The largest Bio-Silica Structure on Earth: The Giant Basal Spicule from the Deep-Sea Glass Sponge Monorhaphis chuni

The depth of the ocean is plentifully populated with a highly diverse fauna and flora, from where the Challenger expedition (1873–1876) treasured up a rich collection of vitreous sponges [Hexactinellida]. They have been described by Schulze and represent the phylogenetically oldest class of siliceous sponges [phylum Porifera]; they are eye-catching because of their distinct body plan, which relies on a filigree skeleton. It is constructed by an array of morphologically determined elements, the spicules. Later, during the German Deep Sea Expedition “Valdivia” (1898-1899), Schulze could describe the largest siliceous hexactinellid sponge on Earth, the up to 3 m high Monorhaphis chuni, which develops the equally largest bio-silica structures, the giant basal spicules (3 m × 10 mm). With such spicules as a model, basic knowledge on the morphology, formation, and development of the skeletal elements could be elaborated. Spicules are formed by a proteinaceous scaffold which mediates the formation of siliceous lamellae in which the proteins are encased. Up to eight hundred 5 to 10 μm thick lamellae can be concentrically arranged around an axial canal. The silica matrix is composed of almost pure silicon and oxygen, providing it with unusual optophysical properties that are superior to those of man-made waveguides. Experiments indicated that the spicules function in vivo as a nonocular photoreception system. In addition, the spicules have exceptional mechanical properties, combining mechanical stability with strength and stiffness. Like demosponges the hexactinellids synthesize their silica enzymatically, via the enzyme silicatein. All these basic insights will surely contribute also to a further applied utilization and exploration of bio-silica in material/medical science

Central Tethyan platform-top hypoxia during Oceanic Anoxic Event 1a

Short-term hypoxia in epeiric water masses is a common phenomenon of modern marine environments and causes mass mortality in coastal marine ecosystems. Here, we test the hypothesis that during the early Aptian, platform-top hypoxia temporarily established in some of the vast epeiric seas of the central Tethys and caused, combined with other stressors, significant changes in reefal ecosystems. Potentially interesting target examples include time intervals characterized by the demise of lower Aptian rudist-coral communities and the establishment of microencruster facies, as previously described from the central and southern Tethys and from the proto-North Atlantic domain. These considerations are relevant as previous work has predominantly focused on early Aptian basinal anoxia in the context of Oceanic Anoxic Event (OAE) 1a, whereas the potential expansion of the oxygen minimum zone (OMZ) in coeval shallow-water environments is underexplored. Wellknown patterns in the δ13C record during OAE 1a allow for a sufficiently time-resolved correlation with previously studied locations and assignment to chemostratigraphic segments. This paper presents and critically discusses the outcome of a multi-proxy study (e.g., rare earth elements (REEs), U isotopes, and redox-sensitive trace elements) applied to lower Aptian shallow-water carbonates today exposed in the Kanfanar quarry in Istria, Croatia. These rocks were deposited on an extensive, isolated high in the central Tethys surrounded by hemipelagic basins. Remarkably, during chemostratigraphic segment C2, the depletion of redox-sensitive trace elements As, V, Mo, and U in platform carbonates, deposited in normal marine oxic waters, record the first occurrence of basinal, organic-rich sediment deposition in which these elements are enriched. During the C3 segment, seawater oxygen depletion established on the platform top as indicated by the patterns in Ce=Ce∗ and U isotopes. Shifts in redox-sensitive proxies coincide with the expansion of microencruster facies. Segment C4 witnesses the return to normal marine reefal faunas on the platform top and is characterized by patterns in redox-sensitive proxies typical of normal marine dissolved oxygen levels. It remains unclear, however, if platform-top hypoxia resulted from the expansion and upwelling of basinal, oxygen-depleted water masses or if spatially isolated, shallow hypoxic water bodies formed on the platform. Data shown here are relevant as they shed light on the driving mechanisms that control poorly understood faunal patterns during OAE 1a in the neritic realm and provide evidence on the intricate relation between basinal and platform-top water masses. © Author(s) 2019

