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Sr-Nd isotopes are widely utilized as reliable tracers in sediment provenance studies. In this study, we compiled 304 Sr and 335 Nd isotope data of fine-grained surface sediments collected from major rivers in eastern China, including the Huanghe River, Changjiang River, southeastern coastal rivers, and rivers in Taiwan Island, as well as from marginal seas (Yellow Sea and East China Sea) and the Okinawa Trough. This comprehensive dataset allowed us to examine the spatial distribution patterns of these isotopes and their implications for provenance analysis. The variations of εNd values in the sediments in Changjiang and Huanghe Basins primarily reflect the diversity of sediment sources, whereas the 87Sr/86Sr ratios are influenced by both grain size and source provenance. Moreover, the reduction in 87Sr/86Sr ratios observed in the middle and lower Changjiang River is attributed to the inputs of sources characterized by distinct 87Sr/86Sr signatures beyond mere grain size effects. In the southeastern coastal and Taiwan rivers, sediments in the tidal reaches of the Jiao River exhibit hybrid characteristics, a mix of Changjiang-derived sediment and those originating from local catchments. Conversely, the Min River and Jiulong River sediments predominantly reflect local sources, with minimal influence from the Changjiang River. The significant isotopic variation of Sr-Nd isotopic characteristics observed between riverine sediments on the eastern and western sides of Taiwan Island underscores the diverse provenance heterogeneity of source rocks in the region. For the marginal seas, our data indicates that the surface sediments in the central mud area of the South Yellow Sea and the southern Yellow Sea are predominantly sourced from the Changjiang River catchment, potentially augmented by inputs from Korean rivers. The inner shelf sediments of the East China Sea are primarily influenced by Changjiang River inputs, whereas rivers in eastern Taiwan Island contribute to the sediments on the middle and outer shelves. Overall, the sediment Sr-Nd isotopic characteristics from the principal sources entering the eastern China marginal seas exhibit considerable similarity, presenting a substantial challenge for quantifying individual river end-member contributions based solely on the Sr-Nd isotopic signatures. To enhance the precision of quantitative assessments in sediment source-to-sink processes, it is imperative to define a narrower range of Sr-Nd isotopic signatures for potential end-members and to expand Sr-Nd isotopic investigations in these marginal seas, with a particular emphasis on regions beyond the current scope of investigations (such as mud areas). [ABSTRACT FROM AUTHOR]

This paper aims to provide an overview of regional carbon fluxes and budgets in the marginal seas adjacent to China. The “China Seas” includes primarily the South China Sea, East China Sea, Yellow Sea, and the Bohai Sea. Emphasis is given to CO2 fluxes across the air-sea interface and their controls. The net flux of CO2 degassing from the China Seas is estimated to be 9.5±53 Tg C yr−1. The total riverine carbon flux through estuaries to the China Seas is estimated as 59.6±6.4 Tg C yr−1. Chinese estuaries annually emit 0.74±0.02 Tg C as CO2 to the atmosphere. Additionally, there is a very large net carbon influx from the Western Pacific to the China Seas, amounting to ∼2.5 Pg C yr−1. As a first-order estimate, the total export flux of particulate organic carbon from the upper ocean of the China Seas is 240±80 Tg C yr−1. This review also attempts to examine current knowledge gaps to promote a better understanding of the carbon cycle in this important region. [ABSTRACT FROM AUTHOR]

Overall abundance and species composition of radiolarian faunas were analyzed in surface sediment samples from representative areas of South China Sea, East China Sea, Sea of Japan, Sea of Okhotsk, Bering Sea, Philippine Sea, and the western boundary current regions of the North Pacific, in order to understand the biogeographic distribution of radiolarians in the Northwest Pacific and explore its relationship with the main environmental factors and the North Pacific circulation. The results showed that radiolarians in the Northwest Pacific surface sediments can be divided into two large biogeographic provinces-cluster A and cluster B. Cluster A is characterized by the dominance of warm-water species and distributed primarily in tropical and subtropical seas with high radiolarian abundance and diversity; whereas cluster B is predominated by cold water species and distributed mainly in the Arctic and subarctic seas with comparably low abundance and diversity. Cluster A is further divided into five subclusters, A1 to A5, which correspond to East China Sea, Philippine Sea, South China Sea, Sea of Japan, and Kuroshio Current, respectively; cluster B is divided into three subclusters, B1 to B3, which correspond to Sea of Okhotsk, Bering Sea, and subarctic gyre area, respectively. Based on the relationships between radiolarian faunas and major environment parameters in different biogeographic provinces, we suggest that the sea surface temperature (SST) and sea surface salinity (SSS) are primary factors that influence productivity, composition, and distribution pattern of the radiolarian fauna in the Northwest Pacific regions, while water depth is likely responsible for regional differences in the radiolarian fauna in each marginal sea. In addition, according to the distribution and abundance patterns of common radiolarian species in different areas, we identified five special radiolarian assemblages, which may be used as indicators for main Kuroshio Current, Kuroshio-East China Sea Branch, Kuroshio-South China Sea Branch, Tsushima Current, and Oyashio Current water masses. [ABSTRACT FROM AUTHOR]