Southern South China Sea Research Articles

Seismic Characteristics and Hydrocarbon Accumulation Associated with Mud Diapir Structures in a Superimposed Basin in the Southern South China Sea Margin

Seismic Characteristics and Hydrocarbon Accumulation Associated with Mud Diapir Structures in a Superimposed Basin in the Southern South China Sea Margin

Subseasonal dynamical prediction of South China Sea summer monsoon

South China Sea (SCS) summer monsoon (SCSSM) is an important component of the Asian monsoon system, of which the onset and intensity exerting critical impacts on surrounding areas. With the Japan Meteorological Agency (JMA) model prediction derived from the S2S project, the predictions of SCSSM, specifically, the annual evolution, onset, and corresponding meteorological variables are investigated with lead times of 1–34 days. The prediction skill on the associated dynamical and thermal background such as wind, vertical motion, pseudo-equivalent potential temperature, and specific humidity decreases with the growing lead times. For the SCS surroundings, the upper- and lower-level circulations are reasonably predicted for lead times of shorter than 3 weeks. Predictions with fair skill on humidity and pseudo-equivalent potential temperature over land area around the northern SCS last for around 4 weeks, better than those over the southern SCS. Predictions on vertical motion and precipitation are reliable within 1 week, while the skill decreases rapidly after 2 weeks. In general, the predictions on the spatial patterns of circulation are relatively poor during the transition period before monsoon onset and are then improved after that. The model capability on predicting the date of monsoon onset decreases with the increasing lead times. Besides, skillful predictions on climate systems such as the tropical vortex pairs over Indian Ocean and the western North Pacific subtropical high are critical for the successful predictions of monsoon onset.

Interdecadal Change in the Interannual Variation of the Western Edge of the Western North Pacific Subtropical High During Early Summer and the Influenceof Tropical Sea Surface Temperature

This study reveals that the interannual variability of the western edge of the western North Pacific (WNP) subtropical high (WNPSH) in early summer experienced an interdecadal decrease around 1990. Correspondingly, the zonal movement of the WNPSH and the zonal extension of the high-pressure anomaly over the WNP (WNPHA) in abnormal years possess smaller ranges after 1990. The different influences of the tropical SSTAs are important for this interdecadal change, which exhibit slow El Niño decaying pattern before 1990 while rapid transformation from El Niño to La Niña after 1990. The early summer tropical SSTAs and the relevant atmospheric circulation anomalies present obvious interdecadal differences. Before 1990, the warm SSTAs over the northern Indian Ocean and southern South China Sea favor the WNPHA through eastward-propagating Kelvin wave and meridional-vertical circulation, respectively. Meanwhile, the warm SSTA over the tropical central Pacific induces anomalous ascent to its northwest through the Gill response, which could strengthen the anomalous descent over the WNP through meridional-vertical circulation and further favor the eastward extension of the WNPHA to central Pacific. After 1990, the warm SSTAs over the Maritime Continent and northern Indian Ocean cause the WNPHA through meridional-vertical and zonal-vertical circulation, respectively. Overall, the anomalous warm SSTs and ascent and the resultant anomalous descent over the WNP are located more westward and southward after 1990 than before 1990. Consequently, the WNPHA features narrower zonal range and less eastward extension after 1990, corresponding to the interdecadal decease in the interannual variability of the western edge of the WNPSH. On the other hand, the dominant oscillation period of ENSO experienced an interdecadal reduction around 1990, contributing to the change of the El Niño SSTA associated with the anomalous WNPSH from slow decaying type to rapid transformation type.

Chemical Weathering of the Mekong River Basin With Implication for East Asian Monsoon Evolution During the Late Quaternary: Marine Sediment Records in the Southern South China Sea

Clay mineralogy, major-element geochemistry, and Sr-Nd isotopic compositions from Core MD05-2896 collected in the southern South China Sea have been utilized to investigate the discrimination of sediment provenance and to reconstruct a history of chemical weathering in the Mekong River basin over the last 45 ka. The results display that the clay mineral assemblage of the core is characterized by abundant smectite (27%–56%) and illite (18%–32%), with moderate kaolinite (13%–23%) and chlorite (11%–18%), and the 87Sr/86Sr ratio and εNd value narrowly vary in the ranges of 0.7232–0.7272 and from –10.9 to –9.6, respectively. According to clay mineralogy and Sr-Nd isotopic compositions, the Mekong River is the main terrigenous sedimentary source to the southern South China Sea, with no detectable change over the time span of the study, despite having strong sea-level fluctuations. Clay mineralogy and elemental geochemistry analyses reveal that higher smectite/(illite + chlorite), smectite/kaolinite, TiO2/K2O, and SiO2/K2O ratios during Marine Isotope Stage (MIS) 3 and 1 suggest enhanced chemical weathering, whereas lower values of these ratios during MIS 2 indicate weakened chemical weathering. These proxies reveal a close relationship with the available climate records of the East Asian monsoon evolution, implying that the chemical weathering in the Mekong River basin has been strongly controlled by the East Asian monsoon rainfall.

