Search

The impact of global change on marine ecosystems is a major concern for the future. Examples from the geological past may provide insight into how ecosystems respond to major shifts in environment. Here we use the progressive closure of the Central American Seaway over the last 10 Myrs, and the resulting new environmental conditions and niches on either side of the Panama Isthmus, as a time series documenting the reaction of planktic foraminifers to environmental change and vicariance. Our main finding is that the size and shape evolution of both investigated species is strongly influenced by temperature, despite their different ecology. The surface dweller Trilobatus sacculifer conserved the same shape on both sides of the Isthmus for most of the studied interval, and diverged only recently when the environment diverged on both sides of the Isthmus. The shape response is a combination of a change in mean shape and in percentage of morphotypes occurring within T. sacculifer . This suggests a minor role of vicariance and the potential to react to changes in the local environment through ecotypic or plastic variation. This interpretation is corroborated by extensive phenotypic variability in the absence of genetic differentiation today in this species. The shape of the deeper-living species Gt. tumida, in contrast, diverged on both sides of the Isthmus at a time that coincides with the cut-off of the connection of its habitat. This divergence combines a response to temperature and to location, suggesting local adaptation in response to vicariance. These different reactions highlight both a high potential for adaptation, but also sensitivity to temperature variations. The species-specific responses to environmental pressures indicate the difficulty in upscaling from one species to foraminifers in general. [ABSTRACT FROM AUTHOR]

Mineral aerosols form a key component of Earth's dynamic biogeochemical systems, yet their composition and mass are variable in time. We reconstruct patterns in mineral aerosol flux from East Asia, the second largest global dust source, in a peat mire in northern Japan. Using geochemical fingerprinting, we show for the past ~3600 years that high but variable tephra flux dominated regional aerosol loads. A human signal was discernible as elevated pollutant metals, along with East Asian mainland dust, identifiable by its geochemical signature. After ~700 years before the present, dust flux increased as the westerly jet intensified and moved south, the summer monsoon strength reduced, and agriculture expanded. From the 20th century, dust flux increased by two times. Attributable largely to human activity, this demarks a major change in aerosol export to the northwestern Pacific with accompanying increases in fluxes for key micronutrients and increased pollution flux by 16 times.

The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO 2 ) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO 2 beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO 2 record spanning the past 66 million years. This newly constructed record provides clearer evidence for higher Earth system sensitivity in the past and for the role of CO 2 thresholds in biological and cryosphere evolution.

The Last Interglacial (LIG: 130,000-115,000 years ago) was a period of warmer global mean temperatures and higher and more variable sea levels than the Holocene (11,700-0 years ago). Therefore, a better understanding of Antarctic ice-sheet dynamics during this interval would provide valuable insights for projecting sea-level change in future warming scenarios. Here we present a high-resolution record constraining ice-sheet changes in the Wilkes Subglacial Basin (WSB) of East Antarctica during the LIG, based on analysis of sediment provenance and an ice melt proxy in a marine sediment core retrieved from the Wilkes Land margin. Our sedimentary records, together with existing ice-core records, reveal dynamic fluctuations of the ice sheet in the WSB, with thinning, melting, and potentially retreat leading to ice loss during both early and late stages of the LIG. We suggest that such changes along the East Antarctic Ice Sheet margin may have contributed to fluctuating global sea levels during the LIG., (© 2023. The Author(s).)

