The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from ODP Site 1240 measured by laser-ablation inductively-coupled-plasma mass spectrometry (LA-IPCMS) as a proxy for deep water carbonate saturation state (Δ[CO32-], and therefore [CO32-]), along with δ13C measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analysed as an indicator of oxygenation changes. Our results show lower [CO32-], δ13C and [O2] values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep-water ventilation. However, the difference between LGM and Holocene [CO32-] observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a ‘counteracting’ mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO2 to be ‘sequestered’ by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO2 during the LGM, specifically due to a more efficient biological carbon pump, but also to an increase in average ocean alkalinity

The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO 2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from Ocean Drilling Program Site 1240 measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy for deep water carbonate saturation state (ΔCO 3 2− , and therefore CO 3 2− ), along with δ 13 C measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower CO 3 2− , δ 13 C, and O 2 values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep water ventilation. However, the difference between LGM and Holocene CO 3 2− observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a “counteracting” mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO 2 to be “sequestered” by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO 2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity

Benthic foraminiferal assemblages and environmental drivers along the Kveithola Trough (NW Barents Sea)

We describe the population density, biodiversity and vertical distribution in the sediment of benthic foraminifera, and their relationship to environmental parameters, in the Kveithola Trough (NW Barents Sea). Two staining methods, Cell Tracker Green (CTG) and Rose Bengal (RB), were used to distinguish between living and dead tests. CTG proved to be more effective than RB, and we therefore used this approach to document faunal assemblage variability along a transect of the Trough. The outer shelf shows a diverse benthic foraminiferal assemblage suggesting an oxygenated and oligotrophic environment. The central part appears to be a disturbed area due to rapid circulation changes and organic matter burial in sediments where opportunistic foraminifera colonize only the first centimetres. In contrast, the inner part of the Trough seems to be a stressed environment where species associated with organic-rich sediment and oxygen-depleted environments dominate the living assemblage. At all sites, delicate monothalamids species form part of the assemblage. The peculiar geomorphological and environmental conditions of this area, and the high regional primary and secondary production, are key drivers of foraminiferal assemblage distribution

Graphene Oxide Quantum Dots as the Support for the Synthesis of Gold Nanoparticles and Their Applications as New Catalysts for the Decomposition of Composite Solid Propellants

Graphene oxide quantum dot (GOQD) and reduced GOOD (rGOQD) were synthetized using a simple and straight methodology based on an oxidative treatment and sonication. GOQD and rGOQD were used as supporting agents for the in situ generation of gold nanoparticles, avoiding the use of additional stabilizers. GOQD resulted as a better support than rGOQD because of the presence of higher functional groups that can interact with gold. Theoretical studies through density functional theory revealed the important role of the epoxy groups of GOQD on the stabilization of gold. GOQD and GOQD-Au were tested for the first time as catalysts for the decomposition of solid composite propellants. GOQD not only lowered the decomposition temperature of ammonium perchlorate (AP) but also enhanced the exothermic heat of AP, in comparison to graphene and GO. GOQD-Au increased the energy release; however, the effect on the decrease of the decomposition temperature of AP was not as significant as other previous reported catalysts

Living and dead foraminiferal assemblages of the last decades from Kveithola Trough: Taphonomic processes and ecological highlights

We examine the living and dead benthic foraminiferal assemblages from the topmost 10 cm (using 150 μm sieve fraction) of three sedimentological short records collected in the Kveithola Trough (northwest Barents Sea). Our aim is to reconstruct the environmental variations of the last decades, connected to the interaction among the North Atlantic and the Arctic water masses. Our samples are collected at water depths between 150 and 380 m during the Eurofleets2-BURSTER oceanographic cruise, on board of the R/V Polarstern (June 2016). In the Cell Tracker Green (CTG) labelled living foraminiferal fauna, the main species are Pullenia bulloides, Globobulimina auriculata, and Nonionellina labradorica, while in the dead assemblages the main species are Cassidulina neoteretis, Cibicidoides lobatulus, and Cassidulina reniforme (outer, inner, and shelf stations, respectively). The dead foraminiferal assemblages show no significant traceable environmental changes in the Kveithola Trough area occurred during the last ca. 100 years. Conversely, the living foraminiferal fauna shows that this area is subject to variations related to circulation changes and organic matter burial in sediments, to which the biota adapts quickly. Moreover, the species that are only observed in the dead foraminiferal assemblages and not in the living CTG-labelled foraminiferal assemblages (e.g. C. reniforme) are typical of colder water and highlight the ongoing warming of the Arctic area. We find that the preservation of foraminiferal tests may bias the paleontological results. The agglutinated tests are often disintegrated, and the delicate calcareous ones are broken. The environmental conditions (style of sedimentation, bottom currents, interaction with other communities) can weaken the foraminiferal tests and make them prone to breakage or dissolution

