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Volume 42 ， Issue 3 ， 2024
- Abstract：Mid-ocean ridge and oceanic transforms are among the most prominent features on the seafloor surface and are crucial for understanding seafloor spreading and plate tectonic dynamics, but the deep structure of the oceanic lithosphere remains poorly understood. The large number of microearthquakes occurring along ridges and transforms provide valuable information for gaining an in-depth view of the underlying detailed seismic structures, contributing to understanding geodynamic processes within the oceanic lithosphere. Previous studies have indicated that the maximum depth of microseismicity is controlled by the 600-℃ isotherm. However, this perspective is being challenged due to increasing observations of deep earthquakes that far exceed this suggested isotherm along mid-ocean ridges and oceanic transform faults. Several mechanisms have been proposed to explain these deep events, and we suggest that local geodynamic processes (e.g., magma supply, mylonite shear zone, long-lived faults, hydrothermal vents, etc.) likely play a more important role than previously thought.Keywords：microearthquake;mid-ocean ridge;oceanic transform fault;oceanic lithosphere;thermal structure;earthquake location29|22|0Updated：2024-10-14
- Abstract：The deep structure, material circulation, and dynamic processes in the Southeast Asia have long been an elusive scientific puzzle due to the lack of systematic scientific observations and recognized theoretical models. Based on the deep seismic tomography using long-period natural earthquake data, in this study, the deep structure and material circulation of the curved subduction system in Southeast Asia was studied, and the dynamic processes since 100 million years ago was reconstructed. It is pointed out that challenges still exist in the precise reconstruction of deep mantle structures of the study area, the influence of multi-stage subduction on deep material exchange and shallow magma activity, as well as the spatiotemporal evolution and coupling mechanism of multi-plate convergence. Future work should focus on high-resolution land-sea joint 3-D seismic tomography imaging of the curved subduction system in the Southeast Asia, combined with geochemical analysis and geodynamic modelling works.Keywords：curved subduction system;deep structure;material recycling;dynamic process;Southeast Asia18|16|0Updated：2024-10-14
- Abstract：The molybdenum (Mo) isotope system is pivotal in reconstructing marine redox changes throughout Earth’s history and has emerged as a promising tracer for igneous and metamorphic processes. Understanding its composition and variation across major geochemical reservoirs is essential for its application in investigating high-temperature processes. However, there is debate regarding the δ98/95Mo value of the Earth’s mantle, with estimates ranging from sub-chondritic to super-chondritic values. Recent analyses of global mid-ocean ridge basalt (MORB) glasses revealed significant δ98/95Mo variations attributed to mantle heterogeneity, proposing a two-component mixing model to explain the observed variation. Complementary studies confirmed the sub-chondritic δ98/95Mo of the depleted upper mantle, suggesting remixing of subduction-modified oceanic crust as a plausible mechanism. These findings underscore the role of Mo isotopes as effective tracers for understanding dynamic processes associated with mantle-crustal recycling.Keywords：molybdenum (Mo) isotope;mantle;crustal recycling;mid-ocean ridge basalt (MORB)15|14|0Updated：2024-10-14
Deep Sea
- Abstract：Internal solitary waves (ISW), characterized by large amplitude and long propagation distance, are widespread in global oceans. While remote sensing images have played an essential role in studying ISWs, they mainly exploit two-dimensional image information. However, with the launch of the surface water ocean topography (SWOT) satellite on December 16, 2022, a unique opportunity has emerged to capture wide-swath three-dimensional ISW-induced sea surface information. In this study, we examine ISWs in the Andaman Sea using data from the Ka-band Radar Interferometer (KaRIN), a crucial sensor onboard SWOT. KaRIN not only provides backscattering satellite images but also employs synthetic aperture interferometry techniques to retrieve wide-swath two-dimensional sea surface height measurements. Our observations in the Andaman Sea revealed the presence of ISWs characterized by dark-bright strips and surface elevation solitons. The surface soliton has an amplitude of 0.32 m, resulting in an estimation of ISW amplitude of approximately 60 m. In contrast to traditional two-dimensional satellite images or nadir-looking altimetry data, the SWOT mission’s capability to capture three-dimensional sea surface information represents a significant advancement. This breakthrough holds substantial promise for ISW studies, particularly in the context of ISW amplitude inversion.Keywords：internal solitary wave (ISW);surface water ocean topography (SWOT);altimeter43|14|0Updated：2024-10-14
