What the geological past can tell us about the future of the ocean’s twilight zone

Paleontological reconstructions of plankton community structure during warm periods of the Cenozoic (last 66 million years) reveal that deep-dwelling ‘twilight zone’ (200–1000 m) plankton were less abundant and diverse, and lived much closer to the surface, than in colder, more recent climates. We suggest that this is a consequence of temperature’s role in controlling the rate that sinking organic matter is broken down and metabolized by bacteria, a process that occurs faster at warmer temperatures. In a warmer ocean, a smaller fraction of organic matter reaches the ocean interior, affecting food supply and dissolved oxygen availability at depth. Using an Earth system model that has been evaluated against paleo observations, we illustrate how anthropogenic warming may impact future carbon cycling and twilight zone ecology. Our findings suggest that significant changes are already underway, and without strong emissions mitigation, widespread ecological disruption in the twilight zone is likely by 2100, with effects spanning millennia thereafter

Arterial Spin Labeling Reveals Disrupted Brain Networks and Functional Connectivity in Drug-Resistant Temporal Epilepsy

Resting-state networks (RSNs) and functional connectivity (FC) have been increasingly exploited for mapping brain activity and identifying abnormalities in pathologies, including epilepsy. The majority of studies currently available are based on bloodoxygenation- level-dependent (BOLD) contrast in combination with either independent component analysis (ICA) or pairwise region of interest (ROI) correlations. Despite its success, this approach has several shortcomings as BOLD is only an indirect and non-quantitative measure of brain activity. Conversely, promising results have recently been achieved by arterial spin labeling (ASL) MRI, primarily developed to quantify brain perfusion. However, the wide application of ASL-based FC has been hampered by its complexity and relatively low robustness to noise, leaving several aspects of this approach still largely unexplored. In this study, we firstly aimed at evaluating the effect of noise reduction on spatio-temporal ASL analyses and quantifying the impact of two ad-hoc processing pipelines (basic and advanced) on connectivity measures. Once the optimal strategy had been defined, we investigated the applicability of ASL for connectivity mapping in patients with drug-resistant temporal epilepsy vs. controls (10 per group), aiming at revealing between-group voxel-wise differences in each RSN and ROI-wise FC changes. We first found ASL was able to identify the main network (DMN) along with all the others generally detected with BOLD but never previously reported from ASL. For all RSNs, ICA-based denoising (advanced pipeline) allowed to increase their similarity with the corresponding BOLD template. ASL-based RSNs were visibly consistent with literature findings; however, group differences could be identified in the structure of some networks. Indeed, statistics revealed areas of significant FC decrease in patients within different RSNs, such as DMN and cerebellum (CER), while significant increases were found in some cases, such as the visual networks. Finally, the ROI-based analyses identified several inter-hemispheric dysfunctional links (controls > patients) mainly between areas belonging to the DMN, right-left thalamus and right-left temporal lobe. Conversely, fewer connections, predominantly intra-hemispheric, showed the opposite pattern (controls < patients). All these elements provide novel insights into the pathological modulations characterizing a “network disease” as epilepsy, shading light on the importance of perfusion-based approaches for identifying the disrupted areas and communications between brain regions

Episodes of intensified biological productivity in the subtropical Atlantic Ocean during the termination of the Middle Eocene Climatic Optimum (MECO)

The Middle Eocene Climatic Optimum (MECO) is an ~500 kyr interval of pronounced global warming from which the climate system recovered in <50 kyr. The deep-sea sedimentary record can provide valuable insight on the marine ecosystem response to this protracted global warming event and consequently on the ecological changes during this time. Here we present new benthic foraminiferal assemblage data from Ocean Drilling Program Site 1051 in the subtropical North Atlantic, spanning the MECO and post-MECO interval (41.1 to 39.5 Ma). We ␣nd little change in the species composition of benthic foraminiferal assemblages during the studied interval, suggesting that the rate of environmental change was gradual enough that these organisms were able to adapt. However, we identify two transient intervals associated with peak warming (higher-productivity interval (HPI)-1; 40.07–39.96 Ma) and shortly after the MECO (HPI-2; 39.68–39.55 Ma), where benthic foraminiferal accumulation rates increase by an order of magnitude. These HPIs at Site 1051 appear to coincide with intervals of strengthened productivity in the Tethys, Southern Ocean, and South Atlantic, and we suggest that an intensi␣ed hydrological cycle during the climatic warmth of the MECO was responsible for eutrophication of marine shelf and slope environments

Ecological response of Tethyan benthic foraminifera to the Middle Eocene Climatic Optimum (MECO) from the Alano section (NE Italy)

none3noneBoscolo Galazzo F.; Giusberti L.; Luciani V.BOSCOLO GALAZZO, Flavia; Giusberti, Luca; Luciani, V