Provenance of Oligocene–Miocene sedimentary rocks in the Cuu Long and Nam Con Son basins, Vietnam and early history of the Mekong River

The offshore Cuu Long (CLB) and Nam Con Son (NCSB) basins of SE Vietnam are two important Cenozoic hydrocarbon-bearing basins in the southern South China Sea (SCS), which can contribute to understanding the evolution of major SE Asian river systems, in particular the Mekong River. The Oligocene to Early Miocene basin fill of the Cuu Long Basin is dominated by sediment sourced locally from the Da Lat Zone basement on land. Sandstones have abundant Cretaceous detrital zircons and heavy mineral assemblages dominated by apatite and epidote. The Bach Ho Unconformity at c. 16 to 20.5 Ma marks a major provenance change and the overlying Middle to Late Miocene Con Son and Dong Nai formations were sourced by a large river system, which drained Indochina or even the Himalaya, resembling the present-day Mekong River. These formations have heterogeneous detrital zircon populations dominated by Triassic ages and zircon–rutile–tourmaline-dominated heavy mineral assemblages. The Oligocene Cau and Early Miocene Dua formations of the Nam Con Son Basin have a similar provenance to the CLB Con Son and Dong Nai formations, indicating a comparable drainage history of a large proto-Chao Phraya. At the Dua Unconformity at c. 15.4 to 17 Ma the Indochina provenance signature changes to a predominant Sibumasu signature.The early Mekong River evolution is suggested to have involved two river systems. A proto-Mekong 1 initially filled the CLB, while at the same time a proto-Chao Phraya River with a capture area into the Himalaya filled the Malay Basin and/or the NCSB. At the end of the Early Miocene drainage was completely reorganised, and the proto-Mekong 1 captured the headwaters of the proto-Chao Phraya and became the proto-Mekong 2, while the NCSB was filled by sediment from the Malay–Thai Peninsula. This major change marks a very important drainage reorganisation in the southern SCS region.

Seasonal oceanographic changes and their implications for the abundance of small pelagic fishes in the southern South China Sea

The seasonal variations in shelf circulation and their implications for the distribution of light fishing vessels positions (VBD) that capture small pelagic fishes in the southern South China Sea (SSCS) are investigated by using multi-datasets between 2008–2014. It is found that the SSCS shelf circulation is indicated by the strong seasonal reversal western boundary current (WBC) and prominent cyclonic circulation (eddy). The southeastward WBC brings homogeneous salty, colder, and high primary production of nanophytoplankton (PPN) water during winter-time from the northern and the cyclonic eddy region into the southern SSCS. In contrast, less salty, warmer, and less PPN are advected northwestward from Karimata into the northern region. These factors significantly influence the distribution of VBD and in turn the production of captured small pelagic fishes (CPUE), revealing two maxima (peaks) of both VBD and CPUE during the monsoon breaks (MB) with a time-lag of 2–3 month from the monsoon peaks. Relationship between oceanographic parameters and CPUE is examined statistically revealing that ocean current and PPN are significantly affect the CPUE. A relatively high PPN and strong current during the peaks of monsoon are correlated with lower CPUE. In contrast, during the MBs period CPUE maxima are associated with a relatively weak ocean current and consumed PPN that favor the abundance of small pelagic fishes.

