Fossil Corals Research Articles

Sea-level oscillations within the last interglacial: Insights from coral reef stratigraphic forward modelling

Understanding past sea-level variations is essential to constrain future patterns of sea-level rise in response to warmer climate conditions. Due to good preservation and the possibility to use various geochemical methods to date fossil sea-level index points, the Last Interglacial (Marine Isotope Stage, MIS, 5e, 130–116 ka) is often regarded as one of the best climate analogs for a future warmer climate. MIS 5e coastal stratigraphic sequences, such as fossil coral reefs, are characterized by abrupt shifts in their geological facies, steps within the reef topography or backstepped morphologies, which have been often interpreted as proxies for abrupt sea-level fluctuations within the interglacial. However, the observational evidence and magnitude of such abrupt changes are controversial. Here, we run nearly 50 thousand simulations of a 2D kinematic reef model that can reproduce coral reef growth and demise through time. Our aim is to investigate the parameters of space, the sea-level scenarios, and the processes which multiple-stepped MIS 5e fossil reefs form. As inputs to the model, we use both published and synthetic sea-level histories (17 sea-level curves, with different sea-level oscillation patterns), and a wide range of reef growth and marine erosion rates, and bedrock foundation slopes. Our results show that the only sea-level history that could explain the generation of an emerged MIS 5e backstepped reef is a first sea-level peak followed by an abrupt rise in sea level and a second short-term peak. Any other multiple-stepped stratigraphy can be explained by the interplay between reef growth, marine erosion, and bedrock slope.

Late Holocene relative sea-level records from coral microatolls in Singapore

Late Holocene relative sea-level (RSL) data are important to understand the drivers of RSL change, but there is a lack of precise RSL records from the Sunda Shelf. Here, we produced a Late Holocene RSL reconstruction from coral microatolls in Singapore, demonstrating for the first time the utility of Diploastrea heliopora microatolls as sea-level indicators. We produced 12 sea-level index points and three marine limiting data with a precision of < ± 0.2 m (2σ) and < ± 26 years uncertainties (95% highest density region). The data show a RSL fall of 0.31 ± 0.18 m between 2.8 and 0.6 thousand years before present (kyr BP), at rates between − 0.1 ± 0.3 and − 0.2 ± 0.7 mm/year. Surface profiles of the fossil coral microatolls suggest fluctuations in the rate of RSL fall: (1) stable between 2.8 and 2.5 kyr BP; (2) rising at ~ 1.8 kyr BP; and (3) stable from 0.8 to 0.6 kyr BP. The microatoll record shows general agreement with published, high-quality RSL data within the Sunda Shelf. Comparison to a suite of glacial isostatic adjustment (GIA) models indicate preference for lower viscosities in the mantle. However, more high quality and precise Late Holocene RSL data are needed to further evaluate the drivers of RSL change in the region and better constrain GIA model parameters.

Multidisciplinary characterisation of the biodiversity, geomorphology, oceanography and glacial history of Bowditch Seamount in the Sargasso Sea

The first multidisciplinary characterisation of Bowditch Seamount in the Sargasso Sea was conducted to provide new baseline knowledge of the biodiversity, geomorphology, oceanography and glacial history of this seamount. A dropframe camera transect 1483–1562 m deep on the seamount documented 77 megafaunal taxa including Vulnerable Marine Ecosystem indicator taxa such as sponges, cold-water corals, and stalked crinoids. Seabed terrain analysis of multibeam echosounder data showed species varied significantly along this transect in response to local geomorphological variability (R2adj = 31%, p < 0.0001), with changes in seafloor relief and substrata driving species composition over the seamount. 14C-calibrated and 230Th-ages of fossil corals (Desmophyllum dianthus) collected by Van Veen grabs 1517 m deep showed corals thrived on the seamount ∼24 ka BP and ∼17 ka BP. Abrupt excursions between higher and lower radiogenic εNd-composition values of the skeletons suggested that D. dianthus persisted on the seamount over times of southern source water input and detrital sediments from the melting Laurentide Ice Sheet, respectively. In agreement with other studies from the western North Atlantic, living D. dianthus were absent in the contemporary setting at these depths, and suggest a significant re-organisation of the seamount community since the deglacial when ice-rafted debris of carbonates likely resulted in a lower aragonite compensation depth allowing D. dianthus to proliferate at deeper depths. New conductivity-depth-temperature profiling revealed the seamount at these depths is now bathed by highly oxygenated Labrador Sea Water (LSW) formed at high latitudes. Co-analysis of a newly constructed 70-year long time series of temperature and salinity for the Labrador Sea and Bermuda regions revealed a 10-year transit time from high latitudes to Bowditch Seamount. This multidisciplinary approach shows how geomorphology drives local biodiversity patterns, but also how upstream climatic forcing in subpolar regions may influence Bermuda's subtropical seamount ecosystem.

