Rock magnetic signature of the Middle Eocene Climatic Optimum (MECO) event in different oceanic basins

The Middle Eocene Climatic Optimum (MECO) event at ~40 Ma was a greenhouse warming which indicates an abrupt reversal in long-term cooling through the middle Eocene. Here, we present environmental and rock magnetic data from sedimentary successions from the Indian Ocean (ODP Hole 711A) and eastern NeoTethys (Monte Cagnero section - MCA). The high-resolution environmental magnetism record obtained for MCA section shows an interval of increase of magnetic parameters comprising the MECO peak. A relative increase in eutrophic nannofossil taxa spans the culmination of the MECO warming and its aftermath and coincides with a positive carbon isotope excursion, and a peak in magnetite and hematite/goethite concentrations. The magnetite peak reflects the appearance of magnetofossils, while the hematite/goethite apex are attributed to an enhanced detrital mineral contribution, likely related to aeolian dust transported from the continent adjacent to the Neo-Tethys Ocean during a drier, more seasonal MECO climate. Seasurface iron fertilization is inferred to have stimulated high phytoplankton productivity, increasing organic carbon export to the seafloor and promoting enhanced biomineralization of magnetotactic bacteria, which are preserved as magnetofossils during the warmest periods of the MECO event. Environmental magnetic parameters show the same behavior for ODP Hole 711A. We speculate that iron fertilization promoted by aeolian hematite during the MECO event has contributed significantly to increase the primary productivity in the oceans. The widespread occurrence of magnetofossils in other warming periods suggests a common mechanism linking climate warming and enhancement of magnetosome production and preservation

Benthic foraminiferal ultrastructural alteration induced by heavy metals

Heavy metals are known to cause deleterious effects on biota because of their toxicity, persistence and bioaccumulation. Here, we briefly document the ultrastructural changes observed in the miliolid foraminifer Pseudotriloculina rotunda (d\u27Orbigny in Schlumberger, 1893) and in the perforate calcareous species Ammonia parkinsoniana (d\u27Orbigny, 1839) induced by exposure to one of three heavy metals (zinc, lead, or mercury). The exposure of these two benthic foraminiferal species to the selected heavy metals appears to promote cytological alterations and organelle degeneration. These alterations include a thickening of the inner organic lining, an increase in number and size of lipid droplets, mitochondrial degeneration, and degradation vacuoles and residual body proliferation. Some of these alterations, including the thickening of the inner organic lining and the proliferation of lipids, might represent defense mechanisms against heavy metal-induced stress

16S rRNA gene metabarcoding and TEM reveals different ecological strategies within the genus Neogloboquadrina (planktonic foraminifer)

CB was supported on a Daphne Jackson Fellowship sponsored by Natural Environmental Research Council (www.nerc.ac.uk) and the University of Edinburgh via the Daphne Jackson Trust. Field collections were supported by the National Science Foundation (www.nsf.gov) grant number OCE-1261519 to ADR and JSF.Uncovering the complexities of trophic and metabolic interactions among microorganisms is essential for the understanding of marine biogeochemical cycling and modelling climate-driven ecosystem shifts. High-throughput DNA sequencing methods provide valuable tools for examining these complex interactions, although this remains challenging, as many microorganisms are difficult to isolate, identify and culture. We use two species of planktonic foraminifera from the climatically susceptible, palaeoceanographically important genus Neogloboquadrina, as ideal test microorganisms for the application of 16S rRNA gene metabarcoding. Neogloboquadrina dutertrei and Neogloboquadrina incompta were collected from the California Current and subjected to either 16S rRNA gene metabarcoding, fluorescence microscopy, or transmission electron microscopy (TEM) to investigate their species-specific trophic interactions and potential symbiotic associations. 53–99% of 16S rRNA gene sequences recovered from two specimens of N. dutertrei were assigned to a single operational taxonomic unit (OTU) from a chloroplast of the phylum Stramenopile. TEM observations confirmed the presence of numerous intact coccoid algae within the host cell, consistent with algal symbionts. Based on sequence data and observed ultrastructure, we taxonomically assign the putative algal symbionts to Pelagophyceae and not Chrysophyceae, as previously reported in this species. In addition, our data shows that N. dutertrei feeds on protists within particulate organic matter (POM), but not on bacteria as a major food source. In total contrast, of OTUs recovered from three N. incompta specimens, 83–95% were assigned to bacterial classes Alteromonadales and Vibrionales of the order Gammaproteobacteria. TEM demonstrates that these bacteria are a food source, not putative symbionts. Contrary to the current view that non-spinose foraminifera are predominantly herbivorous, neither N. dutertrei nor N. incompta contained significant numbers of phytoplankton OTUs. We present an alternative view of their trophic interactions and discuss these results within the context of modelling global planktonic foraminiferal abundances in response to high-latitude climate change.Publisher PDFPeer reviewe

STUDIO DEL COMPORTAMENTO DI UN LAMINATO RINFORZATO IN CARBONIO AD ALTE VELOCITÀ DI DEFORMAZIONE

Negli ultimi anni c’è stata una costante ricerca mirata ad ottenere materiali più leggeri da applicare in differenti settori dell’industria automobilistica e aeronautica con lo scopo di ridurre l’uso del solo alluminio. I laminati, comunemente chiamati FML (Fiber Metal Laminate), sembrerebbero rispondere bene a questo tipo di richiesta, tant’è che il loro uso è già presente nel mondo aeronautico. In generale essi sono strutture ibride con lamine sottili in materiale metallico rinforzare con strati di fibra di materiale polimerico; a seconda del tipo di rinforzo che si usa possono aversi differenti tipologie. In questo lavoro è stato testato in condizioni sia statiche che dinamiche, mediante l’utilizzo della barra di Hopkinson, uno dei tre laminati più diffusi in commercio, il CARALL, dove gli strati di rinforzo sono in carbonio. Lo studio è supportato da una analisi DIC per la misura effettiva delle deformazioni e da un modello numerico opportunamente calibrato