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).
Display Method:
Corrections of shipboard GPS radiosonde soundings and applications on historical records in the eastern tropical Indian Ocean and South China Sea
Zewen Wu, Xin Liu, Yunkai He, Haoyu Jiang, Bo Peng, Ke Huang
 doi: 10.1007/s13131-024-2361-4
[Abstract](104) [FullText HTML](45)
Abstract:
Shipboard radiosonde soundings are important for detecting and quantifying the multiscale variability of atmosphere-ocean interactions associated with mass exchanges. This study evaluated the accuracies of shipboard global positioning system (GPS) soundings in the eastern tropical Indian Ocean and South China Sea through a simultaneous balloon-borne inter-comparison of different radiosonde types. Our results indicate that the temperature and relative humidity (RH) measurements of GPS-TK radiosonde (used at most stations before 2012) have larger biases than those of CF-06-A radiosonde (widely used in current observation) when compared to reference data from Vaisala RS92-SGP radiosonde, with a warm bias of 5℃ and dry bias of 10% during daytimes, and a cooling bias of –0.8℃ and a moist bias of 6% during nighttime. These systematic biases are primarily attributed to the radiation effects and altitude deviation. An empirical correction algorithm was developed to retrieve the atmospheric temperature and RH profiles. The corrected profiles agree well with that of RS92-SGP, except for uncertainties of CF-06-A in the stratosphere. These correction algorithms were applied to the GPS-TK historical sounding records, reducing biases in the corrected temperature and RH profiles when compared to radio occultation data. The correction of GPS-TK historical records illustrated an improvement in capturing the marine atmospheric structure, with more accurate atmospheric boundary layer height, convective available potential energy, and convective inhibition in the tropical ocean. This study contributes significantly to improving the quality of GPS radiosonde soundings and promotes the sharing of observation in the eastern tropical Indian Ocean and South China Sea.
Cold filament frontogenesis and frontolysis induced by thermal convection turbulence using large eddy simulation
Zewen Wu, Guojing Li, Yunkai He, Jintuan Zhang
 doi: 10.1007/s13131-024-2357-0
[Abstract](111) [FullText HTML](44) [PDF 1908KB](5)
Abstract:
The frontogenetic processes of a submesoscale cold filament driven by the thermal convection turbulence are studied by a non-hydrostatic large eddy simulation. The results show that the periodic changes in the direction of the cross-filament secondary circulations are induced by the inertial oscillation. The change in the direction of the secondary circulations induces the enhancement and reduction of the horizontal temperature gradient during the former and later inertial period, which indicates that the frontogenetical processes of the cold filament include both of frontogenesis and frontolysis. The structure of the cold filament may be broken and restored by frontogenesis and frontolysis, respectively. The magnitude of the down-filament currents has a periodic variation, while its direction is unchanged with time. The coupling effect of the turbulent mixing and the frontogenesis and frontolysis gradually weakens the temperature gradient of the cold filament with time, which reduces frontogenetical intensity and enlarges the width of cold filament.
Tide simulation in a global eddy-resolving ocean model
Zhiwei Tian, Caixia Wang, Zipeng Yu, Hailong Liu, Pengfei Lin, Zhuhua Li
 doi: 10.1007/s13131-024-2352-5
[Abstract](137) [FullText HTML](41) [PDF 12857KB](15)
Abstract:
The tide plays a pivotal role in the ocean, affecting the global ocean circulation and supplying the bulk of the energy for the global meridional overturning circulation. To further investigate internal tides and their impacts on circulation, it is imperative to incorporate tidal forcing into the eddy-resolving global ocean circulation model. In this study, we successfully incorporated explicit tides (eight major constituents) into a global eddy-resolving general ocean circulation model and evaluated its tidal simulation ability. We obtained harmonic constants by analyzing sea surface height through tidal harmonic analysis and compared them with the analysis data Topex Poseidon Cross-Overs v9 (TPXO9), the open ocean tide dataset from 102 open-ocean tide observations, and tide gauge stations from World Ocean Circulation Experiment. The results demonstrated that LASG/IAP Climate System Ocean Model 3.0 (LICOM3.0) effectively simulated tides, with errors predominantly occurring in nearshore regions. The tidal amplitude simulated in LICOM3.0 was greater than that of TPXO9, and these high-amplitude areas exhibited greater errors. The amplitude error of the M2 constituent was larger, while the phase error of the K1 constituent was more significant. Furthermore, we further compared our results with those from other models.