High-resolution Oxygen and Carbon Isotopic Records of a Modern and a Fossil Coral from the Lakshadweep Archipelago

High-resolution Oxygen and Carbon Isotopic Records of a Modern and a Fossil Coral from the Lakshadweep Archipelago

Systematics and paleobiogeography of Quaternary corals from Cabo Verde Archipelago

Abstract Although true coral reefs have seldom been reported from the fossil record of the Cabo Verde Archipelago, many single fossil corals and coral colonies can be found reworked in tsunami deposits and in raised marine terraces onshore on these islands. This study provides the first detailed survey of fossil corals from 7 of the 10 islands of the archipelago, sampled from Pleistocene marine terraces and tsunami deposits. A total of 168 scleractinian corals were analyzed and identified to genus and/or species level. Thirteen taxa from the families Acroporidae, Dendrophylliidae, Faviidae, Pocilloporidae, Poritidae, and Rhizangiidae were identified. The zooxanthellate fossil corals found on the Cape Verde Archipelago likely migrated from the Caribbean to the West African coast, while azooxanthellate species likely originated from the Indo-Pacific. Differences between present-day coral assemblages and fossil assemblages are assumed to result from changing environmental factors. Although reef-building taxa occur (e.g., Porites), extensive reef frameworks are absent.

Development and physical characteristics of the Irish shelf-edge Macnas Mounds, Porcupine Seabight, NE Atlantic

Modern cold-water corals (CWCs) occur in a wide range of water depths, with Desmophyllum pertusum being one of the most common species. Pleistocene, Holocene, and modern coral mound formation by living CWC reefs have previously been described in the Porcupine Seabight from water depths greater than 700 m in the vicinity of the transitional zone between the Eastern North Atlantic Water and Mediterranean Outflow Water. Here we document occurrence of fossil corals retrieved from two cores at 370 m depth in the Macnas Mounds, a relatively shallow occurrence for mounds on the Irish shelf-edge. Both cores feature D. pertusum restricted to the upper two metres, immediately overlying an erosive surface and a coeval major down-core change in grain size from sand to mud. Radiocarbon dating of coral specimens indicates the CWC mounds initiated 7.82 Cal ky BP. Our study unequivocally documents the existence of Holocene shelf-edge coral mounds in the eastern Porcupine Seabight and highlights the possibility of other occurrences of CWCs in similar settings elsewhere in the northeast Atlantic. Given that no living CWCs were encountered in the study area, we suggest that the area previously experienced more favourable conditions for CWC mound initiation and development along the shelf-edge margin, possibly due to differing conditions in the European Slope Current which flows northward along the continental slope from south of the Porcupine Bank to the Faroe-Shetland Channel.Graphical

Validation of Advanced Kinematic Model of Earth-Moon System by Observed Length of Day Curve