BURSTER - Bottom Currents in a Stagnant Environment. EUROFLEETS-2 Cruise Summary Report

Eurofleets 2- BURSTER cruise was conducted onboard the German icebreaker RV Polarstern (Expedition PS99-1a) during June 13–23, 2016 (Bremerhaven-Longyearbyen) having the principal objective of investigating the hydrographic and bio-geochemical conditions of the Kveithola glacial trough (south of Svalbard), and to uncover the possible existence of gas seepage activity in the area. Although the BURSTER research was intended as a preparatory study for the writing of a major research project, the amount of planned activities onboard was really ambitious. Thanks to a tireless, enthusiastic group formed by 11 students out of 23 scientists, a Teacher at Sea (GIFT, EU programme), and a technician from a small-medium enterprise operating with a transportable electron microscope (Nanovision Srl,), 89 multi-cores (22.50 m of sediments and 830 sub-samples), 265 water samples, 28 CTD casts along 7 transects and 2.57 km of benthic camera survey (OFOS), were collected during only 48 hours. In addition, according to the project work program, 24 hours were dedicated to the maintenance/recovery of two moorings that were deployed west of Svalbard during the Eurofleets 2- PREPARED project (RV G.O. Sars, June 2014). BURSTER group was actively supported by 4 scientists of the Italian PNRA project DEFROST, 4 AWI scientists of expedition PS99-1 and the Chief scientist, T. Soltwedel. The cruise successfully recovered evidences of chemosynthetic activity in the Kveithola Trough with the presence of benthic fauna and large tabular and/or irregular-shaped rocks that share the same characteristics of methanogenic environments observed in gas seepage areas. The promising preliminary results obtained from this initial survey of the area will represent the base for the writing of a major project for a detailed investigation of the microbial, biologic and oceanographic system of the Kveithola Trough

BURSTER: BOTTOM CURRENTS IN A STAGNANT ENVIRONMENT

The glacigenic Kveithola Trough is an abrupt and narrow (100 km-long and 13 kmwide) sedimentary system located in the NW Barents Sea (Rebesco et al., 2011; Ruther et al., 2012; Bjarnadóttir et al., 2013). Along with the larger Storfjorden glacial system, it hosted, during the last glaciation, ice streams draining ice from the southern Svalbard in the north and Bear Island in the south (Andreassen et al., 2008; Pedrosa et al., 2011). During the CORIBAR Cruise on board RV Maria S. Merian (16.07. - 15.08.2013; Tromsø - Tromsø) a wealth of geophysical data including PARASOUND sub-bottom profiles and multibeam, and sediment samples retrieved by gravity-, multi-, boxcorer, and the seafloor drill rig MeBo (Hanebuth et al., 2013) were collected on the Kveithola Drift, a complex morphological and depositional feature confined in the innermost part of the glacially-erode Kveithola Trough. The internal seismic reflections of the drift show a drastic thinning and termination towards the north. Here a distinct moat can be identified, which implies the strong influence of dense bottom currents, inferred to flow (or at least to have flown in the past) towards the outer shelf. The highly dynamic environment depicted from the morphological and structural characteristics of the sediment drift is in contrast with the sediment facies and preserved biota observed in surface sediments. The retrieved sediments have a strong smell of H2S and are mostly black, organic matter-rich, with abundant black worm tubes (Pogonophora worms), and occasionally with living reddish polychaetes (possibly ampharetid polychaetes). The recent and living benthic foraminiferal assemblage observed in the sediments is characterized by the presence of typically oxygen-depleted environmental taxa. Any bottom current-related sedimentary structure was observed on surface sediments. The Kveithola Drift that formed under persistent dense bottom currents appears today as a “stagnant environment” strongly affected by low-oxygen conditions with likely ongoing seep activity. The presence of an apparently stagnant, possibly chemosynthetic, environment in the sediment drift area of the inner Kveithola Through was an unexpected discovery. We therefore think it is of primary importance to better define the bio-geochemical and oceanographic characteristics of the inner area of the Kveithola Trough in order to better define this “anomalous” sedimentary system and to understand the local and global impact of this type of environment in terms of carbon cycle and the transfer of chemosynthetic-derived products to the deeper environments as consequence of regional oceanographic patterns. The BURSTER project aims to investigate the geodynamic and hydrographic conditions, and the active gas seepage present in the pockmark-field piercing the sediment drift located in the inner part of the Kveithola Trough. The type of investigation is strongly multidisciplinary including physical and biological oceanography, water, sediment and gas geochemistry, micropaleontology, microbiology geophysics, and sedimentology. The investigations will be carried out within three working days with the aim of outlining the principal oceanographic, biological and geological aspects of the area on which building up further investigations