Marine barite morphology as an indicator of biogeochemical conditions within organic matter aggregates

Marine barite is commonly used as a proxy to reconstruct past ocean productivity. Its distribution in the water column mirrors organic carbon fluxes since it precipitates within microenvironments in decomposing organic matter aggregates. Barite and barium proxies are therefore used to study various aspects of organic matter remineralization and the marine carbon cycle. Barite naturally occurs in a wide variety of crystal sizes and morphologies, but barite crystals that form in the ocean water column are dominantly 1–2 μm in length and have barrel-shaped morphologies. Here, we conducted a series of laboratory experiments to determine the physical and chemical conditions that yield barite crystals similar to marine barite. We found that barite saturation index, the presence and identity of organic compounds, and experiment duration all exert a strong influence on barite crystal size and morphology. Barrel-shaped, 1 μm length crystals resembling marine barite were produced in experiments with a barite saturation index of 2.5, soy phospholipid concentrations of ≥50 mg L−1, and experiment durations of ≤10 min. These findings help constrain the plausible biogeochemical conditions within the aggregate microenvironments in which marine barite precipitates. Relatively high experimental concentrations of phospholipids are consistent with the hypothesized involvement of extracellular polymeric substances in marine barite precipitation. Short experiment durations suggest that a favorable saturation state may be short-lived in marine organic matter aggregates. We present detailed mineralogical and crystallographic analyses of the crystals we synthesized to gain insight into barite crystal growth. This work deepens our understanding of the mechanisms behind marine barite precipitation and sheds light on microscale spatial and temporal dynamics within organic matter aggregates.U.S. Department of Defense National Defense Science and Engineering Graduate Student FellowshipGeological Society of Americ

Role of climate variability on deep-water dynamics and deoxygenation during sapropel deposition: New insights from a palaeoceanographic empirical approach

https://doi.org/10.1016/j.palaeo.2023.111601Modern marine settings are experiencing rapid deoxygenation mainly forced by global warming and anthropogenic eutrophication. Therefore, studies that assess the role of climate variability in large spatiotemporal deoxygenations during past climate changes are needed to better comprehend the consequences of the current global warming and ocean deoxygenation. In this respect, deep marine sediments associated to past oxic-toanoxic transitions are useful palaeoarchives for understanding the interplay between climate variability, deepwater dynamics and large-scale deoxygenation. Moreover, they can offer long-term perspectives to modern marine settings that are suffering oxygen depletion due to climate change and anthropogenic pressure. In particular, sapropel layers from the Middle Pleistocene to the Holocene are excellent palaeoarchives of past large-scale deoxygenation events, since (i) they occurred during a similar Mediterranean hydrogeographic configuration to the present, (ii) have a robust chronological control, and (iii) previous studies have reconstructed the climate conditions that ruled during their deposition. In this work, we have applied empirical palaeoceanographic conceptual models to five sapropels (S1, S5, S6, S7 and S8) in three Eastern Mediterranean (EM) settings. The models suggest that the hydrographic regimes of all studied sapropels can be considered as analogues to those observed in certain modern marine restricted settings. The results obtained support the idea that climate and the degree of surface-water freshening are the primary factors that influence deep-water dynamics in marine restricted settings, that in turn control the frequency and intensity of bottom-water deoxygenation and the stability and depth of the chemocline. The deepest EM sites are the most vulnerable locations to develop bottom-water restriction and deoxygenation. Local hydrogeographic factors play an essential role in the extent and frequency of bottom-water deoxygenation. Particulate shuttling was very intense during sapropel deposition and water-mass exchange between EM and Western Mediterranean controlled the intensity of the basin reservoir effect and Mo budget in EM.Grants PID2019-104624RB-I00, PID2019-104625RB-100TED2021-131697B-C22 funded by MCIN/AEI/ 10.13039/5011000110 33,Grants FEDER/Junta de Andalucía P18-RT-3804P18-RT- 4074Groups RNM-179RNM-178 funded by Junta de AndalucaLausanne University (Switzerland) for Rock-eval analyses and TOC measurementsCenter for Scientific Instrumentation (CIC, University of Granada)XRF Unit of the IACT (CSIC-UGR) for the ICP and XRF analyse

Rapid Climate Changes in the Westernmost Mediterranean (Alboran Sea) Over the Last 35 kyr: New Insights From Four Lipid Paleothermometers (UK' 37, TEXH 86, RI-OH', and LDI)

This study was supported by Grant PID2019-104624RB-I00 funded by MCIN/AEI/ 10.13039/501100011033, Grants FEDER/Junta de Andalucia-Consejeria de Economia y Conocimiento P18-RT-3804 and P18-RT- 4074, and Research Group RNM-179 (Junta de Andalucia). The authors also thank the Unidad Cientifica de Excelencia UCE-PP2016-05 (University of Granada). This study also received funding from the Netherlands Earth System Science Center (NESSC) through a gravitation grant (024.002.001) to J. S. Sinninghe Damste and S. Schouten from the Dutch Ministry for Education, Culture and Science. M. Rodrigo-Gamiz acknowledges funding from the Andalucia Talent Hub Program co-funded by the European Union's Seventh Framework Program (COFUND-Grant Agreement No 291780) and the Junta de Andalucia and from the Juan de la Cierva-Incorporacion program in the University of Granada (IJCI-2017-33,755) from Secretaria de Estado de I + D + i, Spain. We thank the captain, crew, and participants of the Gasalb cruise onboard R/V Pelagia for assistance during sampling. We are also grateful to the Poznan Radiocarbon Laboratory (Poland), the Leibniz Laboratory for Radiometric Dating and Stable Isotope Research (Germany), and the Centre for Scientific Instrumentation (CIC, Spain) for analyses. The authors thank Jort Ossebaar, Anchelique Mets, Marianne Baas and Karsten Dekker (all at NIOZ) for laboratory assistance. Thanks to Prof. Giuseppe Siani (Universite Paris-Sud Orsay) and Jose Manuel Mesa Fernandez for their help and comments on the age model. We thank the Associate Editor, Dr. Yige Zhang, two anonymous reviewers, and Dr. Felix J. Elling for their helpful comments that improved the manuscript substantially. Funding for open access charge from Universidad de Granada/CBUA.The westernmost Mediterranean is one of the most sensitive areas to global climate change and high sedimentation rates allow recording high frequency variability. We present a high-resolution paleotemperature reconstruction over the last 35 kyr using, for the first time, four independent organic sea surface temperature (SST) proxies (UK' 37, TEXH 86, RI-OH' and LDI) based on alkenones, (hydroxy) isoprenoid GDGTs, and long-chain diols. We also generated a δ18O of planktonic foraminifera G. bulloides record together with records of bulk parameters (total organic carbon content, δ13Corg) and the accumulation rates of different biomarkers to provide insights into terrestrial input and primary producers. All derived-SST records showed similar trends over the last 35 kyr, revealing abrupt temperature variations during the last seven Dansgaard- Oeschger (D/O) cycles, the three Heinrich (H) events, the Last Glacial Maximum, and the Younger Dryas. H3 is recognized as the coldest event, while H1 was recorded by all SST proxies as the most abrupt one. In general, TEXH 86-, RI-OH'- and LDI-SST estimates were lower than those obtained from UK' 37. The LDI paleothermometer recorded the largest range of absolute SSTs over the whole period (ca. 20°C) followed by RI-OH' (ca. 16°C). TEXH 86, RI-OH' and LDI proxies reflected sudden SST changes during the D/O 6 and 5 particularly well. Low BIT values and the abundance of C32 1,15-diol in range with typical marine values indicated only minor input of continental organic matter. Accumulation rates of different lipid biomarkers were generally modulated by D/O cycles, suggesting enhanced productivity during D/O interstadials and the Bölling- Alleröd period.Grants FEDER/Junta de Andalucia-Consejeria de Economia y Conocimiento PID2019-104624RB-I00 MCIN/AEI/ 10.13039/501100011033 P18-RT-3804 P18-RT- 4074Research Group RNM-179Unidad Cientifica de Excelencia UCE-PP2016-05Netherlands Earth System Science Center (NESSC) through a gravitation grant 024.002.001Andalucia Talent Hub Program - European Union's Seventh Framework Program (COFUND-Grant) 291780 Junta de AndaluciaJuan de la Cierva-Incorporacion program in the University of Granada from Secretaria de Estado de I + D + i, Spain IJCI-2017-33,755Universidad de Granada/CBU

Water column barium sulfate dissolution and shielding by organic matter aggregates: Implications for the pelagic barite proxy

T.L. was partially supported by a U.S. Department of Defense National Defense Science and Engineering Graduate Student Fellowship and a Ruth Newmark Scholarship from the UCSD Friends of the International Center. M. G. was supported by the Triton Research and Experiential Learning Scholars program. The authors thank Benjamin Gruber, Cecilia de la Prada, and Dr. Erica Ferrer and for their valuable assistance.Pelagic barite (BaSO4) and related proxies are useful tools for reconstructing the marine carbon cycle. The factors controlling pelagic barite dissolution in the ocean water column are poorly understood, which adds uncertainty to Ba-based reconstructions. Here, we conducted static laboratory incubations to test the sensitivity of barium sulfate dissolution rate to a range of commonly occurring seawater pH, salinity, and temperature conditions. We observed relatively rapid dissolution rates ranging from 1.7 & PLUSMN; 0.4 to 3.4 & PLUSMN; 0.8 pg BaSO4 day-1 for these experiments, and we did not observe statistically significant differences in the rate of dissolution with varying pH, salinity, or temperature. The slowest dissolution rate observed in these experiments suggests that an average barium sulfate crystal would survive in the ocean water column just 6.2 & PLUSMN; 0.3 days. We estimate that an average isolated pelagic barite crystal would take 67 years to sink down through the water column, so our experiments imply that solitary pelagic barite crystals do not survive this transit. We conducted an additional experiment on a roller table to assess the impact of organic matter aggregates on barium sulfate dissolution. Free barium sulfate crystals incubated on the roller table dissolved even more rapidly than crystals in the static experiment (19 & PLUSMN; 7 pg BaSO4 day � 1), but barium sulfate crystals incubated with organic matter aggregates showed little sign of dissolution over time. Our findings suggest that organic matter aggregates play a vital role in shielding pelagic barite from dissolution in the water column. This implies that pelagic barite in ocean sediments records the arrival of organic detritus to the seafloor, not just barite crystal formation in sinking organic matter in the upper water column. Additional work is needed to determine which aspects of the marine carbon cycle the pelagic barite proxy captures.U.S. Department of Defense National Defense Science and Engineering Graduate Student FellowshipUCSD Friends of the International CenterTriton Research and Experiential Learning Scholars progra

Barite formation in the ocean: Origin of amorphous and crystalline precipitates

We also thank editors and two anonymous reviewers for helpful comments that have significantly improved this contribution.Ocean export production is a key constituent in the global carbon cycle impacting climate. Past ocean export production is commonly estimated by means of barite and Barium proxies. However, the precise mechanisms underlying barite precipitation in the undersaturated marine water column are not fully understood. Here we present a detailed mineralogical and crystallographic analysis of barite from size-fractionated particulate material collected using multiple unit large volume in-situ filtration systems in the North Atlantic and the Southern Ocean. Our data suggest that marine barite forms from an initial amorphous phosphorus-rich phase that binds Ba, which evolves into barite crystals whereby phosphate groups are substituted by sulfate. Scanning electron microscopy observations also show the association of barite particles with organic matter aggregates and with extracellular polymeric substances (EPS). These results are consistent with experimental work showing that in bacterial biofilms Ba binds to phosphate groups in both cells and EPS, which promotes locally high concentrations of Ba leading to saturated microenvironments favoring barite precipitation. These results strongly suggest a similar precipitation mechanism in the ocean, which is consistent with the close link between bacterial production and abundance of Ba-rich particulates in the water column. We argue that EPS play a major role in mediating barite formation in the undersaturated oceanic water column; specifically, increased productivity and organic matter degradation in the mesopelagic zone would entail more extensive EPS production, thereby promoting Ba bioaccumulation and appropriate microenvironments for barite precipitation. This observation contributes toward better understanding of Ba proxies and their utility for reconstructing past ocean export productivity. This article is part of a special issue entitled: “Cycles of trace elements and isotopes in the ocean – GEOTRACES and beyond” - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.This study was supported by the European Regional Development Fund (ERDF) co-financed grants CGL2015-66830-R and CGL2017- 92600-EXP (MINECO Secretaría de Estado de Investigación, Desarrollo e Innovación, Spain), Research Group RNM-179 and BIO 103 (Consejería de Economía, Innovación, Ciencia y Empleo, Junta de Andalucía) and the University of Granada (Unidad Científica de Excelencia UCE-PP2016-05). We thank the Center for Scientific Instrumentation (CIC, University of Granada), the Warm Core Rings project, and NSF OCE- 0961660 for supporting sample collection during MV1101