NASA’s press release of ‘Moon having receded by 1 m from Earth in a quarter of century’ on the Silver Jubilee Anniversary (20 July 1994) of Man’s landing on Moon led to the development of the Kinematic Model(KM) of evolving Earth-Moon System. Best fit KM parameters are adopted for the analysis of evolving E-M system, The present length of day of Earth is assumed to be 24 hours, orbital period of Moon divided by spin period of Earth=LOM/LOD=27.322 and the age of Moon=4.467Gy. Using this best fit model parameters the velocity of recession of Moon is derived as 2.3cm/y as compared to 3.7cm/y by Lunar Laser Ranging experiment.KM is used to plot lengthening of day(LOD) curve from pre-cambrian period (2.5Gy ago) to the present time. This theoretical plot is superimposed on the observed lengthening of day curve. The observed plot is generated from the observed length of day in different geologic epochs by John West Wells, Charles P.Sonnet &amp; Chan and Kaula &amp; Harris by the study of coral fossils, ancient tidalites and marine creatures respectively. The superposition gives more than 25% mismatch in remote past around 2.5Gya. This KM did not consider the obliquity angle 23.44° of Earth and the inclination angle of 5.14° of Lunar Orbital Plane with respect to Ecliptic plane. The classical KM assumed monotonic spiral expansion of Moon from Earth as shown in Figure 1. A recent paper “Tidal evolution of Moon in high angular momentum, high obliquity Earth” has revolutionized the Earth-Moon modeling and paved the way for near-match between observated and theoretical LOD curve. In the new scenario Moon’s tidal evolution is anything but sedate and monotonic. It experienced a bumpy launch through gravitational sling shot at the first geo-synchronous orbit of 15,000Km. Moon was gravitationally catapulted and launched on an expanding spiral path but this expansion was turbulent, chaotic and got stalled at times due to huge lunar obliquity tides during Laplace Plane transition and due to Cassini state transition as shown in Figure 2. Only after Moon settles down in Cassini state II that it resumes its monotonic and sedate spiral expansion as envisaged in the classical picture but this spiral expansion was at accelerated pace so as to reach 3,84,499Km orbital radius in 4.5Gy. It transits in fits , in chaotic and turbulent phase, for 3.3Gy whereas it spends1.2Gy in bounded state therefore this new model is referred to as ‘Fits and Bound’ model of E-M system. On this time scale the modern time recession rate comes to be 3.7cm/y. If this accelerated time frame is adopted then we get near-exact match between theory and observed LOD curve with worst mis-match being -4%. In this accelerated time frame, all E-M system parameters are obtained and it is self consistent model with velocity of recession = 3.7cm/y, LOM/LOD = 27.322 and near match between theory and observed LOD curve and spending 3.3Gy in turbulent and stalled evolutionary phase and spending 1.2Gy in the present accelerated phase. This gives the final vindication to the advanced KM.

Decoding the Interplay Between Tidal Notch Geometry and Sea‐Level Variability During the Last Interglacial (Marine Isotope Stage 5e) High Stand

AbstractRelic coastal landforms (fossil corals, cemented intertidal deposits, or erosive features carved onto rock coasts) serve as sea‐level index points (SLIPs), that are widely used to reconstruct past sea‐level changes. Traditional SLIP‐based sea‐level reconstructions face challenges in capturing continuous sea‐level variability and dating erosional SLIPs, such as tidal notches. Here, we propose a novel approach to such challenges. We use a numerical model of cliff erosion embedded within a Monte Carlo simulation to investigate the most likely sea‐level scenarios responsible for shaping one of the best‐preserved tidal notches of Last Interglacial age in Sardinia, Italy. Results align with Glacial Isostatic Adjustment model predictions, indicating that synchronized or out‐of‐sync ice‐volume shifts in Antarctic and Greenland ice sheets can reproduce the notch morphology, with sea level confidently peaking at 6 m and only under a higher than present erosion regime. This new approach yields insight into sea‐level trends during the Last Interglacial.

Deducing photosymbiosis in extinct heliolitid corals

The matter of photosymbiosis in Paleozoic corals remains unresolved as it is not possible to directly check for the presence of algal symbionts in fossil corals. However, present-day photosymbiotic corals are characterised by a number of features that can be evaluated in fossil corals as well, such as large, highly integrated colonies, growth banding, and platy growth forms in mesophotic conditions. The present study aims to evaluate these features in heliolitid corals. Heliolitids were relatively highly integrated, compared to other Paleozoic corals and could produce large colonies, over 1 m in diameter. In this study, heliolitid corals from different outcrops from the Silurian (~ 444 to 419 ma) of Gotland (Sweden) were analysed, and additional Devonian (~ 419 to 359 ma) specimens from Belgium, Poland and Morocco, featuring cyclic growth banding, were also included. Overall, over 60% of studied specimens from Lower Visby Formation in Ireviken and over 80% from Eke Formation in Lau Käldu are platy or tabular. Those outcrops represent environments that were mesophotic. Specimens from the shallower Upper Visby Formation in Ygne are dominated by branching forms instead. The apparent light-related skeletal plasticity, high colony integration, growth banding, and the absence of heliolitids in deep water environments implies that some of these corals were most likely photosymbiotic.

