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Temperature appears to be the best predictor of species composition of planktonic foraminifera communities, making it possible to use their fossil assemblages to reconstruct sea surface temperature (SST) variation in the past. However, the role of other environmental factors potentially modulating the spatial and vertical distribution of planktonic foraminifera species is poorly understood. This is especially relevant for environmental factors affecting the subsurface habitat. If such factors play a role, changes in the abundance of subsurface-dwelling species may not solely reflect SST variation. In order to constrain the effect of subsurface parameters on species composition, we here characterize the vertical distribution of living planktonic foraminifera community across an east–west transect through the subtropical South Atlantic Ocean, where SST variability was small, but the subsurface water mass structure changed dramatically. Four planktonic foraminifera communities could be identified across the top 700 m of the transect. Gyre and Agulhas Leakage surface faunas were predominantly composed of Globigerinoides ruber, Globigerinoides tenellus, Trilobatus sacculifer, Globoturborotalita rubescens, Globigerinella calida, Tenuitella iota, and Globigerinita glutinata, and these only differed in terms of relative abundances (community composition). Upwelling fauna was dominated by Neogloboquadrina pachyderma, Neogloboquadrina incompta, Globorotalia crassaformis, and Globorotalia inflata. Thermocline fauna was dominated by Tenuitella fleisheri, Globorotalia truncatulinoides, and Globorotalia scitula in the west and by G. scitula only in the east. The largest part of the standing stock was consistently found in the surface layer, but SST was not the main predictor of species composition either for the depth-integrated fauna across the stations or at individual depth layers. Instead, we identified a pattern of vertical stacking of different parameters controlling species composition, reflecting different aspects of the pelagic habitat. Whereas productivity appears to dominate in the mixed layer (0–60 m), physical properties (temperature, salinity) become important at intermediate depths and in the subsurface, a complex combination of factors including oxygen concentration is required to explain the assemblage composition. These results indicate that the seemingly straightforward relationship between assemblage composition and SST in sedimentary assemblages reflects vertically and seasonally integrated processes that are only indirectly linked to SST. It also implies that fossil assemblages of planktonic foraminifera should also contain a signature of subsurface processes, which could be used for paleoceanographic reconstructions.

Millennial-scale variations in the strength and position of the Antarctic Circumpolar Current exert considerable influence on the global meridional overturning circulation and the ocean carbon cycle. The mechanistic understanding of these variations is still incomplete, partly due to the scarcity of sediment records covering multiple glacial-interglacial cycles with millennial-scale resolution. Here, we present high-resolution current strength and sea surface temperature records covering the past 790,000 years from the Cape Horn Current as part of the subantarctic Antarctic Circumpolar Current system, flowing along the Chilean margin. Both temperature and current velocity data document persistent millennial-scale climate variability throughout the last eight glacial periods with stronger current flow and warmer sea surface temperatures coinciding with Antarctic warm intervals. These Southern Hemisphere changes are linked to North Atlantic millennial-scale climate fluctuations, plausibly involving changes in the Atlantic thermohaline circulation. The variations in the Antarctic Circumpolar Current system are associated with atmospheric CO 2 changes, suggesting a mechanistic link through the Southern Ocean carbon cycle. The strength of the Cape-Horn Current, as traced in the sediment cores, varies with sea surface temperature in the Eastern South Pacific. Changes in this current are also associated with North Hemisphere cooling events and atmospheric CO2 outgassing.

