Ecosystem responses in the Rhine-Meuse delta during two decades after enclosure and steps toward estuary restoration     

Henk Smit  Gerard van der Velde  Rob Smits  Hugo Coops 《Estuaries and Coasts》1997,20(3):504-520

Changes in hydrology, and developments in morphology, water quality, and ecology of the Rhine-Meuse estuary after its enclosure in 1970 are analyzed on the basis of existing monitoring data. Annual averages of ammonium, nitrate plus nitrite, total phosphate, total lead, and chlorophyll-a concentrations as well as transparency of the water are presented. Abundances of some water bird species are given for the period 1970–1993, and the relative fish biomass for the period 1971–1988 is discussed. The gradual evolution led toward the dominance of bream. The area has developed toward a system with generally low natural ecological values. Ecological impacts of present sluice management are discussed and include the accumulation of contaminated sediments, disappearance of intertidal areas and nursery grounds for fish, disturbance of fish migration, and less mixing of river and seawater. Recent policy developments have brought the present management of the Haringvliet sluices back in to discussion. A recent policy document has presented several management alternatives, including partial and complete reopening of the sluices to permit saltwater intrusion. Three management options are compared in terms of costs and ecological benefits. It is concluded that a complete reopening, and thus a partial restoration of the estuarine characteristics, is most beneficial for the ecosystems of the area itselt, for the upstream Rhine and Meuse rivers, and for the adjacent North Sea, but costs amount to about 600 million US $.  相似文献   

The Cenozoic evolution of the Roer Valley Rift System integrated at a European scale     

Laurent Michon  Ronald T. Van Balen  Olivier Merle  Henk Pagnier 《Tectonophysics》2003,367(1-2):101-126

The Roer Valley Rift System (RVRS) is located between the West European rift and the North Sea rift system. During the Cenozoic, the RVRS was characterized by several periods of subsidence and inversion, which are linked to the evolution of the adjacent rift systems. Combination of subsidence analysis and results from the analysis of thickness distributions and fault systems allows the determination of the Cenozoic evolution and quantification of the subsidence. During the Early Paleocene, the RVRS was inverted (Laramide phase). The backstripping method shows that the RVRS was subsequently mainly affected by two periods of subsidence, during the Late Paleocene and the Oligocene–Quaternary time intervals, separated by an inversion phase during the Late Eocene. During the Oligocene and Miocene periods, the thickness of the sediments and the distribution of the active faults reveal a radical rotation of the direction of extension by about 70–80° (counter clockwise). Integration of these results at a European scale indicates that the Late Paleocene subsidence was related to the evolution of the North Sea basins, whereas the Oligocene–Quaternary subsidence is connected to the West European rift evolution. The distribution of the inverted provinces also shows that the Early Paleocene inversion (Laramide phase) has affected the whole European crust, whereas the Late Eocene inversion was restricted to the southern North Sea basins and the Channel area. Finally, comparison of these deformations in the European crust with the evolution of the Alpine chain suggests that the formation of the Alps has controlled the evolution of the European crust since the beginning of the Cenozoic.  相似文献   

Long-term fluctuations in fish recruit abundance in the western Wadden Sea in relation to variation in the marine environment   总被引：1，自引：0，他引：1  

Philippart  Catharina J. M.; Lindeboom  Han J.; van der Meer  Jaap; van der Veer  Henk W.; Witte  Johannes IJ. 《ICES Journal of Marine Science》1996,53(6):1120-1129

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Tolerance of five species of tropical marine mussels to continuous chlorination   总被引：5，自引：0，他引：5  

Rajagopal S  Venugopalan VP  Van der Velde G  Jenner HA 《Marine environmental research》2003,55(4):277-291

The paper examines the relative lethal and sublethal response of five important tropical marine mussels (Perna viridis, Perna perna, Brachidontes striatulus, Brachidontes variabilis and Modiolus philippinarum) to different chlorine concentrations varying from 0.25 to 15 mg l(-1). The mussels were observed to co-exist in the cooling water circuits of a coastal power station that adopted intermittent chlorination as a fouling control technique. The five mussel species showed, in response to chlorination, 100% mortality at significantly different exposure times, indicating significant species-specific variability in chlorine tolerance. For example, at 1 mg l(-1) residual chlorine, B. variabilis and P. viridis took 288 and 816 h, respectively, to achieve 100% mortality. The time taken for 100% mortality decreased with increasing chlorine residual concentration. The effect of mussel size (= mussel age) of P. viridis, P. perna, B. striatulus and M. philippinarum on mortality was significant between 1 and 5 mg l(-1) residual chlorine, with larger mussels showing greater resistance than smaller ones. All mussel species showed progressive reduction in physiological activities when chlorine residuals were increased from 0 to 1 mg l(-1). However, species-specific differences in the relative rate of physiological activities were observed. Accordingly, relative reduction in physiological activities in response to chlorination was the lowest in P. viridis and the highest in B. variabilis. The data clearly indicate significant differences in the lethal and sublethal responses of the five mussel species to chlorination. The results, therefore, suggest that for effective fouling control, chlorine treatment against mussels has to be employed judiciously, depending on the mussel species involved.  相似文献   

Changes in abundance of demersal fish species in the North Sea between 1906-1909 and 1990-1995   总被引：4，自引：0，他引：4  

Rijnsdorp  Adriaan D.; van Leeuwen  Piet I.; Daan  Niels; Heessen  Henk J. L. 《ICES Journal of Marine Science》1996,53(6):1054-1062