Geoheritage of the Gua Ikan Karst Complex (GIKC), Stong Geopark, Dabong, Kuala Krai District, Kelantan, Malaysia: Evaluation for Geotourism Opportunities

The Gua Ikan Karst Complex (GIKC) is one of the geosite in the Stong Geopark. It consists of spectacular Middle Permian–Late Triassic Gua Musang Formation karst topography, represented by four (4) caves i.e., Gua Ikan, Gua Keris, Gua Pagar, and Gua Gelap. The GIKC can be potentially developed for nature-based tourism since it holds great geoheritage values. The aim of this research is to evaluate the current state of geotourism condition (qualitatively/quantitatively) and geoheritage features of the GIKC using two (2) values in the Modified Geosite Assessment Model (M- GAM) i.e., the Main Value (MV) and Additional Value (AV). The results indicate that the GIKC offers high Scientific/Educational Value (VSE); in the aspect of karst geomorphology (underground river caves, valley/wang, cave chambers, unique shape of stalactite/stalagmite/columns), lithology (metamorphosed limestone of the Gua Musang Formation and the Taku Shist), and palaeogeographic features (coral fossils, sea notch). In summary, the Total Main Value (∑MV) are Gua Ikan (9.73), Gua Keris (9.39), Gua Pagar (9.27) and Gua Gelap (8.66). The Total Additional Value (∑AV) are Gua Ikan (11.56), Gua Keris (11.25), Gua Pagar (11.04) and Gua Gelap (10.98). This paper’s findings reveal a comprehensive base for the improvement, planning, and management of the GIKC to become a geotourism end-point.

Remodulatory effects of coral fossil on hematobiochemical parameters and histoaccumulation of specific organs in lead intoxicated broilers

ObjectivesThe research aims to assess the impact of coral fossil (CF) on hematobiochemical parameters, organ’s accumulation, and remodulation in lead (Pb) intoxicated broiler birds. Methods45 broilers were used in the experiment, which was divided into 03 groups, each of which contained 15 broilers. The control group was Group A. Pb (280 mg/kg b. w.) was administered orally to the birds in group B. Group C received Pb (280 mg/kg b.w.) and CF (1 gm/kg b.w.) oralsupplements. The research was carried out for 30 days. Blood samples were collected, and sera were prepared for biochemical analysis. Pb accumulation concentration was assessed in muscle, liver and kidney. Moreover, samples of the brain, liver, and kidneys were obtainedand prepared for histological analysis. ResultsPb affected hematological markers (Total RBC, Hb conc., hematocrit value, differential leukocytes and blood indices), which were restored with CF supplementation. In Pb-treated broilers, hepatic enzymes (AST, ALT), renal biomarkers (creatinine, total protein and albumin) and lipid profile (TC, TG, HDL and LDL)increased substantially (p < 0.05), but dropped significantly (p < 0.05)after CF supplementation. Pb accumulation was higher in liver, kidney and muscle tissue that was reduced by CF treatment. The histopathological study demonstrated that there was accumulation of fluid around in brain, hyperplasia of bile duct and glomerular epithelium in Pb intoxicated broilers and these were restored after CF supplementation. ConclusionsTherefore, it can be concluded that CF supplementation restored the lead induced detrimental effects on broilers. So, CF has remodulatory effects on Pb toxicity.

