Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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The variation in basal channels and basal melt rates of Pine Island Ice Shelf
Mingliang Liu, Zemin Wang, Baojun Zhang, Xiangyu Song, Jiachun An
[Abstract](2) [FullText HTML](1)
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In recent years, there has been a significantly acceleration in the thinning, calving and retreat of the Pine Island Ice Shelf (PIIS). The basal channels, results of enhanced basal melting, have the potential to significantly impact the stability of the PIIS. In this study, we used a variety of remote sensing data, including Landsat, REMA DEM, ICESat-1 and ICESat-2 satellite altimetry observations, and IceBridge airborne measurements, to study the spatiotemporal changes in the basal channels from 2003 to 2020 and basal melt rate from 2010 to 2017 of the PIIS under the Eulerian framework. We found that the basal channels are highly developed in the PIIS, with a total length exceeding 450 km. Most of the basal channels are ocean-sourced or grounding-line-sourced basal channels, caused by the rapid melting under the ice shelf or near the grounding-line. A raised seabed prevented warm water intrusion into the eastern branch of the PIIS, resulting in a lower basal melt rate in that area. In contrast, a deep-sea trough facilitates warm sea water into the mainstream and the western branch of the PIIS, resulting in a higher basal melt rate in the main-stream, and the surface elevation changes above the basal channels of the mainstream and west-ern branch are more significant. The El Niño event in 2015–2016 possibly slowed down the basal melting of the PIIS by modulating wind field, surface sea temperature and depth seawater temperature. Ocean and atmospheric changes were driven by El Niño, which can further explain and confirm the changes in the basal melting of the PIIS.
An improved algorithm for retrieving thin sea ice thickness in the Arctic Ocean from SMOS and SMAP L-band radiometer data
Lian He, Senwen Huang, Fengming Hui, Xiao Cheng
[Abstract](35) [FullText HTML](18)
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The aim of this study was to develop an improved thin ice thickness retrieval algorithm in the Arctic Ocean for the Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) L-band radiometer data. This empirical sea ice thickness (SIT) retrieval algorithm was trained using the simulated SIT from the cumulative freezing degree days (CFDD) model during the freeze-up period over 5 carefully selected regions in the Beaufort, Chukchi, East Siberian, Laptev and Kara Seas and utilized the microwave polarization ratio (PR) at incidence angle of 40°. The improvements of the proposed retrieval algorithm include the correction for the sea ice concentration impact, reliable reference SIT data over different representative regions of the Arctic Ocean and the utilization of microwave polarization ratio that is independent of ice temperature. The relationship between the SIT and PR was found to be almost stable across the 5 selected regions. The SIT retrievals were then compared to other two existing algorithms (i.e., UH_SIT from the University of Hamburg and UB_SIT from the University of Bremen) and validated against independent SIT data obtain from moored upward looking sonars (ULS) and airborne electromagnetic (EM) induction sensors. The results suggest that the proposed algorithm could achieve comparable accuracies to UH_SIT and UB_SIT with root mean square error (RMSE) being about 0.20 m when validating using ULS SIT data and outperformed the UH_SIT and UB_SIT with RMSE being about 0.21 m when validation using EM SIT data. The proposed algorithm can be used for thin ice thickness (< 1.0 m) estimation in the Arctic Ocean and requires less auxiliary data in the SIT retrieval procedure which makes its implementation more practical.
A multi-module with a two-way feedback method for Ulva drift-diffusion
Hui Sheng, Jianmeng Li, Qimao Wang, Bin Zou, Lijian Shi, Mingming Xu, Shanwei Liu, Jianhua Wan, Zhe Zeng, Yanlong Chen
 doi: 10.1007/s13131-023-2165-y
[Abstract](95) [FullText HTML](41) [PDF 3217KB](0)
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The outbreak of Ulva in the Yellow Sea has seriously affected marine ecology and economic activities. Therefore, effective prediction of the distribution of Ulva is of great significance for disaster prevention and reduction. However, the prediction method of Ulva is mainly based on numerical simulation. There are two problems with these methods. First is that the initial distribution of Ulva is simulated using independent pixel-level particles. Besides, the influence of Ulva growth and diffusion on the drift is not considered. Therefore, this paper proposes a multi-module with a two-way feedback method (MTF) to solve the above problems. The main contributions of our approach are summarized as follows. First, the initialization module, the generation and elimination module, and the drive module are composed in our way. Second, we proposed an initialization method using rectangle objects to simulate the Ulva distribution extracted from remote sensing images. Thirdly, the drift and diffusion mechanism of the Ulva is considered to realize the two-way feedback between the generation and elimination module and the drive module. The results of our experiments show that the MTF performs better than the traditional method in predicting the drift and diffusion of Ulva.
The impact of typhoons on the biogeochemistry of dissolved organic matter in eutrophic bays in northwestern South China Sea
Xuan Lu, Qibin Lao, Fajin Chen, Guangzhe Jin, Chunqing Chen, Qingmei Zhu
[Abstract](35) [FullText HTML](16)
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Highly productive estuaries facilitate intense decomposition of dissolved organic matter (DOM) as a carbon source. However, the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear. To address this issue, we investigated the spectral characteristics of DOM before and after Typhoon “Ewiniar” in Zhanjiang Bay, a eutrophic semi-enclosed bay in the northwestern South China Sea. The results revealed that intense microbial decomposition of DOM occurred during the pre-typhoon period because high nutrient inputs facilitated the mobilization of DOM in the bay. However, the intrusion of external seawater induced by the typhoon diluted the nutrient levels in Zhanjiang Bay, reducing the impact of microbial decomposition on DOM during the post-typhoon period. Nevertheless, the net addition of DOM occurred in Zhanjiang Bay during the post-typhoon period, possibly because of the decomposition of particulate organic matter (POM) and desorption of particulate matter. In addition, an increase in apparent oxygen utilization, a decrease in DO saturation and the reduced level of Chl a indicated that organic matter (OM) decomposition was enhanced and OM decomposition shifted to POM decomposition in Zhanjiang Bay after the typhoon. Overall, our study highlighted the shift in the intense OM decomposition from DOM to POM decomposition before and after typhoons in eutrophic bays, providing new insights into the response of typhoons to biogeochemistry.
Inter-annual variations of dissolved oxygen and hypoxia off the northern Changjiang River (Yangtze River) Estuary in summer from 1997 to 2014
Anqi Liu, Feng Zhou, Xiao Ma, Qiang Zhao, Guanghong Liao, Yuntao Zhou, Di Tian, Xiaobo Ni, Ruibin Ding
[Abstract](45) [FullText HTML](22)
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Hypoxia off the Changjiang River Estuary has been the subject of much attention, yet systematic observations have been lacking, resulting in a lack of knowledge regarding its long-term change and drivers. By revisiting the repeated surveys of dissolved oxygen (DO) and other relevant hydrographic parameters along the section from the Changjiang River Estuary to the Cheju Island in the summer from 1997 to 2014, rather different trends were revealed for the dual low-DO cores. The nearshore low-DO core, located close to the river mouth and relatively stable, shows that hypoxia has become more severe with the lowest DO descending at a rate of -0.07 mg/L/yr and the thickness of low-DO zone rising at a rate of 0.43m/yr. The offshore core, centered around 40-m isobath but moving back and forth between 123.5°E–125°E, shows large fluctuations in the minimum DO concentration, with the thickness of low-DO zone falling at a rate of -1.55m/yr. The probable factors affecting the minimum DO concentration in the two regions also varies. In the nearshore region, the decreasing minimum DO is driven by the increase in both stratification and primary productivity, with the enhanced extension of the Changjiang River Diluted Water (CDW) strengthening stratification. In the offshore region, the fluctuating trend of the minimum DO concentration indicates that both DO loss and DO supplement are distinct. The DO loss is primarily attributed to bottom apparent oxygen utilization caused by the organic matter decay and is also relevant to the advection of low-DO water from the nearshore region. The DO supplement is primarily due to weakened stratification. Our analysis also shows that the minimum DO concentration in the nearshore region was extremely low in 1998, 2003, 2007 and 2010, related to El Niño signal in these summers.