Author&apos;s personal copy Paleoenvironmental changes during the Middle Eocene Climatic Optimum (MECO) and its aftermath: The benthic foraminiferal record from the Alano section (NE Italy)

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. The Middle Eocene Climatic Optimum (MECO) was one of the most severe, short-term global climate perturbations of the Cenozoic that occurred at ca. 40 Ma and was characterized by a gradual 4-6°C temperature increase of intermediate and deep-waters. We investigated the response to the MECO of the deep-sea ecosystem in the central-western Tethys, through a quantitative study of bathyal benthic foraminiferal assemblages in the expanded and continuous Alano section (northeastern Italy), for which data on stratigraphy, lithology, isotope and trace element geochemistry, and calcareous microplankton were available. During the gradual warming of MECO (lasting between 350 and 650 kyr) marine export productivity increased, causing a significant but transient restructuring of benthic foraminiferal faunas, which changed gradually from assemblages typical for oligo-mesotrophic sea floor conditions to assemblages indicative of more eutrophic conditions. Just after the peak MECO conditions, which lasted less than 100 kyr, a prolonged phase of environmental instability (~500 kyr) occurred, marked by even more highly increased export productivity leading to bottom-water oxygen depletion, as reflected in deposition of organic-rich sediments and multiple peaks of bi-triserial opportunistic benthic foraminiferal taxa, including buliminids, bolivinids and uvigerinids. The high productivity may have been caused by a strong influx of nutrient-bearing fresh water into the basin, due to the increased vigour of the hydrological cycle during the warm period, and this increased fresh-water influx might have been a factor in enhancing water column stratification, thus exacerbating the hypoxic conditions, which persisted about 400-500 kyr. After deposition of the organic-rich layers the environmental perturbation ended, and benthic foraminiferal assemblages recovered while conditions became very similar to what they were before the MECO. The environmental disturbance during and directly after the MECO thus strongly but transiently affected benthic foraminiferal assemblages in the central western Tethys

Paleoenvironmental changes during the Middle Eocene Climatic Optimum (MECO) and its aftermath: the benthic foraminiferal record from the Alano section (NE Italy)

The Middle Eocene Climatic Optimum (MECO) was one of the most severe, short-term global climate perturbations of the Cenozoic, with a duration estimated at between 500-750 kyr (centered at 40.6 to 40.0 Ma), and characterized by a gradual, 4-6°C temperature increase of intermediate and deep-waters. We investigated the response to the MECO of the deep-sea ecosystem in the central-western Tethys, through a quantitative study of bathyal benthic foraminiferal assemblages in the expanded and continuous Alano section (northeastern Italy), for which data on stratigraphy, lithology, isotope and trace element geochemistry, and calcareous microplankton were available. During the gradual warming of MECO (lasting between 350-650 kyr) marine export productivity increased, causing a significant but transient restructuring of benthic foraminiferal faunas, which changed gradually from assemblages typical for oligo-mesotrophic sea floor conditions to assemblages indicative of more eutrophic conditions. Just after the peak MECO conditions, which lasted less than 100 kyr, a prolonged phase of environmental instability (~ 500 kyr) occurred, marked by even more highly increased export productivity leading to bottom-water oxygen depletion, as reflected in deposition of organic-rich sediments and multiple peaks of bi-triserial opportunistic benthic foraminiferal taxa, including buliminids, bolivinids and uvigerinids. The high productivity may have been caused by a strong influx of nutrient-bearing fresh water into the basin, due to the increased vigour of the hydrological cycle during the warm period, and this increased fresh-water influx might have been a factor in enhancing water column stratification, thus exacerbating the hypoxic conditions, which persisted about 400-500 kyr. After deposition of the organic-rich layers the environmental perturbation ended, and benthic foraminiferal assemblages recovered while conditions became very similar to what they were before the MECO. The environmental disturbance during and directly after the MECO thus strongly but transiently affected benthic foraminiferal assemblages in the central western Tethys

Functional Sensitivity of Dual-Echo ASL in Localizing Active and Imagery Hand Movements

Dual-echo arterial spin labeling (DE-ASL) techniques have been recently proposed for thesimultaneous acquisition of ASL and blood-oxygenation-level-dependent (BOLD) functionalmagnetic resonance imaging (fMRI) data (Woolrich et al., 2006). The images acquired at the firstecho time are perfusion weighted (ASL), while the images from the second echo are primarilyT2* weighted, thus sensitive to the BOLD signal (Leontiev and Buxton, 2007). The sequence isuseful when the simultaneous estimation of blood flow and BOLD signal are targeted. Thepurpose of this study was to assess the sensitivity of the DE-ASL sequence in comparison to theconventional one (BOLD-fMRI) in detecting brain activations elicited by active and motor imageryhand movements