Imprint of relative sea level histories on Last Interglacial coral preservation

SUMMARY Fossil corals are commonly used to reconstruct Last Interglacial (∼125 ka, LIG) sea level. Sea level reconstructions assume the water depth at which the coral lived, called the ‘relative water depth’. However, relative water depth varies in time and space due to coral reef growth in response to relative sea level (RSL) changes. RSL changes can also erode coral reefs, exposing older reef surfaces with different relative water depths. We use a simplified numerical model of coral evolution to investigate how sea level history systematically influences the preservation of corals in the Bahamas and western Australia, regions which house &amp;gt;100 LIG coral fossils. We construct global ice histories spanning the uncertainty of LIG global mean sea level (GMSL) and predict RSL with a glacial isostatic adjustment model. We then simulate coral evolution since 132 ka. We show that preserved elevations and relative water depths of modelled LIG corals are sensitive to the magnitude, timing and number of GMSL highstand(s). In our simulations, the influence of coral growth and erosion (i.e. the ‘growth effect’) can have an impact on RSL reconstructions that is comparable to glacial isostatic adjustment. Thus, without explicitly accounting for the growth effect, additional uncertainty is introduced into sea level reconstructions. Our results suggest the growth effect is most pronounced in western Australia due to Holocene erosion, but also plays a role in the Bahamas, where LIG RSL rose rapidly due to the collapsing peripheral bulge associated with Laurentide Ice Sheet retreat. Despite the coral model's simplicity, our study highlights the utility of process-based RSL reconstructions.

Local compositional change and regional stability across 3000 years of coral reef development

AbstractAimMeasuring changes in ecological diversity over time is core to understanding and managing human impacts on natural systems. Observational data do not capture pre‐modern community states or multiple generations of long‐lived taxa, so interpretation of current diversity trends requires comparison with the past. We aimed to estimate diversity trends over long time periods in a series of fossil coral terraces.LocationHuon peninsula, Papua New Guinea.Time Period9817–6433 years before 1950 AD.Major Taxa StudiedThirty‐five genera of Sceleractinian coral.MethodsWe estimated trends in standing richness (α diversity) and turnover (temporal β diversity) in palaeoecological time series of fossil reef terraces. We compared taxonomic and functional group composition estimates of α diversity, using Hill numbers, and β diversity, measured both sequentially along each time series and to the earliest community.ResultsWe found regional‐scale trends of slowly increasing α diversity and directional turnover driven by increased evenness over time. These regional trends were averages of local‐scale trends in α and β diversity that were largely synchronous, even as coral composition diverged between spatial clusters. Our two β diversity estimates provided opposing, but complementary, reference frames to understand the magnitude and rate of compositional change in ecological time series.Main ConclusionsWe provide evidence that prior to strong anthropogenic influence, natural communities were experiencing directional diversity and compositional change. Our results provide a valuable perspective of diversity dynamics in the recent geological past, including how choices in the measurement of diversity can occlude and influence results.

Multidecadal-to-interannual modulations of Late Holocene climate variations reconstructed from oxygen isotope ratios of a 237-year-long lived fossil coral in Kikai Island, southwestern Japan

For this study, to elucidate the East Asian monsoon variations on seasonal, interannual, and decadal timescales during the Late Holocene, we generated a 237-year-long time series of bimonthly resolved oxygen isotope ratios (δ18O) from a 3.5–3.2 ka Porites coral in Kikai Island, southwestern Japan. The coral data clearly show seasonal-to-interdecadal variations reflecting seawater temperature and salinity variations for 237 years, which can be a robust benchmark with respect to subtropical Pacific climate variability during the Late Holocene. Along with modern and fossil coral records published earlier from Kikai Island and Okinawa Island, the time-weighted δ18O averages for overlapped 14C ages demonstrate that the annual and summer values had slightly increased by <0.2‰ for 6–3 ka and that the winter values had increased by ∼0.2‰ for 6–5 ka and decreased by ∼0.2‰ for 5–3 ka. The result indicates that the mean climate state around the island had been almost stable on a centennial-to-millennium timescale throughout the transition from the Middle to Late Holocene, but with several short-term cooling excursions of ∼1 °C at 4–3 ka. On interdecadal-to-interannual timescales, amplitudes of the fossil coral δ18O variations for winter and summer were similar or larger at 3.5–3.2 ka relative to today, revealing significant periodicities at 36–38 years, 20–21 years, 6–9 years, and 3–4 years by spectral analysis at 95% confidence intervals. Furthermore, winter and summer coral δ18O time series of the respective periodic components indicate that interannual variations of SST (and/or seawater δ18O) around the island have changed on interdecadal and decadal timescales, which have been modulated on a multidecadal timescale of approximately 60–90 years/cycle. These results imply that the relationships of the East Asian winter and summer monsoon to the El Niño/Southern Oscillation and Pacific Decadal Oscillation dominant in the North Pacific might have been modulated by or associated with the Atlantic Multidecadal Oscillation dominant in the North Atlantic during the Late Holocene.