The connection of phytoplankton biomass in the Marguerite Bay polynya of the western Antarctic peninsula to the Southern Annular Mode
Ning Jiang, Zhaoru Zhang, Ruifeng Zhang, Chuning Wang, Meng Zhou
 doi: 10.1007/s13131-023-2201-y
[Abstract](297) [FullText HTML](123) [PDF 2970KB](34)
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Antarctic coastal polynyas are biological hotspots in the Southern Ocean that support the abundance of high-trophic-level predators and are important for carbon cycling in the high-latitude oceans. In this study, we examined the interannual variation of summertime phytoplankton biomass in the Marguerite Bay polynya (MBP) in the western Antarctic peninsula area, and linked such variability to the Southern Annular Mode (SAM) that dominated the southern hemisphere extratropical climate variability. Combining satellite data, atmosphere reanalysis products and numerical simulations, we found that the interannual variation of summer chlorophyll-a concentration (Chl-a) in the MBP is significantly and negatively correlated with the spring SAM index, and weakly correlated with the summer SAM index. The negative relation between summer Chl-a and spring SAM is due to weaker spring vertical mixing under a more positive SAM condition, which would inhibit the supply of iron from deep layers into the surface euphotic layer. The negative relation between spring mixing and spring SAM results from greater precipitation rate over the MBP region in positive SAM phase, which leads to lower salinity in the ocean surface layer. The coupled physical-biological mechanisms between SAM and phytoplankton biomass revealed in this study is important for us to predict the future variations of phytoplankton biomasses in Antarctic polynyas under climate change.
Gravity anomalies determined from mean sea surface model data over the Gulf of Mexico
Xuyang Wei, Xin Liu, Zhen Li, Xiaotao Chang, Hongxin Luo, Chengcheng Zhu, Jinyun Guo
 doi: 10.1007/s13131-023-2178-6
[Abstract](210) [FullText HTML](78) [PDF 2741KB](7)
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With the improvements in the density and quality of satellite altimetry data, a high-precision and high-resolution mean sea surface model containing abundant information regarding a marine gravity field can be calculated from long-time series multi-satellite altimeter data. Therefore, in this study, a method was proposed for determining marine gravity anomalies from a mean sea surface model. Taking the Gulf of Mexico (15°–32°N, 80°–100°W) as the study area and using a removal-recovery method, the residual gridded deflections of the vertical (DOVs) are calculated by combining the mean sea surface, mean dynamic topography, and XGM2019e_2159 geoid, and then using the inverse Vening-Meinesz method to determine the residual marine gravity anomalies from the residual gridded DOVs. Finally, residual gravity anomalies are added to the XGM2019e_2159 gravity anomalies to derive marine gravity anomaly models. In this study, the marine gravity anomalies were estimated with mean sea surface models CNES_CLS15MSS, DTU21MSS, and SDUST2020MSS and the mean dynamic topography models CNES_CLS18MDT and DTU22MDT. The accuracy of the marine gravity anomalies derived by the mean sea surface model was assessed based on ship-borne gravity data. The results show that the difference between the gravity anomalies derived by DTU21MSS and CNES_CLS18MDT and those of the ship-borne gravity data is optimal. With an increase in the distance from the coast, the difference between the gravity anomalies derived by mean sea surface models and ship-borne gravity data gradually decreases. The accuracy of the difference between the gravity anomalies derived by mean sea surface models and those from ship-borne gravity data is optimal at a depth of 3–4 km. The accuracy of the gravity anomalies derived by the mean sea surface model is high.
Application and evaluation of layering shear method in LADCP data processing
Zijian Cui, Chujin Liang, Binbin Guo, Feilong Lin, Yong Mu
 doi: 10.1007/s13131-023-2200-z
[Abstract](30) [FullText HTML](10) [PDF 2152KB](2)
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The current velocity observation of LADCP (Lowered Acoustic Doppler Current Profiler) has the advantages of a large vertical range of observation and high operability compared with traditional current measurement methods, and is being widely used in the field of ocean observation. Shear and inverse methods are now commonly used by the international marine community to process LADCP data and calculate ocean current profiles. The two methods have their advantages and shortcomings. The shear method calculates the value of current shear more accurately, while the accuracy in an absolute value of the current is lower. The inverse method calculates the absolute value of the current velocity more accurately, but the current shear is less accurate. Based on the shear method, this paper proposes a layering shear method to calculate the current velocity profile by “layering averaging”, and proposes corresponding current calculation methods according to the different types of problems in several field observation data from the Western Pacific, forming an independent LADCP data processing system. The comparison results have shown that the layering shear method can achieve the same effect as the inverse method in the calculation of the absolute value of current velocity, while retaining the advantages of the shear method in the calculation of a value of the current shear.
When river meets ocean: Distribution and conversion of suspended organic particles in a Sundarban mangrove river-estuary system, Bangladesh
Xiaochun Zou, Yunhai Li, Liang Wang, Mohammad Kawser Ahmed, Keliang Chen, Jianwei Wu, Yonghang Xu, Yunpeng Lin, Baohong Chen, Kankan Wu, Jinwen Liu
[Abstract](44) [FullText HTML](21)
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Global carbon cycle has received extensive attention, among which the river-estuary system is one of the important links connecting the carbon cycle between land and ocean. In this paper, the distribution and control factors of particulate organic carbon (POC) were studied by using the data of organic carbon contents and its carbon isotopic composition (δ13C) in the mainstream and estuary of Passur River in the Sundarban area, combined with the hydrological and biological data measured by CTD. The results show that POC content ranged from 0.263 to 9.292 mg/L, and the POC content in the river section (averaged 4.129 mg/L) was significantly higher than that in the estuary area (averaged 0.858 mg/L). Two distinct stages of POC transport from land to sea in the Sundarban area were identified. The first stage occurred in the river section, where POC distribution was mainly controlled by the dynamic process of runoff and the organic carbon was mainly terrestrial source. The second stage occurred during estuarine mixing, where the POC distribution was mainly controlled by the mixing process of seawater and freshwater. The source of POC was predominantly marine and exhibiting vertical differences. The surface and middle layers were primarily influenced by marine sources, while the bottom layer was jointly controlled by terrestrial and marine sources of organic carbon. These findings are of great significance for understanding the carbon cycle in such a large mangrove ecosystem like the Sundarban Mangrove.
Prediction of three-dimensional ocean temperature in the South China Sea based on time series gridded data and a dynamic spatiotemporal graph neural network
Feng Nan, Zhuolin Li, Jie Yu, Suixiang Shi, Xinrong Wu, Lingyu Xu
[Abstract](48) [FullText HTML](22)
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Ocean temperature is an important physical variable in marine ecosystems, and ocean temperature prediction is an important research objective in ocean-related fields. Currently, one of the commonly used methods for ocean temperature prediction is based on data-driven, but research on this method is mostly limited to the sea surface, with few studies on the prediction of internal ocean temperature. Existing graph neural network-based methods usually use predefined graphs or learned static graphs, which cannot capture the dynamic associations among data. In this study, we propose a novel dynamic spatiotemporal graph neural network (DSTGN) to predict three-dimensional ocean temperature (3D-OT), which combines static graph learning and dynamic graph learning to automatically mine two unknown dependencies between sequences based on the original 3D-OT data without prior knowledge. Temporal and spatial dependencies in the time series were then captured using temporal and graph convolutions. We also integrated dynamic graph learning, static graph learning, graph convolution, and temporal convolution into an end-to-end framework for 3D-OT prediction using time-series grid data. In this study, we conducted prediction experiments using high-resolution 3D-OT from the Copernicus global ocean physical reanalysis, with data covering the vertical variation of temperature from the sea surface to 1,000 m below the sea surface. We compared five mainstream models that are commonly used for ocean temperature prediction, and the results showed that the method achieved the best prediction results at all prediction scales.
