ALBERT

Description: Conceptual models predict counteractive effects of herbivores and nutrient enrichment on plant diversity and reversed effects of grazers under different nutrient regimes. I tested these hypotheses in 11 field experiments with periphyton communities in three different aquatic habitats (a highly eutrophic lake, an meso-eutrophic lake, and an meso-eutrophic part of the Baltic Sea coast) and in different seasons. Grazer access and nutrient supply were manipulated in a factorial design. Species richness and evenness were chosen as response variables. Both manipulated factors had significant and contrasting effects on diversity, with variable effect strength between sites and seasons. From the two aspects of diversity, evenness well reflected the changes in community composition. Fertilization tended to increase the dominance of few species and thus to decrease evenness, whereas grazers counteracted these effects by removing dominant life forms. The response of species richness was not as expected, since grazers decreased richness throughout, whereas nutrients had weaker effects but tended to increase richness. Species richness rather reflected changes in periphyton architecture. Grazers reduced algal richness presumably by co-consumption of rare species in the tightly connected periphyton assemblages, whereas enrichment may increase richness by providing more structure via increased dominance of filamentous species. Although grazer and nutrient effects on richness and evenness were opposing, there was no change in the effect of one factor by manipulation of the other.

Description: In the eastern Karawanken Mountains, the siliciclastic sedimentary succession of the Hochwipfel Formation was deposited within a narrow marginal basin of the western Paleotethys. Variations of detrital sandstone modes define four petrofacies types, and allow the succession to be stratigraphically divided into Lower and Upper Hochwipfel Formation. Petrographical and geochemical provenance analysis indicate that the basal quartz-rich sandstones derived mainly from the Intraalpine Terrane in the north and the passive Gondwana margin in the south. In the sediments of the Upper Hochwipfel Formation, an increase of (meta)sedimentary as well as of magmatic lithoclasts is discernible indicating a convergent tectonic situation and increased sediment supply derived from a magmatic arc. Zusammenfassung: Die klastische Sedimentabfolge der karhonen HochwipfelFormation der Ostkarawanken wurde in einem schmalen Randbecken der westlichen Paläotethys abgelagert. Auf Grund der Modalzusammensetzung der Sandsteine lassen sich vier Petrofaziestypen unterscheiden, und die sedimentäre Abfolge in eine Untere und eine Obere Hochwipfel-Formation gliedern. Petrographische und geochemische Provenienz-Indikatoren deuten darauf hin, dass die basalen quarzreichen Sandsteine der unteren Hochwipfel-Formation überwiegend von dem nördlich gelegenen Intraalpinen Terran bzw. dem südlich gelegenen passiven Kontinentalrand Gondwanas stammen. In den Sedimenten der oberen Hochwipfel-Formation ist eine Zunahme von (meta)sedimentären Lithoklasten sowie magmatischen Gesteinsbruchstücken zu beobachten. Dies zeigt den Übergang zu einer konvergenten tektonischen Situation und den verstärkten Sedimenteintrag aus einem magmatischen Bogen an.

Description: A set of histological characteristics to judge ovarian development was established and used to elaborate morphological criteria of 10 maturity stages of Baltic cod Gadus morhua sampled throughout the annual cycle to represent different macroscopic maturity stages. The applied characteristics confirmed most stages of the macroscopic scale, but the separation of late immature and resting mature females remained imprecise. Atretic vitellogenic oocytes or encapsulated residual eggs identified the resting condition morphologically, but not all ovaries with visible signs of previous spawning showed such features. One ovarian stage that was previously classified as ‘ripening’ was changed to ‘spawning’, owing to the prevalence of hydrated eggs and empty follicles. Ovaries with malfunctions were defined by a separate stage. Macroscopic criteria were revised by comparing the gross anatomy of ovaries with their histology. Female length and gonado-somatic index supported stage definitions, but substantial variation in Fulton's condition factor and the hepato-somatic index rendered these of little use for this purpose. The time of sampling influenced staging accuracy. A female spawner probability function based on the proportion of ripening and ripe specimens in early spring seems to be the most appropriate method to estimate spawner biomass and reproductive potential.