Subduction of the paleo-Pacific plate recorded by arc volcanism in the South China Sea margin

Accretionary prisms along the East Asia continental margin have been interpreted as having formed in response to subduction of the paleo-Pacific plate in the Paleozoic–Mesozoic. However, early arc magmatic records in the East Asia margin have been partly destroyed owing to episodic rifting. Widespread arc magmatism and fold and thrust belts in the South China block have recorded Jurassic and Cretaceous paleo-Pacific plate subduction. In addition, the exterior of the South China continental margin was rifted during the Cenozoic to form the South China Sea, and it is presumed that a relic arc is preserved in the northern and southern South China Sea. In this study, we obtained samples of volcanic rocks through drilling >2000 m in the southern South China Sea. The drill core consisted of interbedded basalts, trachytes, and minor trachy-andesites, with arc-type trace-element patterns. Zircon U–Pb dating of trachyte samples from the drill core yielded clustered ages with an overall weighted mean age of 211.2 ± 1.6 Ma, providing robust evidence for the existence of a volcanic arc in the East Asia margin during the Late Triassic. Primitive basalts with MgO > 8.5 wt% have the highest values of εNd(i) and εHf(i) and indicate derivation from Indian-type sub-arc mantle wedge. The increasing Th/Nb with decreasing Nd−Hf isotope values of the basalt samples indicates the incorporation of sediment into the melts. The trachyte samples have enriched K2O and isotopic compositions and are consistent with a sediment-dominated source. On the basis of a comparison with regional magmatic rocks related to plate subduction during Triassic–Jurassic time, the arc volcanic rocks in the southern South China Sea are interpreted to mark a temporal compositional transition in the mantle source, representing steepening subduction of the paleo-Pacific plate during the Late Triassic.

Potential geochemical evidence of Porites corals responding to coral bleaching in the 20th century in the Nansha Islands, southern South China Sea

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.

Origin of large-scale variegated reef limestones in the southern South China Sea: Implications for Miocene regional and global geological evolution

Marine sediments featuring special colors have always played an important role in disclosing regional or global environmental transitions and geological evolution. A deep well (Nanke-1), drilled on Meiji Atoll in 2017, penetrated Cenozoic reef strata in the central Nansha Block (also referred to as Dangerous Grounds) in the southern South China Sea (SCS) and revealed two pronounced variegated (containing colors of white, reddish and red brown) reef limestone layers in the Miocene. Similar large-scale variegated reef limestones have not been found in other reef drilling cores to date, so its coloration origin, formation mechanism and geological implications are unclear. Here, synthesized mineralogical, petrographic, and geochemical analyses demonstrated that the presence of trace amounts of amorphous microsized hematite with varying crystallinity imparted reddish or red brown colors to reef limestones. Hematite formed during meteoric water-induced karstification after the carbonate platform was exposed subaerially. Long-term exposures were mainly controlled by regional tectonic uplifts closely associated with the subduction of the proto-SCS, the seafloor spreading of the Southwest Sub-basin and the collision between blocks (i.e., the Sabah collision and the Palawan collision). The different tectonic settings have led to the different developments of carbonate platforms in the northern and southern SCS during most of the Early and Middle Miocene, but the major expansion of the high-latitude Antarctic ice sheets and the resultant significant drop in global sea level may have contributed to wide exposure of carbonate platforms both in the northern and southern SCS in the late Middle Miocene. Our studies demonstrated that the occurrences of variegated reef limestones in isolated oceanic reef carbonate platforms have great potential in indicating subaerial exposure, regional tectonic uplift or sea level fall.

Mesoscale Eddy Effects on Nitrogen Cycles in the Northern South China Sea Since the Last Glacial

Archaeal ammonia oxidation is the most important intermediate pathway in regulating the oceanic nitrogen cycle; however, the study of its specific role on a geological time scale is restricted to a specific part of marginal seas; thus far, only in the southern South China Sea (SCS). To explore the spatial pattern of the role of archaeal ammonia oxidation in the SCS, the GDGT-[2]/[3] ratio (Glycerol Dialkyl Glycerol Tetraether), an indicator of the archaeal ammonia oxidation rate, was analyzed and examined from the collected data profiles since the last glacial period in the northern SCS. The results showed that the GDGT-[2]/[3] ratio in the northern SCS was opposite to that in the southern SCS, with higher GDGT-[2]/[3] values during the Holocene compared to the last glacial period. Based on existing published depths of thermocline (DOT) data in the northern SCS since 30 ka, we believe that hydrological structural variations induced by mesoscale eddies caused this difference. Therefore, physical processes are very important factors that control the nitrogen cycle over a long-time scale. This study may provide new insights into the understanding of the role of archaeal ammonia oxidation within the marine nitrogen cycle over geological time scale.

