Geochemistry and microfossil content of surface sediments from the Equatorial Atlantic in samples 207 to 310 from the Meteor expedition in 1925

Als Alfred Merz mich aufforderte, die sedimentpetrographische Bearbeitung der "Meteor"-Expedition zu übernehmen, schwebte mir von vornherein als Ziel vor, die Sedimente nicht nur in größerer Zahl als bisher und im Zusammenhang mit den übrigen Wissenschaften vom Meer nach den bisherigen Untersuchungsmethoden zu beschreiben. Es war mir klar, daß neue Ergebnisse nur zu erwarten waren, wenn die Untersuchung der Sedimente und damit ihre Beschreibung auf Grund vertiefter und neuer Methoden unternommen wurde. Ich erhoffte von einer solchen verfeinerten Beschreibung auch ein klareres Bild der Abhängigkeit der Sedimente von ihrer Umwelt. Wir werden diese Abhängigkeit nur verstehen, wenn wir die allgemeinen Gesetzmäßigkeiten herausarbeiten können. Diese werden dann auch eine Anwendung auf andere Sedimente ermöglichen. Für solche Untersuchungen sind Tiefseesedimente günstig, weil wir bei ihnen relativ einfache Bildungsumstände haben, einfacher jedenfalls, als es in der Flachsee im allgemeinen der Fall ist, ungünstig aber, weil diese Umwelteinflüsse weniger bekannt und schwerer zu erforschen sind und die Auswahl der Untersuchungspunkte nicht nach sedimentpetrographischen Gesichtspunkten erfolgen konnte. Die ersten Jahre nach der Rückkehr von der Expedition wurden deshalb auf methodische Untersuchungen verwandt. Insbesondere kam es mir darauf an herauszubekommen, wie die feinsten Bestandteile der Sedimente zusammengesetzt sind. Diese "tonigen" Bestandteile bilden nicht nur den wesentlichen Anteil der Roten Tone und der Blauschlicke, wir finden sie auch, durch Kalk verdünnt, in den Globigerinenschlämmen wieder. Sie sind von der Wissenschaft bisher recht stiefmütterlich behandelt worden. Die Ausarbeitung der Methoden, die gerade auf diesem Gebiet Neuland betreten mußte, ließ sich nicht rasch erzwingen. Es kam hinzu, daß ich mir in Rostock erst meine Arbeitsmöglichkeiten schaffen mußte. Ich habe hier der Notgemeinschaft der Deutschen Wissenschaft und der Mecklenburgischen Regierung für ihre Unterstützung mit Apparaten und Personal wärmstens zu danken. Ferner mußte als Vorbedingung für die Deutung der Sedimente zunächst festgestellt werden, zu welchen geologischen Zeiten sie gebildet worden sind und wie groß ihre Bildungsgeschwindigkeit überhaupt ist. Diese Untersuchungen hat W. Schott mit Hilfe der Foraminiferenfaunen als Notgemeinschaftsstipendiat durchgeführt. Diese Vorarbeiten, insbesondere der Ausbau der Methoden, hatten den Nachteil, daß die Veröffentlichung der Ergebnisse nicht so rasch erfolgen konnte, wie ich es selbst gewünscht hätte. Bald nachdem die Darstellung der Methoden und die Foraminiferenuntersuchungen als erste Lieferung erschienen waren, stellte es sich als notwendig heraus, eine beträchtliche Kürzung des restlichen Teiles vorzunehmen. Das hat zur Folge, daß die erste Lieferung breiter dargestellt ist als die Ergebnisse. Als die Nachricht von der Kürzung und dem notwendigen raschen Abschluß des Werkes mir bekannt wurde (Januar 1935), mußte eine Reihe von Untersuchungen eingestellt werden, insbesondere mikroskopische Untersuchungen, die besonders viel Zeit und in der Darstellung viel Raum beanspruchen. Deshalb ist systematisch nur das Guinea-Becken durch V. Leinz und das Kapverden-Becken durch O. E. Radczewski untersucht worden.

Oxygen content and paleoproductivity from surface sediment samples Y69-86 to PLDS-004G

Quantitative estimation of surface ocean productivity and bottom water oxygen concentration with benthic foraminifera was attempted using 70 samples from equatorial and North Pacific surface sediments. These samples come from a well defined depth range in the ocean, between 2200 and 3200 m, so that depth related factors do not interfere with the estimation. Samples were selected so that foraminifera were well preserved in the sediments and temperature and salinity were nearly uniform (T = 1.5° C; S = 34.6 per mil). The sample set was also assembled so as to minimize the correlation often seen between surface ocean productivity and bottom water oxygen values (r**2 = 0.23 for prediction purposes in this case). This procedure reduced the chances of spurious results due to correlations between the environmental variables. The samples encompass a range of productivities from about 25 to >300 gC m**-2 yr**-1, and a bottom water oxygen range from 1.8 to 3.5 ml/L. Benthic foraminiferal assemblages were quantified using the >62 µm fraction of the sediments and 46 taxon categories. MANOVA multivariate regression was used to project the faunal matrix onto the two environmental dimensions using published values for productivity and bottom water oxygen to calibrate this operation. The success of this regression was measured with the multivariate r? which was 0.98 for the productivity dimension and 0.96 for the oxygen dimension. These high coefficients indicate that both environmental variables are strongly imbedded in the faunal data matrix. Analysis of the beta regression coefficients shows that the environmental signals are carried by groups of taxa which are consistent with previous work characterizing benthic foraminiferal responses to productivity and bottom water oxygen. The results of this study suggest that benthic foraminiferal assemblages can be used for quantitative reconstruction of surface ocean productivity and bottom water oxygen concentrations if suitable surface sediment calibration data sets are developed and appropriate means for detecting no-analog samples are found.

(Table 2) Calcium carbonate content in deep-sea surface sediments

The reconstruction of paleocarbonate ion concentrations provides an important constraint on the contribution of the CaCO3 cycle to the decrease in atmospheric CO2 content during glacial time. Such reconstructions have been challenging because each of the existing paleo-[CO3]2- indices has serious limitations. In this study, we reexamine the Broecker-Clark CaCO3 size index by analyzing the <20 µm, 20 to 38 µm, and 38 to 63 µm fractions in sediments from the Ontong-Java Plateau and the Ceara Rise. Scanning electron microscope analyses demonstrate that the less than 20 µm CaCO3 is dominated by coccoliths and the greater than 20 µm CaCO3 is dominated by foraminifera. Our results clearly indicate that the coccoliths are far more resistant to dissolution than the foraminifera. Referenced to a core top sample from 2.31 km depth in a core top sample from 4.04 km depth on the Ontong-Java Plateau, ~70% of the foraminifera CaCO3 was dissolved as opposed to only ~7% of the coccolith CaCO3. We found that the dissolution of foraminifera shells did not produce a significant amount of fragments smaller than 63 µm in size, and thus the Broecker-Clark size index is not a measure of the extent of fragmentation. Rather, it is a measure of the extent of differential dissolution of foraminifera relative to coccoliths. On the basis of these results, we propose a new dissolution index which involves the ratio of dissolution-susceptible foraminifera CaCO3 to total CaCO3.

Microparticle surface layering through dry coating:impact of moisture content and process parameters on the properties of orally disintegrating tablets

OBJECTIVES: The aim of this study was to investigate the influence of process parameters during dry coating on particle and dosage form properties upon varying the surface adsorbed moisture of microcrystalline cellulose (MCC), a model filler/binder for orally disintegrating tablets (ODTs). METHODS: The moisture content of MCC was optimised using the spray water method and analysed using thermogravimetric analysis. Microproperty/macroproperty assessment was investigated using atomic force microscopy, nano-indentation, scanning electron microscopy, tablet hardness and disintegration testing. KEY FINDINGS: The results showed that MCC demonstrated its best flowability at a moisture content of 11.2% w/w when compared to control, comprising of 3.9% w/w moisture. The use of the composite powder coating process (without air) resulted in up to 80% increase in tablet hardness, when compared to the control. The study also demonstrated that surface adsorbed moisture can be displaced upon addition of excipients during dry processing circumventing the need for particle drying before tabletting. CONCLUSIONS: It was concluded that MCC with a moisture content of 11% w/w provides a good balance between powder flowability and favourable ODT characteristics.