Bioturbation coefficients and organic carbon degradation rates of deep-sea sediments in the central-eastern tropical Pacific
Feng Lin, Cai Lin, Xiuwu Sun, Hui Lin, Li Lin, Fangfang Deng, Kaiwen Tan, Peng Lin
[Abstract](40) [FullText HTML](19)
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The biogeochemical processes of marine sediments are influenced by bioturbation and organic carbon decomposition, which is crucial for understanding global element cycles and climate change. Two sediment cores were acquired in 2017 from abyssal basins in the central-eastern tropical Pacific to determine the bioturbation and organic carbon degradation processes. The radioactivity concentrations of 210Pb and 226Ra in the sediment cores were measured, indicating the presence of significant excess 210Pb (210Pbex) signals in the sediment cores. Besides, a manganese nodule was discovered in one core, which had a substantial influence on the distribution of 210Pbex. With the exception of this anomalous finding, the bioturbation coefficients in the remaining core were estimated to be 10.6 cm2/a using a steady-state diffusion model, greater than most of the deep-sea sediments from the Equatorial Eastern Pacific. By using a bio-diffusion model, we further calculated the degradation rates of organic carbon (8.02 ka-1), which is also higher than other areas of the Pacific. Our findings displayed the presence of a biologically active benthic ecosystem in the central-eastern tropical Pacific.
Characteristics and main controlling factors of helium resources in the main petroliferous basins of the North China Craton
Zihan Gao, Zhi Chen, Hongyi He, Zhaofei Liu, Chang Lu, Hanyu Wang, Yili Luo, Ying Li
 doi: 10.1007/s13131-024-2290-2
[Abstract](180) [FullText HTML](82)
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At present, the main controlling factors of helium accumulation is one of the key scientific problems restricting the exploration and development of helium reservoir. In this paper, based on the calculation results of He generation rate and the geochemical characteristics of the produced gas, both the similarities and differences between natural gas and He resources in the Bohai Bay, Ordos and the surrounding Songliao Basin are compared and analyzed, discussing the main controlling factors of helium resources in the three main petroliferous basins of the North China Craton. It is found that the three basins of Bohai Bay, Ordos and Songliao have similar characteristics of source rocks, reservoirs and cap rocks, that’s why their methane resource characteristics are essentially the same. The calculated 4He generation per cubic metamorphic crystalline basement in the three basins is roughly equivalent, which is consistent with the measured He resources, and it is believed that the 4He of radiogenic from the crust is the main factor controlling the overall He accumulation in the three basins; there is almost no contribution of the mantle-derived CH4, which suggests that the transport and uplift of mantle-derived 3He carried by the present-day magmatic activities along the deep-large faults is not the main reason for the mantle-derived 3He mixing in the basins. Combined with the results of regional volcanic and geophysical studies, it is concluded that under the background of the destruction of North China Craton, magma intrusion carried a large amount of mantle-derived material and formed basic volcanic rocks in the Bohai Bay Basin and Songliao Basin, which replenished mantle-derived 3He for the interior of the basins, and that strong seismic activities in and around the basins also promoted the upward migration of mantle source 3He. This study suggests that the tectonic zone with dense volcanic rocks in the Cenozoic era and a high incidence of historical strong earthquakes history may be a potential area for helium resource exploration.
Geochemistry of volcanic glass from Mahanadi offshore region, eastern continental margin of India: Constraints on the contribution of latest Toba super-eruption
Muralidhar Kocherla, Durbar Ray, Manavalan Satyanarayanan, Hilda Joao, Virsen Gaikwad, P.B. Ramamurty
[Abstract](23) [FullText HTML](10)
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The tephra layers in multiple sediment cores from the offshore region of the Mahanadi basin in the northern Bay of Bengal were investigated for possible volcanic sources. The glass shards from those tephra layers were studied for size distribution, texture, and elemental geochemistry to establish chronostratigraphic markers for regional and global quaternary correlation. The textural features of fine-grained (silty) volcanic glasses suggest the distal source of these tephra deposits. Major element composition with elevated SiO2 contents ranging between 75–76% and dominance of K2O (> 4.5%) over CaO (< 0.9%) suggest ashes have originated from siliceous rhyolitic melts, similar to the petrographic composition of tephra from the Toba volcano. The bulk trace element compositions of the same glass shards were comparable with those reported in the youngest Toba tephra reported elsewhere. Likewise, the LREE-dominated chondrite normalized REE profiles of tephra from the Mahanadi basin closely resemble the characteristic REE patterns in Toba ash from other parts of the Indian Ocean and thus confirmed the contribution of the youngest Toba super-eruption for this ash layers.
Parameterization, Sensitivity, and Uncertainty of 1-D Thermodynamic Thin-ice Thickness Retrieval
Tianyu Zhang, Mohammed Shokr, Zhida Zhang, Fengming Hui, Xiao Cheng, Zhilun Zhang, Jiechen Zhao, Chunlei Mi
 doi: 10.1007/s13131-023-2210-x
[Abstract](90) [FullText HTML](36)
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Retrieval of thin-ice thickness (TIT) using thermodynamic modeling is sensitive to the parameterization of the independent variables (coded in the model) and the uncertainty of the measured input variables. This article examines the deviation of the classical model’s TIT output when using different parameterization schemes and the sensitivity of the output to the ice thickness. Moreover, it estimates the uncertainty of the output in response to the uncertainties of the input variables. The parameterized independent variables include atmospheric longwave emissivity, air density, specific heat of air, latent heat of ice, conductivity of ice, snow depth, and snow conductivity. Measured input parameters include air temperature, ice surface temperature, and wind speed. Among the independent variables, the results show that the highest deviation is caused by adjusting the parameterization of snow conductivity and depth, followed ice conductivity. The sensitivity of the output TIT to ice thickness is highest when using parameterization of ice conductivity, atmospheric emissivity, and snow conductivity and depth. The retrieved TIT obtained using each parameterization scheme is validated using in situ measurements and satellite-retrieved data. From in situ measurements, the uncertainties of the measured air temperature and surface temperature are found to be high. The resulting uncertainties of TIT are evaluated using perturbations of the input data selected based on the probability distribution of the measurement error. The results show that the overall uncertainty of TIT to air temperature, surface temperature, and wind speed uncertainty is around 0.09 m, 0.049 m, and −0.005 m, respectively.
Photosynthetic response to a winter heatwave in leading and trailing edge populations of the intertidal red alga Corallina officinalis (Rhodophyta)
Regina Kolzenburg, Federica Ragazzola, Laura Tamburello, Katy R. Nicastro, Christopher D. McQuaid, Gerardo I. Zardi
[Abstract](22) [FullText HTML](11)
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Marine heatwaves (MHWs) caused by anthropogenic climate change are becoming a key driver of change at the ecosystem level. Thermal conditions experienced by marine organisms across their distribution, particularly towards the equator, are likely to approach their physiological limits, resulting in extensive mortality and subsequent changes at the population level. Populations at the margins of their species’ distribution are thought to be more sensitive to climate-induced environmental pressures than central populations, but our understanding of variability in fitness-related physiological traits in trailing versus leading-edge populations is limited. In a laboratory simulation study, we tested whether two leading (Iceland) and two trailing (Spain) peripheral populations of the intertidal macroalga Corallina officinalis display different levels of maximum potential quantum efficiency (Fv/Fm) resilience to current and future winter MHWs scenarios. Our study revealed that ongoing and future local winter MHWs will not negatively affect leading-edge populations of C. officinalis, which exhibited stable photosynthetic efficiency throughout the study. Trailing edge populations showed a positive though non-significant trend in photosynthetic efficiency throughout winter MHWs exposure. Poleward and equatorward populations did not produce significantly different results, with winter MHWs having no negative affect on Fv/Fm of either population. Additionally, we found no long-term regional or population-level influence of a winter MHWs on this species’ photosynthetic efficiency. Thus, we found no statistically significant difference in thermal stress responses between leading and trailing populations. Nonetheless, C. officinalis showed a trend towards higher stress responses in southern than northern populations. Because responses rest on a variety of local population traits they are difficult to predict based solely on thermal pressures.
Synthesizing high-resolution satellite salinity data based on multi-fractal fusion
Hengqian Yan, Jian Shi, Ren Zhang, Wangjiang Hu, Yongchui Zhang, Mei Hong
[Abstract](40) [FullText HTML](20)
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The spaceborne platform has unprecedently provided the global eddy-permitting (typically ~0.25°) products of Sea Surface Salinity (SSS), however the existing SSS products can hardly resolve mesoscale motions due to the heavy noises therein and the over-smoothing in denoising processes. By means of the Multi-fractal Fusion (MFF), the high-resolution SSS product is synthesized with the template of Sea Surface Temperature (SST). Two low-resolution SSS products and four SST products are considered as the source data and the templates respectively to determine the best combination. The fused products are validated by the in situ observations and intercompared via SSS maps, Singularity Exponent maps and wavenumber spectra. The results demonstrate that the MFF can perform a good work in mitigating the noises and improving the resolution. The Climate Change Initiative (CCI) SSS + the REMote Sensing System (REMSS) SST can produce the 0.1° denoised product whose global mean STandard Derivation (STD) against Argo is 0.21 psu and the feature resolution can reach 30-40 km.