- Abstract：Duo to fluctuations in atmospheric turbulence and yaw control strategies, wind turbines are often in a yaw state. To predict the far wake velocity field of wind turbines quickly and accurately, a wake velocity model was derived based on the method of momentum conservation considering the wake steering of the wind turbine under yaw conditions. To consider the shear effect of the vertical incoming wind direction, a two-dimensional Gaussian distribution function was introduced to model the velocity loss at different axial positions in the far wake region based on the assumption of nonlinear wake expansion. This work also developed a “prediction-correction” method to solve the wake velocity field, and the accuracy of the model results was verified in wake experiments on the Garrad Hassan wind turbine. Moreover, a 33-kW two-blade horizontal axis wind turbine was simulated using this method, and the results were compared with the classical wake model under the same parameters and the computational fluid dynamics (CFD) simulation results. The results show that the nonlinear wake model well reflected the influence of incoming flow shear and yaw wake steering in the wake velocity field. Finally, computation of the wake flow for the Horns Rev offshore wind farm with 80 wind turbines showed an error within 8% compared to the experimental values. The established wake model is less computationally intensive than other methods, has a faster calculation speed, and can be used for engineering calculations of the wake velocity in the far wakefield of wind turbines.Keywords：far wake;wake model;wake steering;wind shear;wind farm15|11|0Updated：2024-10-14
- Abstract：The accurate identification of marine oil spills and their emulsions is of great significance for emergency response to oil spill pollution. The selection of characteristic bands with strong separability helps to realize the rapid calculation of data on aircraft or in orbit, which will improve the timeliness of oil spill emergency monitoring. At the same time, the combination of spectral and spatial features can improve the accuracy of oil spill monitoring. Two ground-based experiments were designed to collect measured airborne hyperspectral data of crude oil and its emulsions, for which the multiscale superpixel level group clustering framework (MSGCF) was used to select spectral feature bands with strong separability. In addition, the double-branch dual-attention (DBDA) model was applied to identify crude oil and its emulsions. Compared with the recognition results based on original hyperspectral images, using the feature bands determined by MSGCF improved the recognition accuracy, and greatly shortened the running time. Moreover, the characteristic bands for quantifying the volume concentration of water-in-oil emulsions were determined, and a quantitative inversion model was constructed and applied to the AVIRIS image of the deepwater horizon oil spill event in 2010. This study verified the effectiveness of feature bands in identifying oil spill pollution types and quantifying concentration, laying foundation for rapid identification and quantification of marine oil spills and their emulsions on aircraft or in orbit.Keywords：hyperspectral image;spectral analysis;dimensionality reduction;Multiscale Superpixel Level Group Clustering Framework (MSGCF);double-branch dual-attention (DBDA)19|14|0Updated：2024-10-14
Physics
- Abstract：A transfer zone in rift basins preserves important information on regional tectonic evolution and plays significant roles in hydrocarbon accumulation. Based on the systematic analysis of 3D seismic data and hydrocarbon accumulation conditions, the geometry, kinematics, and reservoir control of a large synthetic overlapping transfer zone in the south of the Wenchang A subsag in the Zhujiang (Pearl) River Mouth basin were investigated. Results indicate that the development and evolution of the transfer zone was controlled by the interaction between pre-existing faults and regional stress transformation. The intense rifting of the main faults of the transfer zone controlled the development of source rocks and fault-controlled slope break paleogeomorphology. The strike-slip overprint since the Oligocene is conducive to the formation of a large-scale fault-anticline trap, and the secondary faults in the transfer zone contribute to the hydrocarbon transportation. The conjugate intersection area of the NE- and NW-trending faults offers more opportunity for hydrocarbon migration and accumulation.Keywords：transfer zone;pre-existing fault;regional stress transformation;Cenozoic;Wenchang A Subsag;Zhujiang (Pearl) River Mouth Basin24|19|0Updated：2024-10-14