Strontium isotope stratigraphy and LA-ICP-MS U-Pb carbonate age constraints on the Cenozoic tectonic evolution of the southern South China Sea

Abstract The tectonic evolution of the South China Sea is closely associated with multiple subduction-collision processes in Southeast Asia. When the collision of the Dangerous Grounds terrane with Sabah-Palawan Islands terminated is debated due to poor age constraints at the southern margin of South China Sea. A deep well drilled on Meiji Atoll penetrates Cenozoic carbonate strata in central Dangerous Grounds. Robust strontium isotope ages and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb dates provide critical chronological constraints on the Cenozoic evolution of the southern South China Sea. A middle Miocene hiatus spanning 9 m.y. on Meiji Atoll is thought to be mainly caused by tectonic uplift in the central Dangerous Grounds. The uplift in the central Dangerous Grounds was accompanied by underthrusting beneath the southern Palawan margin and orogenic uplifting in north Borneo during the middle Miocene. Data interpretation indicates an active collision in the southern South China Sea during the middle Miocene. The regrowth of the Meiji Atoll above the middle Miocene hiatus represents the end of this collision event in the southern South China Sea at ca. 11 Ma, after the cessation of seafloor spreading, which occurred at ca. 15 Ma.

Impact of Anticyclonic Eddy on Nonlinear Wave‐Wave Interaction in the Southern South China Sea During Late Summer 2020

AbstractNonlinear wave‐wave interaction (WWI) in the southern South China Sea (SCS) has rarely been investigated due to sparse field observation. By analyzing datasets recorded by two adjacent moorings, we find active nonlinear WWI among diurnal internal tides (D1 ITs), near‐inertial waves (NIWs), and D1‐f waves in this area. Although the blue shift of NIWs can provide part of the energy for D1‐f waves, the bulk of D1‐f energy was generated from the nonlinear WWI. Driven by the summer monsoon, a dipole of mesoscale eddies was formed off the central Vietnam coast and intruded into the study area. The anticyclonic eddy of the dipole reduced the local effective Coriolis frequency by providing negative vorticity and suppressed the nonlinear WWI locally. During the intrusion period, D1‐f waves almost vanished suggesting the important role of mesoscale eddy on adjusting the nonlinear WWI in the SCS.

Spatial and temporal trends of polycyclic aromatic hydrocarbons in sediment cores of Brunei Bay, East Malaysia

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in three sediment cores from Brunei Bay, Southern South China Sea was investigated. The total concentrations of 16 priority PAHs (∑PAH16) and their alkyl-substituted derivatives ranged from 10.4 to 376 ng g−1 and 30.7 to 2263 ng g−1, respectively. PAH biomarker diagnostic ratios and principal component analysis (PCA) combined with absolute principal component score (APCS) and multiple linear regression (MLR) were performed to apportion the source contribution. The results revealed mixed inputs of fuel combustion residues and uncombusted petrogenic products. The downcore PAH profile revealed that the highest peaks could be related to past human activities using biofuel and coal during the industrialization/agriculture revolution period. The 1,7/(2,6+1,7)-dimethylphenanthrene ratio also highlighted wood combustion during forest fire outbreaks, which appeared to coincide with the past climate events.

Impacts of El Niño on the South China Sea surface salinity as seen from satellites

The impacts of El Niño on sea surface salinity (SSS) in the South China Sea (SCS) are investigated using satellite observations, in-situ data, and reanalysis products. Here, we show that positive SSS anomalies cover most of the SCS during the mature phase of El Niño. The physical processes controlling these positive SSS anomalies are different from region to region, and the differences are especially obvious between the northern and southern SCS. In the northern SCS, the positive SSS anomalies are primarily caused by horizontal advection in response to an enhanced Kuroshio intrusion through the Luzon Strait, while changes in surface freshwater fluxes act to reduce SSS. In the southern SCS, the positive SSS anomalies are largely due to reduced surface freshwater fluxes, with ocean dynamics playing a secondary role. An anomalous anticyclone associated with El Niño is mainly responsible for the reduction of surface freshwater fluxes in the southern SCS.

