The response of calcareous nannofossils to Oceanic Anoxic Event 2 and the Middle Cenomanian Event in the tropical Atlantic

Im Cenoman/Turon (C/T) wurde der Höhepunkt der Treibhausverhältnisse erreicht, welche das Klima der mittleren Kreide (Apt-Turon) charakterisierten. Ziele dieser Arbeit sind 1) die paläoökologischen Bedingungen zu rekonstruieren, die während der Ablagerung der Schwarzschiefer des C/T im tropischen Atlantik (Demerara Rise, ODP Leg 207) geherrscht haben und 2) eine hochauflösende Biostratigraphie für diesen Zeitraum zu erstellen. Hierzu wurden kalkige Nannofossilien untersucht und mit Vergesellschaftungen benthischer Foraminiferen und geochemischen Proxies verglichen. Zudem wurden die paläoökologischen Präferenzen bestimmter Nannofossilien-Spezies erneut in Betracht gezogen. Es wird gezeigt, dass im tropischen Atlantik des Mittel-Cenomans stratifizierte und oligotrophe ozeanische Bedingungen einsetzten. Das Oceanic Anoxic Event 2 im Cenoman/Turon Grenzbereich ist durch eine Abschwächung/Zusammenbruch der Wassersäulenstratifikation und Eutrophierung der Oberflächenwässer gekennzeichnet.The Cenomanian/Turonian (C/T) period was characterised by a peak of greenhouse conditions that prevailed in the middle Cretaceous (Aptian-Turonian). The objective of this thesis is the biostratigraphic study and palaeoenvironmental-reconstruction of the C/T black shales recovered in the tropical Atlantic (Demerara Rise) during ODP Leg 207. For this purpose calcareous nannofossil assemblages have been analyzed and compared with benthic foraminiferal data and published geochemical proxies. Furthermore, the palaeoecological preferences of certain nannofossil taxa have been discussed. This thesis shows that a shift to more stratified- and oligotrophic oceanic conditions occurred in the tropical Atlantic in the middle Cenomanian. The subsequent Oceanic Anoxic Event 2 in the Cenomanian-Turonian boundary interval is characterised by a weakening/disruption of the thermal-stratification of the water-column and eutrophication of surface-waters

Calcareous nannofossil assemblages of Ocean Anoxic Event 2 in ODP Sites 207-1258 and 207-1260

The calcareous nannofossils of the Cenomanian/Turonian boundary interval of Sites 1258 and 1260 (Ocean Drilling Program Leg 207) have been studied in order to understand the depositional environment during Oceanic Anoxic Event 2 (OAE2) in the equatorial Atlantic. Nannofossil assemblages show a significant change in relative abundances during the positive d13Corg excursion interval. The strong increase of the high productivity indicator Zeugrhabdotus erectus and the simultaneous decrease of the oligotrophic taxa Watznaueria barnesiae and Watznaueria fossacincta are indicative of enhanced fertility. The decrease of Eprolithus floralis may be attributed to the surface-water temperature increase during OAE2, which is, however, not very significant (~2–3 °C), as suggested by published TEX86 data. It seems more likely that the decrease of E. floralis during OAE2 was evoked by the breakdown of water-column stratification, indicating it as a deep-dwelling species, which prefers stratified waters with a deep nutricline. Prediscosphaera spp. and Retecapsa ficula, which show a significant increase in relative abundances during OAE2, seem to prefer eutrophic environments, while Amphizygus brooksii and Zeugrhabdotus noeliae lower surface-water fertility. Gartnerago segmentatum, Broinsonia spp., Watznaueria biporta, and Seribiscutum gaultensis decrease in abundances during OAE2. It is not clear if they preferred an oligotrophic environment, cooler surface-waters, or if they were inhabitants of the lower photic zone. Published geochemical data suggest that enhanced fertility and higher temperatures during OAE2 may have been caused by submarine volcanic activity through the release of biolimiting micronutrients into the ocean and carbon dioxide into the atmosphere. The breakdown of water-column stratification may have increased further nutrient availability