Evaluating the role of coastal hypoxia on the transient expansion of microencruster intervals during the early Aptian

Worldwide, a growing number of modern coastal marine ecosystems are increasingly exposed to suboxic- or even anoxic conditions. Low seawater oxygen levels trigger significant ecosystem changes and may result in mass mortality of oxygen-sensitive biota. The applicability of observations from recent (anthropogenically influenced) suboxic coastal settings to fossil anoxic shallow-marine environments is, however, as yet poorly explored. The test case documented here are upper Barremian to lower Aptian strata in the Lusitanian Basin (Ericeira section, Portugal). These are characterized by the transient demise of rudist–coral communities and the rapid establishment of microencruster facies in the vacant ecological niches. The hypothesis is tested that the temporal expansion of the microencrusting organism Lithocodium aggregatum took place in response to platform-top seawater oxygen depletion. We critically discuss the outcome of a multi-proxy palaeoseawater redox approach (e.g. Rare Earth Elements (REEs), U isotopes and palaeoecology) and put the robustness of the proxies applied here to the test. This is done by considering issues with these methods in general but also emphasizing the significance of terrigenous contamination and fractionation effects. Data shown here document that evidence for coastal seawater oxygen depletion in the prelude of Oceanic Anoxic Event (OAE) 1a is lacking, and hence, anoxia was not the driving mechanism for the demise of rudist–coral ecosystems in the proto-North Atlantic platform setting studied here. In contrast, well-oxygenated early Aptian platform-top water masses are proposed for this site. Geologically short (decades to millennia) fluctuations in seawater oxygen levels cannot be excluded, however. But even if these took place, they offer no explanation for the Kyr to Myr-scale patterns discussed here. The present paper is relevant as it sheds light on the complexity of mechanisms that drive punctuated Early Cretaceous coral–rudist ecosystem turnover, and assess strengths and weaknesses of redox proxies applied to ancient shallow-marine platform carbonates. © 2020 The Authors. Lethaia published by John Wiley & Sons Ltd on behalf of Lethaia Foundatio

Climate Variability in Central Europe during the Last 2500 Years Reconstructed from Four High-Resolution Multi-Proxy Speleothem Records

The Late Holocene was characterized by several centennial-scale climate oscillations including the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age. The detection and investigation of such climate anomalies requires paleoclimate archives with an accurate chronology as well as a high temporal resolution. Here, we present 230Th/U-dated high-resolution multi-proxy records (δ13C, δ18O and trace elements) for the last 2500 years of four speleothems from Bunker Cave and the Herbstlabyrinth cave system in Germany. The multi-proxy data of all four speleothems show evidence of two warm and two cold phases during the last 2500 years, which coincide with the Roman Warm Period and the Medieval Warm Period, as well as the Dark Ages Cold Period and the Little Ice Age, respectively. During these four cold and warm periods, the δ18O and δ13C records of all four speleothems and the Mg concentration of the speleothems Bu4 (Bunker Cave) and TV1 (Herbstlabyrinth cave system) show common features and are thus interpreted to be related to past climate variability. Comparison with other paleoclimate records suggests a strong influence of the North Atlantic Oscillation at the two caves sites, which is reflected by warm and humid conditions during the Roman Warm Period and the Medieval Warm Period, and cold and dry climate during the Dark Ages Cold period and the Little Ice Age. The Mg records of speleothems Bu1 (Bunker Cave) and NG01 (Herbstlabyrinth) as well as the inconsistent patterns of Sr, Ba and P suggests that the processes controlling the abundance of these trace elements are dominated by site-specific effects rather than being related to supra-regional climate variability

Influence of Compensating Defect Formation on the Doping Efficiency and Thermoelectric Properties of Cu_(2-y)Se_(1–x)Br_x

