Food webs and ecosystem services during soil transformations     

Jeroen P. van Leeuwen  Lia Hemerik  Jaap Bloem  Peter C. de Ruiter 《Applied Geochemistry》2011

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Hemispheric Imaging of Galactic Neutral Hydrogen with a Phased Array Antenna System     

Stefan J. Wijnholds  A. Ger De Bruyn  Jaap D. Bregman  Jan Geralt Bij De Vaate 《Experimental Astronomy》2004,17(1-3):59-64

The thousand element array (THEA) system is a phased array system consisting of 1 m² tiles having 64 Vivaldi elements each, arranged on a regular 8-by-8 grid, which has been developed as a demonstrator of technology and applicability for SKA. In this paper we present imaging results of Galactic neutral hydrogen with THEA. Measurements have been taken using a dense 2-by-2 array of four tiles as a four tile adder. The results are compared with results from the Leiden-Dwingeloo Survey, showing qualitative agreement, but also indicating that further studies are needed on the instrumental characteristics.  相似文献   

Occurrence of gorgosterol in diatoms of the genus Delphineis     

Sebastiaan W. Rampen  John K. Volkman  Sung Bum Hur  Ben A. Abbas  Stefan Schouten  Ian D. Jameson  Daniel G. Holdsworth  Jean Hee Bae  Jaap S. Sinninghe Damsté 《Organic Geochemistry》2009,40(1):144-147

The presence of the C₃₀ sterol gorgosterol (22,23-methylene-23,24-dimethylcholest-5-en-3ß-ol) and its analogues in some marine and freshwater environments is generally associated with invertebrate animals or dinoflagellates since there have been no reports of them in other microalgal classes. Here we show that two unialgal cultures of different species of the marine diatom Delphineis contain gorgosterol in addition to sterols more commonly found in diatoms. Our findings suggest that some reports of gorgosterol in seawater and marine sediments may well have an origin, at least in part, from diatoms.  相似文献   

Biomarker lipids of the freshwater fern Azolla and its fossil counterpart from the Eocene Arctic Ocean     

Eveline N. Speelman  Gert-Jan Reichart  Jan W. de Leeuw  W. Irene C. Rijpstra  Jaap S. Sinninghe Damsté 《Organic Geochemistry》2009,40(5):628-637

Eocene sediments recovered from the Lomonosov Ridge in the central Arctic Ocean during Integrated Ocean Drilling Program Expedition 302 contain high amounts of fossil remains of the free floating freshwater fern Azolla. Both extant Azolla and the sediments from the Arctic Azolla interval were found to contain relatively high quantities of compounds identified as 1,ω20 C₃₀–C₃₆ diols. Furthermore, structurally related mid-chain hydroxy fatty acids, long chain n-alkanols and keto-ols were discovered. The different series have a common feature: there is always a hydroxy group at the ω20 position. In addition, structurally related C₂₉ ω20,ω21 diols, C₂₉ 1,20,21 triols, C₂₉ dihydroxy fatty acids as well as a series of wax esters containing these mono- and dihydroxy lipids are reported. Selective extraction of Azolla surface lipids revealed that these compounds are most likely present in the leaf waxes of the fern. The suite of long-chain, mid-chain ω20 hydroxy wax constituents is described for the first time. As they are well preserved in the Eocene sediments, these lipids may serve as palaeo-environmental indicators of the Arctic Azolla interval and as markers for the past occurrence of Azolla in general.  相似文献   

Impact of temperature on long chain diol and mid-chain hydroxy methyl alkanoate composition in Proboscia diatoms: Results from culture and field studies     

Sebastiaan W. Rampen  Stefan Schouten  Enno Schefuß  Jaap S. Sinninghe Damst 《Organic Geochemistry》2009,40(11):1124-1131

Long chain 1,14-diols and 12-hydroxy methyl alkanoates are biomarker lipids for Proboscia diatoms and occur widely in Quaternary sediments. To determine the effect of temperature on the lipid composition of these algae, a new Proboscia sp. culture grown at 8 °C and Proboscia indica cultures grown at 18, 21, 24 and 27 °C were examined. The results were combined with lipid data from a P. indica culture and a Proboscia alata culture, grown at 20 and 2 °C, respectively, from previous studies. The data showed a strong relationship between long chain diol and 12-hydroxy methyl alkanoate composition and growth temperature, i.e. the chain length increases and the degree of unsaturation of long chain 1,14-diols decreases with increasing growth temperature. To determine the effect of temperature on Proboscia lipid compositions in natural environments, we also analyzed fossil long chain 1,14-diols and 12-hydroxy methyl alkanoates in surface sediments derived from Proboscia diatoms living in the water column of the eastern South Atlantic. The results indicate a significant relationship between sea surface temperature and chain length distribution of saturated long chain diols, but also suggest that the relative abundances of unsaturated long chain diols and 12-hydroxy methyl alkanoates in sediments are predominantly determined by factors other than temperature.  相似文献   

Keeping things in order: multivariate direct gradient analysis of a strongly fluctuating benthic community     