Multi-proxy reconstructions of productivity on the continental slope off the Mekong River in the southern South China Sea over the past 30,000 years

Marine productivity is a key process in controlling the global carbon cycle. To understand the paleo-productivity behavior in the southern South China Sea, multiple geochemical analyses on Core SO18383–3 recovered from the continental slope off the Mekong River were integrated to reveal the response of paleo-productivity to environmental change. The elemental ratios of Bio/Al, bBa/Al, Zn/Al, and Sr/Al allowed the reconstruction of paleo-productivity evolution. The results show that the paleo-productivity was low around the Last Glacial Maximum (LGM) and early deglaciation (29.9–14.8 cal ka BP), then increased during the main deglaciation period (14.8–8.0 cal ka BP), before gradually declining during the Holocene (8.0–1.1 cal ka BP). This variation in paleo-productivity intensity was significantly controlled by the change in phosphorus input driven by the East Asian summer monsoon. Moreover, the opal/CaCO3 proxy, which reflects the relative abundance of siliceous versus calcareous phytoplankton, showed a higher siliceous phytoplankton dominance in the latest Pleistocene (29.9–10.8 cal ka BP) than in the Holocene. This was possibly governed by the upwelling process with cold waters forced by a cold-core eddy during the strengthening of the East Asian winter monsoon. This study greatly increased our understanding of the principal forcing factors on paleo-productivity in the southern South China Sea over the last 30 ka.

The influence of seasonal calcification depth change on the planktonic foraminiferal stable oxygen isotope signal

Seasonal changes in temperature and habitat migration both leave large imprints on the stable oxygen isotope composition (δ18O) of planktonic foraminiferal tests, but little is known about how much the depth habitat change affects the calcite δ18O on seasonal timescales, potentially introducing numerous errors to the study of seasonality applied individual foraminifera. In this study, two time series sediment trap moorings deployed in the northern South China Sea (SCS) from July 2012 to April 2013 and southern SCS (upwelling area) from April to October 2014 were used to infer seasonal calcification depth variations for four commonly used planktonic foraminiferal species, Globigerinoides ruber, Trilobatus sacculifer, without a sac-like final chamber, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei by analyzing their test δ18O values. The findings demonstrate that planktonic foraminifera deposit their tests shallower in the winter and during cold water upwelling activity, and deeper in the summer, with a changing seasonal depth habitat for all species that tends to follow the isothermals. More importantly, we devised a new approach for quantifying the effect of seasonal calcification depth changes on the δ18O signature of planktonic foraminiferal tests. After applying this method to our trap site and nine other published global sediment trap sites, the results show that foraminiferal seasonal δ18O signal is strongly distorted (amplified or damped) by seasonal variations in their habitat depth, particularly for the species living in low latitude, attributed to the strong vertical temperature gradient relative to the seasonal temperature change at a given water depth. Surface water species that live in the homogeneous mixed layer may be able to provide the most comprehensive seasonality information.

Impacts of Climate Oscillation on Offshore Wind Resources in China Seas

The long-term stability and sustainability of offshore wind energy resources are very important for wind energy exploration. In this study, the Cyclostationary Empirical Orthogonal Function (CSEOF) method, which can determine the time varying spatial distributions and long-term fluctuations in the cyclostationary geophysical process, was adopted to investigate the geographical and temporal variability of offshore wind resources in China Seas. The CSEOF analysis was performed on wind speeds at 70 m height above the sea surface from a validated combined Quick Scatterometer (QuikSCAT) and Advanced Scatterometer (ASCAT) wind product (2000–2016) with high spatial resolution of 12.5 km, and Climate Forecast System Reanalysis (CFSR) wind data (1979–2016) with a grid size of 0.5° × 0.5°. The decomposition results of the two datasets indicate that the first CSEOF mode represents the variability of wind annual cycle signal and contributes 77.7% and 76.5% to the wind energy variability, respectively. The principal component time series (PCTS) shows an interannual variability of annual wind cycle with a period of 3–4 years. The second mode accounts for 4.3% and 4.7% of total wind speed variability, respectively, and captures the spatiotemporal contribution of El Niño Southern Oscillation (ENSO) on regional wind energy variability. The correlations between the mode-2 PCTS of scatterometer or CFSR winds and the Southern Oscillation Index (SOI) are greater than 0.7, illustrating that ENSO has a significant impact on China’s offshore wind resources. Moreover, the mode-1 or mode-2 spatial pattern of CFSR winds is basically consistent with that of scatterometer data, but CFSR underestimates the temporal variability of annual wind speed cycle and the spatial changes of wind speed related to ENSO. Compared with reanalysis data, scatterometer winds always demonstrate a finer structure of wind energy variability due to their higher spatial resolution. For ENSO events with different intensities, the impact of ENSO on regional wind resources varies with time and space. In general, El Niño has reduced wind energy in most regions of China Seas except for the Bohai Sea and Beibu Bay, while La Niña has strengthened the winds in most areas except for the Bohai Sea and southern South China Sea.

