Synchronization of particle motion in compressed two-dimensional plasma crystals

The collective motion of dust particles during the mode-coupling induced melting of a two-dimensional plasma crystal is explored in molecular dynamics simulations. The crystal is compressed horizontally by an anisotropic confinement. This compression leads to an asymmetric triggering of the mode-coupling instability which is accompanied by alternating chains of in-phase and anti-phase oscillating particles. A new order parameter is proposed to quantify the synchronization with respect to different directions of the crystal. Depending on the orientation of the confinement anisotropy, mode-coupling instability and synchronized motion are observed in one or two directions. Notably, the synchronization is found to be direction-dependent. The good agreement with experiments suggests that the confinement anisotropy can be used to explain the observed synchronization process.Comment: 6 pages, 4 figure

Review of mangrove foraminifera from the Guaratiba tidal plain, Rio de Janeiro, SE Brazil, collected in the early 70\u27s

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Palynofacies and foraminifera as hidrodynamic indicators of Araguari estuary, Amazon coast, Amapá-Brazil

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Foraminifera and bacterial activity in oil spillimpacted mangrove, Guanabara Bay, Brazil

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Relationship between foraminifera and bacteria in estuarine sediments from Santa Catarina Island, Brazil

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Benthic Foraminifera and Bacterial Activity as a Proxy for Environmental Characterization in Potengi Estuary, Rio Grande do Norte, Brazil

The aim of this study was to identify possible zonation patterns and assess the environmental impact on the Potengi River Estuary, Rio Grande do Norte State, through the distribution of benthic foraminifera associated to bacterial activity and abiotic parameters. Six sediment samples were collected from locations that presented clear signs of pollution. The environment was predominantly anaerobic and fermentation occurred at all sites. Forty-two species of foraminifera were identified. The dominant species were Ammonia tepida and Arenoparrella mexicana, which are known to be opportunistic, and able to adapt to rapidly changing conditions. CCA analyses showed that salinity and organic matter, followed by bacterial carbon, were more strongly linked to organism distribution in the Potengi River Estuary. Dissolved oxygen concentration, temperature and total organic matter were higher at the estuary mouth than at the other sites, creating favorable conditions for foraminiferal growth and allowing the faunistic succession on the upper estuary. As foraminifera assemblages when associated to environmental parameters can be used as efficient proxies for environmental diagnosis, these results suggest that the Potengi Estuary is under great stress from the surrounding urban development

Foraminíferos bentônicos e atividade bacteriana como ferramenta para análise ambiental no Estuário do Rio Pontegi, Rio Grande do Norte, Brasil

The aim of this study was to identify possible zonation patterns and assess the environmental impact on the Potengi River Estuary, Rio Grande do Norte State, through the distribution of benthic foraminifera associated to bacterial activity and abiotic parameters. Six sediment samples were collected from locations that presented clear signs of pollution. The environment was predominantly anaerobic and fermentation occurred at all sites. Forty-two species of foraminifera were identified. The dominant species were Ammonia tepida and Arenoparrella mexicana, which are known to be opportunistic, and able to adapt to rapidly changing conditions. CCA analyses showed that salinity and organic matter, followed by bacterial carbon, were more strongly linked to organism distribution in the Potengi River Estuary. Dissolved oxygen concentration, temperature and total organic matter were higher at the estuary mouth than at the other sites, creating favorable conditions for foraminiferal growth and allowing the faunistic succession on the upper estuary. As foraminifera assemblages when associated to environmental parameters can be used as efficient proxies for environmental diagnosis, these results suggest that the Potengi Estuary is under great stress from the surrounding urban development.Este estudo teve como objetivo estabelecer um modelo de zonação e avaliar o impacto ambiental sofrido pelo estuário do rio Potengi, estado do Rio Grande do Norte, através da distribuição das assembléias de foraminíferos associados à atividade bacteriana e a parâmetros físico-químicos. Seis amostras de sedimento foram coletadas em regiões que apresentavam algum tipo poluição aparente. Predominaram os processos bacterianos anaeróbicos principalmente sulfatoredução no estuário. Foram identificadas quarenta e duas espécies de foraminíferos. As espécies dominantes foram Ammonia tepida e Arenoparrella mexicana, que são conhecidas como oportunistas, pois se adaptam com facilidade as variações ambientais. A análise em CCA mostrou que a salinidade e a matéria orgânica, seguidos pelo carbono bacteriano, conduziram a distribuição dos organismos no estuário. A concentração de oxigênio, temperatura e matéria orgânica total foram mais altas na foz do que em outras estações, criando condições favoráveis ao crescimento de foraminíferos e permitiu uma sucessão faunística em direção ao estuário superior. Assembléias de foraminíferos quando associadas a parâmetros ambientais podem ser usadas como eficientes indicadores para o diagnostico ambiental. Os resultados sugeriram que o estuário do rio Potengi encontra-se sobre condições de grande estresse ambiental provocado pelo desenvolvimento urbano a sua volta

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