Benthic photosynthesis in submerged Wadden Sea intertidal flats

In this study we compare benthic photosynthesis during inundation in coarse sand, fine sand, and mixed sediment (sand/mud) intertidal flats in the German Wadden Sea. In situ determinations of oxygen-, DIC- and nutrient fluxes in stirred benthic chamber incubations were combined with measurements of sedimentary chlorophyll, incident light intensity at the sediment surface and scalar irradiance within the sediment. During submergence, microphytobenthos was light limited at all study sites as indicated by rapid response of gross photosynthesis to increasing incident light at the sea floor. However, depth integrated scalar irradiance was 2 to 3 times higher in the sands than in the mud. Consequently, gross photosynthesis in the net autotrophic fine sand and coarse sand flats during inundation was on average 4 and 11 times higher than in the net heterotrophic mud flat, despite higher total chlorophyll concentration in mud. Benthic photosynthesis may be enhanced in intertidal sands during inundation due to: (1) higher light availability to the microphytobenthos in the sands compared to muds, (2) more efficient transport of photosynthesis-limiting solutes to the microalgae with pore water flows in the permeable sands, and (3) more active metabolic state and different life strategies of microphytobenthos inhabiting sands.     

Das kristalline Grundgebirge von Anatolien

Zusammenfassung In Anatolien gibt es drei grö\ere Kristallin-Massive — Menderes, Kirehir und Bitlis — neben zahlreichen kleineren. Das Kirehir-Massiv ist ganz aus vordevonischem Altkristallin aufgebaut. Menderes- und Bitlis-Massiv enthalten altkristalline Kerne. Eine intra-mesozoische Metamorphose umgab sie mit Hüllen von palÄozoisch-altmesozoischen Phylliten und Marmoren. Die metamorphe Aureole des Menderes-Massivs lÄ\t sich in die ÄgÄis, die des Bitlis-Massivs nach ZentralIran hinein verfolgen. Die Kristallin-Aufbrüche Nord-Anatoliens sind Bruchstücke einer alten Masse, der Nordanatolischen Schwelle; sie besteht aus Altkristallin. Die Taurus-Geosynkline hat ihre SelbstÄndigkeit durch die Schwellenzone gewonnen, die durch die intramesozoische Metamorphose in ihrem Rücklande geschaffen worden ist.

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In Anatolia there are three large crystalline massifs — Menderes, Kirehir and Bitlis — apart from a number of minor ones. The Kirehir Massif consists entirely of pre-Devonian metamorphites. The Menderes and Bitlis massifs both contain cores of old crystalline rocks. In the course of an intra-Mesozoic metamorphism these cores have been surrounded by envelopes of phyllites and marbles derived from beds of Paleozoic and Older Mesozoic age. The aureoles of young metamorphism can be traced from the Menderes Massif into the Aegean Sea and from the Bitlis Massif into Central Iran. The crystalline domes of northern Anatolia are fragments of the North Anatolian Welt, an ancient block composed of crystalline schists of probably pre-Paleozoic age. The Taurus geosyncline came into virtual existence by the ridge built up in its hinterland by the intra-Mesozoic metamorphism.

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Résumé En Anatolie il y a trois vastes massifs cristallins — Mendérès, Kiréhir et Bitlis — sans parler de nombreux autres moins étendus. Le massif de Kiréhir se compose entièrement de roches cristallines pré-dévoniennes. Les massifs du Mendérès et de Bitlis contiennent des noyaux de cristallin ancien. Au cours d'un métamorphisme intra-mésozoique ces noyaux furent entourés des enveloppes de phyllite et de marbre dérivées des couches du Paléozoique et du Mésozoique inférieur. L'auréole métamorphique du massif du Mendérès se poursuit dans la Mer Egée, celle du massif de Bitlis jusqu'à l'Iran central. Les nombreux bombements cristallins de l'Anatolie du Nord représentent des fragments du Seuil Nord-Anatolien, ancien massif constitué par des schistes métamorphiques probablement précambriens. Le géosynclinal du Taurus a gagné son individualité par le ride cristallin s'étendant dans son arrière-pays et formé par le métamorphisme intramésozoique.

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: Menderes, Kirsehir Bitlis — . Kirsehir — -. Menderes Bitlis , , . Menderes , Bitlis — . - , . . , , . .

