2023 Vol. 42, No. 11

2023, 42(11)
2023-11 Contents
2023, 42(11): 1-2.
Review$Marine Biology
Hepatic caecum of amphioxus and origin of vertebrate liver
Shicui Zhang, Zhaokang Shen, Haifeng Li
2023, 42(11): 1-8. doi: 10.1007/s13131-023-2259-6
Liver is characteristic of all vertebrates. As a critical hub for many physiological processes including metabolism, innate immunity, protein synthesis and detoxification, its evolutionary origin was largely underappreciated in history, and only received due attention in recent decades. It has been suggested by morphological, ultrastructural and immunohistochemical studies that the hepatic caecum of amphioxus is homologous to the liver of vertebrate species. Molecular biology studies demonstrated that amphioxus hepatic caecum expresses plenty of vertebrate liver-specific genes. Our functional studies revealed significant similarities between amphioxus hepatic caecum and vertebrate liver. We also found that the functions of hepatic caecum are subjected to the regulation of pituitary hormones just as the liver does. These provide solid evidences supporting the notion that the hepatic caecum is the homologue of liver, which may represent the first stage in chordate evolution, laying a foundation for the subsequent formation of the liver as we know it in vertebrates. Further studies on the specification and morphogenesis of hepatic caecum in amphioxus will shed more lights on the origin and evolution of vertebrate liver.
Articles$Marine Geology
Sources and degradation of organic matter in the surface sediments of the Chukchi Sea: insights from amino acids
Weiwei Li, Zhongqiao Li, Zhuoyi Zhu, Alexander Polukhin, Youcheng Bai, Yang Zhang, Futao Fang, Haiyan Jin, Anatolii S. Astakhov, Xuefa Shi, Jianfang Chen
2023, 42(11): 9-18. doi: 10.1007/s13131-023-2167-9
In the context of global warming and rapid environment change in the Arctic, the supply of organic matter (OM) has increased significantly and a large amount of OM are buried on the Arctic shelf. Studying the fate of OM in Arctic shelf sediments is crucial to understanding the global carbon sink. As a marginal sea of the Arctic Ocean, the Chukchi Sea is one of the most critical areas where OM is buried. Based on the surface sediment samples collected during the sixth Chinese National Arctic Research Expedition in the summer of 2014 and the Sino-Russian joint Arctic Research Expedition in the summer of 2016, this study takes amino acids (AAs) as the primary tool to explore the source and degradation of OM in the surface sediments of the Chukchi Sea. This study shows that total hydrolyzable amino acid (THAA) concentrations (dry weight) are high, with a mean value of (32.7 ± 15.8) μmol/g. Their spatial distribution is related to primary productivity, hydrodynamic conditions, sediment properties and other factors. The source of OM in the surface sediments of the Chukchi Sea is dominated by diatom-dominated marine productivity, with some input from terrestrial sources. Bacteria, as the main source of the D-enantiomer of AA (D-AA), not only have transforming effect on OM, but their cell walls and remnants likewise supply the OM pool. Based on a series of diagenetic indicators, we conclude that the OM in the surface sediments of the Chukchi Sea has undergone extensive degradation [DI (degradation index) = −0.59 ± 0.44], and the degradation degree in the slope is higher than that in the shelf. This study uses AA to explore the sources and degradation of OM in the sediments of the Chukchi Sea, which facilitates our understanding of OM transport and transformation on the Arctic shelf.
