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To better understand the long-term survival of modern coral reefs under global warming, the history of past coral bleaching events prior to modern marine ecological surveys must be investigated. Here, 11 dead Porites and 2 Porites with growth hiatuses growing in the 20th century were collected from the Nansha Islands, southern South China Sea (SCS) for monthly Sr/Ca, δ18O and δ13C analyses to explore the climatic conditions and metabolic information corresponding to these growth structures. Among the 13 episodes, the results showed that 8 mortalities occurred in the summers, coral MJ8 died in spring, and the other 2 mortalities and 2 growth hiatuses occurred in the cooling season. In addition to the dead surface of the coral mortalities, stress bands with significantly reduced growth rates could also be observed in the corals. Negative shifts in δ13C occurred prior to 5 coral mortalities and most stress bands were caused in summer, suggesting a sharp reduction in photosynthesis by decreased symbiotic zooxanthellae or photosynthetic pigments. Overall, the mortalities can be concluded to have occurred in summer and stress bands with abrupt δ13C decreases in the last century were mainly caused by thermal coral bleaching in the southern SCS. This in turn suggests that the repeated coral bleaching and mortalities occurred much earlier before the 1980s, which is a longer-term response to modern global warming during the last century. [ABSTRACT FROM AUTHOR]

Epigenetic modifications based on DNA methylation can rapidly improve the potential of corals to adapt to environmental pressures by increasing their phenotypic plasticity, a factor important for scleractinian corals to adapt to future global warming. However, the extent to which corals develop similar adaptive mechanisms and their specific adaptation processes remain unclear. Here, to reveal the regulatory mechanism by which DNA methylation improves thermal tolerance in Pocillopora damicornis under fluctuating environments, we analyzed genome-wide DNA methylation signatures in P. damicornis and compared the differences in the methylation and transcriptional responses of P. damicornis from fluctuating and stable environments using whole-genome bisulfite sequencing and nanopore-based RNA sequencingtranscriptome sequencing. We discovered low methylation levels in P. damicornis (average methylation 4.14%), with CpG accounting for 74.88%, CHH for 13.27%, and CHG for 11.85% of this methylation. However, methylation levels did not change between coral samples from the fluctuating and stable environments. The varied methylation levels in different regions of the gene revealed that the overall methylation level of the gene body was relatively high and showed a bimodal methylation pattern. Methylation occurs primarily in exons rather than introns within the gene body In P. damicornis , there was only a weak correlation between methylation and transcriptional changes at the individual gene level, and the methylation and gene expression levels generally exhibited a bell-shaped relationship, which we speculate may be due to the specificity of cnidarian species. Correlation analysis between methylation levels and the transcriptome revealed that the highest proportion of the top 20 enriched KEGG pathways was related to immunity. Additionally, P. damicornis collected from a high-temperature pool had a lower metabolic rate than those collected from a low-temperature pool. We hypothesize that the dynamic balance of energy–expenditure costs between immunity and metabolism is an important strategy for increasing P. damicornis tolerance. The fluctuating environment of high-temperature pools may increase the heat tolerance in corals by increasing their immunity and thus lowering their metabolism. • Scleractinian corals are more tolerant in fluctuating reef-dwelling environments. • Low methylation levels in P. damicornis. • Thermal acclimation increase tolerance in corals by increasing coral immunity and thus lowering their metabolism. • Dynamic balance of energy–expenditure costs between immunity and metabolism is an important strategy. [ABSTRACT FROM AUTHOR]