Anion elements incorporation into corals skeletons: Experimental approach for biomineralization and paleo-proxies.

The elemental composition of coral skeletons provides important information for palaeoceanographic reconstructions and coral biomineralization. Partition of anions and their stable isotopes in coral skeleton enables the reconstruction of past seawater carbonate chemistry, paleo-CO2, and past climates. Here, we investigated the partition of B, S, As, Br, I, and Mo into the skeletons of two corals, Acropora cervicornis and Pocillopora damicornis, as a function of calcium and carbonate concentrations.* Anion-to-calcium ratio in the corals (An/CaCoral) were correlated with the equivalent ratios in the culturing seawater (An/CO32-SW). Negative intercepts of these relationships suggest a higher CO32- concentration in the coral extracellular calcifying fluid (ECF) relative to seawater, from which the skeleton precipitates. The enrichment factor of CO32- at the ECF was 2.5 for A. cervicornis and 1.9 for P. damicornis, consistent with their relative calcification rates. The CO32-ECF concentrations thus calculated are similar to those proposed by previous studies based on B/Ca coupled with δ11B, as well as by direct measurements using microsensors and fluorescent dyes. Rayleigh fractionation modeling demonstrates a uniform Ca utilization at various CaSW concentrations, providing further evidence that coral calcification occurs directly from a semiclosed seawater reservoir as reported previously. The partition coefficients reported in this study for B, S, As, Br, I, and Mo open up wide possibilities for past ocean chemistry reconstructions based on Br having long residence time (~160 Ma) in the ocean. Other elements like S, Mo, B, as well as pCO2 may also be calculated based on these elements in fossil coral.

Last interglacial global mean sea level from high-precision U-series ages of Bahamian fossil coral reefs

Accurate characterization of Last Interglacial (MIS 5e; ∼129–116 ka) sea level is important for understanding ice sheet sensitivity to climate change, with implications for predicting future sea-level rise. Here we present a record of MIS 5e sea level based on high-precision U-series ages of 23 corals with precise elevation measurements from reefs around Crooked Island, Long Cay, Long Island, and Eleuthera, The Bahamas. Rigorous screening criteria identified the most pristine samples, and nearly all samples show a narrow δ234Uinitial range between 143.8 and 151.3‰. We infer global mean sea level (GMSL) from these local observations by correcting them for glacial isostatic adjustment (GIA) and long-term subsidence. For GIA, we consider a range of ice histories and Earth viscosity structures. We identify, via Bayesian inference, the range of isostatic and GMSL histories that are consistent with MIS 5e observations across The Bahamas. When applying an open-system correction to our ages, we find that MIS 5e GMSL likely peaked higher than 1 m, but very unlikely exceeded 2.7 m. Our posterior GMSL is lower than previous estimates, but consistent with recent results of modeling and observations. Additionally, sea level observations at other locations (Seychelles, Western Australia, Yucatan) are only slightly above/within the 95% range of predicted local sea level, i.e., GIA plus GMSL, for our open-system/closed-system results. Our relatively constant MIS 5e GMSL indicates that Greenland and Antarctica melted beyond their present extents and, given the insolation forcing, that their contributions to GMSL were likely out-of-phase. These results indicate that the ice sheets may be very sensitive to regional temperature, which has important implications for their combined impact on global sea levels at a time when greenhouse gases increases are causing simultaneous warming at both poles.

Late paleozoic climate revealed by coral fossil patterns.

The study of coral fossils with clear growth lines inShiqiantan Formation (310 Ma) in China showed the growth line increments of a single coral growing in this area is related to the sunlight illumination time. Moreover, the daily increment of the growth line caused by calcium carbonate depositions has an unusual bimodal curve. The study of this bimodal curve indicated Shiqiantan had evident four-season changes in the Late Carboniferous period, and the climate at that time was similar to that of modern North China. The present paper updates the oldest existing record of climate analysis materials and provides important information for the study of Late Paleozoic climate, as well as the ancient obliquity of ecliptic.