Clay minerals and elemental composition of sediments on different sedimentary units in the northern East China Sea shelf: provenance tracing and genetic mechanism analysis
Xiaoyan Xu, Yong Zhang, Yanguang Dou, Jingyi Cong, Beibei Mi, Xiaohui Chen, Xia Li, Chengfen Xu, Yongyu Ye
2023, 42(11): 19-34. doi: 10.1007/s13131-023-2168-8
The composition, provenance, and genetic mechanism of sediment on different sedimentary units of the East China Sea (ECS) shelf are essential for understanding the depositional dynamics environment in the ECS. The sediments in the northern ECS shelf are distributed in a ring-shaped distribution centered on the southwestern Cheju Island Mud. From the inside to the outside, the grain size goes from fine to coarse. Aside from the “grain size effect”, hydrodynamic sorting and mineral composition are important restrictions on the content of rare earth elements (REEs). Based on the grain size, REEs, and clay mineral composition of 300 surface sediments, as well as the sedimentary genesis, the northern ECS shelf is divided into three geochemical zones: southwestern Cheju Island Mud Area (Zone Ⅰ), Changjiang Shoal Sand Ridges (Zone Ⅱ-1), Sand Ridges of the East China Sea shelf (Zone Ⅱ-2). The northern ECS shelf is mostly impacted by Chinese mainland rivers (the Changjiang River and Huanghe River), and the provenance and transport mechanism of sediments of different grain sizes is diverse. The bulk sediments come primarily from the Changjiang River, with some material from the Huanghe River carried by the Yellow Sea Coastal Current and the North Jiangsu Coastal Current, and less from Korean rivers. Among them, surface sediments in the southwestern Cheju Island Mud Area (Zone Ⅰ) come mostly from the Changjiang River and partly from the Huanghe River. It was formed by the counterclockwise rotating cold eddies in the northern ECS shelf, which caused the sedimentation and accumulation of the fine-grained sediments of the Changjiang River and the Huanghe River. The Changjiang Shoal Sand Ridges (Zone Ⅱ-1) were developed during the early-middle Holocene sea-level highstand. It is the modern tidal sand ridge sediment formed by intense hydrodynamic action under the influence of the Yellow Sea Coastal Current, North Jiangsu Coastal Current, and Changjiang Diluted Water. The surface sediments mainly originate from the Changjiang River and Huanghe River, with the Changjiang River dominating, and the Korean River (Hanjiang River) influencing just a few stations. Sand Ridges of the East China Sea shelf (Zone Ⅱ-2) are the relict sediments of the paleo-Changjiang River created by sea invasion at the end of the Last Deglaciation in the Epipleistocene. The clay mineral composition of the surface sediments in the study area is just dominated by the Changjiang River, with the North Jiangsu Coastal Current and the Changjiang Diluted Water as the main transporting currents.
Morphotype dependence of Globigerinoides ruber (white) and Trilobatus sacculifer Mg/Ca ratios in the western tropical Pacific: implications for reconstructing the mixed-layer depth
Qi Jia, Tiegang Li, Zhifang Xiong, Bingbin Qin
2023, 42(11): 35-43. doi: 10.1007/s13131-023-2163-0
Planktonic foraminifer Globigerinoides ruber (white) and Trilobatus sacculifer are the most frequently used mixed-layer dwelling species for reconstructing past oceanic environments. Specifically, the Mg/Ca ratios of these two foraminiferal species have been used for reconstructing tropical/subtropical changes in sea surface temperature (SST). However, these two species have different morphotypes, of which the spatial and temporal differences in Mg/Ca ratios and their influencing factors are still unclear. Our objective is to investigate the potential differences between the Mg/Ca ratios of these different morphotypes of G. ruber (white) and T. sacculifer in the western Philippine Sea (WPS) and determine their implications for the reconstruction of SST and upper-ocean structure. Mg/Ca measurements are made on two basic morphotypes of G. ruber (white) [sensu stricto (s.s.) and sensu lato (s.l.)] and T. sacculifer [with (w) and without (w/o) a sac-like final chamber] on samples of Site MD06-3047B from the WPS. Our results reveal that Mg/Ca ratios of different G. ruber morphotypes show consistent differences; and those of T. sacculifer morphotypes show staged variations since MIS 3. It is suggested to select a single morphotype for reconstructing SST changes using the Mg/Ca ratios of G. ruber and T. sacculifer in the WPS. Furthermore, the Mg/Ca ratios between G. ruber s.s. and G. ruber s.l. [Δ(Mg/Ca)G.ruber s.s.−s.l.] downcore MD06-3047B covaries with indexes of summer monsoon. Combining with the core-top results, showing regional variation of differences in the Δ(Mg/Ca)G.ruber s.s.−s.l. over the western tropical Pacific, we propose that Δ(Mg/Ca)G.ruber s.s.−s.l. may tend to reflect summer mixed layer depth.
