Wenfeng Deng

Coral skeletal trace‐metal compositions are commonly assumed to derive from seawater, yet the extent to which biological processes contribute remains poorly constrained. Here we present the first paired Mo isotope measurements of coral tissue, symbiotic zooxanthellae, and skeleton. All three compartments are depleted in δ ⁹⁸ Mo relative to seawater, with zooxanthellae significantly lighter than host tissue. A strong negative correlation between zooxanthellae and skeletal δ ⁹⁸ Mo, together with a negative power‐law relationship between skeletal Mo concentration and δ ⁹⁸ Mo across species and reef environments, indicates a symbiont‐mediated control on Mo partitioning. Fossil corals further show systematic variability in skeletal δ ⁹⁸ Mo associated with climate variability over the past millennium, suggesting that environmental changes modulate symbiont‐driven biological processes recorded in coral skeletons. These observations suggest that biologically processed Mo contributes substantially to skeletal composition and that coral δ ⁹⁸ Mo may serve as a novel proxy for symbiont metabolic activity and its response to environmental change.

Halogen incorporation into coral carbonate skeletons serves as a valuable proxy for reconstructing paleoenvironments. However, the underlying mechanisms remain poorly understood. This study employed femtosecond laser ablation‐inductively coupled plasma time‐of‐flight mass spectrometry (fs‐LA‐ICP‐TOFMS) to perform multi‐elemental (I, Br, P, Ca, Mg, Sr, S, Ba, and Fe) imaging of cross‐sections from carbonate skeleton of deep‐sea Callogorgia sp. coral (octocoral) collected from the Mariana Arc at a depth of 1,386 m. Previously unrecognized iodine‐rich ring patterns and bromine‐rich fan‐like distributions were identified, likely influenced by the biological rhythms of polyps, such as polyp apoptosis‐replacement or migration, which refresh the polyp‐skeleton interface and facilitate halogen accumulation. Additionally, higher iodine and bromine concentrations were consistently observed in the calcitic layers compared to the aragonitic layer, suggesting that biological factors, particularly halogenated organics, dominate halogen incorporation, outweighing mineralogical controls. A comparison of halogen distributions between Callogorgia and bamboo corals demonstrated species‐specific halogen incorporation patterns. These findings provide new insights into coral biomineralization, emphasizing the role of biological rhythms in skeletal formation and trace element incorporation.

Tropical low‐cloud feedback is the largest source of uncertainty in climate sensitivity, yet multi‐century records of surface shortwave radiation are scarce. We calibrate Porites coral δ ¹³ C against satellite photosynthetically available radiation (PAR) and reconstruct monthly PAR for the northern South China Sea during the Medieval Climate Anomaly (1129–1264 CE) and the Little Ice Age (1631–1771 CE). After correcting for the Suess effect and propagating errors via Monte Carlo resampling techniques, annual PAR during the Little‐Ice‐Age is ∼22% lower and seasonality slightly weaker. The dimming aligns with regional proxies for cooler, wetter conditions and is best explained by brighter low clouds, likely boosted by volcanic aerosol–cloud interactions. CMIP6/PMIP4 past1000 simulations, however, yield <0.2% change over the same interval, indicating that current models understate volcanic microphysics and tropical low‐cloud sensitivity. The coral PAR record thus provides a quantitative pre‐industrial target for evaluating tropical cloud processes and reducing uncertainty in equilibrium climate sensitivity.

Asian dust storms influence climate, air quality, and nutrient supply, yet debate persists over whether their activity peaked during the cold Little Ice Age (LIA, ∼1550–1850 CE) or in the warmer, land‐use‐intensive modern era. Existing reconstructions derive mainly from loess, lake, and ice‐core archives; these capture aspects of dust activity but suffer from chronological uncertainty. High‐resolution downwind marine records at subannual scales remain scarce. We analyzed monthly barium‐to‐calcium (Ba/Ca) ratios in a Porites coral core from the Xisha Islands in the South China Sea (SCS), generating the first monthly resolved marine record of downwind dust‐associated aerosol delivery to the SCS during 1816–2014 CE. After excluding the influences of fluvial input, groundwater, upwelling, sediment resuspension, biological processes, and skeletal growth‐rate effects, we interpret the March–May Ba/Ca spikes as signatures of Ba‐rich aerosols delivered during spring dust activity. A Pettitt change‐point test identified 1870 as the boundary between two regimes: during 1816–1870, the mean spring Ba/Ca was 14.69 μmol mol ⁻¹ (vs. 10.47 μmol mol ⁻¹ thereafter), the variance was greater (3.44 vs. 2.24), and extreme events (>16.49 μmol mol ⁻¹ ) occurred in 31.5% of years (vs. 1.5% after 1870); all differences are significant. The post‐1870 decline in dust delivery parallels a weaker Siberian High, wetter upwind conditions, and fewer El Niño events, with no sustained anthropogenic increase in long‐range dust delivery to the SCS. These findings underscore climate forcing as the primary regulator of long‐range dust export and provide a precisely dated benchmark for testing aerosol–climate models and future dust–climate feedbacks.