Research on the Generation Method of Seawater Sound Velocity Model Based on Perlin Noise
Zhimiao Chang, Fuxing Han, Zhangqing Sun, Zhenghui Gao, Xueqiu Wang
 doi: 10.1007/s13131-023-2230-6
[Abstract](63) [FullText HTML](26)
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In the processing of conventional marine seismic data, seawater is often assumed to have a constant velocity model. However, due to static pressure, temperature difference and other factors, random disturbances may often frequently in seawater bodies. The impact of such disturbances on data processing results is a topic of theoretical research. Since seawater sound velocity is a difficult physical quantity to measure, there is a need for a method that can generate models conforming to seawater characteristics. This article will combine the Munk model and Perlin noise to propose a two-dimensional dynamic seawater sound velocity model generation method, a method that can generate a dynamic, continuous, random seawater sound velocity model with some regularity at large scales. Moreover, the paper discusses the influence of the inhomogeneity characteristics of seawater on wave field propagation and imaging. The results show that the seawater sound velocity model with random disturbance will have a significant influence on the wave field simulation and imaging results.
Evaluation and projection of marine heatwaves in the South China Sea: insights from CMIP6 multi-model ensemble
Kai Liu, Kang Xu, Tongxin Han, Congwen Zhu, Nina Li, Anboyu Guo, Xiaolu Huang
[Abstract](56) [FullText HTML](28)
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This study evaluates the performance of 16 models sourced from the Coupled Model Intercomparison Project phase 6 (CMIP6) in simulating marine heatwaves (MHWs) in the South China Sea (SCS) during the historical period (1982−2014), and also investigates future changes in SCS MHWs based on simulations from three Shared Socioeconomic Pathway (SSP) scenarios (SSP126, SSP245, and SSP585) using CMIP6 models. Results demonstrate that the CMIP6 models perform well in simulating the spatial-temporal distribution and intensity of SCS MHWs, with their multi-model ensemble (MME) results showing the best performance. The reasonable agreement between the observations and CMIP6 MME reveals that the increasing trends of SCS MHWs are attributed to the warming sea surface temperature trend. Under various SSP scenarios, the year 2040 emerges as pivotal juncture for future shifts in SCS MHWs, marked by distinct variations in changing rate and amplitudes. This is characterized by an accelerated decrease in MHWs frequency and a notably heightened increase in mean intensity, duration, and total days after 2040. Furthermore, the projection results for SCS MHWs suggest that the spatial pattern of MHWs remains consistent across future periods. However, the intensity shows higher consistency only during the near-term period (2021−2050), while notable inconsistencies are observed during the medium-term (2041−2700) and long-term (2701−2100) periods under the three SSP scenarios. During the near-term period, the SCS MHWs are characterized by moderate and strong events with high frequencies and relatively shorter durations. In contrast, during the medium-term period, MHWs are also characterized by moderate and strong events, but with longer-lasting and more intense events under the SSP245 and SSP585 scenarios. However, in the long-term period, extreme MHWs become the dominant feature under the SSP585 scenario, indicating a substantial intensification of SCS MHWs, effectively establishing a near-permanent state.
Seasonal variation of mesoscale eddy intensity in the global ocean
Yongcan Zu, Yue Fang, Shuangwen Sun, Libao Gao, Yang Yang, Guijun Guo
 doi: 10.1007/s13131-023-2278-3
[Abstract](224) [FullText HTML](111)
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Mesoscale eddies are a prominent oceanic phenomenon that plays an important role in oceanic mass transport and energy conversion. Characterizing by rotational speed, the eddy intensity is one of the most fundamental properties of an eddy. However, the seasonal spatiotemporal variation in eddy intensity has not been examined from a global ocean perspective. In this study, we unveil the seasonal spatiotemporal characteristics of eddy intensity in the global ocean by using the latest satellite-altimetry-derived eddy trajectory data set. The results suggest that the eddy intensity has a distinct seasonal variation, reaching a peak in spring while attaining a minimum in autumn in the Northern Hemisphere and the opposite in the Southern Hemisphere. The seasonal variation of eddy intensity is more intense in the tropical-subtropical transition zones within latitudinal bands between 15° and 30° in the Western Pacific Ocean, the Northwestern Atlantic Ocean, and the Eastern Indian Ocean because baroclinic instability in these areas changes sharply. Further analysis found that the seasonal variation of baroclinic instability precedes the eddy intensity by a phase lag of 2-3 months due to the initial perturbations needing time to grow into mesoscale eddies.
What induced the trend shift of mixed-layer depths in the Antarctic Circumpolar Current region in the mid-1980s?
Shan Liu, Jingzhi Su, Huijun Wang, Cuijuan Sui
 doi: 10.1007/s13131-023-2268-5
[Abstract](110) [FullText HTML](48)
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An obvious trend shift in the annual mean and winter mixed layer depth (MLD) in the Antarctic Circumpolar Current (ACC) region was detected during the 1960–2021 period. Shallowing trends stopped in mid-1980s, followed by a period of weak trends. The MLD deepening trend difference between the two period were mainly distributed in the western areas in the Drake Passage, the areas north to Victoria Land and Wilkes Land, and the central parts of the South Indian sector. The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South Indian sector. The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.
A positive trend in the stability of global offshore wind energy
Chongwei Zheng
 doi: 10.1007/s13131-023-2187-5
[Abstract](60) [FullText HTML](27)
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The recognition on the trend of wind energy stability is still extremely rare, although it is closely related to acquisition efficiency, grid connection, equipment lifetime, and costs of wind energy utilization. Using the 40-year (1979–2018) ERA-Interim data from the European Center for Medium-Range Weather Forecasts (ECMWF), this study presented the spatial-temporal distribution and climatic trend of the stability of global offshore wind energy as well as the abrupt phenomenon of wind energy stability in key regions over the past 40 years with the climatic analysis method and Mann-Kendall (M-K) test. The results show the following 5 points. (1) According to the coefficient of variation (Cv) of the wind power density (WPD), there are six permanent stable zones of global offshore wind energy: the southeast and northeast trade wind zones in the Indian, Pacific and Atlantic Oceans, the Southern Hemisphere westerly, and a semi-permanent stable zone (North Indian Ocean). (2) There are six low-value zones for both seasonal variability index (Sv) and monthly variability index (Mv) globally, with a similar spatial distribution as that of the six permanent stable zones. The Mv and Sv in the Arabian Sea are the highest in the world. (3) After the Cv, Mv and Sv are comprehensively considered, the six permanent stable zones have an obvious advantage in the stability of wind energy over other sea areas, with Cv below 0.8, Mv within 1.0, and Sv within 0.7 all the year round. (4) The global stability of offshore wind energy shows a positive climatic trend for the past four decades. The Cv, Mv, and Sv have not changed significantly or decreased in most of the global ocean during 1979 to 2018. That is, wind energy is flat or more stable, while the monthly and seasonal variabilities tend to shrink/smooth, which is beneficial for wind energy utilization. (5) The Cv in the low-latitude Pacific and the Mv and Sv in both the North Indian and the low-latitude Pacific have an obvious abrupt phenomenon at the end of the 20th century.
The Morphological changes of basal channels based on multi-source remote sensing data at the Pine Island Ice Shelf
Xiangyu Song, Zemin Wang, Jianbin Song, Baojun Zhang, Mingliang Liu
 doi: 10.1007/s13131-023-2241-3
[Abstract](289) [FullText HTML](135) [PDF 2471KB](22)
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The basal channel is a detailed morphological feature of the ice shelf caused by uneven basal melting. This kind of specifically morphology is widely distributed in polar ice shelves. It is an important research object of sea-ice interaction and plays a vital role in studying the relationship between the ice sheet/ice shelf and global warming. In this paper, high-resolution remote sensing image and ice penetration data were combined to extract the basal channel of the Pine Island ice shelf. The depth variation of Pine Island Ice Shelf in the recent 20 years was analyzed and discussed by using ICESat-1, ICESat-2, and IceBridge data. Combined with relevant marine meteorological elements (sea surface temperature, surface melting days, circumpolar deep water and wind) to analyze the basal channel changes, the redistribution of ocean heat is considered to be the most important factor affecting the evolution and development of the basal channel.