Sedimentary elements, evolutions and controlling factors of the Miocene channel system: a case study of the deep-water Taranaki Basin in New Zealand
Guangxu Wang, Wei Wu, Changsong Lin, Quan Li, Xiaoming Zhao, Yongsheng Zhou, Weiqing Liu, Shiqin Liang
2023, 42(11): 44-58. doi: 10.1007/s13131-023-2191-9
Deep-water channel systems are important petroleum reservoirs, and many have been discovered worldwide. Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration and development. Based on high-resolution 3D seismic data, the Miocene channel system in the deep-water Taranaki Basin, New Zealand, was analyzed by using seismic interpretation techniques such as interlayer attribute extraction and strata slicing. The channel system was divided into five composite channels (CC-I to CC-V) according to four secondary level channel boundaries, and sedimentary elements such as channels, slump deposits, inner levees, mass transport deposits, and hemipelagic drape deposits were identified in the channel system. The morphological characteristics of several composite channels exhibited stark variances, and the overall morphology of the composite channels changed from relatively straight to highly sinuous to relatively straight. The evolution of the composite channels involved a gradual and repeated process of erosion and filling, and the composite channels could be divided into three evolutionary stages: initial erosion-filling, later erosion-filling (multistage), and channel abandonment. The middle Miocene channel system may have formed as a consequence of combined regional tectonic activity and global climatic change, and its intricate morphological alterations may have been influenced by the channel’s ability to self-regulate and gravity flow properties. When studying the sedimentary evolution of a large-scale deep-water channel system in the Taranaki Basin during the Oligocene−Miocene, which transitioned from a passive margin to plate convergence, it can be understood how tectonic activity affected the channel and can also provide a theoretical reference for the evolution of the deep-water channels in areas with similar tectonic conversion environments around the world.
Record of hydrothermal activity in the Yuhuang hydrothermal field and its implications for the Southwest Indian Ridge: evidence from sulfide chronology
Weifang Yang, Chunhui Tao, Shili Liao, Jin Liang, Wei Li, Teng Ding, Ágata Alveirinho Dias, Xuefeng Wang, Lisheng Wang
2023, 42(11): 59-68. doi: 10.1007/s13131-023-2287-2
The Yuhuang hydrothermal field (YHF) is located between the Indomed and Gallieni fracture zones near the top of the off-axis slope on the south rift wall of Segment 29 on the ultraslow Southwest Indian Ridge (SWIR). Previous studies have shown that sulfides in the YHF formed during different mineralization episodes and the YHF has the greatest potential for the formation of large-scale seafloor massive sulfide deposits. However, the sulfide chronology and hydrothermal activity of the YHF remain poorly constrained. In this study, mineralogical analyses and 230Th/U dating were performed. Hydrothermal activity may start about (35.9 ± 2.3) ka from the southwest part of the YHF and may cease about (708 ± 81) a ago from the northeast part of the YHF. The 74 nonzero chronological data from hydrothermal sulfide samples provide the first quantitative characterization of the spatial and temporal history along the SWIR. Hydrothermal activity in the SWIR has been relatively active over the past 20 ka. In contrast, between 40 ka and 100 ka, hydrothermal activity was relatively infrequently and short in duration. The maximum activity occurred at 15–11 ka, 9–7 ka, 6–0.2 ka. There was a slight positive correlation between the maximal age and estimated surface area or estimated tonnage. The minimum mass accumulation rate of YHF is about 278 t/a, which is higher than most HFs related to ultramafic systems. The ultraslow spreading SWIR has the greatest potential to form large-scale seafloor massive sulfides (SMS) deposits. The results of this study provide new insights into the metallogenic mechanism of hydrothermal sulfides along ultraslow-spreading ridges.
Articles$Marine Biology
Comparative mitochondrial genome analysis of Cynoglossidae (Teleost: Pleuronectiformes) and phylogenetic implications
Bilin Hu, Tingqi Jiang, Liming Wei, Nannan Zhang, Kaixin Wang, Liqin Liu, Bingjian Liu, Jing Liu, Zhenming Lü, Li Gong
2023, 42(11): 69-80. doi: 10.1007/s13131-023-2189-3
Generally, a teleostean group (e.g., family or genus) owns one type or a set of similar mitochondrial gene arrangement. It is interesting, however, that four different types of gene arrangement have been found in the mitochondrial genome (mitogenome) of Cynoglossidae species. So far, the possible mechanisms of mitogenomic gene rearrangement and its potential implications have aroused widespread attention and caused lots of controversy. Here, a total of 21 Cynoglossidae mitogenomes and a newly sequenced mitogenome of Cynoglossus puncticpes (Pleuronectiformes: Cynoglossidae) were compared. The length ranges from 16 417 bp to 18 369 bp, which is mainly caused by the length heteroplasmy of control region (CR). Further analysis reveals that the difference of tandem repeats acts as a determining factor resulting in the length heterogeneity. Like most gene rearrangements of Cynoglossinae mitogenomes, tRNA-Gln gene encoded by the L-strand has translocated to the H-strand (Q inversion), accompanied by the translocation of CR in C. puncticpes mitogenome. The typical IQM order (tRNA-Ile-Gln-Met) changed to QIM order. Tandem duplication/random loss and mitochondrial recombination were accepted as the most possible models to account for the rearrangements in C. puncticpes mitogenome. Phylogenetic trees showed a strong correlation between the gap spacer in the rearranged QIM area and phylogeny, which provides a fresh idea for phylogenetic studies in future.