Coral bleaching heat stress products provide real-time and rapid coral bleaching alerts for coral reefs globally. However, geographical variations in the alert accuracy of multi-source coral bleaching heat stress products exist. Taking the coral reefs in the South China Sea (SCS) as the study area, we evaluated and improved the coral bleaching alert capabilities of two coral bleaching heat stress products: Coral Reef Watch (CRW) and Coral Reef Temperature Anomaly Database (CoRTAD). Using in situ coral bleaching survey data and evaluation indicators, the optimized thresholds of degree heating weeks (DHWs) for coral bleaching alerts were determined. The results in the SCS indicated that, first, CRW was better than CoRTAD for coral bleaching event alerts. However, both products underestimated coral bleaching events using the common DHW thresholds of 4°C-weeks and 8°C-weeks. Second, the DHW optimized threshold for CRW was 3.32°C-weeks for coral bleaching event alerts and 4.52°C-weeks for severe coral bleaching event alerts. For CoRTAD products, the DHW optimized threshold was 2.36°C-weeks for coral bleaching event alerts and 4.14°C-weeks for severe coral bleaching event alerts. This study proposed a method to evaluate and optimize the alert capability of multi-source coral bleaching heat stress products, which can provide more accurate basic data for coral reef ecosystem health assessment and contribute to global coral reef ecosystem protection and restoration. • A method to evaluate and optimize the alert capability of coral bleaching heat stress products in the SCS. • Optimized DHW thresholds for coral bleaching alerts were 3.32°C-weeks for CRW and 2.36°C-weeks for CoRTAD. • Optimized DHW thresholds for coral severe bleaching alerts were 4.52°C-weeks for CRW and 4.14°C-weeks for CoRTAD. • CRW was better than CoRTAD for coral bleaching event alerts in the SCS. [ABSTRACT FROM AUTHOR]

In this study, the contamination levels and seasonal variation of 22 PFASs were investigated in coastal reef-building corals (n = 68) from the northern South China Sea (SCS) during wet and dry seasons. Perfluorohexane sulfonate (PFHxS) was the predominant PFASs in all coral samples, representing 43% of the total PFAS. Long-chain PFASs, as well as PFAS alternatives, were frequently detected above the MQL (>88%) but showed relatively low concentrations compared to short-chain PFASs in most species and seasons. Seasonal variation of PFAS concentrations were observed in branching corals, indicating that the accumulation of PFASs may be associated with coral morphological structures. Interspecies differences in PFAS levels agree well with different bioaccumulation potentials among coral species. Redundancy analysis (RDA) showed that seasonal factor and coral genus could partly influence PFAS concentrations in coral tissues. In summary, our study firstly reported the occurrence of PFASs in coral communities from the SCS and highlights the necessity for future investigations on more toxicity data for coral communities. [Display omitted] • This is the first study about PFAS occurrence in coral reef ecosystem. • PFHxS was the predominant PFAS in all coral species. • Short-chain PFASs presented low detection frequencies but relatively high levels. • Branching species are particularly susceptible to PFAS exposure. • Seasonal factor and coral genus have certain effects on the accumulation of PFASs. [ABSTRACT FROM AUTHOR]

Compared with other ocean basins, annual resolution long-term series of sea-level records in the South China Sea (SCS) are still rare. Here we first analyzed the correlation mechanism between the oxygen stable isotopes (δ18O) of Porites coral and instrumental sea-level, sea surface salinity (SSS), sea surface temperature (SST) and rainfall of the SCS, and NINO 3.4 SST during 1980–2015 CE (Common Era); and we then quantitatively reconstructed sea-level at an annual resolution based on the coral δ18O in the SCS. The results show that the sea-level fell slightly (−0.73 ± 0.27 mm/yr) during 1850–1900 CE; then has continuously risen (1.31 ± 0.06 mm/yr) with a total increase of 152 ± 7 mm from 1900 to 2015 CE. On the inter-annual timescale, ENSO by mediating the overflow effect of seawater in the Western Pacific Warm Pool and the location of storm genesis in the western Pacific, indirectly affects sea-level, rainfall and SSS, which is finally reflected in changes in coral δ18O in the SCS. On the long-term timescale, especially since the 1900s, the gradual increase in SST and glaciers and ice sheets meltwater injected into the ocean due to the continuous warming mainly caused by human activities has not only promoted the rise of sea-level, but also caused a gradual negative bias of δ18O seawater (i.e. a gradual decrease of SSS), these processes are faithfully recorded by coral δ18O. Compared with SST, SSS or δ18O seawater may play a more important role in promoting the negative bias of coral δ18O in the SCS. Our study not only provides a better understanding of sea-level history and relationship mechanism around the SCS during 1850–2015 CE, but also may have the potential to provide a valuable proxy for the accurate quantitative reconstruction of sea-level at an annual resolution over a longer time scale for recent past periods. • On the interannual timescale, ENSO is the main driver of coral δ18O via its indirect effects on seawater δ18O in the SCS • On the long-term timescale, SST and injection of meltwater are the main driver of changes in coral δ18O and sea-level • Both SSS and SST are bridges between coral δ18O and sea-level • Coral δ18O is an ideal proxy to indicate sea-level, which has risen by 152 ± 7 mm in total from 1900 to 2015 CE in the SCS [ABSTRACT FROM AUTHOR]