Observation of Arctic surface currents using data from a surface drifting buoy
Hongxia Chen, Lina Lin, Long Fan, Wangxiao Yang, Yinke Dou, Bingrui Li, Yan He, Bin Kong, Guangyu Zuo, Na Liu
 doi: 10.1007/s13131-023-2202-x
[Abstract](66) [FullText HTML](28)
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During the 10th Chinese Arctic scientific expedition carried out in the summer of 2019, the surface current in the high-latitude areas of the Arctic Ocean was observed using a self-developed surface drifting buoy, which was initially deployed in the Chukchi Sea. The buoy traversed the Chukchi Sea, Chukchi Abyssal Plain, Mendeleev Ridge, Makarov Basin, and Canada Basin over a period of 632 d. After returning to the Mendeleev Ridge, it continued to drift toward the pole. Overall, the track of the buoy reflected the characteristics of the transpolar drift and Chukchi Slope Current, as well as the inertial flow, cross-ridge surface flow, and even the surface disorganized flow for some time intervals. The results showed that (1) the transpolar drift mainly occurs in the Chukchi Abyssal Plain, Mendeleev Ridge, and western Canada Basin to the east of the ridge where sea ice concentration is high, and the average northward flow velocity in the region between 79.41°N and 86.32°N was 5.1 cm/s; (2) the average surface velocity of the Chukchi Slope Current was 13.5 cm/s and, while this current moves westward along the continental slope, it also extends northwestward across the continental slope and flows to the deep sea; and (3) when sea ice concentration was less than 50%, the inertial flow was more significant (the maximum observed inertial flow was 26 cm/s, and the radius of the inertia circle was 3.6 km).
A case study of continental shelf waves in the northwestern South China Sea induced by winter storms in 2021
Junyi Li, Chen Zhou, Min Li, Quanan Zheng, Mingming Li, Lingling Xie
 doi: 10.1007/s13131-023-2150-5
[Abstract](210) [FullText HTML](91)
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This study aims to investigate characteristics of continental shelf wave (CSW) on the northwestern continental shelf of the South China Sea (SCS) induced by winter storms in 2021. Mooring and cruise observations, tidal gauge data at stations Hong Kong (HK), Zhapo (ZP) and Qinglan (QL) and sea surface wind data from January 1 to February 28, 2021 are used to examine the relationship between along-shelf wind and sea level fluctuation. Two events of CSWs driven by the along-shelf sea surface wind are detected from wavelet spectra of tidal gauge data. The signals are triply peaked at periods of 56 h, 94 h and 180 h, propagating along the coast with phase speed ranging from 6.9 m/s to18.9 m/s. The dispersion relation shows their property of the Kelvin mode of CSW. We develop a simple method to estimate amplitude of sea surface fluctuation by along-shelf wind. The results are comparable with the observation data, suggesting it is effective. The mode 2 CSWs fits very well with the mooring current velocity data. The results from rare current help to understand wave-current interaction in the northwestern SCS.
Mixed layer warming by the barrier layer in the southeastern Indian Ocean
Kaiyue Wang, Yisen Zhong, Meng Zhou
 doi: 10.1007/s13131-023-2151-4
[Abstract](153) [FullText HTML](68)
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The southeastern Indian Ocean is characterized by the warm barrier layer (BL) underlying the cool mixed layer water in austral winter. This phenomenon lasts almost half a year and thus provides a unique positive effect on the upper mixed layer heat content through the entrainment processes at the base of the mixed layer, which has not been well evaluated due to the lack of proper method and dataset. Among various traditional threshold methods, here we show that the 5 m fixed depth difference can produce a reliable and accurate estimate of the entrainment heat flux (EHF) in this BL region. The comparison between the daily and monthly EHF warming indicates that the account for high-frequency EHF variability almost doubles the warming effect in the BL period, which can compensate for or even surpass the surface heat loss. This increased warming is a result of stronger relative rate of the mixed layer deepening and larger temperature differences between the mixed layer and its immediate below in the daily-resolving data. The interannual EHF shows a moderately increasing trend and similar variabilities to the Southern Annular Mode (SAM), likely because the mixed layer deepening under the positive SAM trend is accompanied by enhanced turbulent entrainment and thus increases the BL warming.
Simulated Indonesian Throughflow in Makassar Strait across the SODA3 products
Tengfei Xu, Zexun Wei, Haifeng Zhao, Shen Guan, Shujiang Li, Guanlin Wang, Fei Teng, Yongcui Zhang, Jing Wang
 doi: 10.1007/s13131-023-2186-6
[Abstract](358) [FullText HTML](155)
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The Indonesian Throughflow (ITF), which connects the tropical Pacific and Indian Oceans, plays important roles in the inter-ocean water exchange and regional or even global climate variability. The Makassar Strait is the main inflow passage of the ITF, carrying about 77% of the total ITF volume transport. In this study, we analyze the simulated ITF in the Makassar Strait in the Simple Ocean Data Assimilation version 3 (SODA3) datasets. A total of nine ensemble members of the SODA3 datasets, of which are driven by different surface forcings and bulk formulas, and with or without data assimilation, are used in this study. The annual mean water transports (i.e., volume, heat and freshwater) are related to the combination of surface forcing and bulk formula, as well as whether data assimilation is employed. The phases of the seasonal and interannual variability in water transports cross the Makassar Strait, are basically consistent with each other among the SODA3 ensemble members. The interannual variability in Makassar Strait volume and heat transports are significantly correlated with El Niño-Southern Oscillation (ENSO) at time lags of −6 to 7 months. There is no statistically significant correlation between the freshwater transport and the ENSO. The Makassar Strait water transports are not significantly correlated with the Indian Ocean Dipole (IOD), which may attribute to model deficiency in simulating the propagation of semi-annual Kelvin waves from the Indian Ocean to the Makassar Strait.
Thermal and exhumation history of the Songnan Low Uplift, Qiongdongnan Basin: constraints from the apatite fission-track and zircon (U-Th)/He thermochronology
Xiaoyin Tang, Kaixun Zhang, Shuchun Yang, Shuai Guo, Xinyan Zhao, Zhizhao Bai
 doi: 10.1007/s13131-023-2253-z
[Abstract](132) [FullText HTML](56)
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Significant advancements have been made in the study of Mesozoic granite buried hills in the Songnan Low Uplift (SNLU) of the Qiongdongnan Basin. These findings indicate that the bedrock buried hills in this basin hold great potential for exploration. Borehole samples taken from the granite buried hills in the SNLU were analyzed using apatite fission track (AFT) and zircon (U-Th)/He data to unravel the thermal history of the basement rock. This information is crucial for understanding the processes of exhumation and alteration that occurred after its formation. Thermal modeling of a sample from the western bulge of the SNLU revealed a prolonged cooling event from the late Mesozoic to the Oligocene period (~80−23.8 Ma), followed by a heating stage from the Miocene epoch until the present (~23.8 Ma to present). In contrast, the sample from the eastern bulge experienced a more complex thermal history. It underwent two cooling stages during the late Mesozoic to late Eocene period (~80−36.4 Ma) and the late Oligocene period (~30−23.8 Ma), interspersed with two heating phases during the late Eocene to early Oligocene period (~36.4−30 Ma) and the Miocene epoch to recent times (~23.8−0 Ma), respectively. The differences in exhumation histories between the western and eastern bulges during the late Eocene to Oligocene period in the SNLU can likely be attributed to differences in fault activity. Unlike typical passive continental margin basins, the SNLU has experienced accelerated subsidence after the rifting phase, which began around 5.2 Ma ago. The possible mechanism for this abnormal post-rifting subsidence may be the decay or movement of the deep thermal source and the rapid cooling of the asthenosphere. Long-term and multi-episodic cooling and exhumation processes play a key role in the alteration of bedrock and contribute to the formation of reservoirs. On the other hand, rapid post-rifting subsidence (sedimentation) promotes the formation of cap rocks.