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Für förderliche Erörterungen habe ich den Kollegen E.Baarir, Izmir,St. Dürr, Marburg, H.Haude, Hannover, E.Izdar, Izmir, F.Karl, Kiel, K.-O.Kopp, München, W.Niehoff, Hannover, J.Papastamatiou, Athen, J.Stöcklin, Teheran, für Fossil-Bestimmungen dem Kollegen E.Flügel, Darmstadt, zu danken. Der Deutschen Forschungs-Gemeinschaft und dem Aratirma Ileri Kurulu (Nr. 966/11) bin ich für Förderung der Feldarbeiten verpflichtet.     

A Raman spectroscopic study on the structural disorder of monazite–(Ce)

This study addresses whether Raman spectra can be used to estimate the degree of accumulated radiation damage in monazite-(Ce) samples whose chemical composition was previously determined. Our results indicate that the degree of disorder in monazite–(Ce), as observed from increasing Raman band broadening, generally depends on both the structural state (i.e., radiation damage) and the chemical composition (i.e., incorporation of non-formula elements). The chemical effects were studied on synthetic orthophosphates grown using the Li-Mo flux method, and non radiation-damaged analogues of the naturally radiation-damaged monazite–(Ce) samples, produced by dry annealing. We found that the “chemical” Raman-band broadening of natural monazite–(Ce) can be predicted by the empirical formula, $$ {\hbox{FWHM}} {\hbox{[c}}{{\hbox{m}}^{ - {1}}}{]} = {3}{.95} + {26}{.66} \times {\hbox{(Th}} + {\hbox{U}} + {\hbox{Ca}} + {\hbox{Pb)}} {\hbox{[apfu]}} $$ where, FWHM = full width at half maximum of the main Raman band of monazite–(Ce) (i.e., the symmetric PO₄ stretching near 970?cm^?1), and (Th+U+Ca+Pb) = sum of the four elements in apfu (atoms per formula unit). Provided the chemical composition of a natural monazite–(Ce) is known, this “chemical band broadening” can be used to estimate the degree of structural radiation damage from the observed FWHM of the ν₁(PO₄) band of that particular sample using Raman spectroscopy. Our annealing studies on a wide range of monazite–(Ce) reference materials and other monazite–(Ce) samples confirmed that this mineral virtually never becomes highly radiation damaged. Potential advantages and the practical use of the proposed method in the Earth sciences are discussed.     

Factors affecting the Nd3+ (REE3+) luminescence of minerals

In this paper, possibilities and limits of the application of REE³⁺ luminescence (especially the Nd^{3+ 4}F_3/2 → ⁴I_9/2 emission) as structural probe are evaluated. Important factors controlling the Nd³⁺ luminescence signal are discussed, including effects of the crystal-field, crystal orientation, structural state, and temperature. Particular attention was paid to the study of the accessory minerals zircon (ZrSiO₄), xenotime–(Y) (YPO₄), monazite–(Ce) (CePO₄) and their synthetic analogues. Based on these examples we review in short that (1) REE³⁺ luminescence can be used as non-destructive phase identification method, (2) the intensities of certain luminescence bands are strongly influenced by crystal orientation effects, and (3) increased widths of REE³⁺-related emission bands are a strong indicator for structural disorder. We discuss the potential of luminescence spectroscopy, complementary to Raman spectroscopy, for the quantitative estimation of chemical (and potentially also radiation-induced) disorder. For the latter, emissions of Nd³⁺-related centres are found to be promising candidates.     

XMM–Newton observations of bright ROSAT selected active galactic nuclei with low intrinsic absorption

We present a sample of 21 ROSAT bright active galactic nuclei (AGNs), representing a range of spectral classes, and selected for follow-up snapshot observations with XMM–Newton . The typical exposure was between 5 and 10 ks. The objects were primarily selected on the bases of X-ray brightness and not on hardness ratio; thus the sample cannot be strictly defined as a 'soft'sample. One of the main outcomes from the XMM–Newton observations was that all of the AGN, including 11 type 1.8–2 objects, required low levels of intrinsic absorption  ( N _H≲ 10²¹ cm⁻²)  . The low absorption in type 2 systems is a challenge to account for in the standard orientation-based unification model, and we discuss possible physical and geometrical models which could elucidate the problem. Moreover, there does not appear to be any relation between the strength and shape of the soft excess, and the spectral classification of the AGN in this sample. We further identify a number of AGN which deserve deeper observations or further analysis: for example, the low-ionization nuclear emission regions (LINERs) NGC 5005 and NGC 7331, where optically thin thermal and extended emission is detected, and the narrow-line Seyfert 1 II Zw 177, which shows a broad emission feature at ∼ 5.8 keV.     

