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| Registros recuperados: 34 | |
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| Soetaert, K.; Herman, P.M.J.; Middelburg, J.J.. |
| We present a numerical model of sedimentary early diagenetic processes that includes oxic and anoxic mineralization. The model belongs to the new wave of early diagenesis models that account for depth-dependent bioturbation and porosity profiles; it can be used both for calculating steady-state conditions and transient simulation. It was developed to reproduce the cycling of carbon, oxygen, and nitrogen along the ocean margin; it resolves the sediment-depth profiles of carbon, oxygen, nitrate, ammonium, and other reduced substances. Organic carbon is modeled as two degradable fractions with different first-order degradation rates and nitrogen:carbon ratios, to account for the decreasing reactivity and N/C ratio of the organic matter with depth into the... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1996 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=8408 |
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| Soetaert, K.; Herman, P.M.J.; Middelburg, J.J.; Heip, C.H.R.. |
| We test whether organic matter degradability, mixing activity, and total sediment mineralization can be estimated by inversion of a coupled nonlinear numerical steady-state diagenetic model. We use a single data set comprising oxygen, nitrate, ammonium and organic carbon versus depth profiles from a slope station in the Goban Spur area (1034 m, Northeast Atlantic). Based on an extensive sensitivity analysis, it appears that (1) when using all data, the total mineralization rates can be determined with reasonable precision; bioturbation and degradability are less well constrained and (2) total mineralization rates can be determined based on nitrate and oxygen profiles only; estimates of organic matter mixing rates and degradability are refined when... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1998 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=8426 |
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| Li, J.; Vincx, M.; Herman, P.M.J.. |
| A time dynamic model was used to estimate carbon flows through nematodes in an intertidal benthic ecosystem in the Westerschelde Estuary, The Netherlands. The model calibrated the nematode biomass observed from March 1991 to February 1992. The forcing functions of the model included meiobenthos biomass, macrobenthos biomass, bacterial density, chlorophyll-a concentration, and other abiotic data such as temperature and day length. We estimate that the nematode population had a low level of standing stock 249 mg C m(-2), but a high level of carbon flow. It consumed 98 mg C m(-2) d(-1) and produced 22 mg C m(-2) d(-1). Defecation was 73 mg C m(-2) d(-1). Losses in respiration, excretion and natural death were only 3 mg C m(-2) d(-1). The annual P/B was 32 for... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Degradation; Ecology; Marine nematodes; Meiobenthos; Respiration. |
| Ano: 1997 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7296 |
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| Middelburg, J.J.; Soetaert, K.; Herman, P.M.J.; Heip, C.H.R.. |
| The rate and factors controlling denitrification in marine sediments have been investigated using a prognostic diagenetic model. The model is forced with observed carbon fluxes. bioturbation and sedimentation rates, and bottom water conditions. It can reproduce rates of aerobic mineralization, denitrification, and fluxes of oxygen, nitrate, and ammonium. The globally integrated rate of denitrification is estimated by this model to be about 230-285 Tg N yr<sup>-1</sup>, with about 100 Tg N yr<sup>-1</sup> occurring in shelf sediments. This estimate is significantly higher than literature estimates (12-89 Tg N yr<sup>-1</sup>), mainly because of a proposed upward revision of denitrification rates in slope and deep-sea... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1996 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=8415 |
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| Soetaert, K.; Herman, P.M.J.; Middelburg, J.J.. |
| We present a dynamic, numerical model of early diagenetic processes that can be used to examine the response of different organic carbon mineralization pathways, concentration vs. depth profiles, and the resultant fluxes to seasonally varying carbon deposition. We show that there can be substantial temporal variability in sediment-water fluxes as well as in the relative contribution of different organic carbon mineralization pathways and oxygen consumption processes in deep-sea sediments. The timing and amplitude of the sediment response are most sensitive to the reactivity of the organic matter. We show that the fluxes of dissolved substances can be approximated by assuming that these constituents are at steady state with the carbon profiles. The model is... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1996 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=8444 |
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| Herman, P.M.J.; Heip, C.H.R.. |
| The ostracod <i>Cyprideis torosa</i> Jones 1850 is a dominant species in brackish water habitats. To assess its importance, growth and respiration were measured. The shells form an increasing part of total weight as the animals grow but there is no correlation between shell weight and soft parts weight in the adults, indicating that tissue growth is a continuous process in these ostracods. Respiration was measured at 20 °C. The slope of the log-log regression of respiration on dry weight was 0.746, showing that <i>Cyprideis torosa</i> follows the general rule for this relationship. The respiration rate per unit biomass was 0.246 nl O<sub>2</sub> µg<sup>-1</sup> h<sup>-1</sup>, which is low but... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Growth; Respiration; Cyprideis torosa. |
| Ano: 1982 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3382 |
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| Soetaert, K.; Herman, P.M.J.; Kromkamp, J.. |
| Net phytoplankton productivity in the Westerschelde, a relatively deep. highly turbid and eutrophic estuary in the Southwest Netherlands, was examined by means of a 13-compartment dynamic simulation model. The description of the light-Iimited primary production was based on the model of Eilers and Peeters (1988. <i>Ecol. Model.</i>, 42, 185-198). This light limitation was parameterized to the different model compartments by integrating the Eilers-Peeters model over a day and over depth taking into account the morphology of the Westerschelde compartments, the daily fluctuating light regime and characteristics of the photosynthesis-Iight curves of the phytoplankton community. The availability of light to the phytoplankters limited primary... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1994 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=8464 |
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| Soetaert, K.; Herman, P.M.J.; Middelburg, J.J.; Heip, C.H.R.; deStigter, H.S.; van Weering, T.C.E.; Epping, E.; Helder, W.. |
| The influence of sediment mixing on activity versus depth profiles of the radionuclide <sup>210</sup>Pb in the upper 20 cm of the sediments has been investigated along a depth transect (208 m-4500 m, 17 stations) in the OMEX study area (Goban Spur, NE Atlantic Ocean). A hierarchical family of bioturbation/nonlocal exchange models was derived. Each member of the hierarchy includes all processes of the previous model, and adds a one- or two-parameter process. The significance of the additional parameters is tested using a one-tailed <i>F</i>-test. It was found that (1) in five cases there is a significant improvement when direct injection of part of the flux into deeper sediment layers (nonlocal exchange) is added to the diffusive... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Chemical kinetics Continental margins Diffusion Lead 210 Modelling Sediment mixing ANE; Goban Spur. |
| Ano: 1996 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=8450 |
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| Soetaert, K.; Herman, P.M.J.. |
| The net growth rate of marine zooplankton entering the Westerschelde estuary was investigated using an advective-dispersive transport model that simulates zooplankton biomass behaving conservatively in the estuary. Total biomass of marine zooplankters in the Westerschelde was much lower than what would be expected based on transport alone, indicating negative growth rates in the estuary. Including a net consumption term in the transport model allowed the estimation of total net mortality. About 3% of all marine zooplankters that enter the Westerschelde with the flood currents are retained in the estuary, where they die. On average, 5% of the total marine zooplankton biomass in the estuary died per day. Each year a net amount of about 1500 t of zooplankton... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1994 |
URL: http://www.vliz.be/imisdocs/publications/227081.pdf |
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| Registros recuperados: 34 | |
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