Reconstructing the precise timing of sea level fall is important for understanding earth system during the geologic time. However, previous studies are limited by the absence of effective indicators for sea level fall. To overcome this limitation, we investigated the 87Sr/86Sr and petrologic features of carbonate strata in a 928.75-m-long coral reef core (CK2) from Xisha Islands, northern South China Sea and their relationship to sea level fluctuations. Ten exposed surfaces were identified by their petrologic features. The Mn and Sr content, Mn/Sr, Sr/Ca and δ18O suggest that most of the coral reef carbonate in the CK2 core preserved the original seawater 87Sr/86Sr except at intervals of 672–616, 596–575, 521–491, 423–414, and 192.5–161 m, which suffered alteration of meteoric water and showed higher 87Sr/86Sr during low sea level period. The 160 carbonate 87Sr/86Sr showed a continuously increasing trend, which is consistent with that of seawater over the same period. The continuously increasing 87Sr/86Sr curve of CK2 was divided into seven units by six 87Sr/86Sr hiatuses. Inconsistency between the sedimentation rate of CK2 and tectonic subsidence rate in the Xisha area suggest that the continuously increasing 87Sr/86Sr was controlled by the coupled effect of tectonic subsidence and sea level change, and the hiatus and higher 87Sr/86Sr interval in the 87Sr/86Sr curve were controlled by sea level fall. The higher 87Sr/86Sr usually produced during low sea level (<5 m), 87Sr/86Sr hiatus usually produced when sea level changed from deeper to shallower. The depth of hiatuses and higher intervals of 87Sr/86Sr correspond well with the exposed surface in CK2 core, verifying that the hiatuses and higher intervals of 87Sr/86Sr in the coral reef carbonate succession provide an effective indicator of sea level fall. Using this indicator and the CK2 87Sr/86Sr profile, we identified eleven large-scale sea level falls and three dramatic regressions during 19.6–0.2 Ma and constrained the age based on strontium isotope stratigraphy. These interpreted sea level falls are mostly consistent with other records of global sea level changes, confirming the reliability of our records. The 87Sr/86Sr profile of a coral reef carbonate is an efficient indicator of past sea level falls, including their timing. • 87Sr/86Sr ratios of carbonate in a coral reef core from Xisha Islands. • The core indicated five hiatuses and six anomalously high ratios in Sr isotope. • Hiatus and high ratios in reef carbonate Sr isotope were produced by sea level fall. • Eleven major lower sea level and three dramatic regressions found during 19.6–0.2 Ma. • This method provides an effective indicator of past sea level fluctuation. [ABSTRACT FROM AUTHOR]