Substantial incorporation of isotopically heavy reduced U species into marine carbonate sediments

The uranium (U) isotope ratio (238U/235U, reported as δ238U) in marine carbonates is an important proxy for reconstructing changes in past oceanic redox conditions, based on the essential assumption that U in carbonates originates from dissolved U(VI) in seawater. However, diagenetic processes may induce the addition of isotopically heavy U(IV) into the carbonates, complicating the application of the U isotope proxy. So far, the valence states of trace amounts of U and its relation with U isotope composition in marine carbonate sediments have not been directly studied. In this study, we have calibrated an ion-exchange chromatographic method to separate U(IV) from U(VI) in geological carbonate samples (e.g., modern and fossil corals, stalagmites, cold seep carbonates) and quantified their contents by mass spectrometry. Our study confirms that modern coral carbonates are faithful archives of U(VI) sourced from seawater. Surprisingly, drill core samples from a modern coral carbonate platform, which bear no sign of alteration inferred from conventional diagenetic proxies (e.g., Mn/Sr), show significant positive correlation between U(IV) fraction and bulk carbonate δ238U, suggesting U(IV) is present in the marine carbonates and drives δ238U toward higher values than that of seawater. We therefore suggest that coupled valence and isotope analyses of U in marine carbonates could provide critical constraints toward reliable reconstruction of marine redox evolution in the Earth’s history.

Extreme events in the multi-proxy South Pacific drought atlas

Droughts are a natural occurrence in many small Pacific Islands and can have severe impacts on local populations and environments. The El Niño-Southern Oscillation (ENSO) is a well-known driver of drought in the South Pacific, but our understanding of extreme ENSO events and their influence on island hydroclimate is limited by the short instrumental record and the infrequency of ENSO extremes. To address this gap, we developed the South Pacific Drought Atlas (SPaDA), a multi-proxy, spatially resolved reconstruction of the November–April Standardised Precipitation Evapotranspiration Index for the southwest Pacific islands. The reconstruction covers the period from 1640 to 1998 CE and is based on nested principal components regression. It replicates historical droughts linked to ENSO events with global influence, compares well to previously published ENSO reconstructions, and is independently verified against fossil coral records from the Pacific. To identify anomalous hydroclimatic states in the SPaDA that may indicate the occurrence of an extreme event, we used an Isolation Forest, an unsupervised machine learning algorithm. Extreme El Niño events characterised by very strong southwest Pacific drought anomalies and a zonal SPCZ orientation are shown to have occurred throughout the reconstruction interval, providing a valuable baseline to compare to climate model projections. By identifying the spatial patterns of drought resulting from extreme events, we can better understand the impacts these events may have on individual Pacific Islands in the future.

Coral fossil: A potential adsorbent of natural source for cadmium removal in broilers

Cadmium (Cd) is a pollutant that poses a health risk for humans and animals. Coral fossil (CF) acts as an adsorbent, yet limited knowledge is available on impacts of CF on Cd toxicities. The work was performed to figure out the effects of CF on hematobiochemical details and specific organs in Cd exposed broilers. The experiment was carried out with 45 broilers and were divided into three groups (15 in each). Group A was served as control. The birds in group B received Cd (75 mg /kg b. w.) orally. Whereas group C was orally supplemented with Cd (75 mg /kg b. w.) and CF (1 gm/kg b. w.). The trial was lasted for 30 days. For hematobiochemical analysis, blood samples were drawn, and sera were separated. Liver, kidney and muscle were collected to assess accumulation concentration. Brain, liver and kidney samples were also collected for histopathological study. The results showed that hematological parameters (TEC, Hb, PCV, MCV, MCH, MCHC and DLC) were altered by Cd but restored with CF supplementation. Liver (AST, ALT and ALP) and kidney (total protein and creatinine) biomarkers were increased significantly in Cd treated broilers while decreased significantly after CF supplementation. CF reduced accumulation concentration of Cd in liver, kidney and muscle. Cd intoxicated broilers showed degenerative changes in brain, hyperplastic bile duct and proliferation of renal tubular epithelium with focal degeneration and necrosis; and these were improved after CF supplementation. Therefore, it can be concluded that CF is a potential adsorbent against Cd toxicities.