- Abstract：The construction of major marine infrastructure projects and the exploration and development of deep-sea mineral resources require fine imaging of seabed strata and structures. The high-resolution marine seismic exploration based on a high broadband sparker source is an important approach to reveal seabed stratum and reservoir structure, and identify geohazard. To optimize the performance of sparker seismic source, we investigated the electro-acoustic characteristics of spark discharge under conditions of different charging voltages and electrode numbers. Results show that the sound source level increased with the increase of the charging voltage, whereas the main frequency decreased when the charging voltage increases. In addition, it was found that the charging capacitance had more obvious influence on the main frequency than the sound source level did. Although the load energy decreased with increasing electrode number, the sound source level still increased but the main frequency decreased. Meanwhile, the primary to bubble (P/B) ratio increased with the increase of the electrode number. To gain a deeper insight into the electro-acoustic characteristics, we investigate the relationship between sound source level and power peak, from which a good correlation was observed. A more practical statistical analysis on the rise rate of current was processed, and a perfect logarithmic function was derived. Furthermore, we found that the main frequency was most possibly subjected to the electrical energy, especially the charging energy per electrode. The results indicate that the charging energy per electrode less than 10 J could increase the main frequency to above 300 Hz. At last, the main frequency could be reduced to 20 Hz when the charging energy of a single-electrode discharge was enhanced to over 4 kJ. This study shall be helpful in developing a sparker seismic source and improving the performance for marine engineering exploration and geohazard assessment.Keywords：high-resolution marine seismic exploration;sparker seismic source;sound source level;main frequency;electro-acoustic characteristics14|11|0Updated：2024-10-14
Geology
- Abstract：A sediment core (YJK19-02) collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size, lignin, bulk elemental composition, stable carbon isotope, and rare earth elements (REEs) to determine the sources and diagenesis of sedimentary organic matter (OM) of the estuary and adjacent areas since the Late Pleistocene. δ13C values (24.80‰–23.60‰), total organic carbon/total nitrogen (TOC/TN) molar ratios (8.00–12.14), and light rare earth element/heavy rare earth element ratios (LREE/HREE=8.34–8.91) revealed the predominance of terrestrial sources of OM, mainly from the Changjiang (Yangtze) River. The lignin parameters of syringyl/vanillyl (S/V=0.20–0.73) and cinnamyl/vanillyl (C/V=0.03–0.19) ratios indicate the predominance of nonwoody angiosperms, and the vanillic acid/vanillin ratios [(Ad/Al)V=0.32–1.57] indicate medium to high degrees of lignin degradation. An increasing trend of Λ (total lignin in mg/100-mg OC) values from ca. 14 500 a BP to ca. 11 000 a BP reflected the increase in temperature during the Late Pleistocene. However, a time lag effect of temperature on vegetation abundance was also revealed. The relatively higher and stable Λ values correspond to the higher temperature during the mid-Holocene from ca. 8 500 a BP to ca. 4 500 a BP. Λ values decreased from ca. 4 000 a BP to the present, corresponding to historical temperature fluctuations during this time. Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change.Keywords：Yongjiang River estuary;sedimentary organic matter;lignin;environmental change;late Pleistocene16|13|0Updated：2024-10-14
Chemistry
- Abstract：Global warming and algal blooms have been two of the most pressing problems faced by the world today. In recent decades, numerous studies indicated that global warming promoted the expansion of algal blooms. However, research on how algal blooms respond to global warming is scant. Global warming coupled with eutrophication promoted the rapid growth of phytoplankton, which resulted in an expansion of algal blooms. Algal blooms are affected by the combined effects of global warming, including increases in temperatures, CO2 concentration, and nutrient input to aquatic systems by extreme weather events. Since the growth of phytoplankton requires CO2, they appear to act as a carbon sink. Unfortunately, algal blooms will release CH4, CO2, and inorganic nitrogen when they die and decompose. As substrate nitrogen increases from decompose algal biomass, more N2O will be released by nitrification and denitrification. In comparison to CO2, CH4 has 28-fold and N2O has 265-fold greenhouse effect. Moreover, algal blooms in the polar regions may contribute to melting glaciers and sea ice (will release greenhouse gas, which contribute to global warming) by reducing surface albedo, which consequently would accelerate global warming. Thus, algal blooms and global warming could form feedback loops which prevent human survival and development. Future researches shall examine the mechanism, trend, strength, and control strategies involved in this mutual feedback. Additionally, it will promote global projects of environmental protection combining governance greenhouse gas emissions and algal blooms, to form a geoengineering for regulating the cycles of carbon, nitrogen, and phosphorus.Keywords：climate change;carbon neutrality;eutrophication;greenhouse gas;glaciers melting;geoengineering19|8|0Updated：2024-10-14