Antarctica is one of the most vulnerable regions to climate change on Earth and studying the past and present responses of this polar marine ecosystem to environmental change is a matter of urgency. Sedimentary ancient DNA (sedaDNA) analysis can provide such insights into past ecosystem-wide changes. Here we present authenticated (through extensive contamination control and sedaDNA damage analysis) metagenomic marine eukaryote sedaDNA from the Scotia Sea region acquired during IODP Expedition 382. We also provide a marine eukaryote sedaDNA record of ~1 Mio. years and diatom and chlorophyte sedaDNA dating back to ~540 ka (using taxonomic marker genes SSU, LSU, psbO). We find evidence of warm phases being associated with high relative diatom abundance, and a marked transition from diatoms comprising <10% of all eukaryotes prior to ~14.5 ka, to ~50% after this time, i.e., following Meltwater Pulse 1A, alongside a composition change from sea-ice to open-ocean species. Our study demonstrates that sedaDNA tools can be expanded to hundreds of thousands of years, opening the pathway to the study of ecosystem-wide marine shifts and paleo-productivity phases throughout multiple glacial-interglacial cycles., (© 2022. The Author(s).)

Ice loss in the Southern Hemisphere has been greatest over the past 30 years in West Antarctica. The high sensitivity of this region to climate change has motivated geologists to examine marine sedimentary records for evidence of past episodes of West Antarctic Ice Sheet (WAIS) instability. Sediments accumulating in the Scotia Sea are useful to examine for this purpose because they receive iceberg-rafted debris (IBRD) sourced from the Pacific- and Atlantic-facing sectors of West Antarctica. Here we report on the sedimentology and provenance of the oldest of three cm-scale coarse-grained layers recovered from this sea at International Ocean Discovery Program Site U1538. These layers are preserved in opal-rich sediments deposited ∼1.2 Ma during a relatively warm regional climate. Our microCT-based analysis of the layer's in-situ fabric confirms its ice-rafted origin. We further infer that it is the product of an intense but short-lived episode of IBRD deposition. Based on the petrography of its sand fraction and the Phanerozoic 40 Ar/ 39 Ar ages of hornblende and mica it contains, we conclude that the IBRD it contains was likely sourced from the Weddell Sea and/or Amundsen Sea embayment(s) of West Antarctica. We attribute the high concentrations of IBRD in these layers to "dirty" icebergs calved from the WAIS following its retreat inland from its modern grounding line. These layers also sit at the top of a ∼366-m thick Pliocene and early Pleistocene sequence that is much more dropstone-rich than its overlying sediments. We speculate this fact may reflect that WAIS mass-balance was highly dynamic during the ∼41-kyr (inter)glacial world., (© 2022. The Authors.)

The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO 2 levels., (© 2022. The Author(s).)

The reconstruction of fire history is essential to understand the palaeoclimate and human history. Polycyclic aromatic hydrocarbons (PAHs) have been extensively used as a fire marker. In this work, the distribution of PAHs in Borneo peat archives was investigated to understand how PAHs reflect the palaeo-fire activity. In total, 52 peat samples were analysed from a Borneo peat core for the PAH analysis. Pyrogenic PAHs consist of 2-7 aromatic rings, some of which have methyl and ethyl groups. The results reveal that the concentration of pyrogenic PAHs fluctuated with the core depth. Compared to low-molecular-weight (LMW) PAHs, the high-molecular-weight (HMW) PAHs had a more similar depth variation to the charcoal abundance. This finding also suggests that the HMW PAHs were mainly formed at a local fire near the study area, while the LMW PAHs could be transported from remote locations., Competing Interests: The authors have declared that no competing interests exist.