The superionic conductor Cu_(2−δ)Se has been shown to be a promising thermoelectric at higher temperatures because of very low lattice thermal conductivities, attributed to the liquid-like mobility of copper ions in the superionic phase. In this work, we present the potential of copper selenide to achieve a high figure of merit at room temperature, if the intrinsically high hole carrier concentration can be reduced. Using bromine as a dopant, we show that reducing the charge carrier concentration in Cu_(2−δ)Se is in fact possible. Furthermore, we provide profound insight into the complex defect chemistry of bromine doped Cu_(2−δ)Se via various analytical methods and investigate the consequential influences on the thermoelectric transport properties. Here, we show, for the first time, the effect of copper vacancy formation as compensating defects when moving the Fermi level closer to the valence band edge. These compensating defects provide an explanation for the often seen doping inefficiencies in thermoelectrics via defect chemistry and guide further progress in the development of new thermoelectric materials

Pancreatic (pro)enzymes treatment suppresses BXPC-3 pancreatic Cancer Stem Cell subpopulation and impairs tumour engrafting

Cancer stem cells (CSCs) subpopulation within the tumour is responsible for metastasis and cancer relapse. Here we investigate in vitro and in vivo the effects of a pancreatic (pro)enzyme mixture composed of Chymotrypsinogen and Trypsinogen (PRP) on CSCs derived from a human pancreatic cell line, BxPC3. Exposure of pancreatic CSCs spheres to PRP resulted in a significant decrease of ALDEFLUOR and specific pancreatic CSC markers (CD 326, CD 44 and CxCR4) signal tested by flow cytometry, further CSCs markers expression was also analyzed by western and immunofluorescence assays. PRP also inhibits primary and secondary sphere formation. Three RT2 Profiler PCR Arrays were used to study gene expression regulation after PRP treatment and resulted in, (i) epithelialmesenchymal transition (EMT) inhibition; (ii) CSCs related genes suppression; (iii) enhanced expression of tumour suppressor genes; (iv) downregulation of migration and metastasis genes and (v) regulation of MAP Kinase Signalling Pathway. Finally, in vivo anti-tumor xenograft studies demonstrated high anti-tumour efficacy of PRP against tumours induced by BxPC3 human pancreatic CSCs. PRP impaired engrafting of pancreatic CSC’s tumours in nude mice and displayed an antigrowth effect toward initiated xenografts. We concluded that (pro)enzymes treatment is a valuable strategy to suppress the CSC population in solid pancreatic tumours

Evagination of Cells Controls Bio-Silica Formation and Maturation during Spicule Formation in Sponges

The enzymatic-silicatein mediated formation of the skeletal elements, the spicules of siliceous sponges starts intracellularly and is completed extracellularly. With Suberites domuncula we show that the axial growth of the spicules proceeds in three phases: (I) formation of an axial canal; (II) evagination of a cell process into the axial canal, and (III) assembly of the axial filament composed of silicatein. During these phases the core part of the spicule is synthesized. Silicatein and its substrate silicate are stored in silicasomes, found both inside and outside of the cellular extension within the axial canal, as well as all around the spicule. The membranes of the silicasomes are interspersed by pores of ≈2 nm that are likely associated with aquaporin channels which are implicated in the hardening of the initial bio-silica products formed by silicatein. We can summarize the sequence of events that govern spicule formation as follows: differential genetic readout (of silicatein) → fractal association of the silicateins → evagination of cells by hydro-mechanical forces into the axial canal → and finally processive bio-silica polycondensation around the axial canal. We termed this process, occurring sequentially or in parallel, bio-inorganic self-organization

MPI-Ding reference glasses for in situ microanalysis: New reference values for element concentrations and isotope ratios

We present new analytical data of major and trace elements for the geological MPI-DING glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, BM90/21-G, T1-G, and ATHO-G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA-ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties (at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive (isotope dilution) and comparative bulk (e.g., INAA, ICPMS, SSMS) and microanalytical (e.g., LA-ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high-precision bulk techniques, such as TIMS and MC-ICPMS. In addition, LA-ICPMS and SIMS isotope data of B, Li, and Pb are presented