- Abstract：Although many studies have found that cadmium (Cd) can be toxic to microalgae, only a few reports focused on the role of extracellular polymeric substances (EPS) in Cd(II) detoxification. The biochemical and physiological endpoints of Microcystis aeruginosa, including the composition and functional groups of soluble EPS (SL-EPS), loosely bound EPS (LB-EPS), and tightly bound EPS (TB-EPS), were detected to elucidate the toxicity and detoxification mechanisms of Cd(II) for cyanobacteria. Toxicological and physiological assays on M. aeruginosa showed that the 0.25-mg/L Cd(II) resulted in a larger inhibition on growth and Fv/Fm. Nevertheless, Cd(II) significantly induced much higher contents of superoxide dismutase (SOD), intracellular microcystin LR (MC-LR), extracellular MC-LR, and EPS. Scanning electron microscopy with energy dispersive X-ray spectroscopy confirmed that Cd(II) was absorbed into the EPS layer. Fourier transform infrared spectrum analysis revealed that the functional groups bound with Cd(II) of algae biomass, SL-EPS, LB-EPS, and TB-EPS were somewhat different. The C=O/C=N groups of δ-lactam or protein were their prominent functional groups, suggesting that amide or proteins in the EPS played a key role in the adsorption in Cd(II). The concentration of 0.25 mg/L of Cd(II) may change the chemical structure of EPS by altering the production of protein-like substances containing tryptophan. This study indicated that M. aeruginosa could detoxify Cd(II) stress via induction of antioxidant capacity (higher SOD activity and MC synthesis), EPS production, and modification in chemical structure of EPS.Keywords：Microcystis aeruginosa;cadmium;extracellular polymeric substances (EPS);microcystin;detoxification18|7|0Updated：2024-10-14
- Abstract：In 2022, Yellow Sea green tide caused by Ulva prolifera reached a historic minimum and the coastal areas of Shandong Peninsula were less affected. However, the largest amount of seaweed biomass has been washed ashore on Lianyungang and Rizhao coasts since 2015. We studied the development pattern of Yellow Sea green tide in 2022, and analyzed the key environmental factors on the growth and drifting, then discussed the possible reasons that resulted in the massive stranding of green tide biomass in Lianyungang and Rizhao. Results show under the combined influence of the east to southeast winds and currents with shoreward anomalies, green tide drifted to the coastal waters between Shandong and Jiangsu provinces and the distribution areas located westward compared with previous years (2008–2021). Floating U. prolifera rafts from the coastal waters of Binhai and Sheyang drifted continuously into the coastal waters of Lianyungang and Rizhao, providing important supplements for Yellow Sea green tide. Because green tide in 2022 distributed close to the coastal waters, the abundant nutrients might support their continuous high growth rate. In addition, the amount of rainfall around Shandong Peninsula from late June to early July were significantly higher than in previous years, which might promote the development of green tide to some extent.Keywords：Yellow Sea green tide;stranding biomass;development pattern;environmental factor19|10|0Updated：2024-10-14
- Abstract：A sudden and unprecedented outbreak of molluscan Philine kinglipini occurred in summer 2022 in Jiaozhou Bay, Shandong, China, causing substantial damage to local mariculture industry of the Manila clam Ruditapes philippinarum. Although P. kinglipini has been found in many coastal regions of China, the molecular research of P. kinglipini has not been extensively studied, making it difficult to accurately identify and track P. kinglipini samples in field using molecular methods. Samples were collected during the outbreak and their morphological features and molecular sequences were analyzed. Results show that the causative species of the outbreak was P. kinglipini. The mitochondrial genome (mtDNA) of P. kinglipini was constructed for the first time, based on which phylogenetic analysis of the mtDNAs of P. kinglipini and related species in the order Cephalaspidea was carried out. As revealed by metabarcoding analysis of 18S rDNA V4, the seasonal change of P. kinglipini and closely related Philine species was striking with peaks between April and August. Therefore, metabarcoding analysis is applicable tool for monitoring the bloom development of P. kinglipini and related species. This study generated for the first time essential molecular marker sequences and mtDNA of P. kinglipini, which provided a reference for future characterization and monitoring of its outbreaks and for phylogenetic analysis of Philine species.Keywords：marine species outbreaks;metabarcoding analysis;mitochondrial genome;Philine kinglipini;phylogenetics;spatial-temporal dynamics14|8|0Updated：2024-10-14