We have previously shown that the coralline algal assemblages (CAAs) of the South China Sea may indicate post-Pliocene paleo-water depth changes; however, the pre-Pliocene coralline algal compositions and related sea-level significance remain to be elucidated. In the present study, we explore the Miocene coralline algal compositions and their role in recording the sea level, and show the distribution, classification, type, abundance, and diversity of Miocene coralline algae from 213 petrologic thin sections using a coral-reef carbonate sequence from the northern South China Sea. The diversity and abundance of coralline algae in the early and late Miocene are higher than those in the middle Miocene. Eleven genera were identified and grouped into seven CAAs, showing a water depth range from <5 m to >25 m. At 18.67–17.98 Ma, the coral reef was in a stagnation/drowning stage, with rising sea levels exceeding the development of the coral reef. At 17.98–16.78 Ma, the coral reef was in a rapid development during a rapid rise in sea level. Additionally, at 16.78–14.79 Ma, low coralline algal abundance was observed, and the corals were sporadically distributed at a relatively stable sedimentation rate, suggesting a decline in coral reef development. At 14.79–10 Ma, the coral reef development was remarkably slow or stagnant. Furthermore, at 10–5.3 Ma, the coral reefs developed slowly, indicating a gradual rise in the sea level. The sea-level changes indicated by coral reef development are consistent with the long-term global sea-level changes, indicating that the composition and assemblage of Miocene coralline algae can be used to accurately relay the sea-level history. • Eleven coralline algal genera were identified in a Miocene carbonate sequence. • Miocene coralline algae were divided into 7 coralline algal assemblages (CAAs). • Sea-level changes due to coral reef development were consistent with global values. [ABSTRACT FROM AUTHOR]

Few reconstructions of sea-surface temperature (SST) have focused on seasonal and interannual variability, two major components of the global climate system, due to the limited temporal resolution of proxies. This study presents a combined 228-year-long, monthly resolved strontium to calcium ratios (Sr/Ca) record covering the period of 2070–1740 a BP (years before 1950 CE (Common Era)) extracted from three U-series-based sub-fossil Porites corals located on the Xisha Islands, northern South China Sea (SCS). The composite time series allowed for accurate assessment of the natural range of SST variations during snapshots of the Roman Warm Period (RWP). Reconstructed SST revealed that the RWP was characterized by cooler conditions compared with the 20th century, consistent with climatic variations in the western Pacific and East Asia. The amplitude of SST seasonality was within the modern range, except for a lower value at 1980–1928 a BP. Interannual variability associated with El Niño–Southern Oscillation (ENSO) activity was enhanced by 39% relative to 1980–2014 CE. The results of the sliding window demonstrate that ENSO variability persistently strengthened during 2070–2010 a BP, followed by an overall fluctuating attenuation during 1980–1928 a BP. Then, the trends of rising first before descending twice during 1852–1800 a BP appeared. Furthermore, ENSO activity played a leading role in steering short-term changes in SST seasonality in the northern SCS, manifested as stronger ENSO activity with more frequent El Niño events and decreased SST seasonality. Considering that the frequency of extreme ENSO events may strengthen in the future under global warming, the climate in the northern SCS might become more variable and complex. • 228-year monthly SST derived from coral Sr/Ca for snapshots of the Roman Warm Period. • Cooler conditions and variable SST seasonality characterize the 2070–1740 a BP. • Stronger interannual variability and ENSO evolution for the RWP are investigated. • ENSO activity modulates changes of SST seasonality in the northern South China Sea. [ABSTRACT FROM AUTHOR]

