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A new matrix-matched reference material has been developed – NFHS-2-NP (NIOZ Foraminifera House Standard-2-Nano-Pellet) – with element mass fractions, and isotope ratios resembling that of natural foraminiferal calcium carbonate. A 180–355 µm size fraction of planktic foraminifera was milled to nano-particles and pressed to pellets. We report reference and information values for mass fractions of forty-six elements measured by six laboratories as well as for 87Sr/86Sr (three laboratories), δ13C, δ18O (five laboratories) and 206,207,208Pb/204Pb isotope ratios (one laboratory) determined by ICP-MS, ICP-OES, MC-ICP-MS, isotope ratio mass spectrometry, WD-XRF and TIMS. Inter- and intra-pellet elemental homogeneity was tested using multiple LA-ICP-MS analyses in two laboratories applying spot sizes of 60 and 70 µm. The LA-ICP-MS results for most of the elements relevant as proxies for palaeoclimate research show RSD values < 3%, demonstrating a satisfactory homogeneous composition. Homogeneity of 87Sr/86Sr ratios of the pellet was verified by repeated LA-MC-ICP-MS by two laboratories. Information values are reported for Pb isotope ratios and δ13C, δ18O values. The homogeneity for these isotope systems remains to be tested by LA-MC-ICP-MS and secondary-ion mass spectrometry. Overall, our results confirm the suitability of NFHS-2-NP for calibration or monitoring the quality of in situ geochemical techniques.

Movies 1-9 and 11 show time series taken with the Leica SP5 microscope and recorded with Leica software. Movies were then recorded and displayed using OBS Studio software to reduce the data size. Movie 10 was directly recorded live during transmitted light microscope investigation. Movie S1. A. lessoni showing cell impermeable Calcein (blue, exc. 488nm em. 505-555), chloroplasts (green, exc. 633nm, em. 660-710nm) and Mg-ACC pools (red, exc. 405 nm, em. 415-455nm) in a series of 92 overlaid images taken during 1802s. Arrows show pores infilling, which are stained with Calcein while encircled area shows chloroplasts, Mg-ACCs and Calcein stained vesicles moving in the cytosol. Movie S2. A. lessoni showing cell impermeable Calcein (blue, exc. 488nm, em. 505-555), chloroplasts (green, exc. 633nm, em. 660-710nm) and Mg-ACC pools (red, exc. 405 nm, em. 415-455nm) moving in the cytosol in a series of 75 images taken in 1462s. Movie S3. Membrane staining using FM1-43 (cyan, exc. 488nm, em. 580-620nm) showing cell membrane and endocytotic vesicles. Mg-ACC pools and shell autofluorescence (red, exc. 405nm, em. 420-490nm) and autofluorescence of symbionts (green, exc. 633nm, em. 670-730nm). 95 overlaid images are shown in a time series of 2847s. Movie S4. Membrane staining using FM1-43 (cyan, exc. 488nm, em. 580-620nm) showing cell membrane and endocytotic vesicles moving below the pores in the cytosol. 20 overlaid images series during 243s. Movie S5. Autofluorescence of Mg-ACC pools (red, exc. 405nm, em. 420-500nm) and symbiontic chloroplasts (green, exc. 633nm, em. 660-720nm) showing that Mg-ACC pools are surrounded and in close contact to symbionts and in permanent motion. 120 image series during 548s. Movie S6. Autofluorescence of Mg-ACC pools (red, exc. 405nm, em. 420-490nm) and symbiontic chloroplasts (green, exc. 633nm, em. 660-700nm) showing that Mg-ACC pools are surrounded and in close contact with symbionts and in permanent motion. The Mg-ACCs are moving to the reticulopodia meshwork of the newly built chamber, which seems to be gradually retracted during measurement. 645 overlaid images series during 7033s. Movie S7. LysoGlow84 showing more alkaline vesicles (white) entering through the pores and more acidic vesicles (pink). Exc. MP 730nm, em. 380-415nm indicating more alkaline, whereas em. 440-470nm indicating more acidic vesicles. Mg-ACC pools and symbionts are shown in red (exc. 405nm, em. 420-490nm) and green (em. 650-700nm), respectively. 