Tropical South American hydroclimate sustains the world’s highest biodiversity and hundreds of millions of people. Whitin this region, Amazonia and northeastern Brazil have attracted much attention due to their high biological and social vulnerabilities to climate change (i.e. considered climate change hotspots). Still, their future response to climate change remains uncertain. On precession timescale, it has been suggested that periods of decreased western Amazonian precipitation were accompanied by increased northeastern Brazilian precipitation and vice-versa, setting an east–west tropical South American precipitation dipole. However, the very existence of this precession-driven precipitation dipole remains unsettled given the scarcity of long and appropriate northeastern Brazilian records. Here we show that the precession-driven South American precipitation dipole has persisted over the last 113 ka as revealed by a northern northeastern Brazilian precipitation record obtained from quartz thermoluminescence sensitivity measured in marine sediment cores. Precession-induced austral summer insolation changes drove the precipitation dipole through the interhemispheric temperature gradient control over the regional Walker circulation and the Intertropical Convergence Zone seasonal migration range. Since modern global warming affects the interhemispheric temperature gradient, our study provides insights about possible future tropical South American hydroclimate responses.

Abstract Continental shelves have the potential to remove atmospheric carbon dioxide via the biological pump, burying it in seafloor sediments. The efficiency of marine carbon sequestration changes rapidly due to variations in biological productivity, organic carbon oxidation, and burial rate. Here we present a high temporal resolution record of marine carbon sequestration changes from a western South Atlantic shelf site sensitive to Brazil Current-driven upwelling. The comparison of biological records to rare earth element (REE) patterns from authigenic oxides shows a strong relationship between higher biological productivity and stronger particle reactive element cycling (i.e. REE cycling) during rapid climate change events. This is the first evidence that authigenic oxides archive past changes in upper ocean REE cycling by the exported organic carbon. In addition, our data suggest that Brazil Current-driven upwelling varies on millennial-scales and in time with continental precipitation anomalies as registered in Brazilian speleothems during the Holocene. This indicates an ocean–atmosphere control on the biological pump, most probably related to South American monsoon system variability.

The oceanic anoxic events (OAEs) are characterized by enhanced accumulation of organic matter in marine sediments. However, there is still an ongoing debate regarding the interplay between production and preservation during these events. Moreover, few studies provide quantitative estimations of primary productivity and/or the amount of carbon preserved during the OAEs. Here, we used geochemical data from multiple wells located at the Espírito Santo Basin that cover the intervals of events OAE1d and OAE2 to provide quantitative estimates of preservation factors. Our results show enhanced preservation during OAEs compared to modern conditions and a stronger preservation during OAE1d compared to OAE2 in the Espírito Santo Basin. The amount of preserved carbon could reach up to 8.6% during OAE1d, depending on the productivity of the system. In addition, we show that such improvement in preservation is linked to the bottom water with low-O2 concentrations and not due to fast burial caused by high sedimentation rates. Our findings are extremally relevant for organic carbon and source rock modelling studies since model simulations need quantitative estimations.

The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability 1 – 3 . Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity 4 . Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial–interglacial cycles 5 – 8 , the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3 million years ago (Ma), in contrast to global cooling 9 and increasing global ice volume 10 . Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings 11 – 13 . We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability 14 . A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO 2 during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming. The strength of the Antarctic Circumpolar Current, as traced in sediment cores from the Pacific Southern Ocean, shows no linear long-term trend over the past 5.3 Myr; instead, the strongest flow occurs consistently in warmer-than-present intervals.