- Abstract：Sea cucumber Apostichopus japonicus is an ideal model organism for marine invertebrate aestivation; it annually enters a “sleeping state” for nearly 3 months when ambient water temperature range is 25–30 °C. The natural fasting is accompanied by remodeling the intestinal biota and function, which is a part of host biology and could affect the gut microbiota. We investigatesd the impact of annual aestivation on gut microbiota using high-throughput sequencing of 16S rRNA amplicons. Results reveal a notable alteration in the composition of gut bacteria during aestivation during which various indigenous families and genera that exhibit a preference for dietary glycans (e.g., family Rhodobacteraceae and Flavobacteriaceae) decreased, while the taxa capable of utilizing substrates derived from the host (e.g., genus Akkermansia and Prevotella) increased, and so did certain opportunistic pathogenic bacteria. Moreover, the investigation delved into the gut morphology and immunity response of A. japonicus and reveal that the intestine of A. japonicus undergoes substantial atrophy and degeneration during aestivation. However, there was an observed augmentation in the levels of acid and neutral mucin within mucous cells, as well as an enhanced immune defense response (as evidenced by increased gene expression of AjTLR3, LITAF, Ajp105, and LYZ). These results imply that the composition of sea cucumber gut microbiota differed between aestivation and active periods, which potentially affects the intestinal functions of the host and the symbiotic relationship between host and its microbiota over the active-aestivation cycle.Keywords：Apostichopus japonicus;aestivation;gut microbiota;diet;illumina sequencing13|5|1Updated：2024-10-14
Ecology
- Abstract：Sepiellajaponica is a worldwide marine cuttlefish species of high economic value. S. japonica routinely modifying behaviors in reproductive life, such as rapid aging until death after spawning, has been recognized in artificial breeding. However, reproductive behavior at the level of genes is rarely reported, thus, the research on the genetic basis of behavior, reproduction, and artificial breeding was limited. We applied RNA-seq in different stages of reproduction to investigate the reason of rapid aging after spawning, pre-maturity, pre-spawning after maturity, and post-spawning. The retinoid X receptor (RXR) gene family in S. japonica was identified, and 1 343–1 452 differentially expressed genes (DEGs) in all 3 stages of reproductive life were identified from pairwise mRNA comparisons. Furthermore, through the GO term and KEGG analysis, S. japonica could handle neuronal development and network formation before maturity and have a functional degradation of neural communication, signal transduction, vision, and gene expression after spawning. Eight SjRXRαs have been identified and they played different roles in growth development or reproduction. Therefore, the regulation of several channels and receptors is the intrinsic molecular mechanism of rapid aging after spawning in S. japonica. This study revealed the survival strategy and provided fundamental data on the level of genes for understanding the reproductive behavior and the reproduction of S. japonica.Keywords：Sepiellajaponica;RAN-seq;retinoid X receptor (RXR) gene family;rapid aging;intrinsic molecular mechanism17|4|0Updated：2024-10-14
- Abstract：To understand the reproductive biology of Hemitripterus villosus in the Bohai Strait, and fill the key knowledge gap in verifying reproductive seasonality and documenting gonadotropin dependent reproductive cycle of this species, a year‐round detail study was conducted for the first time. In total, 263 individuals were randomly sampled off the coasts of the Bohai Strait. Results show that and the overall female‐to‐male ratio (1.35꞉1) did not differ significantly from the 1꞉1 sex ratio. The length and weight relationship for females and males were regressed, depicting an isometric growth for both sexes. Four reproductive phases of the complete gonadotropin dependent reproductive cycle in both sexes were identified. The monthly variations in the gonadosomatic and hepatosomatic indexes for both sexes further indicated that this species spawns a single batch of eggs per year and the peak spawning period is from October to December. The average diameter of eggs ranged from 2.10 to 3.57 mm. The length at first sexual maturity was 224.87 mm for females and 241.26 mm for males. Significant positive relationships between absolute fecundity and fish size, and also gonadal weight were observed. H. villosus from the Bohai Strait exhibited smaller body size, smaller egg diameter, lower gonadosomatic index, lower absolute fecundity, and higher population extinction risk than the other populations’ studied previously. Our findings contribute to understanding the status of this isolated westernmost population, and we emphasize that more efficient protection measures for the species and control measures are urgently required to improve the coastal environment in the Bohai Strait.Keywords：Hemitripterus villosus;Bohai Strait;fecundity;length at first maturity;reproductive seasonality14|9|0Updated：2024-10-14
