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1.
Iron-rich concretions are frequently found around plant roots in Tagus estuary (Portugal) where radial delivery of O2 takes place. Salt marsh sediments exhibit cracks that are an additional feature to introduce O2 and other solutes in the upper sediments. Metal concentrations in salt marsh sediments are clearly above the background levels reflecting the anthropogenic sources from a large city with 2.5 million inhabitants, and several industrial centres. In order to evaluate how both oxidised structures influences the redistribution of redox sensitive elements in salt marsh sediments, concretions were collected from roots of Halimione portucaloides below the oxygenated zone. These tubular cylindrical structures were analysed for Fe, Al, Mn, As, and P along 1-cm radial transect in a millimetre scale from the inner part to the adjacent anoxic sediment. In addition, oxidised cracks were analysed for the same spatial resolution, from the sediment–water interface to anoxic layers (2-cm transept). The parallelism between Fe, As, and P concentrations at this microscale is the most noticeable aspect. Iron and As presented very high concentrations in the 4-mm concretions (3.4 mmol g−1 and 3.1 μmol g−1, respectively) and decreased sharply to the host sediment. Oxygen released from roots oxidise the solid sulphides, and the reduced Fe and As are transported towards the root by both diffusion and pore water flow associated with the root water uptake. Subsequently, Fe(III) precipitates and As is retained by sorption and/or coprecipitation. These elements are also enriched in the first 2-mm of oxidised cracks, but in lower concentrations (50% and 30%, respectively). Manganese concentrations in concretions were low (11.8 μmol g−1), indicating that Fe dominates the sediment chemistry. Phosphorus and iron concentrations in the ascorbate fraction were higher in the oxidising surfaces of concretions (10.7 μmol g−1 and 1.6 mmol g−1, respectively) and of cracks (5.1 μmol g−1 and 0.47 mmol g−1). The parallelism of Fe and As distributions includes not only their similar redox chemistries, but also that to phosphate, including control by coprecipitation of the host iron phases. The mechanisms involved in the mobilisation of As and P are however different, whereas As comes from the oxidation of iron sulphides; dissolved P derives from reduction of ferri-hydroxide phases. 相似文献
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Abner Carvalho‐Batista Joo Alberto Farinelli Pantaleo Antonio Leo Castilho Rogrio Caetano da Costa 《Marine Ecology》2019,40(2)
Upwelling areas are among the most productive ecosystems on the planet, influencing the biology of marine organisms. This study investigated the population dynamics of the shrimp Artemesia longinaris in two regions in southeastern Brazil, one inside (Macaé—Rio de Janeiro State) and one outside (Ubatuba—State of São Paulo) the Cabo Frio upwelling area. The aim was to verify the influence of the upwelling phenomenon on the abundance, growth, longevity, size of sexual maturity, and reproductive period of the species. In total, 188,902 individuals were captured at Macaé and 3,461 at Ubatuba. Individuals captured at Macaé showed larger maximum size, higher longevity, and slower growth rate, besides reaching sexual maturity at larger sizes than at Ubatuba. Continuous reproduction was observed in both regions, with juvenile recruitment peaks in spring and summer. Local conditions observed at Macaé were influenced by the Cabo Frio upwelling zone, characterized by productive and cooler waters that are around 20°C during most of the year. The upwelling phenomenon is probably the main factor influencing the population parameters studied here, changing the geographic patterns previously observed for the variation of these parameters in A. longinaris. 相似文献
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Costa PM Caeiro S Lobo J Martins M Ferreira AM Caetano M Vale C DelValls TÁ Costa MH 《Marine pollution bulletin》2011,62(1):55-65
Juvenile Senegalese soles were exposed through 28-day laboratory and field (in situ) bioassays to sediments from three sites of the Sado estuary (W Portugal): a reference and two contaminated by metallic and organic contaminants. Fish were surveyed for ten hepatic histopathological alterations divided by four distinct reaction patterns and integrated through the estimation of individual histopathological condition indices. Fish exposed to contaminated sediments sustained more damage, with especial respect to regressive changes like necrosis. However, differences were observed between laboratory- and field-exposed animals, with the latest, for instance, exhibiting more pronounced fatty degeneration and hepatocellular eosinophilic alteration. Also, some lesions in fish exposed to the reference sediment indicate that in both assays unaccounted variables produced experimental background noise, such as hyaline degeneration in laboratory-exposed fish. Still, the field assays yielded results that were found to better reflect the overall levels of contaminants and physico-chemical characteristics of the tested sediments. 相似文献
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Ricardo Prego Miguel Caetano Carlos Vale Judith Marmolejo-Rodríguez 《Continental Shelf Research》2009
The abundance and distribution of rare earth elements (REE) and their signatures in the Vigo Ria were studied from 50 samples of surface sediments and related to the geological formation in its watershed. The total amount of REE in the Ria is heterogeneous. It ranges from 220 mg kg−1 in the southern middle Ria margin in the vicinity of the Galiñeiro geological shore complex, which contains REE-enriched minerals, to 2 mg kg−1 near the Ria mouth due to dilution with high levels of carbonated biogenic particles (31% of Ca). Rare earth elements of the Ria sediments are considerably enriched in light-REE relative to heavy-REE (a LREE/HREE ratio of 9.7±1.6) and also show a slightly negative Eu-anomaly. Low European shale normalised REE patterns were distinguished in the innermost sediments of Vigo Ria, but were not correlated with Al. This suggests a minor contribution of REE from upstream freshwater inputs to the sediments in the middle Vigo Ria zone. Normalised REE ratios in the middle Ria imply that fine particles enriched in REE may be exported from the Ria to shelf mud patches and REE can be useful as sediment tracers of Ria input on the shelf. 相似文献
5.
Redox Chemistry in the Root Zone of a Salt Marsh Sediment in the Tagus Estuary,Portugal 总被引：5，自引：1，他引：4
Measurements of O2, Fe(II), Mn(II)and HS5 in salt marshsediments in the Tagus Estuary, Portugal, made with a voltammetric microelectrode, reveal strong seasonal differences in pore water composition within the 20~cm deep root zone. In spring, oxygen was below detection limit except close to the sediment surface. Fe(II) was present below 5 cm in concentrations ranging from detection limit to 1700 M. In summer, oxygen was present in the pore water almost to the bottom of the root zone in concentrations ranging from detection limit to more than 100 M. The spatial variability was intense: O2 concentrations as high as 78 M and as low as 25 M existed within 2~mm of each other. Fe(II) was below detection limit except towards the bottom of the root zone. In late fall, oxygen was found to 8 cm depth, but in concentrations lower than in summer, and Fe(II) was present below 9 cm. Mn(II) was found at levels declining from typical values of 200 M in spring to less than 20 M in late fall. With one exception, sulfide was below the detection limit in all measurements. During periods when dissolved Fe(II) is available in the pore water at the same time as 2 is delivered by roots, iron-rich concretions can form on roots. These conditions, which lead to precipitation of iron oxide in the sediment adjacent to roots, exist in spring, when new roots infiltrate anoxic Fe(II) containing sediment. They do not exist in summer, when dissolved Fe(II) is unavailable, or in winter, when oxygen is unavailable. The seasonal redox pattern revealed by the pore water chemistry is driven by the annual cycle of growth and decay of roots. 相似文献
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Geslaine Rafaela Lemos Gonçalves Luana Ferraz da Silveira Palomares Aline Nonato Sousa Gilson Stanski Gustavo Sancinetti Rogerio Caetano da Costa Antonio Leão Castilho 《Marine Ecology》2020,41(4):e12606
The Brazilian coast is home to two species of Majoid crabs: Libinia ferreirae and Libinia spinosa, with similar habits, as they live in symbiosis with the jellyfish Lychnorhiza lucerna during their juvenile stage and dwell on the bottom of the ocean near the coast when adults. This study investigated the spatial and temporal distribution of L. ferreirae and L. spinosa during different ontogenic phases on the south and south-eastern coast of Brazil, between latitudes 22º and 27ºS. Our results showed that both species have different distributions during their development in the three studied regions. Libinia ferreirae were more abundant associated with jellyfish, and L. spinosa were more abundant in the free-living phase. Environmental factors, especially temperature and salinity, for associated and free-living crabs, respectively, are the main factors that need to be supported for the establishment of these specimens. We were able to identify that the presence or absence of hosts (given the ecological interactions between the species) is determinant in finding the associated crabs. Geographical variations (morphology of the regions, marine currents and the strength of the tide) are linked directly to the movement of the jellyfish hosts to the coast, influencing the abundance of L. fereirae and L. spinosa populations and affecting their distribution patterns. We can infer that both species are connected with other populations because of the association with the jellyfish, crabs could be passively transported along the south and south-eastern coast of Brazil, maintaining the connection between metapopulations. 相似文献
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The systematic collection of benthic organisms in tidal flats of coastal lagoons should be taken into account for the management of these systems, once sediment disturbance affects biogeochemical processes by favouring pore water renewal during tidal inundation. The objective of the present work was to evaluate the effects of infauna harvesting on the phosphorus dynamics of muddy and sandy intertidal areas in the Ria Formosa. Sediment cores and overlying water were collected during August 2000 and February 2001 from reworked and undisturbed sediment before and after flooding. Results obtained showed that during the first minutes of flooding there was a marked decrease of phosphate in pore water of disturbed sediments. However, phosphate tidal fluxes from sandy sediment were clearly higher (17 nmol cm(-2) d(-1) in summer and 3 nmol cm(-2) d(-1) in winter) than in muddy sediment (0.4 nmol cm(-2) d(-1) in summer and -0.01 nmol cm(-2) d(-1) in winter). After muddy sediment disturbance concentrations of iron oxides increased quickly (from 5 to 16 micromol g(-1)) and phosphate was sorbed onto these iron oxides, resulting in a buffering of phosphate pore water concentrations at low values in the oxidized sediment zone. The estimated P-output from muddy sediment decreased one to two orders of magnitude after sediment disturbance in contrast to sandy sediments in which the impact of infauna harvesting was minimal. Consequently, the P-cycle is influenced by the disruption of muddy habitats in tide-driven systems. Such information could be useful for the management of the lagoon. 相似文献
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Lena Virgínia Soares Monteiro Jorge Silva Bettencourt Caetano Juliani Tolentino Flvio de Oliveira 《Gondwana Research》2007,11(3):362-381
The Vazante Group hosts the Vazante nonsulfide zinc deposit, which comprises high-grade zinc silicate ore (ZnSiO4), and late-diagenetic to epigenetic carbonate-hosted sulfide-rich zinc deposits (e.g. Morro Agudo, Fagundes, and Ambrósia). In the sulfide-rich deposits, hydrothermal alteration involving silicification and dolomitization was related with ground preparation of favorable zones for fluid migration (e.g. Fagundes) or with direct interaction with the metalliferous fluid (e.g. Ambrósia). At Vazante, hydrothermal alteration resulted in silicification and dolomite, siderite, jasper, hematite, and chlorite formation. These processes were accompanied by strong relative gains of SiO2, Fe2O3(T), Rb, Sb, V, U, and La, which are typically associated with the nonsulfide zinc mineralization. All sulfide-rich zinc ores in the district display a similar geochemical signature suggesting a common metal source from the underlying sedimentary sequences.Oxygen and carbon isotope compositions of hydrothermally altered rocks reveal a remarkable alteration halo at the Vazante deposit, which is not a notable feature in the sulfide-rich deposits. This pattern could be attributed to fluid mixing processes involving the metalliferous fluid and channelized meteoric water, which may control the precipitation of the Vazante nonsulfide ore. Sulfide deposition resulted from fluid–rock interaction processes and mixing between the ascending metalliferous fluids and sulfur-rich tectonic brines derived from reduced shale units. 相似文献