Paleoceanographic interpretations of Plio-Pleistocene climate variability over the past 5 million years rely on the evaluation of event timing of proxy changes in sparse records across multiple ocean basins. In turn, orbital-scale chronostratigraphic controls for these records are often built from stratigraphic alignment of benthic foraminiferal stable oxygen isotope (δ18O) records to a preferred dated target stack or composite. This chronostratigraphic age model approach yields age model uncertainties associated with alignment method, target selection, the assumption that the undated record and target experienced synchronous changes in benthic foraminiferal δ18O values, and the assumption that any possible stratigraphic discontinuities within the undated record have been appropriately identified. However, these age model uncertainties and their impact on paleoceanographic interpretations are seldom reported or discussed. Here, we investigate and discuss these uncertainties for conventional manual and automated tuning techniques based on benthic foraminiferal δ18O records and evaluate their impact on sedimentary age models over the past 3.5 Myr using three sedimentary benthic foraminiferal δ18O records as case studies. In one case study, we present a new benthic foraminiferal δ18O record for International Ocean Discovery Program (IODP) Site U1541 (54°13′ S, 125°25′ W), recently recovered from the South Pacific on IODP Expedition 383. The other two case studies examine published benthic foraminiferal δ18O records of Ocean Drilling Program (ODP) Site 1090 and the ODP Site 980/981 composite. Our analysis suggests average age uncertainties of 3 to 5 kyr associated with manually derived versus automated alignment, 1 to 3 kyr associated with automated probabilistic alignment itself, and 2 to 6 kyr associated with the choice of tuning target. Age uncertainties are higher near stratigraphic segment ends and where local benthic foraminiferal δ18O stratigraphy differs from the tuning target. We conclude with recommendations for community best practices for the development and characterization of age uncertainty of sediment core chronostratigraphies based on benthic foraminiferal δ18O records.

Campylobacter spp. and Arcobacter spp. are recognized etiological agents of gastroenteritis worldwide. While poultry is their best-known reservoir, human exposure can also occur via environmental pathways, particularly through contaminated water sources, which play a significant role in their transmission dynamics. In addition to their pathogenicity and widespread environmental prevalence, increasing antibiotic resistance has contributed to the global emergence of multidrug-resistant strains, hindering effective treatment. Here, the distribution and antibiotic resistance potential of Campylobacter spp. and Arcobacter spp. isolates collected from water bodies in Portugal were investigated. Water samples were collected from rivers, their tributaries, and springs, at 25 sites over a six-month period. Campylobacter spp. were isolated from 13.3% of the samples, whereas Arcobacter spp. were detected in 57.6% of the samples. Of the 27 isolated Campylobacter isolates, 44.0% were resistant to at least one antibiotic, while only one strain exhibited a multidrug-resistant (MDR) phenotype. In contrast, 98.9% of the 177 Arcobacter isolates were resistant to at least one antibiotic, with 15.8% classified as MDR. These findings contribute to the surveillance of Campylobacter spp. and Arcobacter spp., highlighting the critical role of aquatic environments in their epidemiology and supporting the need to incorporate waterborne transmission pathways into integrated surveillance and control strategies within the One Health framework.

We reconstruct paleoredox conditions in the Western Equatorial Atlantic (WEA) over the glacial-interglacial cycle (~130 ka) by using new high-resolution REEs data and their anomalies from a marine sediment core (GL-1248) collected from the equatorial margin off the continental shelf of NE Brazil. This approach aims to improve the understanding of the dynamics of paleoclimatic and sedimentary inputs on the coast of northeastern Brazil. Marine sediments were analyzed via Mass Spectrometry (ICP-MS) after total digestion with HF/HNO 3 . REEs proxies are a useful tool in understanding the transport and origin of sediments due to their physicochemical properties. Our data showed the Parnaíba River was the main source of REEs content in the western South Atlantic. Fe minerals (Fe-oxyhydroxides) produced via weathering of continental and tropical soils were the principal REE-carrier phase during transportation and ultimate deposition at core site GL-1248. Several regional climatic factors mainly rainfall changes contributed significantly to continental-REEs erosion of sedimentary layers of the Parnaíba Basin, and transport and deposition of the mobilized REEs from the continent to the study site. Furthermore, changes in the negative Ce-anomaly showed low variation along the core indicating a reduction in deep ocean oxygenation during the interglacial relative to the last glacial period. That variation, probably, was associated with glacial-interglacial variations in sea level with the exposure of the continental shelf. The origin of positive Eu anomalies in siliciclastic sediment, also observed in the core, was explained by preferential retention by feldspars such as plagioclases and potassium feldspars mostly from the assimilation of felspar during fractionation crystallization of felsic magma in the Parnaíba basin since the Last Interglacial.