43 overlaid image series during 1726s. Movie S8. BCECF AM showing acidic vesicles (yellow, exc. MP1000nm, em. 510-550nm) in the cytosol in close contact with Mg-ACC pools (red, exc. 405nm, em. 420-470nm), and chloroplasts (green, em. 650-700nm). 35 overlaid images in 1024s. Movie S9. Autofluorescence of reticulopodia transporting carbonate nanovesicles; exc. 561nm, em. 590-620nm. 58 overlaid images series in 333s. Movie S10. Transmitted light microscopy imaging showing liquid ACC (blue) portions moving within POS during new shell construction (before crystallization). Movie S11. Mag-Fura2 AM staining showing excess Mg2+ in red (MP730nm em415-490nm) and second wavelength excitation in cyan (405nm 500-545nm) in a series of 55 overlaid images during 1597s. Movies 1-9 and 11 show time series taken with the Leica SP5 microscope and recorded with Leica software. Movies were then recorded and displayed using OBS Studio software to reduce the data size. Movie 10 was directly recorded live during transmitted light microscope investigation. Movie S1. A. lessoni showing cell impermeable Calcein (blue, exc. 488nm em. 505-555), chloroplasts (green, exc. 633nm, em. 660-710nm) and Mg-ACC pools (red, exc. 405 nm, em. 415-455nm) in a series of 92 overlaid images taken during 1802s. Arrows show pores infilling, which are stained with Calcein while encircled area shows chloroplasts, Mg-ACCs and Calcein stained vesicles moving in the cytosol. Movie S2. A. lessoni showing cell impermeable Calcein (blue, exc. 488nm, em. 505-555), chloroplasts (green, exc. 633nm, em. 660-710nm) and Mg-ACC pools (red, exc. 405 nm, em. 415-455nm) moving in the cytosol in a series of 75 images taken in 1462s. Movie S3. Membrane staining using FM1-43 (cyan, exc. 488nm, em. 580-620nm) showing cell membrane and endocytotic vesicles. Mg-ACC pools and shell autofluorescence (red, exc. 405nm, em. 420-490nm) and autofluorescence of symbionts (green, exc. 633nm, em. 670-730nm). 95 overlaid images are shown in a time series of 2847s. Movie S4. Membrane staining using FM1-43 (cyan, exc. 488nm, em. 580-620nm) showing cell membrane and endocytotic vesicles moving below the pores in the cytosol. 20 overlaid images series during 243s. Movie S5. Autofluorescence of Mg-ACC pools (red, exc. 405nm, em. 420-500nm) and symbiontic chloroplasts (green, exc. 633nm, em. 660-720nm) showing that Mg-ACC pools are surrounded and in close contact to symbionts and in permanent motion. 120 image series during 548s. Movie S6. Autofluorescence of Mg-ACC pools (red, exc. 405nm, em. 420-490nm) and symbiontic chloroplasts (green, exc. 633nm, em. 660-700nm) showing that Mg-ACC pools are surrounded and in close contact with symbionts and in permanent motion. The Mg-ACCs are moving to the reticulopodia meshwork of the newly built chamber, which seems to be gradually retracted during measurement. 645 overlaid images series during 7033s. Movie S7. LysoGlow84 showing more alkaline vesicles (white) entering through the pores and more acidic vesicles (pink). Exc. MP 730nm, em. 380-415nm indicating more alkaline, whereas em. 440-470nm indicating more acidic vesicles. Mg-ACC pools and symbionts are shown in red (exc. 405nm, em. 420-490nm) and green (em. 650-700nm), respectively. 43 overlaid image series during 1726s. Movie S8. BCECF AM showing acidic vesicles (yellow, exc. MP1000nm, em. 510-550nm) in the cytosol in close contact with Mg-ACC pools (red, exc. 405nm, em. 420-470nm), and chloroplasts (green, em. 650-700nm). 35 overlaid images in 1024s. Movie S9. Autofluorescence of reticulopodia transporting carbonate nanovesicles; exc. 561nm, em. 590-620nm. 58 overlaid images series in 333s. Movie S10. Transmitted light microscopy imaging showing liquid ACC (blue) portions moving within POS during new shell construction (before crystallization). Movie S11. Mag-Fura2 AM staining showing excess Mg2+ in red (MP730nm em415-490nm) and second wavelength excitation in cyan (405nm 500-545nm) in a series of 55 overlaid images during 1597s. &nbsp