- Abstract：Manganese superoxide dismutase (MnSOD) is an antioxidant that exists in mitochondria and can effectively remove superoxide anions in mitochondria. In a dark, high-pressure, and low-temperature deep-sea environment, MnSOD is essential for the survival of sea cucumbers. Six MnSODs were identified from the transcriptomes of deep and shallow-sea sea cucumbers. To explore their environmental adaptation mechanism, we conducted environmental selection pressure analysis through the branching site model of PAML software. We obtained night positive selection sites, and two of them were significant (97F→H, 134K→V): 97F→H located in a highly conservative characteristic sequence, and its polarity change might have a great impact on the function of MnSOD; 134K→V had a change in piezophilic ability, which might help MnSOD adapt to the environment of high hydrostatic pressure in the deepsea. To further study the effect of these two positive selection sites on MnSOD, we predicted the point mutations of F97H and K134V on shallow-sea sea cucumber by using MAESTROweb and PyMOL. Results show that 97F→H, 134K→V might improve MnSOD’s efficiency of scavenging superoxide anion and its ability to resist high hydrostatic pressure by moderately reducing its stability. The above results indicated that MnSODs of deep-sea sea cucumber adapted to deep-sea environments through their amino acid changes in polarity, piezophilic behavior, and local stability. This study revealed the correlation between MnSOD and extreme environment, and will help improve our understanding of the organism’s adaptation mechanisms in deep sea.Keywords：Holothuroidea;environmental adaptation;positive selection;point mutation13|4|0Updated：2024-10-14
- Abstract：A new isochromanone, cladosporinisochromanone (1), accompanied by 15 known compounds (2–16) were obtained from secondary metabolites produced by marine-derived fungus Cladosporium sp. DLT-5. NMR and HRESIMS spectra elucidation determined the planar structure of 1. Subsequent electronic circular dichroism (ECD) experiment assigned the absolute configuration of 1. Compounds 1, 2, 4–6, and 10 displayed different degrees of neuroprotective activities on human neuroblastoma cells SH-SY5Y. Five compounds (1, 3–5, and 13) emerged resistance to protein tyrosine phosphatase 1B (PTP1B), further kinetic analysis and molecular docking study indicated that the most potent compound 13 (IC50 value of 10.74±0.61 μmol/L) was found as a noncompetitive inhibitor for PTP1B. Surface plasmon resonance (SPR) and molecular docking studies also demonstrated the interaction between compound 12 and Niemann-Pick C1 Like 1 (NPC1L1), which has been identified as significant therapeutic target for hypercholesteremia. In addition, compounds 3, 6, and 14 showed attractive inhibitory activity against the phytopathogenic fungi: Colletotrichum capsici. Therefore, library of Cladosporium metabolites is enriched and new active uses of known compounds are explored.Keywords：Cladosporium sp.;marine-derived fungus;neuroprotective effects;protein tyrosine phosphatase 1B (PTP1B);Niemann-Pick C1 Like 1 (NPC1L1);antifungal activity13|9|0Updated：2024-10-14
- Abstract：Stylonema alsidii (Zandardini) Drew f. ramosum Zheng et Li is a common species in the genus Stylonema, but there are limited reports on morphological taxonomy and a lack of studies on life history and the regulation of early development. The early development, discoid formation, and erect thallus growth of Stylonema alsidii f. ramosum were observed under laboratory conditions. In addition, the influence of main environmental factors such as temperature and light intensity on its development was briefly studied, and various stages of its life history were observed. The result shows: (1) there are two reproductive modes: asexual reproduction and sexual reproduction; (2) the morphology of this species varies in different degrees under laboratory culture conditions; (3) sexual reproduction and asexual reproduction can coexist under suitable conditions. Five pathways of life history were inferred from experimental phenomena. Mature sporophytes form mature gametophytes by producing initially isolated or initially attached monospore, and mature gametophytes form mature sporophytes by fertilization of eggs and sperms. The sexual and asexual reproduction processes of Stylonema alsidii f. ramosum were reported for the first time, and this is also the first report on sexual reproduction in the genus Stylonema.Keywords：Stylonema alsidii (Zandardini) Drew f. ramosum Zheng et Li;life history;environmental factor;asexual reproduction;sexual reproduction16|13|0Updated：2024-10-14
- Abstract：In our recent investigations of diatom diversity, we studied three species, namely, Skeletonemacostatum, Skeletonemasubsalsum, and Skeletonemapotamos. Although they have been found frequently in Changjiang (Yangtze) River Basin, their morphological and molecular identification is difficult in taxonomy. Therefore, to integrate morphological and molecular biological approaches, we compared systematically their morphological characters and performed phylogenetic analysis. Twelve strains of Skeletonema were collected and isolated from Shanghai and Jiangsu, China, and their morphological characteristics were examined by light microscopy (LM) and the scanning electron microscopy (SEM). Based on morphological comparison, we determined that S. potamos is easy to distinguish from the other two species. The heavily silicified areolae, undulated or cleft distal ends of terminal fultoportula processes (TFPPs), absence