Description: During peak spawning of sprat Sprattus sprattus in the Baltic Sea in May–June egg specific gravity averaged ±s.d. 1·00858 ± 0·00116 g cm−3 but was significantly higher in the beginning and significantly lower towards the end of the spawning season. A close relationship was found between egg diameter and egg specific gravity (r2 = 0·71). This relationship, however, changed during the spawning season indicating that some other factor was involved causing the decrease in specific gravity during the spawning period. The vertical egg distribution changed during the spawning season: eggs were distributed mainly in the deep layers early in the season, occurred in and above the permanent halocline during peak spawning, and above the halocline towards the end of the spawning season. Consequently, poor oxygen conditions in the deep layers and low temperatures in layers between the halocline and the developing thermocline may affect egg development. Thus, opportunities for egg development vary over the spawning season and among spawning areas, and depending on frequency of saline water inflows into the Baltic Sea and severity of winters, between years

Description: The Archean Murchison greenstone belt, Northern Province, South Africa, represents a rifted volcanic arc sequence hosting the largest volcanogenic massive sulfide (VMS) district in Southern Africa. The VMS deposits of the "Cu-Zn line" developed during the initial phases of highly evolved felsic volcanism between 2971 and 2965 Ma and are closely associated with quartz-porphyritic rhyolite domes. Elevated heat supply along slow-spreading rift segments ensured regional hydrothermal convection along the entire rift axis. Recurrent volcanism resulted in frequent disruption of hydrothermal discharge and relative short-lived episodes of hydrothermal activity. Stable thermal conditions favoured the local development of mature hydrothermal vent fields from focused fluid discharge and sulfide precipitation in thin layers of volcaniclastic rocks. Ore mineralogy and geochemical composition attest to hydrothermal activity at moderate temperatures of 〈= 250 °C for the entire rift axis, with short-lived pulses of higher temperature(~ 300 °C) fluid upflow. Major and trace metal composition of the deposits attests to the highly differentiated felsic source rocks. Fluid and host rock compositions constrained favourable conditions for the enrichment of indium in the massive sulfide deposits defining the "Cu-Zn line" as a type example for the enrichment of indium in the volcanogenic environment.

Description: A compilation of δ44/40Ca (δ44/40Ca) data sets of different calcium reference materials is presented, based on measurements in three different laboratories (Institute of Geological Sciences, Bern; Centre de Géochimie de la Surface, Strasbourg; GEOMAR, Kiel) to support the establishment of a calcium isotope reference standard. Samples include a series of international and internal Ca reference materials, including NIST SRM 915a, seawater, two calcium carbonates and a CaF2 reference sample. The deviations in δ44/40Ca for selected pairs of reference samples have been defined and are consistent within statistical uncertainties in all three laboratories. Emphasis has been placed on characterising both NIST SRM 915a as an internationally available high purity Ca reference sample and seawater as representative of an important and widely available geological reservoir. The difference between δ44/40Ca of NIST SRM 915a and seawater is defined as -1.88 O.O4%o (δ44/42CaNISTSRM915a/Sw= -0.94 0.07%o). The conversion of values referenced to NIST SRM 915a to seawater can be described by the simplified equation δ44/40CaSa/Sw=δ44/40CaSa/NIST SRM 915a - 1.88 (δ44/42CaSa/Sw=δ44/42CaSa/NIST SRM 915a - 0.94). We propose the use of NIST SRM 915a as general Ca isotope reference standard, with seawater being defined as the major reservoir with respect to oceanographic studies.

