tasmania.

Mesodictyon, A New Fossil Genus of the Centric Diatom Family Thalassiosiraceae from the Miocene Chalk Hills Formation, Western Snake River Plain, Idaho

Three new centric diatom species assigned to a new genus are described from Miocene lacustrine deposits of Idaho. Species of the new genus, Mesodictyon, have the areola cribrum in the middle of the loculus, strutted processes and radiating, non-fasciculated striae. The strutted processes of M. magnum (diameter 60-150 μm) have long (2-3 μm) tubular extensions. The strutted processes of M. fovis (diameter 14-80 μm) are in distinct pits near the junction of the face and mantle. The valve face of M. undulatum (diameter 10-44 μm) is weakly tangentially undulate. Preliminary evidence indicates that Mesodictyon has a wide geographic distribution and may be a useful biostratigraphic marker.

Laminitos microbiais no membro Crato (Neoaptiano), bacia do Araripe, nordeste do Brasil

Pós-graduação em Geociências e Meio Ambiente - IGCE

Estratigrafia do Andar Alagoas na sub-bacia do Tucano Norte, Bahia

Pós-graduação em Geociências e Meio Ambiente - IGCE

Benthic responses to organic matter variation in a subtropical coastal area off SE Brazil

Organic matter quality, expressed as the proportion of chlorophyll a (Chl a) to degraded organic material (i.e. phaeopigments), is known to influence the structure of benthic associations and plays an important role in the functioning of the ecosystem. This study investigates the vertical distribution of microbial biomass, meiofauna and macrofauna with respect to organic matter variation in Ubatuba, Brazil, a southeastern, subtropical coastal area. On three occasions, samples were collected in exposed and sheltered stations, at high and low hydrodynamic conditions. We hypothesize that benthic assemblages will have high meio- and macrofaunal densities and high microbial biomass at the sediment surface at the sheltered site, and lower and vertically homogeneous microbial biomass and densities of meio- and macrofauna are expected at the exposed site. The accumulation of fresh organic matter at the sediment surface was observed at both stations over the three sampling dates, which contributed to the higher densities of meiofauna in the first layers of the sediment column. Macrofauna followed the same trend only at the exposed station, but changes in the number of species, biodiversity and feeding groups were registered for both stations. Microbial biomass increased at the sheltered station over the three sampling dates, whereas at the exposed station, microbial biomass was nearly constant. Physical exposure did not influence organic matter loading at the sites and therefore did not affect overall structure of benthic assemblages, which negates our original hypothesis. Most of the benthic system components reacted to organic matter quality and quantity, but relationships between different-sized organisms (i.e. competition and/or predation) may explain the unchanged microbial profiles at the exposed site and homogeneous vertical distribution of macrofauna at the sheltered site. In conclusion, the high quality of organic matter was a crucial factor in sustaining and regulating the benthic system, but coupled results showed that interactions between micro-, meio- and macrofauna can be highly complex.

Macrofaunal abundance and composition on the West Antarctic Peninsula continental shelf: Evidence for a sediment `food bank` and similarities to deep-sea habitats

To assess the impact and fate of the summer phytoplankton bloom on Antarctic benthos, we evaluated temporal and spatial patterns in macrofaunal abundance and taxonomic composition along a transect crossing the West Antarctic Peninsula (WAP) continental shelf As part of the FOODBANCS project, we sampled three sites at 550-625 m depths during five cruises occurring in November 1999, February-March 2000, June 2000, October 2000 and March 2001. We used a combination of megacore and box-core samplers to take 81 samples, and collected over 30,000 macrofaunal individuals, one of the largest sampling efforts on the Antarctic shelf to date. Comparison of the two sampling methodologies (box core and megacore) indicates similar macrofaunal densities, but with significant differences in taxonomic composition, a reflection of the different spatial scales of sampling. Macrorfaunal abundances on the WAP shelf were relatively high compared to other Antarctic shelf settings. At two of the three sampling sites, macrofaunal abundance remained constant throughout the year, which is consistent with the presence of a sediment `food bank`. Differences were observed in taxonomic composition at the site closest to the coast (Station A), driven by higher abundances of subsurface-deposit feeders. A significant temporal response was observed in the ampharetid polychaetes at Station A, with an abundance peak in the late fall post-bloom period; this may have resulted from juvenile recruitment during the summer bloom. Familial composition of macrofaunal polychaetes on the WAP shelf is more closely related to deep-sea abyssal fauna than to other shelf regions, and we hypothesize that this is a result of both local ecological conditions (low temperatures) and a reflection of historical processes such as extinctions on the Antarctic shelf during previous glacial maxima followed by recolonization from the deep sea. (C) 2008 Elsevier Ltd. All rights reserved.

Trophic structure on the West Antarctic Peninsula shelf: Detritivory and benthic inertia revealed by delta(13)C and delta(15)N analysis

Summer bloom-derived phytodetritus settles rapidly to the seafloor on the West Antarctic Peninsula (WAP) continental shelf, where it appears to degrade relatively slowly, forming a sediment ""food bank"" for benthic detritivores. We used stable carbon and nitrogen isotopes to examine sources and sinks of particulate organic material (POM) reaching the WAP shelf benthos (550-625 m depths), and to explore trophic linkages among the most abundant benthic megafauna. We measured delta(13)C and delta(15)N values in major megafaunal taxa (n = 26) and potential food sources, including suspended and sinking POM, ice algae, sediment organic carbon, phytodetritus, and macrofaunal polychaetes. The range in delta(13)C values (> 14 parts per thousand) of suspended POM was considerably broader than in sedimentary POC, where little temporal variability in stable isotope signatures was observed. While benthic megafauna also exhibited a broad range of VC values, organic carbon entering the benthic food web appeared to be derived primarily from phytoplankton production, with little input from ice algae. One group of organisms, primarily deposit-feeders, appeared to rely on fresh phytodetritus recovered from the sediments, and sediment organic material that had been reworked by sediment microbes. A second group of animals, including many mobile invertebrate and fish predators, appeared to utilize epibenthic or pelagic food resources such as zooplankton. One surface-deposit-feeding holothurian (Protelpidia murrayi) exhibited seasonal variability in stable isotope values of body tissue, while other surface- and subsurface-deposit-feeders showed no evidence of seasonal variability in food source or trophic position. Detritus from phytoplankton blooms appears to be the primary source of organic material for the detritivorous benthos; however, seasonal variability in the supply of this material is not mirrored in the sediments, and only to a minor degree in the benthic fauna. This pattern suggests substantial inertia in benthic-pelagic coupling, whereby the sediment ecosystem integrates long-term variability in production processes in the water column above. Published by Elsevier Ltd.