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.