Wave energy assessment based on reanalysis data calibrated by buoy observations in the southern South China Sea

This study assesses wave energy by combining long-term model reanalysis data with in situ observations in a multi-island region. A buoy was deployed in the center area of the southern South China Sea (SCS) for 16 consecutive months. Neural network models are introduced to calibrate the significant wave height and the mean wave period of the European Center for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis data. Based on the calibrated reanalysis data, wave energy potential in the region is assessed. The results show relatively available wave resources from October to February in climatology, with an average energy density higher than 5 kW m−1 and an available level frequency higher than 50%. Wave energy potential is relatively poor in other months. In the last 40 years, the wave energy density, available level frequency, and rich level frequency have shown significant increasing trends, consistent with the wind enhancement in the northeast SCS. It is suggested that the growth trend of waves in the northeast SCS may spread to the south region as swell propagation. The analysis emphasizes that there can be significant differences in the results of wave energy assessments, whether the data are calibrated or not. Therefore, the data accuracy needs to be fully evaluated when adopting model results for the planning and utilization of wave energy in such region.

Production of short-chain n-fatty acids in coral reefs in the southern South China Sea since the Late Miocene

The monsoon system modulates surface production in the South China Sea (SCS). The winter monsoon has long been recognized as the primary factor regulating surface production in the northern SCS; however, the role of monsoon remains in debate in the southern SCS. Here, we present a long record of short-chain n -fatty acids ( n -FAs) in reefal carbonates from one deep well (NK1) on an isolated coral atoll (Meiji) in order to provide new insights into the change of surface production in the southern SCS since the Late Miocene (ca. 10.5 Ma). Short-chain n -FAs indicative of total marine organic matter input are rather feasible to reflect the total production associated with mixotrophic reef-building corals that feed on various marine biotas (i.e., phytoplankton, zooplankton and bacteria). By ruling out the significant influence of diagenetic and degradation processes, short-chain n -FAs can be further applied to reconstruct paleo-production in Well NK1 coral reefs. The temporal distribution of short-chain n -FAs changes similarly with many other independent paleo-production records (i.e., Ln(Ba/Ti) and opal) in Well NK1 and adjacent ODP Site 1143, demonstrating the close coupling between coral reef production and surface water production. This occurs through the common factor of nutrients in modulating production of symbiotic autotrophic coralgae and asymbiotic phytoplankton and/or the large heterotrophic dependence of corals on phytoplankton-governed food webs in surface waters. Short-chain n -FAs inferred surface production displays a progressively decreased trend from the Late Miocene to Pliocene (ca. 10.5–2.6 Ma) followed by a substantial increase since the Pleistocene on million-year timescales, which follows the variation of terrigenous supply to the coral atoll and responds almost inversely to the sea-level change. Accordingly, we propose that long-term paleo-production in the southern SCS was associated with terrestrial nutrient input which was controlled by relative sea-level change since the Late Miocene. This study highlights the feasibility of short-chain n -FAs as appropriate production recorders in shallow-water coral reefs which are widespread in tropical-subtropical oceans, providing valuable perspectives on long-term paleo-production evolution in surface waters. • A long coral reef well (NK1) in the southern SCS was studied. • OM-poor coral reef carbonates were decalcified and extracted for biomarkers. • Short-chain n -FAs reflect paleo-production in coral reefs since the Late Miocene. • Long-term production was governed by terrestrial nutrient related to sea level.

Legacy and emerging persistent organic pollutants in the marginal seas of China: Occurrence and phase partitioning

Emerging per-and polyfluoroalkyl substances (PFASs) and traditional organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) in the marginal seas of China were analyzed to study the occurrence, transport and phase partitioning. The influence of organic carbon (OC) and element carbon (EC) on particulate emerging pollutants in seawater was studied for the first time. The concentrations of PFASs, OCPs and PAHs in the seawater (dissolved phase plus particulate phase) ranged from 1.4 to 8.6, 0.76 to 4.3 and 8.4 to 130 ng L−1, respectively. Pollutants in the northern East China Sea were generally higher than that in the southern East China Sea and South China Sea, which may be attribute to river discharges and land sources in the Yangtze River Delta. The Yellow Sea Coastal Current and Yangtze River Dilute Water drove the transport of contaminants from north to south marginal seas. Positive correlations between EC and PAHs were found, which can be explained by co-emission of them during combustion. Moreover, positive correlations between OC, EC and Log Kd for BkF, BeP, HCB, 6:2 FTSA were found, which demonstrated that OC and EC promoted the partitioning of these high oleophilic compounds to suspended particle.