of basal pores of fultoportula processes (FPPs), the root-like protrusions of FPPs, and no interlocking connection are the stable characteristics that can be used to identify S. potamos. However, there are only two features that can distinguish S. costatum from S. subsalsum, namely the location of terminal rimoportulae (TRPs) and the distal shape of TFPPs. In addition, we amplified and sequenced nine common genetic markers from the strains, from which 101 sequences were obtained, constructed phylogenetic trees based on the nine genes and evaluated that seven genes can be used to identify S. potamos, and revealed that S. subsalsum is the closest known relative of S. costatum, and only ATP synthetase beta-subunit gene (atpB) is able to distinguish them from each other, which strongly support that it is an effective molecular marker for Skeletonema. This work provided a theoretical basis for the taxonomic study of Skeletonema.Keywords：Skeletonema;Changjiang River;morphological change;distinguishing morphological characteristics;molecular marker15|13|0Updated：2024-10-14
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Mitochondrial genomes of
Tapes dorsatus andCardita variegata : insights into Heteroconchia phylogenyAbstract：Heteroconchia, a widespread and abundant aquatic invertebrate, is an important clade of bivalve mollusks. The relationship between the three branches of Heteroconchia, Palaeoheterodonta, Archiheterodonta, and Euheterodonta has become a main controversy in molecular studies of the relationships between bivalves. In the present study, we assembled the complete mitochondrial genomes of Tapes dorsatus (Veneridae) and Cardita variegata (Carditidae) using high-throughput sequencing. C. variegata is the first mitochondrial genome belonging to the family Carditidae to be reported. We used 12 protein coding genes (excluding atp8) from the complete mitochondrial genomes of 146 species to recover the internal relationships of Heteroconchia. Our results support the traditional view of early branching of Palaeoheterodonta and the recovery of the monophyly of Palaeoheterodonta, Anomalodesmata, Imparidentia. Rearrangement analysis show that gene arrangement within Venerida was highly variable. Time-calibrated phylogenetic studies based on a relaxed molecular clock model suggested that Veneridae originated approximately 337.62 million years ago (Ma) and split into two major clades, whereas Carditidae originated approximately 510.09 Ma. Our results provide evidence of the internal relationships of Heteroconchia.Keywords：Tapes dorsatus;Cardita variegata;mitochondrial genome;phylogeny14|12|0Updated：2024-10-14
Biology
- Abstract：As an economically critical pelagic migratory species, yellowfin tuna (Thunnusalbacores, YFT) is very sensible to physical and environmental conditions, such as sea surface temperature (SST), ocean heat content (OHC), and the mixed layer depth (MLD). We investigated the impact of SST, OHC, and MLD on fluctuations of YFT catch in the western/eastern Indian Ocean using the long time series of 63-year environmental and YFT datasets. We found that the impact of SST on YFT was heavily overestimated in the past, and MLD plays a more critical role in the YFT catch fluctuation. When the MLD deepens (>34.8 m), SST was more influential in predicting the catches of YFT than OHC in the western Indian Ocean, and OHC was more critical to YFT than SST in the eastern Indian Ocean. However, when the MLD shallows (<34.8 m), MLD was more vital to predict the catch per unit effort (CPUE) of YFT than SST/OHC in the western. After 2000, there was an asynchronous pattern of YFT CPUE induced by higher frequency variations and ocean hiatus of SST/OHC signals in the western and eastern Indian Oceans basins. The impact of the subsurface hiatus may induce the decrease of YFT in the eastern Indian Ocean. The above findings clarified a non-stationary relationship between the environmental factors and catches of YFT and provided new insights into variations in YFT abundance.Keywords：yellowfin tuna;Indian Ocean;sea surface temperature (SST);ocean heat content (OHC);mixed layer depth (MLD);hiatus20|4|0Updated：2024-10-14
- Abstract：Bigeye tuna Thunnus obesus is an important migratory species that forages deeply, and El Niño events highly influence its distribution in the eastern Pacific Ocean. While sea surface temperature is widely recognized as the main factor affecting bigeye tuna (BET) distribution during El Niño events, the roles of different types of El Niño and subsurface oceanic signals, such as ocean heat content and mixed layer depth, remain unclear. We conducted A spatial-temporal analysis to investigate the relationship among BET distribution, El Niño events, and the underlying oceanic signals to address this knowledge gap. We used monthly purse seine fisheries data of BET in the eastern tropical Pacific Ocean (ETPO) from 1994 to 2012 and extracted the central-Pacific El Niño (CPEN) indices based on Niño 3 and Niño 4 indexes. Furthermore, we employed Explainable Artificial Intelligence (XAI) models to identify the main patterns and feature importance of the six environmental variables and