Tetrabromobisphenol A and hexabromocyclododecane in sediments from the Pearl River Estuary and South China Sea
Chuyue Long, Weiyan Yang, Jiaxun Lu, Yuanyue Cheng, Ning Qiu, Sen Du, Li Zhang, Shejun Chen, Yuxin Sun
 doi: 10.1007/s13131-023-2267-6
[Abstract](106) [FullText HTML](45)
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Marine sediments were collected from the Pearl River Estuary (PRE) and South China Sea (SCS) to study the occurrence and spatial distribution of tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDD). The levels of TBBPA and HBCDD in sediments ranged from not detected (nd) to 6.14 ng/g dry weight (dw) and nd to 0.42 ng/g dw. TBBPA concentrations in marine sediments were substantially higher than HBCDD. The concentrations of TBBPA and HBCDD in the PRE sediments were significantly greater than those in the SCS. α-HBCDD (48.7%) and γ-HBCDD (46.2%) were the two main diastereoisomers of HBCDD in sediments from the PRE, with minor contribution of β-HBCDD (5.1%). HBCDD were only found in one sample from the northern SCS. The enantiomeric fraction of α-HBCDD in sediments from the PRE was obviously greater than 0.5, indicating an accumulation of (+)-α-HBCDD. The enantiomers of HBCDD were not measured in sediments from the SCS. This work highlighted the environmental behaviors of TBBPA and HBCDD in marine sediments.
Predictability of the upper ocean heat content in a CESM ensemble prediction system
Ting Liu, Wenxiu Zhong
 doi: 10.1007/s13131-023-2239-x
[Abstract](103) [FullText HTML](42)
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Upper ocean heat content (OHC) has been widely recognized as a crucial precursor to high-impact climate variability, especially for that being indispensable to the long-term memory of the ocean. Assessing the predictability of OHC using state-of-the-art climate models is invaluable for improving and advancing climate forecasts. Recently developed retrospective forecast experiments, based on a Community Earth System Model ensemble prediction system, offer a great opportunity to comprehensively explore OHC predictability. Our results indicate that the skill of actual OHC predictions varies across different oceans and diminishes as the lead time of prediction extends. The spatial distribution of the actual prediction skill closely resembles the corresponding persistence skill, indicating that the persistence of OHC serves as the primary predictive signal for its predictability. The decline in actual prediction skill is more pronounced in the Indian and Atlantic Oceans than in the Pacific Ocean, particularly within tropical regions. Additionally, notable seasonal variations in the actual prediction skills across different oceans align well with the phase-locking features of OHC variability. The potential predictability of OHC generally surpasses the actual prediction skill at all lead times, highlighting significant room for improvement in current OHC predictions, especially for the North Indian Ocean and the Atlantic Ocean. Achieving such improvements necessitates a collaborative effort to enhance the quality of ocean observations, develop effective data assimilation methods, and reduce model bias.
Coral records of Mid-Holocene sea-level highstands and climate responses in the northern South China Sea
Yuanfu Yue, Lichao Tang, Kefu Yu, Rongyong Huang
 doi: 10.1007/s13131-023-2264-9
[Abstract](1456) [FullText HTML](714)
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High-resolution sea-level data and high-precision dating of corals in the northern South China Sea (SCS) during the Holocene provide a reference and historical background for current and future sea-level changes and a basis for scientific assessment of the evolutionary trend of coral reefs in the SCS. Although sporadic studies have been performed around Hainan Island in the northern SCS, the reconstructed sea level presents different values or is controversial because the indicative meaning of the sea-level indicators were neither quantified nor uniform criteria. Here, we determined the quantitative relationship between modern living coral and sea level by measuring the top surfaces of 27 live Porites corals from the inner reef flat along the east coast of Hainan Island and assessed the accuracy of results obtained using coral as sea-level indicators. Additionally, three in situ fossil Porites corals were analyzed based on elevation measurements, digital X-Ray radiography, and U-Th dating. The survey results showed that the indicative meanings for the modern live Porites corals is (−146.09 ± 8.35) cm below the mean tide level (MTL). It suggested that their upward growth limit is constrained by the sea level, and the lowest low water is the highest level of survival for the modern live Porites corals. Based on the newly defined indicative meanings, 6 new sea-level index points (SLIPs) were obtained and 19 published SLIPs were recalculated. Those SLIPs indicated a relative sea level fluctuation between (227.7 ± 9.8) cm to (154.88 ± 9.8) cm MTL between (5 393 ± 25) cal a BP and (3 390 ± 12) cal a BP, providing evidences of the Mid-Holocene sea-level highstand in the northern SCS. Besides that, our analysis demonstrated that different sea-level histories may be produced based on different indicative meanings or criteria. The dataset of 276 coral U-Th ages indicates that coral reef development in the northern SCS comprised the initial development, boom growth, decline, and flourishing development again. A comparison with regional records indicated that synergistic effects of climatic and environmental factors were involved in the development of coral reefs in the northern SCS. Thus, the cessation of coral reef development during the Holocene in the northern SCS was probably associated with the dry and cold climate in South China, as reflected in the synchronous weakening of the ENSO and East Asian summer monsoon induced by the reduction of the 65°N summer insolation, which forced the migration of the Intertropical Convergence Zone.
Satellite-observed significant improvement in nearshore transparency of the Bohai Sea during past 20 years
Xuyan Li, Jinzhao Xiang, Liudi Zhu, Zhibin Yang, Ting Wei, Bing Mu, Xiaobo Zhang, Tingwei Cui
 doi: 10.1007/s13131-023-2180-z
[Abstract](278) [FullText HTML](116)
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The Bohai Sea (BS) is the unique semi-closed inland sea of China, characterized by degraded water quality due to significant terrestrial pollution input. In order to improve its water quality, a dedicated action named “Uphill Battles for Integrated Bohai Sea Management” (UBIBSM, 2018–2020) was implemented by the Chinese government. To evaluate the action effectiveness toward water quality improvement, variability of the satellite-observed water transparency (Secchi disk depth, ZSD) was explored, with special emphasis on the nearshore waters (within 20 km from the coastline) prone to terrestrial influence. (1) Compared to the status before the action began (2011–2017), majority (87.3%) of the nearshore waters turned clear during the action implementation period (2018–2020), characterized by the elevated ZSD by 11.6%±12.1%. (2) Nevertheless, the improvement was not spatially uniform, with higher ZSD improvement in provinces of Hebei, Liaoning, and Shandong (13.2%±16.5%, 13.2%±11.6%, 10.8%±10.2%, respectively) followed by Tianjin (6.2%±4.7%). (3) Bayesian trend analysis found the abrupt ZSD improvement in April 2018, which coincided with the initiation of UBIBSM, implying the water quality response to pollution control. More importantly, the independent statistics of land-based pollutant discharge also indicated that the significant reduction of terrestrial pollutant input during the UBIBSM action was the main driver of observed ZSD improvement. (4) Compared with previous pollution control actions in the BS, UBIBSM was found to be the most successful one during the past 20 years, in terms of transparency improvement over nearshore waters. The presented results proved the UBIBSM-achieved remarkable water quality improvement, taking the advantage of long-term consistent and objective data record from satellite ocean color observation.
Exploring spatial non-stationarity of near-miss ship collisions from AIS data under the influence of sea fog using geographically weighted regression: A case study in the Bohai Sea, China
Yongtian Shen, Zhe Zeng, Dan Liu, Pei Du
 doi: 10.1007/s13131-022-2137-7
[Abstract](202) [FullText HTML](75)
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Sea fog is a disastrous weather phenomenon, posing a risk to the safety of maritime transportation. Dense sea fogs reduce visibility at sea and have frequently caused ship collisions. This study used a geographically weighted regression (GWR) model to explore the spatial non-stationarity of near-miss collision risk, as detected by a vessel conflict ranking operator (VCRO) model from automatic identification system (AIS) data under the influence of sea fog in the Bohai Sea. Sea fog was identified by a machine learning method that was derived from Himawari-8 satellite data. The spatial distributions of near-miss collision risk, sea fog, and the parameters of GWR were mapped. The results showed that sea fog and near-miss collision risk have specific spatial distribution patterns in the Bohai Sea, in which near-miss collision risk in the fog season is significantly higher than that outside the fog season, especially in the northeast (the sea area near Yingkou Port and Bayuquan Port) and the southeast (the sea area near Yantai Port). GWR outputs further indicated a significant correlation between near-miss collision risk and sea fog in fog season, with higher R-squared (0.890 in fog season, 2018), than outside the fog season (0.723 in non-fog season, 2018). GWR results revealed spatial non-stationarity in the relationships between-near miss collision risk and sea fog and that the significance of these relationships varied locally. Dividing the specific navigation area made it possible to verify that sea fog has a positive impact on near-miss collision risk.