Contribution of the winter salinity barrier layer to summer ocean-atmosphere variability in the Bay of Bengal
Shanshan Pang, Xidong Wang, Gregory R. Foltz, Kaigui Fan
 doi: 10.1007/s13131-024-2360-5
[Abstract](98) [FullText HTML](41) [PDF 7210KB](5)
Abstract:
It is found that the winter (December–February) barrier layer (BL) in the Bay of Bengal (BoB) acts as a dynamical thermostat, modulating the subsequent summer BoB sea surface temperature (SST) variability and potentially affecting the Indian summer monsoon (ISM) onset and associated rainfall variability. In the years when the prior winter BL is anomalously thick, anomalous sea surface cooling caused by intensified latent heat flux loss appears in the BoB starting in October and persists into the following year by positive cloud-SST feedback. During January–March, the vertical entrainment of warmer subsurface water induced by the anomalously thick BL acts to damp excessive cooling of the sea surface caused by atmospheric forcing and favors the development of deep atmospheric convection over the BoB. During March–May, the thinner mixed layer linked to the anomalously thick BL allows more shortwave radiation to penetrate below the mixed layer. This tends to maintain existing cold SST anomalies, advancing the onset of ISM and enhancing June ISM precipitation through an increase in the land-sea tropospheric thermal contrast. We also find that most of the coupled model intercomparison project phase 5 (CMIP5) models fail to reproduce the observed relationship between June ISM rainfall and the prior winter BL thickness. This may be attributable to their difficulties in realistically simulating the winter BL in the BoB and ISM precipitation. The present results indicate that it is important to realistically capture the winter BL of the BoB in climate models for improving the simulation and prediction of ISM.
Mangrove monitoring and extraction based on multi-source remote sensing data: A deep learning method based on SAR and optical image fusion
Yiheng Xie, Xiaoping Rui, Yarong Zou, Heng Tang, Ninglei Ouyang
 doi: 10.1007/s13131-024-2356-1
[Abstract](140) [FullText HTML](58) [PDF 26253KB](18)
Abstract:
Mangroves are indispensable to coastlines, maintaining biodiversity, and mitigating climate change. Therefore, improving the accuracy of mangrove information identification is crucial for their ecological protection. Aiming at the limited morphological information of synthetic aperture radar (SAR) images, which is greatly interfered by noise, and the susceptibility of optical images to weather and lighting conditions, this paper proposes a pixel-level weighted fusion method for SAR and optical images. Image fusion enhanced the target features and made mangrove monitoring more comprehensive and accurate. To address the problem of high similarity between mangrove forests and other forests, this paper is based on the U-Net convolutional neural network, and an attention mechanism is added in the feature extraction stage to make the model pay more attention to the mangrove vegetation area in the image. In order to accelerate the convergence and normalize the input, batch normalization (BN) layer and Dropout layer are added after each convolutional layer. Since mangroves are a minority class in the image, an improved cross-entropy loss function is introduced in this paper to improve the model’s ability to recognize mangroves. The AttU-Net model for mangrove recognition in high similarity environments is thus constructed based on the fused images. Through comparison experiments, the overall accuracy of the improved U-Net model trained from the fused images to recognize the predicted regions is significantly improved. Based on the fused images, the recognition results of the AttU-Net model proposed in this paper are compared with its benchmark model, U-Net, and the Dense-Net, Res-Net, and Seg-Net methods. The AttU-Net model captured mangroves’ complex structures and textural features in images more effectively. The average OA, F1-score, and Kappa coefficient in the four tested regions were 94.406%, 90.006%, and 84.045%, which were significantly higher than several other methods. This method can provide some technical support for the monitoring and protection of mangrove ecosystems.
