Large areas of muddy sediments on the coastal shelves of China provide important samples for studying climate and ecological changes.Analysis of a large number of such samples,which is essential for systematic study on environmental information recorded in mud areas because of complicated sedimentary environment and variable sedimentary rate,requires a fast and economical method.In this study,we investigated the potential of X-ray fluorescence core scanner(XRFS),a fast analytical instrument for measuring the elemental concentrations of muddy sediments,and observed a significant correlation between the element concentrations of muddy sediments determined by regular X-ray fluorescence spectrometer(XRF)and XRFS,respectively.The correlations are mainly determined by excitation energy of elements,but also influenced by solubility of element ions.Furthermore,we found a striking link between Al concentrations and marine-originated organic carbon(MOC),a proxy of marine primary productivity.This indicates that MOC is partly controlled by sedimentary characteristics.Therefore,XRFS method has a good potential in fast analysis of a large number of muddy sediment samples,and it can also be used to calibrate MOC in ecological study of coastal seas.
Relocation of the Yellow River estuary has significant impacts on not only terrestrial environment and human activities,but also sedimentary and ecological environments in coastal seas.The responses of regional geochemical characteristics to the relocation event,however,have not been well studied.In the present study,we performed detailed geochemical elemental analyses of a sediment core from the northern Yellow Sea and studied their geochemical responses to the 1855 AD relocation of the Yellow River estuary.The results show that TOC/TN,Co/Al2O3,Cr/Al2O3,Ni/Al2O3and Se/Al2O3ratios all decreased abruptly after 1855 AD,and similar decreases are observed in the sediments of the mud area southwest off the Cheju Island.These abrupt changes are very likely caused by the changes in source materials due to the relocation of the Yellow River estuary from the southern Yellow Sea to the Bohai Sea,which the corresponding decreasing trends caused by the changes in main source materials from those transported by the Liaohe River,the Haihe River and the Luanhe River to those by the Yellow River.Because the events have precise ages recorded in historical archives,these obvious changes in elemental geochemistry of sediments can be used to calibrate age models of related coastal sea sediments.
Relatively short historical catch records show that anchovy populations have exhibited large variability over multi-decadal timescales.In order to understand the driving factors(anthropogenic and/or natural) of such variability,it is essential to develop long-term time series of the population prior to the occurrence of notable anthropogenic impact.Well-preserved fish scales in the sediments are regarded as useful indicators reflecting the fluctuations of fish populations over the last centuries.This study aims to validate the anchovy scale deposition rate as a proxy of local anchovy biomass in the Yellow Sea adjoining the western North Pacific.Our reconstructed results indicated that over the last 150 years,the population size of anchovy in the Yellow Sea has exhibited great fluctuations with periodicity of around 50 years,and the pattern of current recovery and collapse is similar to that of historical records.The pattern of large-scale population synchrony with remote ocean basins provides further evidence proving that fish population dynamics are strongly affected by global and basin-scale oceanic/climatic variability.