Retrieval of snow depth on Antarctic sea ice from the FY-3D MWRI data
Zhongnan Yan, Xiaoping Pang, Qing Ji, Yizhuo Chen, Chongxin Luo, Pei Fan, Zeyu Liang
 doi: 10.1007/s13131-023-2179-5
[Abstract](278) [FullText HTML](120)
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The snow depth on sea ice is an extremely critical part of the cryosphere. Monitoring and understanding changes of snow depth on Antarctic sea ice is beneficial for research on sea ice and global climate change. The Microwave Radiation Imager (MWRI) sensor aboard the Chinese FengYun-3D (FY-3D) satellite has great potential for obtaining information of the spatial and temporal distribution of snow depth on the sea ice. By comparing in-situ snow depth measurements during the 35th Chinese Antarctic Research Expedition (CHINARE-35), we took advantage of the combination of multiple gradient ratio (GR (36V, 10V) and GR (36V, 18V)) derived from the measured brightness temperature of FY-3D MWRI to estimate the snow depth. This method could simultaneously introduce the advantages of high and low GR in the snow depth retrieval model and perform well in both deep and shallow snow layers. Based on this, we constructed a novel model to retrieve the FY-3D MWRI snow depth on Antarctic sea ice. The new model validated by the ship-based observational snow depth data from CHINARE-35 and the snow depth measured by snow buoys from the Alfred Wegener Institute (AWI) suggest that the model proposed in this study performs better than traditional models, with root mean square deviations (RMSDs) of 8.59 cm and 7.71 cm, respectively. A comparison with the snow depth measured from Operation IceBridge (OIB) project indicates that FY-3D MWRI snow depth was more accurate than the released snow depth product from the U.S. National Snow and Ice Data Center and the National Tibetan Plateau Data Center. The spatial distribution of the snow depth from FY-3D MWRI agrees basically with that from ICESat-2; this demonstrates its reliability for estimating Antarctic snow depth, and thus has great potential for understanding snow depth variations on Antarctic sea ice in the context of global climate change.
A typhoon-induced storm surge numerical model with GPU acceleration based on an unstructured spherical centroidal Voronoi tessellation grid
Yuanyong Gao, Fujiang Yu, Cifu Fu, Jianxi Dong, Qiuxing Liu
 doi: 10.1007/s13131-023-2175-9
[Abstract](146) [FullText HTML](60)
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Storm surge is often the marine disaster that poses the greatest threat to life and property in coastal areas. Accurate and timely issuance of storm surge warnings to take appropriate countermeasures is an important means to reduce storm surge-related losses. Storm surge numerical models are important for storm surge forecasting. To further improve the performance of the storm surge forecast models, we developed a numerical storm surge forecast model based on an unstructured spherical centroidal Voronoi tessellation (SCVT) grid. The model is based on shallow water equations in vector-invariant form, and is discretized by Arakawa C grid. The SCVT grid can not only better describe the coastline information but also avoid rigid transitions, and it has a better global consistency by generating high-resolution grids in the key areas through transition refinement. In addition, the simulation speed of the model is accelerated by using the openACC-based GPU acceleration technology to meet the timeliness requirements of operational ensemble forecast. It only takes 37 seconds to simulate a day in the coastal waters of China. The newly developed storm surge model was applied to simulate typhoon-induced storm surges in the coastal waters of China. The hindcast experiments on the selected representative typhoon-induced storm surge processes indicate that the model can reasonably simulate the distribution characteristics of storm surges. The simulated maximum storm surges and their occurrence times are consistent with the observed data at the representative tide gauge stations, and the mean absolute errors are 3.5 cm and 0.6 h respectively, showing high accuracy and application prospects.
Modeling wave attenuation by vegetation with accompanying currents in SWAN
Hong Wang, Zhan Hu
 doi: 10.1007/s13131-023-2199-1
[Abstract](293) [FullText HTML](130)
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Coastal wetlands such as salt marshes and mangroves provide important protection against stormy waves. Accurate assessments of wetlands’ capacity in wave attenuation are required to safely utilize their protection services. Recent studies have shown that tidal currents have a significant impact on wetlands’ wave attenuation capacity, but such impact has been rarely considered in numerical models, which may lead to overestimation of wave attenuation in wetlands. This study modified the SWAN (Simulating Waves Nearshore) model to account for the effect of accompanying currents on vegetation-induced wave dissipation. Furthermore, this model was extended to include automatically derived vegetation drag coefficients, spatially varying vegetation height, and Doppler Effect in combined current-wave flows. Model evaluation against an analytical model and flume data shows that the modified model can accurately simulate wave height change in combined current-wave flows. Subsequently, we applied the new model to a mangrove wetland on Hailing Island in China with a special focus on the effect of currents on wave dissipation. It is found that the currents can either increase or decrease wave attenuation depending on the ratio of current velocity to the amplitude of the horizontal wave orbital velocity, which is in good agreement with field observations. Lastly, we used Hailing Island site as an example to simulate wave attenuation by vegetation under hypothetical storm surge conditions. Model results indicate that when currents are 0.08–0.15 m/s and the incident wave height is 0.75–0.90 m, wetlands’ wave attenuation capacity can be reduced by nearly 10% compared with pure wave conditions, which provides implications for critical design conditions for coastal safety. The obtained results and the developed model are valuable for the design and implementation of wetland-based coastal defense. The code of the developed model has been made open source, in the hope to assist further research and coastal management.
A VGGNet-based correction for satellite altimetry-derived gravity anomalies to improve the accuracy of bathymetry to depths of 6 500 m
Xiaolun Chen, Xiaowen Luo, Ziyin Wu, Xiaoming Qin, Jihong Shang, Huajun Xu, Bin Li, Mingwei Wang, Hongyang Wan
 doi: 10.1007/s13131-023-2203-9
[Abstract](196) [FullText HTML](76)
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Understanding the topographic patterns of the seafloor is a very important part of understanding our planet. Although the science involved in bathymetric surveying has advanced much over the decades, less than 20% of the seafloor has been precisely modeled to date, and there is an urgent need to improve the accuracy and reduce the uncertainty of underwater survey data. In this study, we introduce a pretrained VGGNet method based on deep learning. To apply this method, we input gravity anomaly data derived from ship measurements and satellite altimetry into the model and correct the latter, which has a larger spatial coverage, based on the former, which is considered the true value and is more accurate. After obtaining the corrected high-precision gravity model, it is inverted to the corresponding bathymetric model by applying the gravity-depth correlation. We choose four data pairs collected from different environments, i.e., the Southern Ocean, Pacific Ocean, Atlantic Ocean and Caribbean Sea, to evaluate the topographic correction results of the model. The experiments show that the R2 reaches 0.834 among the results of the four experimental groups, signifying a high correlation. The standard deviation (SD) and normalized root mean square error (NRMSE) are also evaluated, and the accuracy of their performance improved by up to 24.2% compared with similar research done in recent years. The evaluation of the R2 values at different water depths shows that our model can achieve performance results above 0.90 at certain water depths and can also significantly improve results from mid-water depths when compared to previous research. Finally, the bathymetry corrected by our model is able to show an accuracy improvement level of more than 21% within 1% of the total water depths, which is sufficient to prove that the VGGNet-based method has the ability to perform a gravity-bathymetry correction and achieve outstanding results.