Description: The simplified representation of clouds as horizontally homogeneous layers leads to qualitatively well known systematic errors in calculations of the domain averaged solar radiative fluxes. The present work tries to correlate the domain averaged radiative fluxes from three-dimensional (3d) cloud fields with the domain averaged properties of the cloudy atmosphere. The results will help to estimate the applicability of radiative transfer parameterizations in non-cloud-resolving circulation models. Three-dimensional cloud fields have been calculated from the mesoscale atmospheric circulation model GESIMA, and serve as input to a Monte Carlo radiative transfer code. The cloud fields have a pronounced 3d structure in extinction, scattering and absorption properties of the cloud hydrometeors (mixed-phase clouds). It is shown that domain averaged albedo is strongly correlated with cloud cover. The correlation coefficient is improved by adding cloud thickness or the combination of liquid water path and cloud top temperature. Absorption is described best by cloud top temperature together with liquid water path for small and ice water path for large solar zenith angles (SZA). Cloud thickness further improves the correlation with absorption. Total transmission as well as its parts diffuse and direct transmission correlate best with cloud cover and liquid water path, further with cloud top temperature or cloud thickness in case of the diffuse transmission. Nonlinear regressions based on the optimal three cloud parameters yield smallest correlation coefficients of 0.88 for albedo, 0.84 for absorption and 0.92 for total transmission. Only the correlation coefficient for diffuse transmission falls below 0.8 for very large SZAs. Because of this high correlation we conclude that it appears possible to parameterize domain averaged radiative fluxes for 3d cloud fields without information of the internal cloud structure. Die vereinfachte Annahme horizontal homogener Wolkenschichten führt zu qualitativ gut bekannten systematischen Fehlern in der Berechnung der gebietsgemittelten solaren Strahlungsflüsse. Die vorliegende Arbeit stellt den Zusammenhang zwischen gebietsgemittelten Strahlungsflüssen dreidimensionaler (3d) Wolkenfelder und den ebenso gemittelten Wolkeneigenschaften her. Die Ergebnisse dienen zur EinschÄtzung der Anwendbarkeit von Parametrisierungen der Strahlungsbilanz in nicht-wolkenauflösenden Zirkulationsmodellen. Mit Hilfe des mesoskaligen atmosphÄrischen Zirkulationsmodells GESIMA wurden die Eingangsfelder für ein Monte Carlo Strahlungstransportmodell berechnet. Die Wolkenfelder haben eine ausgeprÄgte 3d Strukur sowohl in der Extinktion als auch in den Streu- und Absorptionseigenschaften der Wolkenhydrometeore (Mischphasenwolken). Es stellt sich heraus, dass die gebietsgemittelte Albedo am stÄrksten mit dem Bedeckungsgrad, verbessert noch durch Hinzunahme der vertikalen Wolkenausdehnung beziehungsweise der Kombination aus Flüssigwasserpfad und Wolkenoberkantentemperatur, korreliert ist. Die Absorption lÄsst sich am besten durch die Wolkenoberkantentemperatur zusammen mit dem Flüssigwassergehalt bei kleinen und dem Eiswasserpfad bei großen Sonnenzenitwinkeln wiedergeben, weiter verbessert durch die vertikale Wolkenausdehnung. Sowohl die Gesamttransmission als auch ihre beiden Anteile, die diffuse und die direkte Transmission, korrelieren optimal mit dem Bedeckungsgrad und dem Flüssigwasserpfad und weiterhin mit der Wolkenoberkantentemperatur beziehungsweise der vertikalen Wolkenerstreckung bei der diffusen Transmission. Nichtlineare Regressionen mit drei jeweils optimalen Wolkenparametern ergeben kleinste Korrelationskoeffizienten von 0,88 für die Albedo, 0,84 für die Absorption und 0,92 für die Gesamttransmission. Einzig der Korrelationskoeffizient für die diffuse Transmission sinkt für sehr flache SonnenstÄnde unter 0,8. Aufgrund dieser hohen Korrelation schließen wir, dass es möglich erscheint, gebietsgemittelte Strahlungsflüsse dreidimensionaler Wolkenfelder ohne Informationen zur internen Wolkenstruktur zu parametrisieren.

Description: Modern models for the development and evolution of the geochemical heterogeneity in the Earth's mantle and the genesis of mantle magmas attach much importance to the processes of interaction between deepseated rocks and metasomatic fluids, which are able, when occurring under mantle conditions, to dissolve significant amounts of major and trace elements (see, for example, [1]). Fluorine is one of the major anions of natural fluids and also one of the principal complex-forming ligands of several metals. To evaluate the possible role of fluorine in the processes of mantle magma genesis and to identify the source of this element in natural magmas in various geodynamic environments, it is necessary to know the fluorine concentration in primitive mantle melts. These data are still relatively scarce, particularly for low alkaline magmas [2-4]. The fluorine concentrations in magmas from suprasubduction zones, whose genesis is largely controlled by the interaction between mantle rocks and fluids, remain poorly known and need further refinement. Data presented in this paper are among the first to characterize the concentrations of fluorine in primitive magmas of suprasubduction zones. These data were obtained by secondary ion mass spectrometry of chill glasses from the lava complex of the Troodos ophiolites in Cyprus. Along with information on the concentrations of major and trace elements, H2O, and Cl in the glasses, our results make it possible to utilize the example of the Troodos ophiolites to characterize the main regularities in the geochemistry of fluorine during the origin of magmas above subduction zones and to assay the contributions of various components that participated in the processes of mantle melting. These data are among the first to demonstrate that subduction-related melts became enriched in F relative to LREE.

Description: In this study, the water vapour transport is investigated together with cyclone tracks across the North Atlantic Ocean and their relation to the North Atlantic Oscillation, NAO. During high NAO winters, the maximum of the water vapour transport across 10°W (defined as transport towards Europe) is observed between 50° and 55°N, during low NAO winters, the maximum reduces from 160 kg/m·s to 120 kg/m·s and shifts to about 44°N. In order to understand this change the NCEP/NCAR reanalysis data (1958-1998) are used and a composite is performed of the cyclone's water vapour transport relative to the cyclone centre. The transport is strongest in the south-east sector of a cyclone. Its maximum increases with decreasing central pressure of the cyclone. Thus, deep cyclones transport more water vapour than shallow ones. During high NAO winters, deep cyclones are more frequent than in low NAO winters. Additionally, cyclone tracks are concentrated north of 55°N during high NAO winters and are rather equally distributed in meridional direction over the North Atlantic in low NAO winters. Since the water vapour content of the atmosphere over the North Atlantic increases towards the tropics, we found that during low NAO winters, the cyclones south of 55°N transport 60% more water vapour than those north of 55°N. This fact and the relation between cyclone properties and NAO can explain the shift of the maximum water vapour transport towards Europe from 55°N during high NAO winters to 44°N during low NAO winters.