Despite organophosphate esters (OPEs) are widely prevalent in the environment, however, limited information is available regarding their occurrence, trophodynamics, and exposure risks in coral reef ecosystems. In this study, 11 OPEs were investigated in a tropical marine food web (7 fish species and 9 benthos species) from the Xisha (XS) Islands, South China Sea (SCS). The ∑ 11 OPEs were 1.52 ± 0.33 ng/L, 2227 ± 2062 ng/g lipid weight (lw), 1024 ± 606 ng/g lw, and 1800 ± 1344 ng/g lw in seawater, fish, molluscs, and corals, respectively. Tris (2-chloroisopropyl) phosphate (TCIPPs) were the dominant OPEs in seawater, fish, and molluscs, while tris (2-butoxyethyl) phosphate (TBOEP) predominated in coral tissues. Abiotic and biotic factors jointly affect the OPEs enrichment in marine organisms. Trophic magnification factors (TMFs) (range: 1.31–39.2) indicated the biomagnification potency of OPEs. A dietary exposure risk assessment indicated that OPEs at current levels in coral reef fish posed a low risk to human health but were not negligible. Overall, this study contributes to a further understanding of the environmental behaviors of OPEs in coral reef ecosystems. [Display omitted] • OPEs profiles in seawater and marine organisms are different. • Fish tend to enrich Cl-alkyl OPEs and benthos prefer to accumulate aryl OPEs. • Abiotic and biotic factors jointly affect the OPEs enrichment in marine organisms. • OPEs pose a low risk to human health by coral reef fish ingestion. • Emerging pollutants are dominating the pollution status in the Xisha Islands. [ABSTRACT FROM AUTHOR]

The El Niño-Southern Oscillation (ENSO) is the most influential climatic phenomenon on an interannual timescale. Studying the relationship between sea surface temperature (SST) and ENSO events during typical geological periods is helpful for understanding the trends of ENSO activities in the future, especially under the background of global warming. Here we quantitatively reconstructed a 115-year history of SST and ENSO activity around 282 ka during Marine Isotope Stage 8 (MIS8) by using the growth rate of Porites corals from Xisha Islands in the South China Sea. The results show that the average coral growth rate (6.0 ± 1.0 mm/yr (1σ)) around 282 ka was only 56.1% of the modern average value (10.7 ± 0.9 mm/yr; 1937–2014 CE), and the average SST (26.0 ± 0.3 °C (1σ)) was 0.7 ± 0.4 °C and 1.1 ± 0.4 °C lower than that in the Little Ice Age (LIA; 1520–1676 CE; 26.7 ± 0.2 °C) and the present (1937–2014; 27.1 ± 0.2 °C), respectively. The reconstructed results show that there was significant ENSO activity with moderate intensity or above at 282 ka, while the frequency of ENSO activity at that time was lower than that of the LIA and the present. This seems to indicate that the frequency of moderate intensity ENSO activity increases with rising SST. Given the current rapid warming, the future trend of ENSO activities deserves close attention. • The growth rate of Porites coral is a reliable paleoenvironmental proxy. • The coral growth rate at 282 ka was only equivalent to 56.1% of the present. • Coral–SST at 282 ka was 0.7 °C and 1.1 °C lower than the LIA and present, respectively. • The ENSO frequency at 282 ka was lower than the present. [ABSTRACT FROM AUTHOR]

The levels, fate, and potential sources of 22 organochlorine pesticides (OCPs) in coral tissues and the surrounding air-seawater system from the South China Sea (SCS) were elucidated for the first time. ∑ 22 OCPs (total concentration of 22 OCPs) (16.1–223 pg L−1) was relatively higher in coastal seawater than in offshore seawater, which may be the widespread influence of coastal pollution inputs under the western boundary current. The atmospheric ∑ 22 OCPs were predominantly distributed in the gas phase (48.0–2264 pg m−3) and were mainly influenced by continental air mass origins. The air-seawater exchange of selected OCPs showed that OCPs tended to migrate from the atmosphere to seawater. The distribution of ∑ 22 OCPs in coral tissues (0.02–52.2 ng g−1 dw) was significantly correlated with that in air samples, suggesting that OCPs may have a migration pattern of atmosphere-ocean corals in the SCS. Corals exhibited higher bioaccumulation ability (Log BAFs : 2.42–7.41) for OCPs. Source analysis showed that the new application of technical Chlordanes (CHLs) was primarily responsible for the current levels of CHLs in the surrounding environment over the SCS, while historical residues were the primary sources of other OCPs. [Display omitted] • Pioneer OCPs study of coral tissues from the South China Sea (SCS). • Corals presented a higher bioaccumulative ability to OCPs. • Ocean currents and monsoons played essential roles in the OCPs' spatial distribution. • Net atmospheric deposition of OCPs occurred in the coral reef regions (CRRs), SCS. • OCPs may have a migration pattern of atmosphere-ocean-corals in the CRRs, SCS. [ABSTRACT FROM AUTHOR]