Calcareous nannofossils and benthic foraminifera abundance in ODP Site 207-1260

In addition to Oceanic Anoxic Event 2 (OAE2), other perturbations of the carbon cycle occurred during the Cenomanian and Turonian, of which the Middle Cenomanian Event (MCE) is the most prominent one. In palaeoecological publications, however, this event is strongly underrepresented in contrast to the well-studied OAE2. In order to fill this gap, we have studied Early Cenomanian to Late Turonian calcareous nannofossil and benthic foraminiferal assemblages of Ocean Drilling Program Site 1260 at Demerara Rise (western equatorial North Atlantic), in order to decipher biotic changes throughout this interval and especially across the MCE. Our data show distinctive changes in the relative abundance of certain calcareous nannofossil taxa and a drastic decrease in benthic foraminiferal diversities and abundances associated with the MCE. In the lower part of the studied section and prior to the MCE, a mixed water-column with high nutrient availability in the upper photic zone is suggested based on very high relative abundances of the mesotrophic/eutrophic nannofossil species Biscutum constans. Around the MCE interval, certain nannofossil taxa (e.g., Rhagodiscus asper) show a distinctive decrease in relative abundance while others become more dominant. Taxa which increase in relative abundance after the MCE (e.g., Eprolithus floralis) are interpreted as either having favoured less eutrophic surface-waters or having inhabited deeper parts of the photic zone in a well stratified water-column. This interpretation is supported by published oxygen isotope and TEX86 data, which suggest increased water-column stratification starting with the MCE and lasting to the end of the Cenomanian stage, as a result of the implementation of a saline intermediate- to deep-water mass during this interval. Our study shows that the MCE was a significant biotic event in the Cenomanian/Turonian equatorial Atlantic, characterised by a lasting change of surface- and bottom-water ecosystems

In Vivo Biodistribution of Amino-Functionalized Ceria Nanoparticles in Rats Using Positron Emission Tomography

A variety of nanoparticles have been proposed for several biomedical applications. To gauge the therapeutic potential of these nanoparticles, in vivo biodistribution is essential and mandatory. In the present study, ceria nanoparticles (5 nm average particle size) were labeled with F-18 to study their in vivo biodistribution in rats by positron emission tomography (PET). The F-18 isotope was anchored by reaction of N-succinimidyl 4-[F-18]fluorobenzoate (F-18-SFB) with a modified nanoparticle surface obtained by silylation with 3-aminopropylsilyl. Radiolabeled ceria nanoparticles accumulated mainly in lungs, spleen, and liver. Metabolic products of the radiolabeled nanoparticulate material were excreted into the urinary tract.The present work was supported by the Spanish MICINN (Grants CTQ-2009-11586, CTQ2006-06785, and CTQ2007-67805-AR07, PI10/1195, AP192/11); the Fondo de Investigacion Sanitaria (FIS) of the Instituto de Salud Carlos III (Grants PS09/02620, PI10/1195, and PS09/02217), the Generalitat Valenciana (Grant ACOMP/2012/045), La Marato Fundation (Grant 090530), and by CDTI under the CENIT Programme (AMIT Project) and the Spanish Ministry of Science and Innovation. V.M.V. is a recipient of a contract from the Regional Ministry of Health of the Valencian Regional Government and Carlos III Health Institute (CES10/030).Rojas, S.; Domingo Gispert, J.; Abad Fuentes, S.; Buaki-Sogo, M.; Victor, VM.; García Gómez, H.; Herance Camacho, JR. (2012). In Vivo Biodistribution of Amino-Functionalized Ceria Nanoparticles in Rats Using Positron Emission Tomography. Molecular Pharmaceutics. 9(12):3543-3550. https://doi.org/10.1021/mp300382nS3543355091

Biokinetics of nanomaterials: The role of biopersistence

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices