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Marine sediments can be used to reconstruct the evolution of seawater [SO42-] and δ34S over time, two key parameters that contribute to refine our understanding of the sulfur cycle and thus of Earth's redox state. δ34S evolution can be measured from carbonates, barites and sulfate evaporites. [SO42-] variations can be reconstructed using fluid inclusions in halites, a method that only allows a low-resolution record. Reconstruction of the past sulfur cycle could be improved if carbonates allowed the tracking of both seawater δ34S and [SO42-] variations in a sole, continuous sedimentary repository. However, most primary carbonates formed in the ocean are biogenic, and organisms tend to overprint the geochemical signatures of their carbonates through a combination of processes often collectively referred to as vital effects. Hence, calibrations are needed to allow seawater δ34S and [SO42-] reconstructions based on biogenic carbonates. Because foraminifera are important marine calcifiers, we opted to focus on calcite synthesized by individuals of rosalinid benthic foraminifera cultured in the laboratory under controlled conditions, with varying seawater [SO42-] (ranging from 0 to 180 mM). Our experimental design allowed us to obtain foraminiferal asexual reproduction over several generations. We measured bulk carbonate-associated sulfate (CAS) content and sulfur isotopic composition (δ34SCAS) on samples of tens to hundreds of specimens from a selection of culture media, where [SO42-] varied from 5 to 60 mM. Increasing or decreasing [SO42-] with respect to modern-day seawater concentration (28 mM) impacted foraminiferal population size dynamics and the total amount of bioprecipitated carbonate. Foraminiferal CAS concentration increased proportionally with [SO42-] concentration from 5 mM up to 28 mM and then showed a plateau from 28 to 60 mM. The existence of a threshold at 28 mM is interpreted as the result of a control on the precipitation fluid chemistry that foraminifera exert on the carbonate precipitation loci. However, at high seawater sulfate concentrations (> 40 mM) the formation of sulfate complexes with other cations may partially contribute to the non-linearity of the CAS concentration in foraminiferal tests at high increases in [SO42-]. Yet, despite the significant effect of seawater [SO42-] on foraminiferal reproduction and on CAS incorporation, the isotopic fractionation between CAS and seawater remains stable through varying seawater [SO42-]. Altogether, these results illustrate that CAS in biogenic calcite could constitute a good proxy for both seawater [SO42-] and δ34S and suggests that sulfate likely plays a role in foraminiferal biomineralization and biological activity.

Abstract Large Benthic Foraminifera are a crucial component of coral-reef ecosystems, which are currently threatened by ocean acidification. We conducted culture experiments to evaluate the impact of low pH on survival and test dissolution of the symbiont-bearing species Peneroplis spp., and to observe potential calcification recovery when specimens are placed back under reference pH value (7.9). We found that Peneroplis spp. displayed living activity up to 3 days at pH 6.9 (Ωcal 1), despite the dark and unfed conditions. Dissolution features were observed under low Ωcal values, such as changes in test density, peeled extrados layers, and decalcified tests with exposed organic linings. A new calcification phase started when specimens were placed back at reference pH. This calcification’s resumption was an addition of new chambers without reparation of the dissolved parts, which is consistent with the porcelaneous calcification pathway of Peneroplis spp. The most decalcified specimens displayed a strong survival response by adding up to 8 new chambers, and the contribution of food supply in this process was highlighted. These results suggest that porcelaneous LBF species have some recovery abilities to short exposure (e.g., 3 days to 1 month) to acidified conditions. However, the geochemical signature of trace elements in the new calcite was impacted, and the majority of the new chambers were distorted and resulted in abnormal tests, which might hinder the specimens’ reproduction and thus their survival on the long term.

The Southwest Pacific region is of great importance to global climate variability, but instrumental climate observations before the 1980s lack in numbers and quality. Despite efforts in complementing instrumental records with proxy sea surface temperature (SST) and sea surface salinity (SSS) reconstructions based on coral Sr/Ca and δ18Osw records, few of them are longer than a century. This study introduces a northwestern extension to the existing records of South Pacific coral study sites with monthly‐resolved Sr/Ca, δ18O, and δ18Osw reconstructions from Rotuma dating back to 1821. Additionally, we present new monthly‐resolved Sr/Ca and reconstructed δ18Osw from a coral from Tonga dating back to 1848. Results reveal 1.5°C warming in the Western Pacific Warm Pool, while the adjacent coral from Tonga shows 1°C warming over the twentieth century. The Rotuma Sr/Ca record reveals thermal stress events impacting the Sr/Ca‐SST relationship in the following months. Coral δ18Osw results reveal significant freshening of 0.45 Sp (practical salinity unit) in Tonga since the early twentieth century, suggesting the southeastward expansion of the South Pacific Convergence Zone salinity front. The δ18Osw inferred SSS provides a valuable extension into the past considering the short and inconsistent instrumental records available. This study demonstrates the utility of coral‐based reconstructions in capturing long‐term and regional climate variations in the Southwest Pacific and the necessity of expanding replicated studies to other underrepresented areas to enhance our understanding of regional climate dynamics. Plain Language Summary: The Southwest Pacific has limited historical climate data. This makes studying anthropogenic climate change, and how it is changing our oceans, very challenging. This study addresses this gap by using massive tropical corals from Rotuma and Tonga to reconstruct climatic key parameters back to the mid‐1800s. Our findings show that the Western Pacific Warm Pool (WPWP) has warmed by 1.2°C, much more than the adjacent subtropical waters around Tonga (0.5°C) between 1850 and 1998. The Rotuma coral record is one of the rare long records from the WPWP area where the average annual temperatures are very high (29°C). It reveals the coral was repeatedly affected by temperature stress, and probably unreported bleaching episodes throughout history. We also observe a significant freshening of 0.45 Sp in Tonga, indicating that fresher waters from the South Pacific Convergence Zone are spreading southeastward. Our coral‐derived records provide valuable historical perspectives in the absence of consistent instrumental records. Our study emphasizes the reliability of coral‐based reconstructions as indicators of local to regional conditions in the Southwest Pacific and the need for more research to better understand and address climate variability of this key area for Pacific‐wide climate. Key Points: Rotuma coral Sr/Ca and δ18Osw records provide the first reconstructions of surface seawater temperature and salinity from this locationCoral Sr/Ca‐SST shows long‐term warming in the Southwest Pacific, with higher rates in the Western Pacific Warm Pool, compared to subtropicsδ18Osw‐SSS reconstruction from Tonga shows significant long‐term freshening [ABSTRACT FROM AUTHOR]

Over the last decades, sea surface temperature (SST) reconstructions based on the Mg∕Ca of foraminiferal calcite have frequently been used in combination with the δ18O signal from the same material to provide estimates of the δ18O of water (δ18Ow), a proxy for global ice volume and sea surface salinity (SSS). However, because of error propagation from one step to the next, better calibrations are required to increase the accuracy and robustness of existing isotope and element to temperature proxy relationships. Towards that goal, we determined Mg∕Ca, Sr∕Ca and the oxygen isotopic composition of Trilobatus sacculifer (previously referenced as Globigerinoides sacculifer) collected from surface waters (0–10 m) along a north–south transect in the eastern basin of the tropical and subtropical Atlantic Ocean. We established a new paleotemperature calibration based on Mg∕Ca and on the combination of Mg∕Ca and Sr∕Ca. Subsequently, a sensitivity analysis was performed in which one, two or three different equations were considered. Results indicate that foraminiferal Mg∕Ca allows for an accurate reconstruction of surface water temperature. Combining equations, δ18Ow can be reconstructed with a precision of about ± 0.5 ‰. However, the best possible salinity reconstruction based on locally calibrated equations only allowed for a reconstruction with an uncertainty of ± 2.49. This was confirmed by a Monte Carlo simulation, applied to test successive reconstructions in an “ideal case” in which explanatory variables are known. This simulation shows that from a purely statistical point of view, successive reconstructions involving Mg∕Ca and δ18Oc preclude salinity reconstructions with a precision better than ± 1.69 and hardly better than ± 2.65 due to error propagation. Nevertheless, a direct linear fit to reconstruct salinity based on the same measured variables (Mg∕Ca and δ18Oc) was established. This direct reconstruction of salinity led to a much better estimation of salinity (± 0.26) than the successive reconstructions.

Variability of the Leeuwin current (LC) off Western Australia is a footprint of interannual and decadal climate variations in the tropical Indo-Pacific. La Niña events often result in a strengthened LC, high coastal sea levels and unusually warm sea surface temperatures (SSTs), termed Ningaloo Niño. The rarity of such extreme events and the response of the southeastern Indian Ocean to regional and remote climate forcing are poorly understood owing to the lack of long-term records. Here we use well-replicated coral SST records from within the path of the LC, together with a reconstruction of the El Niño-Southern Oscillation to hindcast historical SST and LC strength from 1795 to 2010. We show that interannual and decadal variations in SST and LC strength characterized the past 215 years and that the most extreme sea level and SST anomalies occurred post 1980. These recent events were unprecedented in severity and are likely aided by accelerated global ocean warming and sea-level rise.

The ground-breaking ceremony of Istanbul’s Third Bosphorus Bridge took place on 29th May 2013. The date chosen by the then Prime Minister, Recep Tayyip Erdoğan, to launch the construction of this urban mega-project transformed the inauguration into a commemoration of the 560th anniversary of the Ottoman Conquest of Istanbul by Fatih Sultan Mehmet. After explaining the significance of the 29th May 1453 commemorations in Turkey, in this article, we argue that the building of mega-infrastructures, such as the Third Bosphorus Bridge, has become the occasion for Erdoğan to (re)conquer the city of Istanbul, thus mirroring Fatih Sultan Mehmet more than five centuries ago. In the end, we argue that the “Conquest Festival” in Istanbul today is perhaps more than just a celebration of the 15th century Ottoman siege of the city, but instead a diverted way for the nation to commemorate - without necessarily ever acknowledging it openly - the ethnic and religious “purification” of Turkey during the 20th century.

Ocean acidification due to the industrial era is a major marine environmental concern, yet little is known on the historical ocean pH changes prior to human influence. Here, Wu et al. show that tropical South Pacific seawater pH is linked to ENSO pacing and has recently been decreasing rapidly.

The international and multidisciplinary Keban Dam Rescue Project, which took place between 1966 and 1975 in Eastern Turkey, brought scientists together to document and study the past of a landscape about to be submerged. The archaeological teams at Keban each constituted separate groups united around what they were to do in the field. This article examines the manner in which members of these archaeological ‘communities of practice’ learned how to undertake Turkey’s first salvage excavations. If such communities can form the basis for both archaeological knowledge and learning, they can also become the source of exclusionary practices, historical erasures and epistemic injustices.

Arapgir in Eastern Turkey has recently embarked upon an ambitious renovation project in order to attract visitors. Through the restoration of its architectural heritage and promotion of specific cultural and natural assets, the municipality is “giving a direction” to the town and simultaneously reinventing its identity to promote tourism. This article analyzes heritage production in Arapgir and describes the absence-presence of the town’s Armenian past within this broader push. I discuss in the end the simultaneous exposure and erasure of Armenian heritage in Turkey today by examining Arapgir’s restored Armenian cemetery.

Marine sediments can be used to reconstruct the evolution of seawater [SO 42- ] and δ34 S over time, two key parameters that contribute to refine our understanding of the sulfur cycle and thus of Earth's redox state. δ34 S evolution can be measured from carbonates, barites and sulfate evaporites. [SO 42- ] variations can be reconstructed using fluid inclusions in halites, a method that only allows a low-resolution record. Reconstruction of the past sulfur cycle could be improved if carbonates allowed the tracking of both seawater δ34 S and [SO 42- ] variations in a sole, continuous sedimentary repository. However, most primary carbonates formed in the ocean are biogenic, and organisms tend to overprint the geochemical signatures of their carbonates through a combination of processes often collectively referred to as vital effects. Hence, calibrations are needed to allow seawater δ34 S and [SO 42- ] reconstructions based on biogenic carbonates. Because foraminifera are important marine calcifiers, we opted to focus on calcite synthesized by individuals of rosalinid benthic foraminifera cultured in the laboratory under controlled conditions, with varying seawater [SO 42- ] (ranging from 0 to 180 mM). Our experimental design allowed us to obtain foraminiferal asexual reproduction over several generations. We measured bulk carbonate-associated sulfate (CAS) content and sulfur isotopic composition (δ34 S CAS) on samples of tens to hundreds of specimens from a selection of culture media, where [SO 42- ] varied from 5 to 60 mM. Increasing or decreasing [SO 42- ] with respect to modern-day seawater concentration (28 mM) impacted foraminiferal population size dynamics and the total amount of bioprecipitated carbonate. Foraminiferal CAS concentration increased proportionally with [SO 42- ] concentration from 5 mM up to 28 mM and then showed a plateau from 28 to 60 mM. The existence of a threshold at 28 mM is interpreted as the result of a control on the precipitation fluid chemistry that foraminifera exert on the carbonate precipitation loci. However, at high seawater sulfate concentrations (> 40 mM) the formation of sulfate complexes with other cations may partially contribute to the non-linearity of the CAS concentration in foraminiferal tests at high increases in [SO 42- ]. Yet, despite the significant effect of seawater [SO 42- ] on foraminiferal reproduction and on CAS incorporation, the isotopic fractionation between CAS and seawater remains stable through varying seawater [SO 42- ]. Altogether, these results illustrate that CAS in biogenic calcite could constitute a good proxy for both seawater [SO 42- ] and δ34 S and suggests that sulfate likely plays a role in foraminiferal biomineralization and biological activity. [ABSTRACT FROM AUTHOR]

Background The roles of hypoxia and hypoxia inducible factor (HIF) during chronic kidney disease (CKD) are much debated. Interventional studies with HIF-α activation in rodents have yielded contradictory results. The HIF pathway is regulated by prolyl and asparaginyl hydroxylases. While prolyl hydroxylase inhibition is a well-known method to stabilize HIF-α, little is known about the effect asparaginyl hydroxylase factor inhibiting HIF (FIH). Methods We used a model of progressive proteinuric CKD and a model of obstructive nephropathy with unilateral fibrosis. In these models we assessed hypoxia with pimonidazole and vascularization with three-dimensional micro-computed tomography imaging. We analysed a database of 217 CKD biopsies from stage 1 to 5 and we randomly collected 15 CKD biopsies of various severity degrees to assess FIH expression. Finally, we modulated FIH activity in vitro and in vivo using a pharmacologic approach to assess its relevance in CKD. Results In our model of proteinuric CKD, we show that early CKD stages are not characterized by hypoxia or HIF activation. At late CKD stages, some areas of hypoxia are observed, but these are not colocalizing with fibrosis. In mice and in humans, we observed a downregulation of the HIF pathway, together with an increased FIH expression in CKD, according to its severity. Modulating FIH in vitro affects cellular metabolism, as described previously. In vivo , pharmacologic FIH inhibition increases the glomerular filtration rate of control and CKD animals and is associated with decreased development of fibrosis. Conclusions The causative role of hypoxia and HIF activation in CKD progression is questioned. A pharmacological approach of FIH downregulation seems promising in proteinuric kidney disease. [ABSTRACT FROM AUTHOR]