Nutrient dynamics and cross shelf transport in the East China Sea
Shuhang Dong, Sumei Liu, Jingling Ren, Feng Zhou, Jing Zhang
[Abstract](98) [FullText HTML](47)
Abstract:
To understand the temporal and spatial variations in nutrient dynamics, as well as the potential cross-shelf transport of nutrients between the East China Sea (ECS) shelf and the Northwestern Pacific Ocean, six field observations covering the ECS were conducted in spring, summer, and autumn in 2011 and 2013. Nutrient dynamics in the ECS and nutrient exchange between shelf water and the open ocean were examined. High concentrations of dissolved inorganic nutrients were detected in the nearshore surface layer and offshore bottom layer in different seasons, and the concentrations of dissolved inorganic nutrients in surface seawater were lower in summer and autumn than in spring. The concentrations of dissolved organic nutrients in Kuroshio surface water were slightly lower in summer than in spring, but the concentrations in Kuroshio subsurface water were slightly higher in summer than in spring. There were abundant nutrient reservoirs in the euphotic zone of the ECS, which explained the high primary productivity. The evaluation of cross-shelf transport indicated that nutrients from shelf water were transported out across the 200 m isobath through the surface layer with the σ less than 23.0 kg/m3 in spring. The flux of dissolved inorganic nitrogen transported from the East China Sea shelf to the Northwest Pacific Ocean in spring was equivalent to 21% of the atmospheric nitrogen deposition in the Northwest Pacific Ocean. In summer, the onshore flux in the surface and bottom layers accounted for 80% of the total flux, and the transportation of nutrients along the surface layer to the continental shelf contributed to the nutrient storage and primary productivity of the euphotic zone in the ECS shelf in summer.
Stratification in central Bohai Sea and how it has shaped hypoxic events in summer
Jie Guo, Diansheng Ji, Xiangyang Zheng, Yanfang Li, Haitian Tang, Chawei Hou
 doi: 10.1007/s13131-024-2362-3
[Abstract](167) [FullText HTML](69)
Abstract:
In the last 10 years (2012–2021), five hypoxic events have been observed in summer in the central Bohai Sea (CBS). Frequent and persistent hypoxia will have an impact on the ecosystem of the CBS. In this paper, historical sea temperature (ST), salinity (SAL), density (Den), and dissolved oxygen (DO) concentration data from three stations in the CBS are analyzed via the linear regression method, and the correlations between the stratification factors (ST, SAL, and Den) and DO concentration are determined. The thresholds of the stratification factors at the three stations in June in the year in which hypoxia occurred were determined and applied to survey data from 29 stations in late May to early June in 2022 in the CBS; this assessment found that the data from 19 stations indicated that hypoxia was about to occur. In August, the survey data showed that 14 out of the 29 stations indicated hypoxic conditions, of which 12 were from the predicted 19 stations, meaning that the estimation accuracy reached 63%. The same approach was applied to data from June 2023. The data for August from a bottom-type online monitoring system in the CBS verified the occurrence of hypoxic events around Station M2. The results show that the strength of the seawater stratification plays a leading role in hypoxic events in the summer in the CBS, and the thresholds of the stratification factors can be used to predict the occurrence of hypoxic events.
Dynamic of phytoplankton community during varying intensities of the northeast monsoon in the Taiwan Strait
Yanping Zhong, Peixuan Wang, Jinxin Chen, Xin Liu, Edward A. Laws, Bangqin Huang
 doi: 10.1007/s13131-024-2381-0
[Abstract](102) [FullText HTML](43)
Abstract:
The characteristics of the terrain of a strait can lead to a “fine tube” effect that enhances a monsoon and thereby affects the physical, chemical, and biological processes of marine ecosystems. This effect is a highly dynamic and complex phenomenon involving interactions among atmospheric, oceanic, and terrestrial systems, as well as biogeochemical cycles and biological responses driven by it. However, current understanding has been focused mainly on the differences between monsoons, and there have been few studies concerned with the weakening or strengthening of monsoons. To explore the biogeochemical and phytoplankton responses during varying intensities of the northeast (NE) monsoon in the Taiwan Strait (TWS), high-resolution, across-front observations combined with FerryBox online data and satellite observations were conducted in this study during a strong, moderate, and weak NE monsoon. The spatiotemporal changes of nutrient concentrations and phytoplankton communities were regulated by the dynamics of ocean currents forced by NE winds. The weakening of the NE monsoon caused shrinkage of the coastal currents that led to a reduction of nutrient concentrations and an alteration of the distribution patterns of phytoplankton communities along cross-front sections. Specifically, there was a notable decrease in the proportions of dinoflagellates and cryptophytes in inshore regions and of prasinophytes in offshore areas. This study showed for the first time the dynamics of phytoplankton with changes of ocean currents during varying intensities of the NE monsoon in a strait system. The findings helped to elucidate the general spatial patterns of the phytoplankton community based on satellite-derived surface temperature and wind patterns and further enhanced the understanding of biogeochemical cycles in marine systems.
Spatiotemporal distribution patterns of macrobenthic communities and their relationship with environmental factors in the Shengsi Archipelago (Zhejiang, China)
Lingxiang Jin, Yibo Liao, Peisong Yu, Yanbin Tang, Qinghe Liu, Rongliang Zhang, Lu Shou, Jiangning Zeng, Quanzhen Chen
 doi: 10.1007/s13131-024-2303-1
[Abstract](155) [FullText HTML](60)
Abstract:
Macrobenthic organisms are commonly employed as biomonitors for environmental risk assessment. In this study, we aimed to investigate the spatial and temporal patterns of the macrobenthic community, which is influenced by environmental factors of sediments and bottom water layer. We sampled a total of 12, 11, 10, and 11 stations in the Shengsi Archipelago during June 2010, August 2010, November 2020, and April 2021 respectively. A total of 124 species of macrobenthos were identified, with polychaetes being the dominant group. The abundance, biomass, and diversity indices exhibited no significant temporal differences. Similarly, biodiversity did not exhibit a clear spatial gradient, likely due to the small study area and the absence of significant differences in key factors such as depth. However, the stations with the lowest biodiversity values consistently appeared in the southwest region, possibly due to the impact of human activities. Significant differences in the macrobenthic community were observed between all months except between June and August, and mollusk Endopleura lubrica and polychaete Sigambra hanaokai were important contributors to these differences according to the results of the Similarity Percentages analysis. Suspended particulate matter (SPM) was identified as the primary driving factors of macrobenthic variability. In summary, the community structure underwent temporal changes influenced by complex current patterns, while biodiversity remained relatively stable. This study contributes to our understanding of the key environmental factors affecting macrobenthic communities and biodiversity. It also provides valuable data support for the long-term monitoring of macrobenthos and the environment in the Shengsi Archipelago.
Influence of typhoon “MITAG” on the Kuroshio intrusion in the Luzon Strait during early fall 2019
Meng Liu, Fukang Qi, Yunpeng Lin, Yuping Yang, Jingping Xu
 doi: 10.1007/s13131-024-2350-7
[Abstract](178) [FullText HTML](80)
Abstract:
Typhoons in the Western Pacific have a significant impact on the transport of heat, salt and particles through the Luzon Strait. However, there are very limited field observations of this impact because of extreme difficulties and even dangers for ship-based measurements during the rough weather. Here, we present the preliminary results from analyzing a dataset collected by a glider deployed west of the Luzon Strait a few days prior to the arrival of typhoon “MITAG”. The gilder data revealed an abnormally salinity (>34.8) subsurface water apparently sourced from Kuroshio intrusion during the typhoon. When typhoon “MITAG” traveled on the east of the Luzon Strait, the positive wind stress curl strengthened the cyclonic eddy and weakened the anti-cyclonic eddy. This led to a slowdown of Kuroshio and made its intrusion easier. The main axis of the Kuroshio at the northern part of the strait shifted westward after the typhoon and did not return to its original position until a week later. The Ekman transport from persistent northerly wind of typhoon “MITAG” was significant, but its importance in enhancing the Kuroshio intrusion is only secondary relative to the eddies variations.
Influence of mixed layer depth on chlorophyll-a concentration in the Southern Ocean
Yuxin Shi, Hailong Liu, Quanan Zheng
 doi: 10.1007/s13131-024-2353-4
[Abstract](208) [FullText HTML](76)
Abstract:
The element iron limitation is one of the crucial factors contributing to High Nutrient Low Chlorophyll in the Southern Ocean (SO). Mixed layer dynamics regulate the availability of iron to phytoplankton. In this study, we investigate the influence of surface iron supplementation triggered by the mixed layer depth (MLD) variation on chlorophyll-a concentration (Chl-a) in the SO on seasonal and interannual timescales. This analysis is based on the Biogeochemical Southern Ocean State Estimate for the period from 2013 to 2021. We provide a comprehensive and systematic mapping of the regions within the SO, where Chl-a is affected by iron input related to MLD deepening. The relationship between the MLD and the Chl-a varies with the latitude on the seasonal time scale. Both the MLD and sea ice melting affect the distribution of Chl-a. On the interannual scale, iron supply due to MLD deepening occurs primarily north of 60°S. Horizontal advection-induced entrainment enhances the surface iron input during the austral summer, which favors Chl-a increase. In addition to the MLD, the melting of sea ice and cooling of the sea surface can also alter iron input and subsequently affect Chl-a distribution in the austral summer. During the austral winter, entrainment can boost iron stocks, stimulating a subsequent spring increase of Chl-a in the SO. Furthermore, sea surface temperature declines during the austral winter, promoting an increased iron supply and creating favorable conditions for the subsequent spring Chl-a increase in the SO.
