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| Registros recuperados: 34 | |
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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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| 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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| Huys, R.; Herman, P.M.J.; Heip, C.H.R.; Soetaert, K.. |
| During a synoptic survey carried out in April-May 1986, 171 localities were sampled in the North Sea as delimited by the Straits of Dover in the south and approximately by the 100m isobath in the north. Meiobenthos included Nematoda, Copepoda, Turbellaria, Gastrotricha, Polychaeta, Oligochaeta, Priapulida, Kinorhyncha, Ostracoda, Halacarida, Isopoda, Tanaidacea, Bryozoa, Cnidaria, Sipunculida, Echiurida, Nemertini and Tardigrada. Nematodes were the dominant group in virtually all stations, their densities ranging from 61 to 4167 individuals. 10cm<sup>-2</sup>. Only in the Southern Bight, where nematode numbers were low, did harpacticoids sometimes represent the dominant meiobenthic taxon. There was a tendency for nematode (and total... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1992 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7250 |
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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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| 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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| 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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| 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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| 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.; 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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| 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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| Registros recuperados: 34 | |
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