The host galaxies of active galactic nuclei

We examine the properties of the host galaxies of 22 623 narrow-line active galactic nuclei (AGN) with  0.02 < z < 0.3  selected from a complete sample of 122 808 galaxies from the Sloan Digital Sky Survey. We focus on the luminosity of the [O  iii ]λ5007 emission line as a tracer of the strength of activity in the nucleus. We study how AGN host properties compare with those of normal galaxies and how they depend on L [O  iii ]. We find that AGN of all luminosities reside almost exclusively in massive galaxies and have distributions of sizes, stellar surface mass densities and concentrations that are similar to those of ordinary early-type galaxies in our sample. The host galaxies of low-luminosity AGN have stellar populations similar to normal early types. The hosts of high-luminosity AGN have much younger mean stellar ages. The young stars are not preferentially located near the nucleus of the galaxy, but are spread out over scales of at least several kiloparsecs. A significant fraction of high-luminosity AGN have strong Hδ absorption-line equivalent widths, indicating that they experienced a burst of star formation in the recent past. We have also examined the stellar populations of the host galaxies of a sample of broad-line AGN. We conclude that there is no significant difference in stellar content between type 2 Seyfert hosts and quasars (QSOs) with the same [O  iii ] luminosity and redshift. This establishes that a young stellar population is a general property of AGN with high [O  iii ] luminosities.     

Climate change and North Sea storm surge extremes: an ensemble study of storm surge extremes expected in a changed climate projected by four different regional climate models

The coastal zones are facing the prospect of changing storm surge statistics due to anthropogenic climate change. In the present study, we examine these prospects for the North Sea based on numerical modelling. The main tool is the barotropic tide-surge model TRIMGEO (Tidal Residual and Intertidal Mudflat Model) to derive storm surge climate and extremes from atmospheric conditions. The analysis is carried out by using an ensemble of four 30-year atmospheric regional simulations under present-day and possible future-enhanced greenhouse gas conditions. The atmospheric regional simulations were prepared within the EU project PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change risks and Effects). The research strategy of PRUDENCE is to compare simulations of different regional models driven by the same global control and climate change simulations. These global conditions, representative for 1961–1990 and 2071–2100 were prepared by the Hadley Center based on the IPCC A2 SRES scenario. The results suggest that under future climatic conditions, storm surge extremes may increase along the North Sea coast towards the end of this century. Based on a comparison between the results of the different ensemble members as well as on the variability estimated from a high-resolution storm surge reconstruction of the recent decades it is found that this increase is significantly different from zero at the 95% confidence level for most of the North Sea coast. An exception represents the East coast of the UK which is not affected by this increase of storm surge extremes.     

The generation of phytoplankton patchiness by mesoscale current patterns

 Elken et al. (1994) suggested that phytoplankton patchiness can be generated by mesoscale eddies in light-limited, nutrient-replete environments. This hypothesis is explored using two ecological models of different physical complexity. The model results support the idea that the coupling of mesoscale eddy circulation and phytoplankton growth leads to differential growth rates and thus generates variability in phytoplankton distributions. The specific circulation of a cyclonic eddy isolates a phytoplankton population in its core. Due to the reduced vertical mixing, a higher growth rate is supported in the core, and phytoplankton concentrations increase compared to the surrounding environment. A one-dimensional model is used to explore the hypothesis in general and to perform sensitivity studies. A more realistic simulation uses a coupled three- dimensional model for the western Baltic Sea. Starting from vertically and horizontally homogeneous distributions for nutrients and plankton, the models generate patchiness due to the proposed mechanism. The described mechanism may apply for other mesoscale variable environments during light-limited growth periods as well, e.g., the frontal region of the Southern Ocean. Received: 31 March 2001 / Accepted: 31 August 2001     

Bio-electricity and land use in the Future Agricultural Resources Model (FARM)

Bio-electricity is an important technology for Energy Modeling Forum (EMF-27) mitigation scenarios, especially with the possibility of negative carbon dioxide emissions when combined with carbon dioxide capture and storage (CCS). With a strong economic foundation, and broad coverage of economic activity, computable general equilibrium models have proven useful for analysis of alternative climate change policies. However, embedding energy technologies in a general equilibrium model is a challenge, especially for a negative emissions technology with joint products of electricity and carbon dioxide storage. We provide a careful implementation of bio-electricity with CCS in a general equilibrium context, and apply it to selected EMF-27 mitigation scenarios through 2100. Representing bio-electricity and its land requirements requires consideration of competing land uses, including crops, pasture, and forests. Land requirements for bio-electricity start at 200 kilohectares per terawatt-hour declining to approximately 70 kilohectares per terwatt-hour by year 2100 in scenarios with high bioenergy potential.