Dietary nutrient status modulates nutrient regeneration in the marine ciliate Euplotes vannus
Xuejia He, Zhang Lu, Weijie Chen, Zhen Shi, Linjian Ou, Ren Hu
2023, 42(11): 81-89. doi: 10.1007/s13131-023-2172-z
Marine ciliates play important roles not only in linking the microbial loop to the classic pelagic and benthic food chains but also in regenerating nutrients, yet how dietary nutrient imbalance impacts their nutrient regeneration has not been thoroughly addressed. The growth and physiological responses of Euplotes vannus to low dietary nitrogen (LN) and low dietary phosphorus (LP) conditions were studied, with the bacterium Pseudomonas putida as prey. Feeding on LN prey reduced the growth rate of E. vannus. Dietary nutrient limitation changed the types and quantities of nutrient recycling. Feeding on LP prey enhanced dissolved organic carbon excretion but reduced orthophosphate excretion, whereas feeding on LN prey generally resulted in decreases in the excretion rate in all N forms (ammonium, urea, and nitrate). In addition, the proportion of ammonium in regenerated N increased significantly under the LN condition. These findings indicate that a nutrient-imbalanced diet triggers E. vannus to retain limited macronutrients and promotes the recycling of excessive macronutrients, which may potentially form positive and negative feedback to ambient N and P limitations, respectively.
Effects of main ecological factors on the growth of marine green alga Caulerpa sertularioides using the response surface methodology
Bingxin Huang, Yue Chu, Rongjuan Wang, Yixiao Wang, Lanping Ding
2023, 42(11): 90-97. doi: 10.1007/s13131-023-2171-0
Caulerpa sertularioides is an invasive potential blooming green alga in China but it remains poorly studied. We studied the effects of ecological factors on its growth. Optimum conditions of ecological factors, i.e., irradiance, temperature, and salinity, for the growth of its fragments were determined in the response surface methodology (RSM). The specific growth rates (SGR) of the fragments were determined in single-factor experiment. The results show that the SGR of C. sertularioides peaked under the conditions of irradiance 37.5 μmol/(m2·s), temperature 25℃, and salinity 30. Meanwhile, using the Box-Behnken design, the conditions were further optimized and verified to be: irradiance 39.03 μmol/(m2·s), temperature 25.29℃, and salinity 30.06, under which the SGR reached 4.66%. The results provide new theoretical data and solutions for the cultivation, invasion prediction, and monitoring of Caulerpa species in China and the world. The RSM method may have great potential applications in the environmental adaptation characteristics of new macroalgal cultivars, intensive orientation cultured germplasm, and environmental hazard analysis of cultivated species in the field.
Study of screening, transport pathway, and vasodilation mechanisms on angiotensin-I converting enzyme inhibitory peptide from Ulva prolifera proteins
Zhiyong Li, Yuan He, Hongyan He, Caiwei Fu, Mengru Li, Aiming Lu, Dongren Zhang, Tuanjie Che, Songdong Shen
2023, 42(11): 98-106. doi: 10.1007/s13131-023-2170-1
In this study, Ulva prolifera protein was used for preparing angiotensin-I converting enzyme (ACE)-inhibitory peptide via virtual gastrointestinal digestion and in silico screening. Some parameters of the obtained peptide, such as inhibition kinetics, docking mechanism, stability, transport pathway, were explored by Lineweaver-Burk plots, molecular docking, in vitro stimulate gastrointestinal (GI) digestion and Caco-2 cells monolayer model, respectively. Then, a novel anti-ACE peptide LDF (IC50, (1.66 ± 0.34) μmol/L) was screened and synthesized by chemical synthesis. It was a no-competitive inhibitor and its anti-ACE inhibitory effect mainly attributable to four Conventional Hydrogen Bonds and Zn701 interactions. It could keep activity during simulated GI digestion in vitro and was transported by peptide transporter PepT1 and passive-mediated mode. Besides, it could activate Endothelial nitric oxide synthase (eNOS) activity to promote the production of NO and reduce Endothelin-1 (ET-1) secretion induced by Angiotensin II (Ang II) in Human Umbilical Vein Endothelial Cells (HUVECs). Meanwhile, it could promote mice splenocytes proliferation in a concentration-dependent manner. Our study indicated that this peptide was a potential ingredient functioning on vasodilation and enhancing immunity.