Holocene coral reef development is valuable to understanding the behavior and impacts of paleoclimate and sea level changes. This study focuses on the Holocene carbonate sequences of a drill core extracted from Well CK2 in the northern South China Sea (SCS). This drill core consists of an 873.55 m thick carbonate layer overlying 55.20 m of volcanic basement. High precision U-series dating of 22 coral samples suggests that the Holocene coral reef, which has a thickness of 16.7 m, initiated at ~7800 yr BP (years before 1950 CE) and stopped vertical accretion at 3900 yr BP. The mean vertical accretion rate in the Holocene in Well CK2 was 3.48 m kyr−1, varying from 6.44 m kyr−1 during 7800–6000 yr BP to 0.87 m kyr−1 during 6000–3900 yr BP. After 3900 yr BP, the vertical development of the reef ceased, indicating that the reef development likely involved lateral accretion. The Holocene section mostly consists of unconsolidated coarse sediments, mainly including corals, coralline algae, large benthic foraminifera, and mollusks. Based on the relationship between coral reef development and sea level, together with the age profile, we determined that the relative sea level near Chenhang Island rose rapidly between 7800 and 6000 yr BP, slowed at ~6000 yr BP, and reached a position of about 2 m above the present-day mean sea level by 3900 yr BP. After 3900 yr BP, the sea level was stable or fell, resulting in a cessation in the reef's upward development. • 22 230Th ages of a SCS reef core suggest the Holocene reef initiated at 7800 yr BP. • Vertical development decreased from 6.44 to 0.87 m kyr−1 at 3900 yr BP. • Sea level at 7800 yr BP was ~13.8 m below present and rose rapidly. • Sea level has stabilized/fallen since 3900 yr BP, as indicated by reef development. [ABSTRACT FROM AUTHOR]

Coral probiotics can improve the tolerance of corals to heat stress, thus mitigating the process of coral thermal bleaching. Sensitive and specific detection of coral probiotics at low abundances is highly desirable but remains challenging, especially for rapid and on-site detection of coral probiotics. Since the electrochemical biosensor has been recently used in the field of environmental DNA (eDNA) detection, herein, an efficient electrochemical biosensor was developed based on CoS 2 /CoSe 2 -NC HNCs electrode material with a specific DNA probe for the C. marina detection. After optimization, the lower limit of detection (LOD) values of such biosensors for the target DNA and genomic DNA were 1.58 fM and 6.5 pM, respectively. On this basis, a portable device was constructed for the practical detection of C. marina eDNA, and its reliability and accuracy were verified by comparison with the ddPCR method (P > 0.05). For each analysis, the average cost was only ∼ $1.08 and could be completed within 100 min with reliable sensitivity and specificity. Overall, the biosensor could reflect the protective effect of probiotics on coral heat stress, and the proposed technique will put new insights into the rapid and on-site detection of coral probiotics to assist corals against global warming. [ABSTRACT FROM AUTHOR]