Jaap van der Meer 《Journal of Sea Research》1999,42(4):1583

Two spatial surveys of the macrobenthos of an estuarine intertidal area, the Oosterschelde in the southwestern part of The Netherlands, were conducted in different years. In the period between the surveys changes in the hydrodynamics of the estuary took place as a result of the construction of a storm-surge barrier. The works reduced the tidal volume in the basin and as a consequence the altitude of the tidal flats decreased by approximately 0.1 to 0.2 m. Considerable differences in species densities were found between the two surveys, but these large differences could not be explained by changes in the ‘spatial' environmental variables (such as altitude) that were taken into account in a direct gradient analysis. Unknown and ‘only-to-time-related' (e.g. weather-related) factors had considerably influenced species abundance. This implies that the impact of the works on the macrobenthos could not be evaluated on the basis of observed species densities in the before- and after-the-works surveys. Generally, it implies that even if the levels of future ‘spatial' environmental variables are known, direct gradient analysis based on a single survey cannot be used for prediction of future densities in absolute terms in such strongly fluctuating communities. Yet, the gradient analyses for the two years revealed rather similar estimates of the major environmental gradients. The same was true for the parameters that described the relative change in species densities in response to a change in the environmental gradient levels. Hence the most appropriate way of evaluating the changes that have occurred in the benthic community as a result of the works was in terms of the observed changes in the ‘spatial' environmental gradient levels. The levels of the first environmental gradient, which was strongly related to the sediment structure, did not change between years. Levels of the second gradient, which could be interpreted as a tidal zone gradient, decreased. This suggests that the works particularly affected taxa that are strongly related to this second gradient, such as Corophium living in the upper tidal areas and Nephthys living in the lower tidal zone.  相似文献   

Very precise orbits of 1998 Leonid meteors     

Hans BETLEM  Peter JENNISKENS  Jaap van &#x;t LEVEN  Casper ter KUILE  Carl JOHANNINK  Haibin ZHAO  Chenming LEI  Guanyou LI  Jin ZHU  Steve EVANS  Pavel SPURNÝ 《Meteoritics & planetary science》1999,34(6):979-986

Abstract— Seventy-five orbits of Leonid meteors obtained during the 1998 outburst are presented. Thirty-eight are precise enough to recognize significant dispersion in orbital elements. Results from the nights of 1998 November 16/17 and 17/18 differ, in agreement with the dominant presence of different dust components. The shower rate profile of 1998 November 16/17 was dominated by a broad component, rich in bright meteors. The radiant distribution is compact. The semimajor axis is confined to values close to that of the parent comet, whereas the distribution of inclination has a central condensation in a narrow range. On the other hand, 1998 November 17/18 was dominated by dust responsible for a more narrow secondary peak in the flux curve. The declination of the radiant and the inclination of the orbit are more widely dispersed. The argument of perihelion, inclination, and the perihelion distance are displaced. These data substantiate the hypothesis that trapping in orbital resonances is important for the dynamical evolution of the broad component.  相似文献   

Debris‐covered glaciers,M. Nakawo,C. F. Raymond and A. Fountain,International Association of Hydrological Sciences,Publication No. 264, IAHS Press,Wallingford 2000 (288 pp) ISBN 1‐901502‐31‐7     

Jaap J. M. van der Meer 《第四纪科学杂志》2002,17(8):804-805

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Effect of offshore waves and vegetation on the sediment budget in the Virginia Coast Reserve (VA)     

William Nardin  Sara Lera  Jaap Nienhuis 《地球表面变化过程与地形》2020,45(12):3055-3068

The potential for rapid coastline modification in the face of sea-level rise or other stressors is alarming, since coasts are often densely populated and support valuable infrastructure. In addition to coastal submergence, nutrient-related water pollution is a growing concern for coastal wetlands. Previous studies found that the Suspended Sediment Concentration (SSC) of coastal wetlands acts as a first-order control of their sustainability, but SSC dynamics are poorly understood. Our study focuses on the Virginia Coast Reserve (VCR) Long Term Ecological Research (LTER) site, a shallow multiple tidal inlet system in the USA. We apply numerical modelling (Delft3D-SWAN) and subsequent analyses to determine SSC dynamics within the VCR. In particular, we consider two important controls on SSC in the system: vegetation (seagrass and salt marsh) and offshore waves. Our results show that vegetation colonies and increased wave energy lengthen water residence time. The reduction in the tidal prism decreases SSC export from the bay via tidal inlets, leading to increased sediment retention in the bay. We found that alongshore currents can enhance lagoon SSC by importing fine sediments from an adjacent inlet along the coastline. Our numerical experiments on vegetation seasonality can improve the understanding of wave climate impact on coastal bay sediment budget. Offshore waves increase sediment export from coastal bays, particularly during winter seasons with low vegetation density. Therefore, our study can help managers and stakeholders to understand how to implement restoration strategies for the VCR. © 2020 John Wiley & Sons, Ltd.  相似文献   

Modeling permafrost distribution over the river basins of Mongolia using remote sensing and analytical approaches     

Zorigt  Munkhtsetseg  Myagmar  Khulan  Orkhonselenge  Alexander  van Beek  Eelco  Kwadijk  Jaap  Tsogtbayar  Jargaltulga  Yamkhin  Jambaljav  Dechinlkhundev  Dorjsuren 《Environmental Earth Sciences》2020,79(12):1-1

The Editors-in-Chief of Environmental Earth Sciences are issuing an editorial expression of concern to alert readers that this article.  相似文献