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

Towards a more integrative approach for environmental decision-making in Brazilian transitional waters: improving biomonitoring surveys with a benthic foraminiferal biotic index

This study represents the first attempt to determine the indicator values of benthic foraminiferal species in Brazilian transitional waters. It also uses a regionally adapted species list to explore the potential application of Foram-AMBI, a biotic index for ecological quality. To test this, we assigned 95 living (rose-bengal-stained) benthic foraminiferal species into five ecological groups (EGs), based on the weighted-averaging (WA) optimum and tolerance to the total organic carbon (TOC) contents. Selected and published regional studies were used as the database, while independent Brazilian datasets from Sepetiba Bay and Guanabara Bay – the most polluted regions – were used to validate the ecological group assignments through Foram-AMBI. Furthermore, ecological quality status (EcoQS) criteria adapted to Brazil were developed for Foram-AMBI. The index accurately reflects the degraded environmental conditions in these two ecosystems, with moderate to poor ecological quality status in the most polluted areas. This was further confirmed by significant correlations between Foram-AMBI and TOC in both bays. This study highlights the importance of developing regional species lists and EcoQS criteria for Foram-AMBI, as the accuracy of the Brazilian list was better than that of the European list. While further research across broader pollution gradients is needed, our findings confirm the suitability and reliability of benthic foraminifera as biological indicators for assessing environmental quality in transitional waters.</p

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