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  • 1
    Digitale Medien
    Digitale Medien
    Porewater dynamics and the formation of iron sulfides in a mangrove ecosystem, Sepetiba Bay, Brazil (1999)
    Springer
    Mangroves and salt marshes 3 (1999), S. 85-93 
    Details
    ISSN: 1572-977X
    Schlagwort(e): Brazil ; iron sulfides ; mangroves ; porewater ; Sepetiba Bay
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Porewater dynamics and the formation of iron sulfides were studied in the Brazilian mangrove. Porewater samples were collected during tidal cycles using in situ equipment and physical–chemical and chemical data were obtained. The advective transport of porewater by tidal currents was found to be more effective between 0 and 5 cm depth than below 15 cm. The diffusive input of atmospheric oxygen during low tides resulted in oxidation of porewater dissolved sulfides. Thermodynamic considerations identified pyrite as the main iron sulfide forming at this depth, and the amorphous iron hydroxides are probably the main iron source. Below 15 cm depth, irregular root distribution underground and benthic faunal bioturbation caused considerable spatial variation in a small scale (20 cm). The correlation between alkalinity and total dissolved sulfide suggests that the main pathway for organic matter decomposition is sulfate reduction. Formed in the highly sulfidic diagenetic zone, the dissolved iron went through iron sulfide formation process. Crystalline iron oxides like hematite and magnetite may constitute an important iron source below 15 cm, whereas pyrite is still the most probably occurring iron sulfide, according to thermodynamic considerations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009960218748
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    A versatile in situ sediment pore water sampler (1997)
    Springer
    Mangroves and salt marshes 1 (1997), S. 73-78 
    Details
    ISSN: 1572-977X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A simple versatile in situ sampler for extracting pore water fromsediments has been developed, working as a convective samplingdevice (harpoon) or a solute diffusion device (peeper). Used asa harpoon, it avoids modification of vertical gradients of soluteconcentrations, because no suction is applied. Used as a peeper,because of its higher diffusion/volume ratio, its contact timewith the sediment is reduced by 50%, compared to that of theconventional peeper, which makes a higher sampling rate possible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009988000065
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Benthic influence on the metabolism of a shallow tropical lagoon (Lagoa da Barra, Brazil) (1998)
    Springer
    Hydrobiologia 373-374 (1998), S. 89-100 
    Details
    ISSN: 1573-5117
    Schlagwort(e): tropical lagoon ; autotrophic activity ; heterotrophic activity ; pelagic carbon metabolism ; benthic carbon metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Pelagic and benthic carbon metabolism in the shallow tropical Barra Lagoon was studied weekly between 1990 and 1993, in periods characterized by temporary nitrogen limitation, fish kills and transitory colonization of the bottom by macro-algae. Diurnal and nocturnal metabolic rates were measured by monitoring changes in CO2 content in entire water columns (free water and waters incubated in plexiglass tubes with and without inclusion of sediment). Total community carbon metabolism exhibited a marked autotrophism and high short term changes, dampening seasonal trends. Autotrophism and heterotrophism of the lagoon were controlled by phytoplankton biomass variations. In the presence of sediment, diurnal net benthic production was 11 to 64% of total diurnal net production, and nocturnal net benthic mineralization was 21 to 52% of total nocturnal net mineralization. The imbrication between the pelagic and benthic organic carbon cycles regulated carbon metabolism of the total community. A severe temporary nitrogen limitation, a fish kill and a temporary shift in primary producers did not substantially change metabolic rates because appropriate shifts occurred from the pelagic carbon cycle to the benthic carbon cycle, and vice-versa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017048128271
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Trophic state and water turn-over time in six choked coastal lagoons in Brazil (1991)
    Springer
    Biogeochemistry 14 (1991), S. 149-166 
    Details
    ISSN: 1573-515X
    Schlagwort(e): chlorophyll-a ; flushing half-life ; nutrients ; phosphorus loading ; trophic state ; water turn-over time
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Comparison of total phosphorus and chlorophyll-a concentration, nutrient loading, and water turn-over time in six shallow choked lagoons along the coast of the state of Rio de Janeiro, Brazil, established that water turn-over time is related to the trophic state of the lagoons with additional anthropogenic nutrient loading affecting this relationship. Turnover time was calculated as a flushing half-life from rainfall, evaporation, runoff, and tidal exchange data, and trophic state was calculated from the quantity and quality of dissolved inorganic nutrients, total phosphorus, and chlorophyll-a standing stock. Flushing half-life of the lagoons ranged between 1 and 27 days, annual phosphorus areal loading from 3 to 18 mg m−2d−1, and chlorophyll-a standing stock from 6 to 160 mg M−2
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00002903
    Standort Signatur Einschränkungen Verfügbarkeit
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