The middle Miocene climate transition ∼ 14 Ma marks a fundamental step towards the current “ice-house” climate, with a ∼ 1 ‰ δ18O increase and a ∼ 1 ‰ transient δ13C rise in the deep ocean, indicating rapid expansion of the East Antarctic Ice Sheet associated with a change in the operation of the global carbon cycle. The variation of atmospheric CO2 across the carbon-cycle perturbation has been intensely debated as proxy records of pCO2 for this time interval are sparse and partly contradictory. Using boron isotopes (δ11B) in planktonic foraminifers from Ocean Drilling Program (ODP) Site 1092 in the South Atlantic, we show that long-term pCO2 varied at 402 kyr periodicity between ∼ 14.3 and 13.2 Ma and follows the global δ13C variation remarkably well. This suggests a close link to precessional insolation forcing modulated by eccentricity, which governs the monsoon and hence weathering intensity, with enhanced weathering and decreasing pCO2 at high eccentricity and vice versa. The ∼ 50 kyr lag of δ13C and pCO2 behind eccentricity in our records may be related to the slow response of weathering to orbital forcing. A pCO2 drop of ∼ 200 µatm before 13.9 Ma may have facilitated the inception of ice-sheet expansion on Antarctica, which accentuated monsoon-driven carbon cycle changes through a major sea-level fall, invigorated deep-water ventilation, and shelf-to-basin shift of carbonate burial. The temporary rise in pCO2 following Antarctic glaciation would have acted as a negative feedback on the progressing glaciation and helped to stabilize the climate system on its way to the late Cenozoic ice-house world.

International audience; 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

Oceanic uptake of anthropogenic CO2 emissions induced global seawater pH decrease by 0.1 since the Industrial Revolution by altering ocean chemistry with the reduction of carbonate ion concentrations and the saturation states of aragonite. Massive tropical corals are ideal palaeoceanographic archives providing high-resolution records of the most recent few hundred years and offer a valuable extension to instrumental measurements. The South Pacific Convergence Zone (SPCZ), the largest persistent precipitation band in the Southern Hemisphere with an associated salinity front modulated by large-scale ocean-atmospheric interactions (El Niño/Southern Oscillation, Interdecadal Pacific Oscillation) may influence regional seawater CO2 absorption and pH variability. Here we present coral-based paleoclimatic reconstructions from two Porites sp. corals of the Southwest Pacific region from Tonga and Rotuma. The corals are analyzed using a multi-proxy approach (δ18O, Sr/Ca, Li/Mg, U/Ca, Sr-U) to assess optimal sea surface temperature reconstruction. Preliminary δ18O results from both corals suggest similar freshening and/or warming of the surface water for the last 30 years of the 20th century (Tonga: -0.0038‰ δ18O per year; Rotuma: -0.0033‰ δ18O per year). Coral B/Ca and δ11B results for the reconstruction of carbonate chemistry changes and to establish the longer-term variability of seawater pH were completed. Tonga Porites sp. δ11B signature indicate a significant decreasing trend since 1779, with a pronounced depletion in δ11B since the 1950s of -0.0626 per year. Ultimately, this study will explore the regional-scale oceanic response to increasing pCO2 and temperature, as well as the influence of interannual and decadal-interdecadal climatic fluctuations.