A field study was conducted to clarify sources of atmospheric black carbon and related carbonaceous components at Rishiri Island, Japan. We quantified equivalent black carbon (eBC) particle mass and the absorption Ångström exponent (AAE), atmospheric CO and CH 4 , in addition to levoglucosan in total suspended particles, a typical tracer of biomass burning. Sixteen high eBC events were identified attributable to either anthropogenic sources or biomass burning in Siberia/China. These events were often accompanied by increases of co-emitted gases such as CH 4 and CO. Specifically, we observed pollution events with elevated eBC, AAE, levoglucosan, and CH 4 CO slope in late July 2014, which were attributed to forest fires in Siberia by reference to the FLEXPART model footprint and fire hotspots. In autumn, drastic increases of eBC, AAE, and levoglucosan were observed, accompanied by an eBC-CO slope of >15 ng m -3 /ppb, resulting from long-range transport of emissions from extensive burning of crop residue on the Northeast China Plain. Other than the sources of fossil fuel combustion in China and forest fires in Siberia, we report for the first time that pollution events in northern Japan are caused by crop residue burning in China. This study elucidated valuable information that will improve understanding of the effects of biomass burning in East Asia on atmospheric carbonaceous components., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Carbonaceous aerosols influence the climate via direct and indirect effects on radiative balance. However, the factors controlling the emissions, transport and role of carbonaceous aerosols in the climate system are highly uncertain. Here we investigate organic tracers in ice cores from Greenland and Kamchatka and find that, throughout the period covered by the records (1550 to 2000 CE), the concentrations and composition of biomass burning-, soil bacterial- and plant wax- tracers correspond to Arctic and regional temperatures as well as the warm season Arctic Oscillation (AO) over multi-decadal time-scales. Specifically, order of magnitude decreases (increases) in abundances of ice-core organic tracers, likely representing significant decreases (increases) in the atmospheric loading of carbonaceous aerosols, occur during colder (warmer) phases in the high latitudinal Northern Hemisphere. This raises questions about causality and possible carbonaceous aerosol feedback mechanisms. Our work opens new avenues for ice core research. Translating concentrations of organic tracers (μg/kg-ice or TOC) from ice-cores, into estimates of the atmospheric loading of carbonaceous aerosols (μg/m(3)) combined with new model constraints on the strength and sign of climate forcing by carbonaceous aerosols should be a priority for future research.

Warming of high northern latitudes in the Pliocene (5.33-2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling.

Total nucleated cell (TNC) count, CD34(+) cell count, colony-forming unit-granulocyte-macrophage (CFU-GM) content, and cell viability impact the outcome of umbilical cord blood (UCB) transplantation. Assessments of unit quality have usually been provided by cord blood banks (CBBs), but it is unclear whether pre-freezing tests or pre-transplant release tests performed by CBBs are reproducible. The aim of this study was to compare the UCB characteristics analyzed at the site of infusion of the UCB with those provided by CBBs. Samples were taken from 54 UCB units for assessment of post-thaw characteristics. TNC counts and CD34(+) cell contents measured at our hospital before infusion showed good correlations with values assessed in pre-freezing tests (r = 0.900 and 0.943, respectively) and pre-transplant release tests (r = 0.829 and 0.930, respectively). Our data reveal that the TNC counts and CD34(+) cell contents determined by pre-freezing and pre-transplant release tests, which are the most important UCB unit selection criteria, accurately reflected the quality of infused UCB units. However, CFU-GM content was poorly correlated (r = 0.560 and 0.606). Correlation of post-thaw cell viabilities measured before infusion and during the pre-transplant release tests was also poor (r = 0.308). We suggest that the TNC count and CD34(+) cell content estimated before cryopreservation and in pre-transplant release tests provided by CBBs are reproducible and can assist the transplant physicians in selection of appropriate UCB units.

Background: It is sometimes difficult to detect the bone marrow infiltration of lymphoma cells, because lymphoma cells are not distinguishable from normal lymphocytes due to the similarity of their phenotype., Methods: Bone marrow involvement of 17 samples of 15 patients with follicular lymphoma, whose lymphoma cells were confirmed to harbor the translocation of chromosome14q32, were examined by microscopic analysis of bone marrow smear and biopsy, flow cytometorical analysis (FCM), chromosomal analysis of G-banding and fluorescence in situ hybridization (FISH). FISH was performed using a probe, which detects the split of IGH gene on 14q32., Results: The positivity of FISH was highest among these methods and FISH was able to detect the bone marrow involvement in one case who was defined as negative by bone marrow biopsy., Conclusions: FISH can be used for detection of bone marrow involvement of malignant lymphoma that carries chromosomal rearrangement involving 14q32., (Copyright 2004 Elsevier B.V.)