Forecasting of surface current velocities using ensemble machine learning algorithms for the Guangdong-Hong Kong-Macao Greater Bay Area based on the High Frequency radar data
Lei Ren, Lingna Yang, Yaqi Wang, Peng Yao, Jun Wei, Fan Yang, Fearghal O’ Donncha
 doi: 10.1007/s13131-024-2363-2
[Abstract](82) [FullText HTML](36)
Abstract:
Forecasting of ocean currents is critical for both marine meteorological research and ocean engineering and construction. Timely and accurate forecasting of coastal current velocities offers a scientific foundation and decision support for multiple practices such as search and rescue, disaster avoidance and remediation, and offshore construction. This research established a framework to generate short-term surface current forecasts based on ensemble machine learning trained on High Frequency radar observation. Results indicate that an ensemble algorithm that used random forests to filter forecasting features by weighting them, and then used the AdaBoost method to forecast can significantly reduce the model training time, while ensuring the model forecasting effectiveness, with great economic benefits. Model accuracy is a function of surface current variability and the forecasting horizon. In order to improve the forecasting capability and accuracy of the model, the model structure of the ensemble algorithm was optimized, and the random forest algorithm was used to dynamically select model features. The results show that the error variation of the optimized surface current forecasting model has a more regular error variation, and the importance of the features varies with the forecasting time-step. At ten-step ahead forecasting horizon the model reported RMSE, MAE and correlation coefficient by 2.84 cm/s, 2.02 cm/s, and 0.96, respectively. The model error is affected by factors such as topography, boundaries, and geometric accuracy of the observation system. This paper demonstrates the potential of ensemble-based machine learning algorithm to improve forecasting of ocean currents.
Accuracy assessment of global vertical displacement loading tide models for the equatorial and Indian Ocean
Xiaoqing Xu, Haidong Pan, Fei Teng, Zexun Wei
 doi: 10.1007/s13131-024-2358-z
[Abstract](108) [FullText HTML](44)
Abstract:
The three-dimensional displacements caused by ocean loading effects are significant enough to impact spatial geodetic measurements on sub-daily or longer timescales, particularly in the vertical direction. Currently, most tide models incorporate the distribution of vertical displacement loading tides; however, their accuracy has not been assessed for the equatorial and Indian Ocean regions. Global Positioning System (GPS) observations provide high-precision data on sea-level changes, enabling the assessment of the accuracy and reliability of vertical displacement tide models. However, because the tidal period of the K2 constituent is almost identical to the orbital period of GPS constellations, the estimation of the K2 tidal constituent from GPS observations is not satisfactory. In this study, the principle of smoothness is employed to correct the systematic error in K2 estimates in GPS observations through quadratic fitting. Using the adjusted harmonic constants from 31 GPS stations for the equatorial and Indian Ocean, the accuracy of eight major constituents from five global vertical displacement tide models (FES2014, EOT11a, GOT4.10c, GOT4.8, and NAO.99b) is evaluated for the equatorial and Indian Ocean. The results indicate that the EOT11a and FES2014 models exhibit higher accuracy in the vertical displacement tide models for the equatorial and Indian Ocean, with root sum squares (RSS) errors of 2.29 mm and 2.34 mm, respectively. Furthermore, a brief analysis of the vertical displacement tide distribution characteristics of the eight major constituents for the equatorial and Indian Ocean was conducted using the EOT11a model.
Assessing the degree of impact from iceberg activities on penguin colonies of Clarence Island
Hong Lin, Xiao Cheng, Teng Li, Qian Shi, Qi Liang, Xinyu Meng, Shaoyin Wang, Lei Zheng
 doi: 10.1007/s13131-024-2355-2
[Abstract](186) [FullText HTML](88)
Abstract:
During August and September 2023, three giant icebergs, each bigger than Paris, successively grazed Clarence Island in the northeast of the Antarctic Peninsula, a home to a population of over 100 000 penguins. This incident may serve as a clarion call for the increasing iceberg calving due to global warming and its subsequent impact on the Antarctic ecosystem. Here we investigate this unexpected event and employ historical records and probabilistic analyses of iceberg grounding to assess the degree of impact on penguin colonies of Clarence Island. Among the eleven colonies, there is one with low impact, eight with medium impact, and two with high impact. The low-impact colony, Cape Lloyd, is located in the northern part of the island, while the high-impact colonies, False Ridge and Pink Pool, are in the southeast. The eight medium-impact colonies are distributed along both the eastern and western coasts of the island. This study provides essential support for evaluating the impact of iceberg activity on penguin colonies. We argue that penguin colonies located in areas prone to iceberg drift, such as Clarence Island, may become more vulnerable to the heightened risk of iceberg collisions or groundings in the warming future. Therefore, we hope the public will become more aware of the grave impacts of climate change on penguins and underscore the urgent need for effective conservation strategies.
