Neoichnological characterization of modern depositional settings addresses the response of benthic animals to ecological conditions and their fluctuations,usually on a relatively short time scale.In this way,analogue ...Neoichnological characterization of modern depositional settings addresses the response of benthic animals to ecological conditions and their fluctuations,usually on a relatively short time scale.In this way,analogue models for interpretation of sedimentary strata in the geological record can be developed.Macrophthalmus japonicus(De Haan,1835),a crab,is commonly found in the Pearl River Delta front of southern China.The burrows of M.japonicus are vertical or inclined,I-,U-,Y-,J-and L-shaped tubes,and these are imaged in 7.5-cm-diameter sediment cores.The cores were studied by X-ray radiography,computed tomography,and VG Studio MAX reconstruction to obtain three-dimensional images for elaborate morphological study.This crab's burrows are analogous to the trace fossil Psilonichnus.Several environmental parameters,i.e.,sediment grain size and its total organic carbon(TOC)content,and turbidity and salinity of water,have been measured.The results indicated that M.japonicus prefers to live in mesohaline water with turbidity levels of 20-170 NTU,where bioturbation is more abundant.It prefers to occur in mud and silty sand substrates,with TOC content decreasing as particle size increases.The sedimentary environment,grain size and ichnofacies of analogical trace fossils Psilonichnus are discussed which supports the interpretation that Psilonichnus is a good indicator of delta front environments.展开更多
The spatial and temporal variability of primary productivity in the China seas from 2003 to 2005 was estimated using a size-fractionated primary productivity model. Primary productivity estimated from satellite-derive...The spatial and temporal variability of primary productivity in the China seas from 2003 to 2005 was estimated using a size-fractionated primary productivity model. Primary productivity estimated from satellite-derived data showed spatial and temporal variability. Annual averaged primary productivity levels were 564.39, 363.08, 536.47, 413.88, 195.77, and 100.09 gCm2a1 in the Bohai Sea, northern Yellow Sea （YS）, southern YS, northern East China Sea （ECS）, southern ECS, and South China Sea （SCS）, respectively. Peaks of primary productivity appeared in spring （April-June） and fall （October and November） in the northern YS, southern YS, and southern ECS, while a single peak （June） appeared in the Bohai Sea and northem ECS. The SCS had two peaks in primary productivity, but these peaks occurred in winter （January） and summer （August）, with the winter peak far higher than the summer peak. Monthly averaged primary productivity values from 2003 to 2005 in the Bohai Sea and southern YS were higher than those in the other four seas during most months, while those in the southem ECS and SCS were the lowest. Primary productivity in spring （March-June in the southern ECS and April-July in the other five areas） contributed approximately 41% on average to the annual primary productivity in all the study seas except the SCS. The largest interannual variability also occurred in spring （average standard deviation = 6.68）, according to the satellite-derived estimates. The contribution during fall （October-January in the southern ECS and August-November in the other five areas） was approximately 33% on average; the primary productivity during this period also showed interannual variability. However, in the SCS, the winter （December-March） contribution was the highest （about 42%）, while the spring （April-July） contribution was the lowest （28%）. The SCS did share a feature with the other five areas： the larger the contribution, the larger the interarmual variability. Spatial and temporal variability of satellite-derived ocean primary productivity may be influenced by physicochemical environmental conditions, such as the chlorophyll-a concentration, sea surface temperature, photosynthetically available radiation, the seasonally reversed monsoon, river discharge, upwelling, and the Kuroshio and coastal currents.展开更多
基金supported by the National Science Foundation of China(No.42172130)the Undergraduate University Youth Backbone Teacher Training Program of Henan Province(No.2023GGJS055)
文摘Neoichnological characterization of modern depositional settings addresses the response of benthic animals to ecological conditions and their fluctuations,usually on a relatively short time scale.In this way,analogue models for interpretation of sedimentary strata in the geological record can be developed.Macrophthalmus japonicus(De Haan,1835),a crab,is commonly found in the Pearl River Delta front of southern China.The burrows of M.japonicus are vertical or inclined,I-,U-,Y-,J-and L-shaped tubes,and these are imaged in 7.5-cm-diameter sediment cores.The cores were studied by X-ray radiography,computed tomography,and VG Studio MAX reconstruction to obtain three-dimensional images for elaborate morphological study.This crab's burrows are analogous to the trace fossil Psilonichnus.Several environmental parameters,i.e.,sediment grain size and its total organic carbon(TOC)content,and turbidity and salinity of water,have been measured.The results indicated that M.japonicus prefers to live in mesohaline water with turbidity levels of 20-170 NTU,where bioturbation is more abundant.It prefers to occur in mud and silty sand substrates,with TOC content decreasing as particle size increases.The sedimentary environment,grain size and ichnofacies of analogical trace fossils Psilonichnus are discussed which supports the interpretation that Psilonichnus is a good indicator of delta front environments.
基金Major Project of National Natural Science Foundation of China, No.40490260
文摘The spatial and temporal variability of primary productivity in the China seas from 2003 to 2005 was estimated using a size-fractionated primary productivity model. Primary productivity estimated from satellite-derived data showed spatial and temporal variability. Annual averaged primary productivity levels were 564.39, 363.08, 536.47, 413.88, 195.77, and 100.09 gCm2a1 in the Bohai Sea, northern Yellow Sea （YS）, southern YS, northern East China Sea （ECS）, southern ECS, and South China Sea （SCS）, respectively. Peaks of primary productivity appeared in spring （April-June） and fall （October and November） in the northern YS, southern YS, and southern ECS, while a single peak （June） appeared in the Bohai Sea and northem ECS. The SCS had two peaks in primary productivity, but these peaks occurred in winter （January） and summer （August）, with the winter peak far higher than the summer peak. Monthly averaged primary productivity values from 2003 to 2005 in the Bohai Sea and southern YS were higher than those in the other four seas during most months, while those in the southem ECS and SCS were the lowest. Primary productivity in spring （March-June in the southern ECS and April-July in the other five areas） contributed approximately 41% on average to the annual primary productivity in all the study seas except the SCS. The largest interannual variability also occurred in spring （average standard deviation = 6.68）, according to the satellite-derived estimates. The contribution during fall （October-January in the southern ECS and August-November in the other five areas） was approximately 33% on average; the primary productivity during this period also showed interannual variability. However, in the SCS, the winter （December-March） contribution was the highest （about 42%）, while the spring （April-July） contribution was the lowest （28%）. The SCS did share a feature with the other five areas： the larger the contribution, the larger the interarmual variability. Spatial and temporal variability of satellite-derived ocean primary productivity may be influenced by physicochemical environmental conditions, such as the chlorophyll-a concentration, sea surface temperature, photosynthetically available radiation, the seasonally reversed monsoon, river discharge, upwelling, and the Kuroshio and coastal currents.