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Chlorination by-products in chlorinated cooling water of some European coastal power stations     

H.A. Jenner  C.J.L. Taylor  M. van Donk  M. Khalanski 《Marine environmental research》1997,43(4):279-293

Chlorination by-products (CBPs) are formed as a result of the cnlorination of power station cooling water for anti-fouling purposes. Their production was studied at 10 coastal power stations in the UK, France and The Netherlands. Three categories of CBPs were determined: trihalomethanes; haloacetonitriles; and halophenols. Bromoform was the CBP most abundantly present in the effluents of all 10 power stations. At a mean chlorine dosage of 0.5–1.5 mg/litre (as Cl₂) the mean bromoform concentration was 16.32 ± 2.10 μg/litre. The CBP found in second highest concentrations was dibromoacetonitrile (DBAN) with mean concentrations of 1.48 ± 0.56 μg/litre. Other CBPs detected were dibromochloromethane, bromodichloromethane and 2,4,6-trichlorophenol; concentrations of these three compounds were very low (< 1 μg/litre). At those sites at which bromoform was measured in the dispersing effluent plume it was found to behave as a conservative parameter (Significant direct correlation with plume ΔT).  相似文献   

Competition between topography- and compaction-driven flow in a confined aquifer: Some analytical results   总被引：1，自引：0，他引：1  

Henk Kooi 《Hydrogeology Journal》1999,7(3):245-250

 An analysis is presented of the competition between topography- and compaction-driven flow in a confined aquifer. The aquifer crops out and is unconfined in an area with an elevated water table. In the absence of compaction, the elevated water table drives the flow toward areas with a lower water table, and leakage occurs from the aquifer through an overlying aquitard. Under these conditions, recharge occurs in the outcrop area. When sedimentation occurs above the aquifer away from the outcrop area, compaction tends to reverse the flow direction in the aquifer, causing expulsion of groundwater in the outcrop area. The actual flow field arises from the competition between the two driving mechanisms. An analytical expression for the combined flow field is derived in which the contribution from both mechanisms is apparent. The expression is useful as a practical guideline for estimating whether or not compaction can be safely ignored in regional groundwater-flow studies of confined aquifers. Received, July 1998 / Revised, February 1999 / Acccepted, February 1999  相似文献   

Petrologic implications of trace element variation in clinopyroxene megacrysts from the Nógrád volcanic province, north Hungary: a study by laser ablation microprobe-inductively coupled plasma-mass spectrometry     

G. Dobosi  G. A. Jenner   《Lithos》1999,46(4):14-749

Clinopyroxene megacrysts in alkali basalts are an important source of information about the evolution of magmatic systems at depth. In this study, we have undertaken a detailed examination of the trace element contents in a suite of megacrysts from 2.5 Ma old alkali basalts in the Nógrád volcanic province of Hungary and Slovakia. The megacrysts range in composition from Mg-rich and in equilibrium with their host magmas, to those that are Fe-rich and must have evolved in more fractionated magmas. The conditions of crystallization of these megacrysts, as calculated from the Al^VI/Al^IV ratios, suggests they all formed at about 30 km, or the crust–mantle boundary in this area. Using the most magnesian megacrysts and compositions of the host lavas, we have calculated the partition coefficients for a range of trace elements. However, the trace element contents in the megacrysts show a systematic variation with major element composition. Moreover, the rate of increase or change in the trace element concentrations is not consistent with models involving constant or steady state partition coefficients. Using a series of assumptions and models, we hypothesize that the partition coefficients between clinopyroxene and melt change substantially during the magmatic evolution of the system. This change is not constant for each element group, with the high field strength elements showing the most substantial increases. Electrostatic charge balance may have been the most important factor in controlling the mineral/melt partitioning.  相似文献   

Three-dimensional semi-idealized model for tidal motion in tidal estuaries     

Mohit Kumar  Henk M. Schuttelaars  Pieter C. Roos  Matthias Möller 《Ocean Dynamics》2016,66(1):99-118

In this paper, a three-dimensional semi-idealized model for tidal motion in a tidal estuary of arbitrary shape and bathymetry is presented. This model aims at bridging the gap between idealized and complex models. The vertical profiles of the velocities are obtained analytically in terms of the first-order and the second-order partial derivatives of surface elevation, which itself follows from an elliptic partial differential equation. The surface elevation is computed numerically using the finite element method and its partial derivatives are obtained using various methods. The newly developed semi-idealized model allows for a systematic investigation of the influence of geometry and bathymetry on the tidal motion which was not possible in previously developed idealized models. The new model also retains the flexibility and computational efficiency of previous idealized models, essential for sensitivity analysis. As a first step, the accuracy of the semi-idealized model is investigated. To this end, an extensive comparison is made between the model results of the semi-idealized model and two other idealized models: a width-averaged model and a three-dimensional idealized model. Finally, the semi-idealized model is used to understand the influence of local geometrical effects on the tidal motion in the Ems estuary. The model shows that local convergence and meandering effects can have a significant influence on the tidal motion. Finally, the model is applied to the Ems estuary. The model results agree well with observations and results from a complex numerical model.  相似文献   

Resonance properties of a closed rotating rectangular basin subject to space- and time-dependent wind forcing     

Wen L. Chen  Pieter C. Roos  Henk M. Schuttelaars  Suzanne J. M. H. Hulscher 《Ocean Dynamics》2015,65(3):325-339

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