Estimating peak wave period from surface texture motion in videos
Haipeng Yu, Xiaoliang Chu, Guang Yuan
 doi: 10.1007/s13131-024-2359-y
[Abstract](97) [FullText HTML](35)
Abstract:
Wave information retrieval from videos captured by a single camera has been increasingly applied in marine observation. However, when the camera observes ocean waves at low grazing angles, the accurate extraction of wave information from videos will be effected by the interference of the fine ripples on the sea surface. To solve this problem, this study develops a method for estimating peak wave periods from videos captured at low grazing angles. The method extracts the motion of the sea surface texture from the video and obtains the peak wave period via the spectral analysis. The calculation results captured from real-world videos are compared with those obtained from X-band radar inversion and tracking buoy movement, with maximum deviations of 8% and 14%, respectively. The analysis of the results shows that the peak wave period of the method has good stability. In addition, this paper uses a pinhole camera model to convert the displacement of the texture from pixel height to actual height and performs moving average filtering on the displacement of the texture, thus conducting a preliminary exploration of the inversion of significant wave height. This study helps to extend the application of sea surface videos.
Observed features of stable surface seawater isotopes across the Pacific, Indian and Southern oceans
Xuemei Wu, Weijun Sun, Biao Tian, Baojuan Huai, Zhiheng Du, Minghu Ding
 doi: 10.1007/s13131-024-2378-8
[Abstract](125) [FullText HTML](47)
Abstract:
The marine hydrological process is still unclear due to scarce observations. Based on stable water isotopes in surface seawater along the 33rd Chinese National Antarctic Science Expedition from November 2016 to April 2017, this study explored the hydrological processes in the Pacific, Indian and Southern Oceans. The results show that the Northwest Pacific (0—26° N) is a region with strong evaporation (the δ18O-δD slope is 6.58), while the southern Indian Ocean is a region with strong precipitation (the δ18O-δD slope is 9.57). The influence of continental runoff and water mass mixing reduces the correlation between δ18O and salinity in the eastern Indian Ocean. The characteristics of the isotopes and hydrological parameters indicate that the Agulhas front and subtropical convergence do not merge in the Antarctic–Indian Ocean region. The freezing of sea ice near the Antarctic continent decreases the δ18O and δD by 0.40‰ and 7.0‰, respectively, compared with those near 67°S. This study is helpful for understanding marine hydrological processes and promoting the understanding and research of the nature of ocean responses in the context of climate change.
Scale effect of coastal landscape pattern stability and driving forces: a case study of Guangdong Province, China
Kanglin Chen, Yushi Li, Jianzhou Gong, Gangte Lin
 doi: 10.1007/s13131-024-2351-6
[Abstract](96) [FullText HTML](42)
Abstract:
The long-term dynamic evolution and underlying mechanisms of coastal landscape pattern stability, driven by strong anthropogenic interference and consequently climate change, are topics of major interest in national and international scientific research. Guangdong Province, located in southeastern China, has been undergoing rapid urbanization over several decades. In this study, we quantitatively determined the scale threshold characteristics of coastal landscape pattern stability in Guangdong Province, from the dual perspective of spatial heterogeneity and spatial autocorrelation. An analysis of the spatiotemporal evolution of the coastal landscape was conducted after the optical scale was determined. Then, we applied the geodetector statistical method to quantitatively explore the mechanisms underlying coastal landscape pattern stability. Based on the inflection point of landscape metrics and the maximum value of the Moran I index, the optimal scale for analyzing coastal landscape pattern stability in Guangdong Province was 240 m × 240 m. Within the past several decades, coastal landscape pattern stability increased slightly and then decreased, with a turning point around 2005. The most significant variations in coastal landscape pattern stability were observed in the transition zone of rural-urban expansion. A q-statistics analysis showed that the explanatory power of paired factors was greater than that of a single driving factor; the paired factors with the greatest impact on coastal landscape pattern stability in Guangdong Province were the change in gross industrial output and change in average annual precipitation from 2010 to 2015, based on a q value of 0.604. These results will contribute to future efforts to achieve sustainable coastal development and provide a scientific basis and technical support for the rational planning and utilization of resources in large estuarine areas, including marine disaster prevention and seawall ecological restoration.