Description: In late 1999, seismic and seismological investigations were carried out on the Continental margin of Costa Rica. Besides conventional wide angle refraction profiles, airgun shots were fired on a sub circular profile around Osa Peninsula into Golfo Dulce and were recorded by 20 ocean bottom hydrophones deployed along the crest of Cocos Ridge and by 13 Seismometers across the ridge. The resulting uneven distribution of shots and receivers does not allow for a full 3Dtomographic inversion. However, for selected parts detailed velocity information can be obtained providing constraints on the structure of the subsurface. Preliminary results indicate that Cocos Ridge has a bowl-shaped crustal root with a thickness of nearly 20 km in its center and only small changes along strike within the first 50 km seaward of the Middle America trench.

Description: In this modelling study the effects of cloud inhomogeneities on the observations of the passive microwave radiometer SSM/I (Special Sensor Microwave/Imager) are investigated. Brightness temperatures in the radiometer's field-of-view are calculated by using the results of a numerical cloud model as input for a 3-dimensional radiative transfer model. These brightness temperatures are compared with those obtained by the assumption of a plane parallel homogeneous cloud with the equivalent mean liquid water path (LWP). Differences between the two temperatures (the so-called 'beam-filling effect') are related to the mean LWP and to cloud inhomogeneity. It was found that not only the strength of the beam-filling effect but also its dependencies on mean LWP and its inhomogeneity are different for the different microwave frequencies. For 19 and 22 GHz the beam-filling effect increases monotonically with the mean LWP and inhomogeneity, while the beam-filling effect decreases with increased LWP at 37 and 85 GHz at large LWP. In general the beam-filling effect is more pronounced in the horizontal polarisation. Its maximum is found for 37 GHz with differences up to -60 Kelvin compared to the homogeneous case. The effect of the lowered brightness temperatures of inhomogeneous clouds in a LWP algorithm (WENG and GRODY, 1994) is analysed. The largest effect arises from decreased 37 GHz brightness temperature. The mean underestimation of LWP is 0.0179 kg/m2 and the maximum amounts to 0.7 kg/m2. In einer Modellstudie werden die Effekte von Wolkeninhomogenitäten auf die Helligkeitstemperaturen, die das passive Mikrowellenradiometer SSM/I (Special Sensor Microwave/Imager) misst, untersucht. Die Helligkeitstemperaturen im Radiometerblickwinkel werden dazu mit einem dreidimensionalen Strahlungstransportmodell für die Wolken eines numerischen Wolkenmodells berechnet. Sie werden verglichen mit Helligkeitstemperaturen plan-parallel homogener Wolken mit äquivalentem mittlerem Flüssigwasserpfad (LWP). Die Differenz dieser beiden Helligkeitstemperaturen, der sogenannte ,,Beam-Filling“ Effekt, wird untersucht bezüglich seiner Abhängigkeit vom mittleren LWP und der Wolkeninhomogenität. Dabei ergibt sich, dass nicht nur die Größe des Beam-Filling Effektes frequenzabhängig ist, sondern auch dessen Abhängigkeit von mittlerem LWP und Wolkeninhomogenität: Für 19 und 22 GHz steigt der Beam-Filling Effekt monoton mit zunehmendem LWP und Inhomogenität, wohingegen bei 37 und 85 GHz der Beam-Filling Effekt bei hohen mittleren Flüssigwassergehalten abnimmt. Insgesamt ist der Beam-Filling Effekt in der horizontalen Polarisationsebene ausgeprägter und ist maximal für 37 GHz mit einer Differenz von -60 Kelvin verglichen mit einer homogenen Wolke. Anhand eines vielfach angewendeten Algorithmus (WENG und GRODY, 1994) werden Auswirkungen von Wolkeninhomogenität auf den abgeleiteten LWP gezeigt. Dabei spiegeln sich die erniedrigten Helligkeitstemperaturen im 37 GHz Kanal besonders deutlich wider und führen zu einer mittleren Unterschätzung des LWPs von 0,0179 kg/m2 und einer maximalen Unterschätzung von 0,7 kg/m2.