Current challenges in carbonate dual clumped isotope ( Δ ₄₇ – Δ ₄₈ ) analyses include the high cost of commercial systems and the low throughput associated with manual preparation across different laboratories. To address these limitations, we developed a fully automatic preparation system for carbonate samples, coupled to a ThermoFisher Scientific 253 Plus isotope ratio mass spectrometer. The system integrates a programmable logic controller with units for acid digestion, cryogenic purification, and temperature control, enabling continuous operation with minimal supervision. The flexible and low‐cost design achieved through open‐source hardware allows customisation for various research needs and can potentially be adapted for other isotope systems. The system was tested using a series of carbonate reference materials, including in‐house barium carbonates (BSD‐1, BSD‐2), ETH‐1/2/3/4, C1, C2, GU1, and ISTB‐1. The results demonstrate high data repeatability (expressed as 1 standard deviation, 1 s ), with Δ ₄₇ ranging from 0.003‰ to 0.023‰ and Δ ₄₈ from 0.029‰ to 0.078‰. The system's stability was validated over several months, showing no significant drift in normalised values between sessions. We also compared the Δ ₄₇ and Δ ₄₈ values with previously published results, suggesting the potential of carbonate‐based normalisation for achieving consistent Δ ₄₇ – Δ ₄₈ data across different laboratories. Future efforts should include a comprehensive inter‐laboratory comparison using equilibrated gases as primary anchors alongside a wider range of carbonate reference materials to rigorously establish measurement reproducibility across laboratories.

Coral biomineralization typically yields either aragonite (in most scleractinians) or calcite (in octocorals), yet the drivers of this polymorph choice remain debated. Here we report a deep‐sea gorgonian coral ( Callogorgia sp.) with a coaxial calcite–aragonite–calcite skeleton. Growing at 1,400 m under nearly constant temperature and seawater chemistry, this specimen rules out environmental forcing as a control. High‐resolution elemental mapping, Raman microscopy, and infrared nano‐spectroscopy show that acidic, aspartate‐rich macromolecules are enriched in the calcitic layers but depleted in the aragonitic layer. These macromolecules lower the nucleation barrier for calcite while inhibiting aragonite growth, driving abrupt, layer‐by‐layer phase switches. Temporal shifts in macromolecule distribution correlate with biological imprints, implying regulation via changes in calcifying tissues or symbionts. Our results provide direct in situ evidence that organic molecules, rather than external conditions, govern carbonate polymorph selection in octocorals, offering a natural template for biomimetic control of CaCO ₃ phase architecture.

Elemental imaging of quartz by fs-LA-ICP-TOFMS.

Carbonate stable isotope paleoaltimetry, including clumped (Δ ₄₇ ) and oxygen (δ ¹⁸ O _w ) isotopes, is extensively applied across the Tibetan Plateau. However, traditional archives such as lacustrine and soil carbonates typically require extensive sedimentary basins, which are not always available, especially in erosion‐dominated regions. This highlights the critical need for more accessible archives to diversify the options available for paleoelevation reconstruction. Widespread terrestrial carbonates such as tufas and speleothems offer a promising alternative, but their utility is often complicated by disequilibrium isotope effects from rapid CO ₂ degassing. Therefore, a systematic evaluation of these non‐equilibrium archives is critically needed before they can be reliably applied to paleoelevation reconstruction. This study presents δ ¹³ C, δ ¹⁸ O, and Δ ₄₇ data from modern tufas and speleothems along a 0–3,500 m elevation transect in the Yunnan region, the southeastern margin of the Tibetan Plateau. We find that despite being influenced by disequilibrium effects, site‐averaged Δ ₄₇ values exhibit a robust positive correlation with elevation, yielding a temperature lapse rate (−5.2 ± 0.4°C/km) consistent with the regional modern air temperature lapse rate (−5.1°C/km), confirming temperature as the primary control on Δ ₄₇ variations. Furthermore, carbonate‐derived δ ¹⁸ O _w values show a strong negative correlation with elevation above 1,100 m, reflecting Rayleigh fractionation of oxygen isotopes during precipitation. The broader applicability of these relationships was further evaluated by reconstructing the elevations of Holocene carbonate coatings from the southeastern and central Tibetan Plateau. This study validates the potential of tufas and speleothems as alternative paleoelevation archives and establishes a foundational framework for their application in the Tibetan Plateau.

The fractionation of lithium (Li) isotopes in saprolites under intense weathering conditions, particularly in relation to precipitation and mineral types, remains a crucial yet complex aspect of geochemical studies. This study reports Li isotope compositions from saprolites and unaltered bedrock within a basalt weathering profile on Hainan Island, China, a region known for its high rainfall and low dust levels. We observe that Li concentrations in weathering products (ranging from 2.36 to 10.65 μg g−1) are generally higher than in the unaltered bedrock (6.54 μg g−1). Correspondingly, the δ7Li values of these products range from −9.3‰ to +7.4‰, typically lower than those of unaltered bedrock (+4.3‰). Our findings suggest that the impact of rainwater Li on saprolite Li isotopes is not a straightforward mixing of rainwater and bedrock, but rather is modulated by adsorption and desorption processes involving secondary minerals. Notably, the δ7Li values in saprolites correlate with the proportion of specific secondary minerals; saprolite δ7Li values rise with increased kaolin minerals and drop with more Fe and Al oxide/hydroxide minerals. Integrating these results with previous studies on suspended sediment leaching, we propose that the higher dissolved δ7Li values in basaltic catchments, compared to granitic ones, are due to a greater abundance of Fe-Al (hydro)oxides in basaltic catchments. This mineralogical control on saprolite Li isotopes also implies a potential explanation for the observed variations in river δ7Li values under different precipitation regimes, influenced by diverse secondary minerals in riverine suspended loads.