[Display omitted] • Blue light increases the thermal bleaching tolerance of coral holobiont. • Blue light decreases photosynthesis, respiration and ROS release of Symbiodiniaceae under heat stress. • Blue light reduces respiration and lipid peroxidation of host under heat stress. • The up-regulation of the DAO gene indicates a coral bleaching model that dependents on the host. Given the high degree of heterogeneity of coral bleaching, there is potential for abiotic approaches to improve the thermal tolerance of coral. However, there is limited knowledge about such factors and causes that regulating acclimation of coral to warming. Here, a study was conducted on the reef building coral Acropora tenuis to investigate the impact of light qualities on the physiological, cellular, and molecular biochemical responses of the coral holobiont to heat stress. The results showed that after subjecting the samples to heat stress at 32 ℃ for 9 days, over 90% corals exposed to compound light experienced bleaching on the fifth day, while corals exposed to blue light showed no significant signs of bleaching even on the ninth day. This indicates that blue light may enhanced the coral's thermal bleaching tolerance. Further analysis revealed blue light primarily increased coral's resistance to thermal bleaching by remodeling the interactions between Symbiodiniaceae (i.e. decreased photosynthesis, respiration and ROS release) and coral (i.e. decreased respiration and lipid peroxidation). The study also found that the host's of reactive oxygen species (ROS) played a role in causing coral bleaching besides the ROS released by Symbiodiniaceae. The up-regulation of the DAO gene (encoding D-amino-acid oxidase, up-regulated nearly 1000 times under warming conditions) in the host highlights the mechanism of coral bleaching, whereby the catalysis of amino acids by the D-amino-acid oxidase produces ROS. In summary, the present study reveals novelty insights into the molecular processes related to thermal bleaching of coral, identifies blue light as a positive environmental factor that enhances coral's tolerance to global warming. [ABSTRACT FROM AUTHOR]

Oil pollution can release trace metals (TMs) with cumulative toxicity into seawater, harming marine ecosystems in the long term. However, the lack of studies has inhibited our understanding of the effects and mechanisms of oil pollution on TMs in seawater. Hence, we investigated the 10-year monthly variation of TMs in Porites coral skeletons from the northern South China Sea (SCS), complemented by spatial distribution of TMs in seawater, sediments and characterization of TMs in fuel oil. The results of principal component-multivariate linear regression showed that the total contribution of oil pollution as a source to TMs in surface seawater was 77.2%, where the residence time of TMs (Ni, V, Cr, Co, Cu, Mn, Fe, and Mo) released from oil spills in surface seawater was approximately 1.4 months. Due to the geochemical nature of the metals, their seasonal variations are controlled by tropical cyclones (Ni, V, Cr, Co, Cu, Mn, Fe, and Mo), winter monsoons (Pb, Cd, Ba, and Zn) and sea surface temperature (Sr). This study shows that coral skeletons can be used as a new tool to study marine oil pollution. This provides valuable reference data for accurately identifying and quantifying the effects of oil pollution on TMs in seawater from a spatial and temporal perspective. [Display omitted] • High-resolution coral skeletons can be used as a novel tool for marine pollution. • Contribution of oil pollution to each trace metal in surface seawater was estimated. • Effects of oil spills on trace metal in surface seawater can last for ∼1.4 months. [ABSTRACT FROM AUTHOR]

Most studies on coral bleaching alerts use common Degree Heating Week (DHW) thresholds; however, these may underestimate historical patterns of heat stress for coral reef ecosystems. Taking an optimized DHW threshold for coral bleaching alerts for Coral Reef Watch (CRW) and Coral Reef Temperature Anomaly Database (CoRTAD) products, we analyzed the precise spatial and temporal pattern of heat stress on China's coral reefs from 2010 to 2021 in the South China Sea (SCS) and the Beibu Gulf (BG). We compared acute heat stress using common and optimized thresholds. Results indicated that the ocean warming rate in 2010–2021 was approximately 0.43 ± 0.22 °C/10a, showing a significant increase in the northern SCS and the BG. More severe bleaching events were predicted by the optimized thresholds and the high-frequency areas were mainly in the northern SCS. The number and intensity of years with severe heat stress anomalies was in the order 2020 > 2014 > 2010 > 2015. Heat stress duration was the longest in the Xisha Islands among offshore archipelagos, and longest in 2020–2021 in Weizhou Island in BG in the relative high-latitude inshore reefs. These abnormal events were mainly caused by El Niño, but La Niña was also involved in 2020. • The most intense severe heat stress anomaly years were 2010 > 2014>2020 > 2015. • The anomaly duration of offshore islands was Xisha > Dongsha > Zhongsha > Nansha Islands. • High-latitude reefs were predicted not to be future thermal refuges for SCS reefs. • The optimized DHW threshold more accurately predicted spatiotemporal heat stress. [ABSTRACT FROM AUTHOR]