used information flow analysis to determine the causality between the selected factors and BET distribution. Finally, we analyzed Argo datasets to calculate the vertical, horizontal, and zonal mean temperature differences during CPEN and normal years to clarify the oceanic thermodynamic structure differences between the two types of years. Our findings reveal that BET distribution during the CPEN years is mainly driven by advection feedback of subsurface warmer thermal signals and vertically warmer habitats in the CPEN domain area, especially in high-yield fishing areas. The high frequency of CPEN events will likely lead to the westward shift of fisheries centers.Keywords：Bigeye Tuna;Central-Pacific El Niño (CPEN);ocean heat content;Argo;explainable artificial intelligence (XAI);information flow21|6|0Updated：2024-10-14
- Abstract：Heat stress (HS) has been shown to adversely affect fish livers and can lead to extensive apoptosis. To investigate the relationship between endoplasmic reticulum (ER) stress and HS-induced apoptosis in fish livers, we isolated and cultured primary hepatocytes of largemouth bass, Micropterus salmoides by trypsin method, then established an in-vitro model of liver cells under HS (35 ℃). The contents of lactic dehydrogenase (LDH) and hydrogen peroxide (H2O2) were determined to evaluate the effects of HS on hepatocyte injury and oxidative stress. RT-qPCR was performed to discover the key genes in unfolded protein response (UPR) pathways involved at different HS duration. ERS inhibitor 4-PBA and IRE1α inhibitor 4μ8C were used to further investigate the effects of HS on IRE1α apoptosis pathway in hepatocytes. Results show that HS led to significant increases in the release of LDH, the content of H2O2, and the expressions of oxidative protein folding genes (ero1α and pdi) under HS, suggesting severe hepatocyte injury and oxidative stress happened in heat-stressed largemouth bass hepatocytes. The continuous activation of IRE1α pathway genes (grp78, grp94, atf6, perk, eif2a, atf4, chop, ire1α, traf2, ask1, jnk1, and jnk2) indicated that HS led significantly to ER stress. In particular, the mRNA expression levels of ER stress-related genes (grp78, grp94, atf6, perk, ire1α, chop, jnk1, and jnk2) in the high temperature (HT) +4-PBA group and the HT+4μ8C group were significantly down-regulated under HS. After 4μ8C treatment, the expression levels of apoptosis-related genes (caspase-2, caspase-3, caspase-6, caspase-7, caspase-8, caspase-9, and caspase-10) and LDH content were significantly decreased, whereas the cell survival rate was significantly increased when given 4-PBA or 4μ8C treatment. These findings demonstrate that HS could induce liver apoptosis of largemouth bass through the IRE1α pathway, which may act as a key switch mediating liver apoptosis of largemouth bass under HS.Keywords：heat stress;Micropterus salmoides;endoplasmic reticulum stress;apoptosis;oxidative stress14|6|0Updated：2024-10-14
- Abstract：Nanomaterials, particularly titanium dioxide nanoparticles (TiO2-NPs), are extensively utilized across various industries. However, their environmental release has raised concerns regarding their potential ecological and environmental impacts. The reproductive toxicity of TiO2-NPs in fish species has attracted considerable attention, yet conflicting research outcomes have been reported. We investigated the effects of TiO2-NPs exposure on the liver of juvenile Amur sturgeon Acipenserschrenckii using label-free proteomic and untargeted metabolomic analyses. The experiment included a control group and three groups exposed to different concentrations of TiO2-NPs (low, TL; medium, TM; high, TH). Compared to the control group, 9, 19, and 25 proteins and 35, 73, and 158 metabolites were differentially expressed in the TH, TM, and TL TiO2-NP-exposed groups, respectively. The differentially expressed genes (DEGs) were enriched in the Kyoto Encyclopedia for Genes and Genomes (KEGG) pathways related to glycolysis and gluconeogenesis. Moreover, among the 126 correlated proteins, the most enriched pathways were associated with endocytosis and protein processing in the endoplasmic reticulum. Notably, syringic acid was significantly downregulated across all three TiO2-NP-exposed groups. To obtain a comprehensive overview of the TiO2-NP-induced expression changes, a co-regulated network of proteins and metabolites associated with TiO2-NPs exposure was constructed. Exposure to TiO2-NPs led to enrichment and alteration of pathways related to immune responses, including endocytosis, protein processing in the endoplasmic reticulum, and peroxisome proliferator-activated receptor (PPAR) signaling. In conclusion, our findings indicate that exposure to TiO2-NPs might disrupt glucose metabolism and induce immune responses, thus contributing to our understanding of the environmental impacts of nanomaterials and highlighting the need for further research and development of potential mitigation strategies.Keywords：TiO2-nanoparticle exposure;proteomics;metabolomics;glucose metabolism;immune response14|5|0Updated：2024-10-14
Aquaculture and Fisheries
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