Religion: Interrelationships and Opinions in Children and Adolescents. Interaction between Age and Beliefs

The current trend of secularization seems to be leading to a gradual withdrawal of religion from public spaces. However, in an increasingly internationalized world, it is becoming more and more important to study the roles of religion and religiosity and their potential in relation to dialogue and social conflicts and tensions. Education is a vital field within which to address this religious issue and create an educational dialogue in order to promote coexistence. By following a quantitative, descriptive, cross-sectional study, based on a quasi-experimental methodology with a social–analytical character, our aim is to assess the existing connections between religion, interrelation and opinion in Spanish children and adolescents. Special attention is paid to the interaction between age and beliefs. We carried out our study with the use of a questionnaire distributed to eleven secondary schools, with students aged between 11 and 16 years old, in three regions of southern Spain (Andalusia, Ceuta, and Melilla) characterized by high religious diversity and multiculturalism. The multivariate analysis carried out in this study identifies the effects of variance on the influence of age and religion, highlighting the interaction between the two. It is observed that the youngest students are those who express their opinions about religion the least, while those belonging to younger age groups and majority religions are those who express a greater religious coexistence, with Muslims externalizing their religious condition the most.UNES. Universidad, escuela y sociedad. Ciencias Sociales (Cod.: HUM985

On-Surface Hydrogen-Induced Covalent Coupling of Polycyclic Aromatic Hydrocarbons via a Superhydrogenated Intermediate

The activation and subsequent covalent coupling of polycyclic aromatic hydrocarbons (PAHs) are of great interest in fields like chemistry, energy, biology, or health, among others. However, this is not a trivial process. So far, it is based on the use of catalysts that drive and increase the efficiency of the reaction. Here, we report on an unprecedented method in which the dehydrogenation and covalent coupling is thermally activated in the presence of atomic hydrogen and a surface. This mechanism, which requires of the superhydrogenation of the PAHs, has been characterized by high-resolution scanning tunnelling microscopy (STM) and rationalized by density functional theory (DFT) calculations. This work opens a door toward the formation of covalent, PAH-based, macromolecular nanostructures on low-reactive surfaces, thus facilitating its applicability.Comment: This manuscript version is made available under the CC-BY-NC-ND 4.0 licens

Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean

Mud volcanoes (MVs) are the most prominent indicators of active methane/hydrocarbon venting at the seafloor on both passive and active continental margins. Their occurrence in the western Mediterranean is patent at the West Alboran Basin, where numerous MVs develop overlaying a major sedimentary depocentre containing overpressured shales. Although some of these MVs have been studied, the detailed biogeochemistry of expelled mud so far has not been examined in detail. This work provides the first results on the composition and origin of organic matter, anaerobic oxidation of methane (AOM) processes and general characteristics on MV dynamics using lipid biomarkers as the main tool. Lipid biomarker analysis was performed on MV expelled material (mud breccias) and interbedded hemipelagic sediments from Perejil, Kalinin and Schneider's Heart MVs located in the northwest margin of the Alboran Sea. The n alkane distributions and n alkane-derived indices (CPI and ACL), in combination with the epimerization degree of hopanes (22S/(22S+22R)) indicate that all studied mud breccia have a similar biomarker composition consisting of mainly thermally immature organic matter with an admixture of petroleum-derived compounds. This concordant composition indicates that common source strata must feed all three studied MVs. The past or present AOM activity was established using lipid biomarkers specific for anaerobic methanotrophic archaea (irregular isoprenoids and dialkyl glycerol diethers) and the depleted carbon isotope composition (δ13C) of crocetane/phytane. The presence of these lipid biomarkers, together with the low amounts of detected glycerol dialkyl glycerol tetraethers, is consistent with the dominance of anaerobic methanotrophs of the ANME-2 over ANME-1, at least in mud breccia from Perejil MVs. In contrast, the scarce presence or lack of these AOM-related lipid biomarkers in sediments from Kalinin and Schneider's Heart MVs, suggests that no recent active methane seepage has occurred at these sites. Moreover, the observed methane concentrations support the current activity of Perejil MV, and the very low methane seepage activity in Kalinin and Schneider's Heart MVs.This study was supported by Project CTM2009-07715, CGL2011-1441 and CGL2012-32659 (MINECO, Spain), by the VENI grant from the Netherlands Organization for Scientific Research (NWO) and the Royal Netherland Institute for Sea Research (NIOZ via ZKOprogramme) (Texel, The Netherlands). C. F. López-Rodríguez was funded by a JAE-PhD fellowship from the CSIC (Spain)