Nutrient enrichment is a widely recognized threat to coastal coral reefs. Yet its impact on open ocean reefs is largely unknown due to the lack of long-term observations at remote sites and the entanglement of various environmental factors affecting coral growth. Here we determined growth rates and the carbonate chemistry of calcifying fluid (CF) of massive corals over the last 550 years at a remote South China Sea reef ecosystem. We show that large growth variations cannot be fully explained by changes in seawater pH or temperature due to the antiphase relationship between growth rate and pH cf as well as small sea surface temperature variations before the 1960s. Instead, coral growth rate decreases proportionally with past seabird populations over the past centuries. We suggest that excess nutrient loads through monsoon pumping and seabird migration played an important role in controlling coral growth at this remote reef ecosystem. Specifically, episodic eutrophication as indicated by a ∼ 3 per mil increase in coral δ13C has depressed coral growth by ∼30% during 15th to 18th centuries, which is comparable to the modern decline. Thus, accurate projections of future coral growth for remote reefs under ongoing human activities and climate change needs to take into account the history of past nutrient inputs into these ecosystems under pre-anthropogenic conditions, which has been overlooked previously due to a lack of historical observations. • Coral cores from an open ocean reef that grew from ∼1450 to present were analyzed. • Temperature affects multi-decadal variability in coral calcifying fluid DIC but not pH. • Reef-water pH modified by monsoon controls calcifying fluid pH and [CO 3 2−] • Eutrophication caused by monsoon and seabirds depressed coral growth during the Little Ice Age • An analog to the responses of corals to the projected rise in anthropogenic nutrient inputs. [ABSTRACT FROM AUTHOR]

Multiple environmental pressures caused by global warming and human activities have aroused widespread concern about PAHs pollution in tropical marine coral reef regions (CRRs). However, the trophodynamics of PAHs in the food webs of the CRRs and the related influence factors have not been reported. This study investigated the occurrence, trophic amplification, and transmission of PAHs in various organisms selecting between at least representative species for each level in CRRs of the South China Sea (SCS); revealed their driving mechanisms; and explored the trophodynamics of PAHs in the food web of the coral reef ecosystem. Results showed that more PAHs can be accumulated in the mantle tissue of Tridacnidae, and the proportion of mantle tissue of Tridacnidae increases with the increase of latitude (y = 0.01x + 0.17, R2 = 0.49, p < 0.05). Latitude drives the differential occurrence level and bioaccumulation of PAHs in tropical marine organisms, and also affects the trophodynamics of PAHs in aquatic ecosystem food webs. PAHs undergo trophic amplification in the food webs of tropical marine ecosystems represented by coral reefs, thus further aggravating the negative environmental impact on coral reef ecosystems. The cancer risk caused by accidental ingestion of PAHs by humans through consumption of seafood in CRRs is very low, but we should be alert to the biomagnification effect of PAHs. [Display omitted] • Reported PAHs' occurrence in the coral reef food web for the first time. • Latitude affected PAHs' occurrence and bioaccumulation in the organisms. • Latitude drove the PAHs' trophodynamics in aquatic ecosystem food webs. • PAHs underwent trophic amplification in the food webs of coral reef ecosystems. [ABSTRACT FROM AUTHOR]