Benthic bacterial communities indicate anthropogenic activity footprints in coastal area under long-term marine spatial planning practice
Yi Sun, Hongjun Li, Daixi Liu, Xiaocheng Wang, Quanming Wang, Xiaoyu Cui, Jingfeng Fan
2023, 42(11): 107-116. doi: 10.1007/s13131-023-2166-x
Marine spatial planning (MSP) is designed to divide the sea area into different types of functional zones, to implement corresponding development activities. However, the long-term impacts of anthropogenic activities associated with MSP practice on the marine microbial biosphere are still unclear. Yalu River Estuary, a coastal region in northeast of China, has been divided into fishery & agricultural (F&A) zone, shipping & port (S&P) zone and marine protected area (MPA) zone by a local MSP guideline that has been run for decades. To examine the effects of long-term executed MSP, benthic bacterial communities from different MSP zones were obtained and compared in this study. The results revealed significant differences in the bacterial community structure and predict functions among different zones. Bacterial genera enriched in different zones were identified, including SBR1031 in MPA, Woeseia and Sva0996 in S&P, and Halioglobus in F&A. In addition, correlations between some bacterial genera and sediment pollutants were uncovered. Furthermore, bacteria related to sulphide production were more abundant in the F&A zone, which was according to the accumulation of sulphides in this area. Moreover, bacteria associated with chemoheterotrophy and fermentation were more predominant in the S&P zone, consistent with high levels of organic matter and petroleum caused by shipping. Our findings indicated benthic bacterial communities could bring to light the anthropogenic activity footprints by different activities induced by long-term MSP practice.
Analysis of differentially expressed genes in the sea cucumber Apostichopus japonicus under heat stress
Dongxue Xu, Jingjing Zhang, Wenqi Song, Lina Sun, Ji Liu, Yuanxue Gu, Yanru Chen, Bin Xia
2023, 42(11): 117-126. doi: 10.1007/s13131-023-2196-4
The sea cucumber Apostichopus japonicus plays important roles in marine benthic ecosystem as environmental cleaners, and it is the important aquaculture species in China. High water temperature poses critical threat for the survival of A. japonicus, which has resulted in extensive death in summer. To explore the genes expression profiles under different levels of heat stress, the high-throughput RNA-seq was applied in this study. Our results revealed a total of 1371, 1225 and 1408 differentially expressed genes (DEGs) in 26℃ for 6 h, 26℃ for 48 h and 30℃ for 6 h respectively in comparison with Control group. The pathway analysis suggested “Protein processing in endoplasmic reticulum (ER)” was significantly enriched in all these heat stress (HS) treatment groups. The expression results of key DEGs in this pathway (Hsp70, Derlin, NEF, PDI, GPR94 and ERP57) by qRT-PCR was in accordance with the RNA-seq data. The subcluster analysis of DEGs revealed that a variety of heat shock proteins (HSPs) and calcium ion binding proteins had an obvious up-regulated expression in 26℃ for 6 h, comparatively low expression in 26℃ for 48 h, and the highest expression in 30℃ for 6 h. The other DEGs subcluster, consisting of critical components of extracellular matrix (ECM) and a subset of peptidases and proteases, showed significantly rising tendency in 30℃ for 6 h. Additionally, the expression of matrix metalloproteases (MMP1, MMP16 and MMP19) was prominently affected by HS, and peaked in 30℃ for 6 h. This study provides a series of candidate genes for further study about heat shock response in A. japonicus, especially genes associated with protein processing in ER and regulation of ECM, which also offers new insights into cellular homeostasis under stressful conditions in marine invertebrates.