A los adolescentes que no les gusta la educación física tienen peor condición física y más obesidad ¿Mito o realidad? Los estudios AVENA y UP&DOWN

Introduction: In the physical education context a well-known myth suggest that obese and unfit youth dislike physical education. Objective: To examine if adolescents who dislike physical education have higher levels of fatness and lower of fitness than their peers. Methods: Participants included 2606 (49.3% girls) adolescents from AVENA and UP&DOWN studies. physical education enjoyment was assessed with a 7-point Likert scale. Fatness was assessed with BMI, skinfolds and waist circumference. Physical fitness was assessed with cardiorespiratory, motor and muscular fitness tests. Results: Boys who dislike physical education had similar levels of fatness and fitness than their peers (all P>0.05). Adolescent girls who dislike physical education had higher levels in body fat (P=0.035), and lower levels in muscular (P=0.007) and motor (P=0.007) fitness than their peers. Conclusion: Since only girls who dislike physical education seem to have, albeit weak, higher levels of fatness and lower of fitness than their peers, it partially confirms the myth in adolescent girls.Introducción: En el contexto de la EF (educación física), un mito bien conocido podría sugerir que a los jóvenes obesos y con baja condición física no les gusta la EF. Objetivo: Examinar si a los adolescentes a los que no les gusta la EF tienen niveles más altos de obesidad y niveles más bajos de forma física que sus compañeros. Métodos: Se tomó a 2606 participantes (49.3% chicas) adolescentes de los estudios AVENA y UP&DOWN. El disfrute de la EF se evaluó empleando una escala Likert de 7 puntos. La obesidad se evaluó mediante el IMC, pliegues cutáneos y circunferencia de la cintura. La condición física fue evaluada mediante pruebas cardiorespiratorias, motoras y musculares. Resultados: Los chicos a los que no les gusta la EF presentaron niveles similares de obesidad que sus compañeros (total P>0.05). Las chicas adolescentes a las que no les gusta la EF presentaron niveles más altos de grasa corporal (P=0.035), y niveles más bajos en condición física muscular (P=0.007) y motora (P=0.007) que sus compañeros. Conclusión: Dado que solo las chicas a las que no les gusta la EF parecen presentar, sin bien levemente, niveles más altos de obesidad y niveles menores de forma física que sus compañeros, el mito se confirma parcialmente para las chicas adolescentes.The AVENA study was supported by the Spanish Ministry of Health (FIS Nº 00/0015) and the UP&DOWN study was supported by the Spanish Ministry of Economy and Competitiveness (DEP 2010-21662-C04)

Barium bioaccumulation by bacterial biofilms and implications for Ba cycling and use of Ba proxies

Supplementary Information accompanies this paper at https://doi.org/10.1038/s41467- 018-04069-z.Data availability. The datasets generated during the current study are available from the corresponding author.Ba proxies have been broadly used to reconstruct past oceanic export production. However, the precise mechanisms underlying barite precipitation in undersaturated seawater are not known. The link between bacterial production and particulate Ba in the ocean suggests that bacteria may play a role. Here we show that under experimental conditions marine bacterial biofilms, particularly extracellular polymeric substances (EPS), are capable of bioaccumulating Ba, providing adequate conditions for barite precipitation. An amorphous P-rich phase is formed at the initial stages of Ba bioaccumulation, which evolves into barite crystals. This supports that in high productivity regions where large amounts of organic matter are subjected to bacterial degradation, the abundant EPS would serve to bind the necessary Ba and form nucleation sites leading to barite precipitation. This also provides new insights into barite precipitation and opens an exciting field to explore the role of EPS in mineral precipitation in the ocean.This study was supported by the European Regional Development Fund (ERDF) cofinanced grant CGL2015-66830-R (MINECO Secretaría de Estado de Investigación, Desarrollo e Innovación, Spain), Research Groups BIO 103 and RNM-179 (Junta de Andalucía), and the University of Granada (Unidad Científica de Excelencia UCEPP2016-05)