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| Registros recuperados: 34 | |
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| Herman, P.M.J.; Heip, C.H.R.; Guillemijn, B.. |
| The secondary production of the harpacticoid copepod <i>Tachidius discipes</i> Giesbrecht 1881 was estimated during spring 1979. The population was sampled every 3 d. Three generation peaks were observed. These were clearly distinct in the first copepodite stages, but gradually showed more overlap in older stages. Production of copepodites and adults was estimated in 2 ways: (1) Peaks were separated and the forward shifting of peaks in consecutive stages was used to estimate stage durations; (2) the size frequency method was applied. Both estimates of the production of copepodites and adults are in good agreement: 1.10 g dwt m<sup>-2</sup> and 1.02 g dwt m<sup>-2</sup>. Egg production amounts to 0.31 g dwt... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Secondary production Tachidius discipes Giesbrecht; 1881. |
| Ano: 1984 |
URL: http://www.vliz.be/imisdocs/publications/238548.pdf |
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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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| 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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| Middelburg, J.J.; Barranguet, C.; Boschker, H.T.S.; Herman, P.M.J.; Moens, T.; Heip, C.H.R.. |
| At two intertidal sites (one sandy and one silty, in the Scheldt estuary, The Netherlands), the fate of microphytobenthos was studied through an in situ <sup>13</sup>C pulse- chase experiment. Label was added at the beginning of low tide, and uptake of <sup>13</sup>C by algae was linear during the whole period of tidal exposure (about 27 mg m<sup>-2</sup> h<sup>-1</sup> in the top millimeter at both sites). The <sup>13</sup>C fixed by microphytobenthos was rapidly displaced toward deeper sediment layers (down to 6 cm), in particular at the dynamic, sandy site. The residence times of microphytobenthos with respect to external losses (resuspension and respiration) were about 2.4 and 5.6 d at the... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: ANE; Netherlands; Westerschelde; Molenplaat. |
| Ano: 2000 |
URL: http://www.vliz.be/imisdocs/publications/54615.pdf |
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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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| Heip, C.H.R.; Goosen, N.K.; Herman, P.M.J.; Kromkamp, J.; Middelburg, J.J.; Soetaert, K.. |
| The question is reviewed whether a balance exists between production and consumption of biological particles in temperate tidal estuaries and what the relationships are between the magnitude of production and consumption processes and system carbon metabolism. The production terms considered are primary production by phytoplankton, microphytobenthos, macroalgae and vascular plants and the chemoautotrophic production, mainly by nitrifying bacteria. The consumption terms are generalized by considering pelagic and benthic mineralization, but major consumer compartments, heterotrophic bacteria, zooplankton, meiobenthos, and macrobenthos are considered in detail. The proposition that estuaries are heterotrophic systems, and become more so when nutrient inputs... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1995 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=8311 |
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| Herman, P.M.J.; Vranken, G.; Heip, C.H.R.. |
| The direct estimation of energy flow through marine meiobenthic populations poses several difficulties, mainly relating to sampling problems. The usefulness of some indirect estimation methods is discussed. Direct production estimates and respiration measurements for three brackish water crustacean populations are given, indicating a relative constant proportion between population production and respiration.The production: assimilation ratio for these populations fluctuates between 0.3 and 0.4. This is contrasted to literature data revealing much higher production: assimilation ratios as determined in the laboratory for nematode populations. Using data on laboratory cultures of the nematode <i>Monhystera disjuncta</i> some factors that can... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Energy flow; Meiobenthos. |
| Ano: 1984 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3265 |
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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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| Herman, P.M.J.; Heip, C.H.R.. |
| The predictability of temporal changes was analysed in the population density of three meiobenthic copepod species, and for three parameters characterizing this community. For <i>Paranychocamptus nanus</i> and <i>Tachidius discipes</i> a large part of the variation in time scales longer than 1 year is explainable as cyclic factors. In <i>P. nanus</i> clear cycles with periods of 2 years and 1.5 years were found. These cyclic factors can be extrapolated for prediction. In <i>Canuella perplexa</i> almost all the variation was due to unpredictable long-term drift. Community parameters are generally better predicted than population densities. In our data set total density of the copepods was the best parameter to... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Meiobenthos; Monitoring; Prediction; Time series; Copepoda [copepods]. |
| Ano: 1986 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3238 |
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| Tackx, M.L.M.; Herman, P.M.J.; Van Rijswijk, P.; Vink, M.; Bakker, C.. |
| Phytoplankton and zooplankton biomass distributions were calculated on a carbon basis for the inland part of the Oosterschelde, in the period before (1983), during (1984, 1986) and after (1987, 1988) the construction of the storm-surge barrier. In all years studied, both phytoplankton and zooplankton distributions are very irregular, and little consistent patterns emerge. The data were used to test the model of Sheldon et al. (1977). The observed standing stock ratios of zooplankton to phytoplankton agree with the model predictions in 1983, and are slightly higher during the period 1984-1987. In 1988, the model predictions are very different from the observed values, because of important changes in the zooplankton species abundance occurring in this year. |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Particles; Particles; Particles; Plankton; Size distribution; Spectra; Zooplankton; Netherlands. |
| Ano: 1994 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=2675 |
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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.. |
| 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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| 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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| Herman, P.M.J.; Heip, C.H.R.. |
| The dependency of respiration rate on body weight at 20°C was determined for five meiobenthic copepods from a brackish-water habitat. The respiration rate of the four smaller species was generally high, = 10-14 nl O<sub>2</sub>.h<sup>-1</sup>.µg dry wt<sup>-1</sup>, but was much lower for larger species, <i>Canuella perplexa</i> T. & A. Scott 1893 (2-3 nl O<sub>2</sub>.h<sup>-1</sup>.µg<sup>1</sup>). This pattern is discussed in terms of the adaptive behaviour of the populations. The significance of respiration rates in the evolution of populations is illustrated by differences between the respiration rates of Belgian <i>Tachidius discipes</i> Giesbrecht... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Respiration; Copepoda [copepods]; Harpacticoida. |
| Ano: 1983 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3288 |
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| Registros recuperados: 34 | |
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