Chemical diversity of scleractinian corals revealed by untargeted metabolomics and molecular networking
Jiying Pei, Yuxia Zhou, Shiguo Chen, Kefu Yu, Zhenjun Qin, Ruijie Zhang, Yitong Wang
2023, 42(11): 127-135. doi: 10.1007/s13131-023-2173-y
The chemical diversity of scleractinian corals is closely related to their physiological, ecological, and evolutionary status, and can be influenced by both genetic background and environmental variables. To investigate intraspecific variation in the metabolites of these corals, the metabolomes of four species (Pocillopora meandrina, Seriatopora hystrix, Acropora formosa, and Fungia fungites) from the South China Sea were analyzed using untargeted mass spectrometry-based metabolomics. The results showed that a variety of metabolites, including amino acids, peptides, lipids, and other small molecules, were differentially distributed among the four species, leading to their significant separation in principal component analysis and hierarchical clustering plots. The higher content of storage lipids in branching corals (P. meandrina, S. hystrix, and A. formosa) compared to the solitary coral (F. fungites) may be due to the high densities of zooxanthellae in their tissues. The high content of aromatic amino acids in P. meandrina may help the coral protect against ultraviolet damage and promote growth in shallow seawater, while nitrogen-rich compounds may enable S. hystrix to survive in various challenging environments. The metabolites enriched in F. fungites, including amino acids, dipeptides, phospholipids, and other small molecules, may be related to the composition of the coral’s mucus and its life-history, such as its ability to move freely and live solitarily. Studying the chemical diversity of scleractinian corals not only provides insight into their environmental adaptation, but also holds potential for the chemotaxonomy of corals and the discovery of novel bioactive natural products.
Impacts of species depletion on the food web structure of a marine ecosystem based on topological network analysis
Congjun Xu, Jun Xu, Fan Li, Yiping Ren, Ying Xue
2023, 42(11): 136-145. doi: 10.1007/s13131-023-2190-x
Single-species management ignores the interactions between species, and ecosystem-based fisheries management (EBFM) has become a main method to fisheries management. Understanding food web structures and species interactions is essential for the implementation of EBFM and maintenance of ecosystem functions. Overfishing is one of the main reasons behind the depletion, which could even lead to the depletion of some target species in local areas. So understanding the impacts of species depletion on food web structures is important for the implementation of EBFM. The impacts of species depletion can be transmitted through the food web and cause the local extinction of both target and non-target species. In this study, topological network analysis was applied to examine the impacts of species depletion on the food web structure of Haizhou Bay. Results showed that fine crayfish Leptochela gracilis, squid Loligo sp., and Japanese snapping shrimp Alpheus japonicus have the highest numbers of outgoing links (48, 32 and 31 respectively); thus, these species may be considered key prey species. Whitespotted conger Conger myriaster, fat greenling Hexagrammos otakii, and bluefin gurnard Chelidonichthys kumu were key predators with the highest number of incoming links (37, 36 and 35 respectively). The competition graphs derived from the Haizhou Bay food web were highly connected (more than 40% predators sharing over 10 common prey species), and showed close trophic interaction between high trophic level fishes. Simulation analysis showed that the food web structure has small changes to the depletion of species in a highly complex food web. The most-connected target species did not necessarily indicate high structural importance; however, some species with low connectivity may demonstrate stronger trophic interactions and play important ecological roles in the food web. But most species were more sensitive to the depletion of the most-connected target species than other target species (for instance, for zooplankton, closeness centrality 13.876 in D6, but closeness centrality 82.143 in original food web). Therefore, EBFM should focus on the most-connected target species, but also on those species with few but strong links and feeding relationships in the food web.
Articles$Marine Technology
Study on strength properties and soil behaviour type classification of Huanghe River Delta silts based on variable rate piezocone penetration test
Yunuo Liu, Guoqing Lin, Yan Zhang, Shenggui Deng, Lei Guo, Tao Liu
2023, 42(11): 146-158. doi: 10.1007/s13131-022-2113-2
Fine-grained silt is widely distributed in the Huanghe River Delta (HRD) in China, and the sedimentary structure is complex, meaning that the clay content in the silt is variable. The piezocone penetration test (CPTu) is the most widely approved in situ test method. It can be used to invert soil properties and interpret soil behavior. To analyse the strength properties of surface sediments in the HRD, this paper evaluated the friction angle and its inversion formula through the CPTu penetration test and monotonic simple shear test and other soil unit experiments. The evaluation showed that the empirical formula proposed by Kulhawy and Mayne had better prediction and inversion effect. The HRD silts with clay contents of 9.2%, 21.4% and 30.3% were selected as samples for the CPTu variable rate penetration test. The results show as follows. (1) The effects of the clay content on the tip resistance and the pore pressure of silt under different penetration rates were summarized. The tip resistance Qt is strongly dependent on the clay content of the silt, the \begin{document}$ {B}_{q} $\end{document} value of the silt tends to 0 and is not significantly affected by the change of the CPTu penetration rate. (2) Five soil behavior type classification charts and three soil behavior type indexes based on CPTu data were evaluated. The results show that the soil behavior type classification chart based on soil behavior type index \begin{document}${I}_{{\rm{SBT}}}$\end{document}, the Robertson 2010 behavior type classification chart are more suitable for the silty soil in the HRD.