Three-dimensional constrained gravity inversion of Moho depth and crustal structural characteristics at Mozambique continental margin
Shihao Yang, Zhaocai Wu, Yinxia Fang, Mingju Xu, Jialing Zhang, Fanlin Yang
 doi: 10.1007/s13131-023-2220-8
[Abstract](208) [FullText HTML](57)
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Mozambique’s continental margin in East Africa was formed during the break-off stage of the east and west Gondwana lands. Studying the geological structure and division of continent-ocean boundary (COB) in Mozambique’s continental margin is considered of great significance to rebuild Gondwana land and understand its movement mode. Along these lines, in this work, the initial Moho was fit using the known Moho depth from reflection seismic profiles, and a 3D multi-point constrained gravity inversion was carried out. Thus, high-accuracy Moho depth and crustal thickness in the study area were acquired. According to the crustal structure distribution based on the inversion results, the continental crust at the narrowest position of the Mozambique Channel was detected. According to the analysis of the crustal thickness, the Mozambique ridge is generally oceanic crust and the COB of the whole Mozambique continental margin is divided.
Differences in Spring Precipitation over Southern China associated with Multiyear La Niña Events
Guangliang Li, Licheng Feng, Wei Zhuang, Fei Liu, Ronghua Zhang, Cuijuan Sui
 doi: 10.1007/s13131-023-2147-0
[Abstract](483) [FullText HTML](188)
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Composite analyses were performed in this study to reveal the differences in spring precipitation over southern China during multiyear La Niña events from 1901-2015. It was found that there is significantly below normal precipitation in the first boreal spring, but above normal in the second year. The differences in spring precipitation over southern China are correlative to the changes in anomalous atmospheric circulations over the northwest Pacific, which can in turn be attributed to different anomalous sea surface temperatures (SSTs) over the tropical Pacific. During multiyear La Niña events, anomalous SSTs were stronger in the first spring than those in the second spring. As a result, the intensity of abnormal cyclones (WNPC) in the western North Pacific Ocean (WNP) in the first year is stronger, which is more likely to reduce moisture transport, leading to prolonged precipitation deficits over southern China. In contrast, the tropical SST signal is too weak to induce appreciable changes in the WNPC and precipitation over South China in the second year. The difference in SST signals in two consecutive springs leads to different spatial patterns of precipitation in southern China by causing different WNPC.
Erratum to: Acta Oceanologica Sinica (2022) 41(10): 119–130DOI: 10.1007/s13131-022-2023-3The atmospheric hinder for intraseasonal sea-air interaction over the Bay of Bengal during Indian summer monsoon in CMIP6
Ze Meng, Lei Zhou, Baosheng Li, Jianhuang Qin, Juncheng Xie
 doi: 10.1007/s13131-022-2131-0
[Abstract](168) [FullText HTML](53)
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Forecasting the western Pacific subtropical high index during typhoon activity using a hybrid deep learning model
Jianyin Zhou, Jie Xiang, Huadong Du, Suhong Ma
[Abstract](325) [FullText HTML](121)
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Seasonal location and intensity changes in the western Pacific subtropical high (WPSH) are important factors dominating the synoptic weather and the distribution and magnitude of precipitation in the rain belt over East Asia. Therefore, this article delves into the forecast of the western Pacific subtropical high index during typhoon activity by adopting a hybrid deep learning model. Firstly, the predictors, which are the inputs of the model, are analysed based on three characteristics: the first is the statistical discipline of the WPSH index anomalies corresponding to the three types of typhoon paths; the second is the correspondence of distributions between sea surface temperature (SST), 850 hPa zonal wind (u), meridional wind (v), and 500 hPa potential height field; and the third is the numerical sensitivity experiment, which reflects the evident impact of variations in the physical field around the typhoon to the WPSH index. Secondly, the model is repeatedly trained through the backward propagation algorithm to predict the WPSH index using 2011-2018 atmospheric variables as the input of the training set. The model predicts the WPSH index after 6 h, 24 h, 48 h, and 72 h. The validation set using independent data in 2019 is utilized to illustrate the performance. Finally, the model is improved by changing the CNN2D module to the DeCNN module to enhance its ability to predict images. Taking the 2019 Typhoon Lekima as an example, it shows the promising performance of this model to predict the 500 hPa potential height field.
Diversity of protease-producing bacteria in the Bohai Bay sediment and their extracellular enzymatic properties
Zhenpeng Zhang, Chaoya Wu, Shuai Shao, Wei Liu, En-Tao Wang, Yan Li
 doi: 10.1007/s13131-020-1589-x
[Abstract](627) [FullText HTML](184)
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Protease-producing bacteria play key roles in the degradation of organic nitrogen materials in marine sediments. However, their diversity, production of proteases and other extracellular enzymes, even in situ ecological functions remain largely unknown. In this study, we investigated the diversity of cultivable extracellular protease-producing bacteria in the sediments of the Bohai Bay. A total of 109 bacterial isolates were obtained from the sediments of 7 stations. The abundance of cultivable protease-producing bacteria was about 104 CFU/g of sediment in all the samples. Phylogenetic analysis based on 16S rRNA gene sequences classified all the isolates into 14 genera from phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria, with Pseudoalteromonas (63/109, 57.8%), Bacillus (9/109, 8.2%), Sulfitobacter (8/109, 7.3%) and Salegentibacter (6/109, 5.5%) as the dominant taxa. Enzymatic inhibition tests indicated that all the tested isolates produced serine and/or metalloprotease, with only a small proportion producing cysteine and/or aspartic proteases. Several extracellular enzyme activities, including alginase, lipase, amylase and cellulose, and nitrate reduction were also detected for strains with higher protease activities. According the results, the protease-producing bacteria could also be participate in many biogeochemical processes in marine sediments. Our study broadened understanding and knowledge on the potential ecological functions of protease-producing bacteria in marine sediments.
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2023, 42(11).  
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2023-11 Contents
2023, 42(11): 1-2.  
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Review$Marine Biology
Hepatic caecum of amphioxus and origin of vertebrate liver
Shicui Zhang, Zhaokang Shen, Haifeng Li
2023, 42(11): 1-8.   doi: 10.1007/s13131-023-2259-6
[Abstract](39) [FullText HTML](19) [PDF 0KB](2)
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Liver is characteristic of all vertebrates. As a critical hub for many physiological processes including metabolism, innate immunity, protein synthesis and detoxification, its evolutionary origin was largely underappreciated in history, and only received due attention in recent decades. It has been suggested by morphological, ultrastructural and immunohistochemical studies that the hepatic caecum of amphioxus is homologous to the liver of vertebrate species. Molecular biology studies demonstrated that amphioxus hepatic caecum expresses plenty of vertebrate liver-specific genes. Our functional studies revealed significant similarities between amphioxus hepatic caecum and vertebrate liver. We also found that the functions of hepatic caecum are subjected to the regulation of pituitary hormones just as the liver does. These provide solid evidences supporting the notion that the hepatic caecum is the homologue of liver, which may represent the first stage in chordate evolution, laying a foundation for the subsequent formation of the liver as we know it in vertebrates. Further studies on the specification and morphogenesis of hepatic caecum in amphioxus will shed more lights on the origin and evolution of vertebrate liver.
Articles$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
[Abstract](118) [FullText HTML](52) [PDF 0KB](17)
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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
[Abstract](81) [FullText HTML](33) [PDF 0KB](9)
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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
[Abstract](113) [FullText HTML](55) [PDF 0KB](15)
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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
[Abstract](78) [FullText HTML](32) [PDF 0KB](7)
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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
[Abstract](178) [FullText HTML](77) [PDF 0KB](16)
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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
[Abstract](86) [FullText HTML](35) [PDF 0KB](2)
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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
[Abstract](40) [FullText HTML](19) [PDF 0KB](0)
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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
[Abstract](80) [FullText HTML](31) [PDF 0KB](5)
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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
[Abstract](86) [FullText HTML](38) [PDF 0KB](1)
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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
[Abstract](76) [FullText HTML](36) [PDF 0KB](14)
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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
[Abstract](24) [FullText HTML](12) [PDF 0KB](0)
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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
[Abstract](105) [FullText HTML](51) [PDF 0KB](16)
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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
[Abstract](68) [FullText HTML](31) [PDF 0KB](5)
Abstract:
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
[Abstract](71) [FullText HTML](25) [PDF 0KB](2)
Abstract:
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.

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