Changes in area fraction of sediment-laden sea ice in the Arctic Ocean during 2000 to 2021
Yuanyang Xie, Tingting Liu, Na Li, Ruibo Lei
[Abstract](270) [FullText HTML](133)
Abstract:
Sediment-laden sea ice plays an important role in Arctic sediment transport and biogeochemical cycles, as well as the shortwave radiation budget and melt onset of ice surface. However, at present, there is a lack of efficient observation approach from both space and in situ for the coverage of Arctic sediment-laden sea ice. Thus, both spatial distribution and long-term changes in area fraction of such ice floes are still unclear. This study proposes a new classification method to extract Arctic sediment-laden sea ice on the basic of the difference in spectral characteristics between sediment-laden sea ice and clean sea ice in the visible band using the MOD09A1 data with the resolution of 500 m, and obtains its area fraction over the pan Arctic Ocean during 2000−2021. Compared with Landsat-8 true color verification images with a resolution of 30 m, the overall accuracy of our classification method is 92.3%, and the Kappa coefficient is 0.84. The impact of clouds on the results of recognition and spatiotemporal changes of sediment-laden sea ice is relatively small from June to July, compared to that in May or August. Spatially, sediment-laden sea ice mostly appears over the marginal seas of the Arctic Ocean, especially the continental shelf of Chukchi Sea and the Siberian Seas. Associated with the retreat of Arctic sea ice extent, the total area of sediment-laden sea ice in June–July also shows a significant decreasing trend of 8.99 × 104 km2 per year. The occurrence of sediment-laden sea ice over the Arctic Ocean in June–July leads to the reduce of surface albedo over the ice-covered ocean by 14.1%. This study will help thoroughly understanding of the role of sediment-laden sea ice in the evolution of Arctic climate system and marine ecological environment, as well as the heat budget and mass balance of sea ice itself.
Preliminary study on the depositional model in the wave-dominated delta evolution during the Anthropocene: a case study of the Hanjiang River Delta in China
Hongyue Wang, Zhongbo Wang, Yang Wang, Haiyan Tang, Xiaodong Zhang, Xiaofeng Luo, Yongxin Mai, Xuhong Huang, Yilin Zheng, Ping Yin, Zhongping Lai
 doi: 10.1007/s13131-024-2313-z
[Abstract](178) [FullText HTML](80) [PDF 2924KB](6)
Abstract:
The deltas serve as the primary interactive zone where terrestrial and marine environments converge, playing a pivotal role in the coastal deposition. In the Holocene, climate changes and sea level fluctuation are the principal driving factors in the evolution of deltas. However, human activities such as the construction of dams and reservoirs in the Anthropocene have significantly altered sediment transport in rivers, leading to depositional pattern variation during deltaic evolution. In this study, we have conducted a comparative analysis of the morphological variations (1986–2021) in the barrier system of the Hanjiang River Delta (HRD) using satellite remote sensing (SRS) method. Additionally, we have examined the lithological changes and facies alterations observed in eight boreholes on the present barrier spit. Our findings indicate that the intensification of anthropogenic activities led to a significant reduction in the sediment flux of the Hanjiang River (HR), resulting in depocenter landward migration at the estuary. SRS analysis reveals their periodical morphological characteristics and spatial variations of estuarine sandbars (1986–1992), barrier islands-lagoons (1993–2009), and barrier spits (2010–2021) during 1986 to 2021. The stratigraphy of boreholes demonstrates a south-to-north facies transition from lagoon to lagoon-barrier spit and barrier spit in vertical lithology. Therefore, the depositional evolution of the HRD barrier system is categorized into three phases: estuarine sandbar-barrier island phase (1986–1998); barrier island-lagoon phase (1999–2009); and barrier spit phase (2010–2021). During the estuarine sandbar-barrier island phase, fluvial processes played a predominate role in the deposition. Consequently, with a significant decrease in river sediment load, the dominant factors driving depositional processes shifted towards wave action and alongshore current. Based on the conceptual model in the Holocene, we propose a modified depositional model of wave-dominated deltas during Anthropocene that encompasses three evolutionary phases: estuarine sandbars and delta front platforms, barrier island-lagoon formation and landward migration of barrier spits. This pattern highlights that human-induced reduction in river sediment flux has led to a seaward deltaic progradation driven by barrier landward migration.