(Table 1) TOC content, BIT, TEX86 and UK'37 indices, and sea surface temperature reconstruction for the middle Miocene to Pliocene of ODP Hole 175-1085A

The initiation of the Benguela upwelling has been dated to the late Miocene, but estimates of its sea surface temperature evolution are not available. This study presents data from Ocean Drilling Program (ODP) Site 1085 recovered from the southern Cape Basin. Samples of the middle Miocene to Pliocene were analyzed for alkenone-based (UK'37, SSTUK) and glycerol dialkyl glycerol tetraether (GDGT) based (TEX86, TempTEX) water temperature proxies. In concordance with global cooling during the Miocene, SSTUK and TempTEX exhibit a decline of about 8°C and 16°C, respectively. The temperature trends suggest an inflow of cold Antarctic waters triggered by Antarctic ice sheet expansion and intensification of Southern Hemisphere southeasterly winds. A temperature offset between both proxies developed with the onset of upwelling, which can be explained by differences in habitat: alkenone-producing phytoplankton live in the euphotic zone and record sea surface temperatures, while GDGT-producing Thaumarchaeota are displaced to colder subsurface waters in upwelling-influenced areas and record subsurface water temperatures. We suggest that variations in subsurface water temperatures were driven by advection of cold Antarctic waters and thermocline adjustments that were due to changes in North Atlantic deep water formation. A decline in surface temperatures, an increased offset between temperature proxies, and an increase in primary productivity suggest the establishment of the Benguela upwelling at 10 Ma. During the Messinian Salinity Crisis, between 7 and 5 Ma, surface and subsurface temperature estimates became similar, likely because of a strong reduction in Atlantic overturning circulation, while high total organic carbon contents suggest a "biogenic bloom." In the Pliocene the offset between the temperature estimates and the cooling trend was reestablished.

Mercury content and isotopic composition of frost flower, surface snow and brine samples near Barrow, Alaska

Frost flowers are ice crystals that grow on refreezing sea ice leads in Polar Regions by wicking brine from the sea ice surface and accumulating vapor phase condensate. These crystals contain high concentrations of mercury (Hg) and are believed to be a source of reactive halogens, but their role in Hg cycling and impact on the fate of Hg deposited during atmospheric mercury depletion events (AMDEs) are not well understood. We collected frost flowers growing on refreezing sea ice near Barrow, Alaska (U.S.A.) during an AMDE in March 2009 and measured Hg concentrations and Hg stable isotope ratios in these samples to determine the origin of Hg associated with the crystals. We observed decreasing Delta199Hg values in the crystals as they grew from new wet frost flowers (mean Delta199Hg = 0.77 ± 0.13 per mil, 1 s.d.) to older dry frost flowers (mean Delta199Hg = 0.10 ± 0.05 per mil, 1 s.d.). Over the same time period, mean Hg concentrations in these samples increased from 131 ± 6 ng/L (1 s.d.) to 180 ± 28 ng/L (1 s.d.). Coupled with a previous study of Hg isotopic fractionation during AMDEs, these results suggest that Hg initially deposited to the local snowpack was subsequently reemitted during photochemical reduction reactions and ultimately accumulated on the frost flowers. As a result of this process, frost flowers may lead to enhanced local retention of Hg deposited during AMDEs and may increase Hg loading to the Arctic Ocean.

ATP content in surface sediments of the Northeast Atlantic (Table 1)

1. ATP in deep-sea sediments can be determined after it is adsorbed on a mixture of the sediment and calcium carbonate by measuring the luminescence of the reaction of the mixture and luciferin-luciferase. 2. ATP contents of the toplayer of northeastern Atlantic sediments (Josephine Bank and northern Canary Basin) decrease with increasing depths of 252, 408, 1445, 1769, 2149, 4897, 5510m: 0.96, 0.61, 0.13, 0.10, 0.21, 0.05, 0.07 µg ATP/ml wet sediment. The decreasing values are in accordance with the decrease of macrobenthos and meiobenthos biomass in the deep-sea. 3. The ATP content of deep-sea nematodes is about 1 ? of their wet weight. 4. At the two deepest stations, less than 50% of the ATP measured in the sediment is represented by nematodes, copepods, other "hard" meiofauna groups and bacteria.