The significant role of submarine groundwater discharge in an Arctic fjord nutrient budget
Xueqing Yu, Jianan Liu, Zhuoyi Zhu, Xiaogang Chen, Tong Peng, Jinzhou Du
 doi: 10.1007/s13131-023-2282-7
[Abstract](176) [FullText HTML](75)
Abstract:
Under global climate change, water flow and related nutrient biogeochemistry in the Arctic are changing at an unprecedented rate, and potentially affect nutrient cycling in the Arctic Ocean. However, nutrient fluxes via submarine groundwater discharge (SGD) are potentially important yet poorly understood in the Arctic. Here we quantified that nutrient fluxes through radium-derived SGD were three orders of magnitude higher than those from the local river and constituted 25-96% of the total nutrient inputs into the Kongsfjorden. These large groundwater nutrient fluxes with high N/P ratio (average 99) may change the biomass and community structure of phytoplankton. Meanwhile, combining other SGD study cases around the Arctic region, SGD rates tend to increase over the past three decades, possibly on account of the effects of global warming. The SGD-derived nutrient may cause the increase of net primary productivity in the Arctic Ocean. The results will provide important basic data for land-ocean interactions in the typical fjord of the Arctic under the influence of global warming.
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](174) [FullText HTML](84)
Abstract:
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.
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](144) [FullText HTML](69)
Abstract:
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.
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](335) [FullText HTML](118)
Abstract:
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](419) [FullText HTML](167)
Abstract:
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](750) [FullText HTML](229)
Abstract:
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.
Display Method:
Cover
2024-8 Cover
2024, 43(8): .  
[Abstract](46) [PDF 8493KB](16)
Abstract:
2024-8 Contents
2024, 43(8): 1-2.  
[Abstract](28) [FullText HTML](12) [PDF 99KB](3)
Abstract:
Articles$Marine Geology
Identification of the Caroline Plate boundary: constraints from magnetic anomaly
Yongtao Fu, Guoliang Zhang, Wanyin Wang, An Yang, Tao He, Zhangguo Zhou, Xiao Han
2024, 43(8): 1-12.   doi: 10.1007/s13131-023-2272-9
[Abstract](254) [FullText HTML](92) [PDF 7998KB](45)
Abstract:
The Caroline Plate is located among the Pacific Plate, the Philippine Sea Plate, and the India Australia Plate, and plays a key role in controlling the spreading direction of the Philippine Sea Plate. The Caroline Submarine Plateau (or Caroline Ridge) and the Eauripik Rise on the south formed a remarkable T-shaped large igneous rock province, which covered the northern boundary between the Caroline Plate and the Pacific Plate. However, relationship between these tectonic units and magma evolution remains unclear. Based on magnetic data from the Earth Magnetic Anomaly Grid (2-arc-minute resolution) (V2), the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) technique was used to study the boundary of the Caroline Plate. Results show that the northern boundary is a transform fault that runs 1400 km long in approximately 28 km wide along the N8° in E-W direction. The eastern boundary is an NNW-SSE trending fault zone and subduction zone with a width of tens to hundreds of kilometers; and the north of N4° is a fracture zone of dense faults. The southeastern boundary may be the Lyra Trough. The area between the southwestern part of the Caroline Plate and the Ayu Trough is occupied by a wide shear zone up to 100 km wide in nearly S-N trending in general. The Eauripik transform fault (ETF) in the center of the Caroline Plate and the fault zones in the east and west basins are mostly semi-parallel sinistral NNW-SSE–trending faults, which together with the eastern boundary Mussau Trench (MT) sinistral fault, the northern Caroline transform fault (CTF), and the southern shear zone of the western boundary, indicates the sinistral characteristics of the Caroline Plate. The Caroline hotspot erupted in the Pacific Plate near the CTF and formed the west Caroline Ridge, and then joined with the Caroline transform fault at the N8°. A large amount of magma erupted along the CTF, by which the east Caroline Ridge was formed. At the same time, a large amount of magma developed southward via the eastern branch of the ETF, forming the northern segment of the Eauripik Rise. Therefore, the magmatic activity of the T-shaped large igneous province is obviously related to the fault structure of the boundary faults between the Caroline Plate and Pacific Plate, and the active faults within the Caroline Plate.
Tomographic inversion of OBS converted shear waves: case study of profile EW6 in the Dongsha area
Genggeng Wen, Kuiyuan Wan, Shaohong Xia, Xiuwei Ye, Huilong Xu, Chaoyan Fan, Jinghe Cao, Shunshan Xu
2024, 43(8): 13-25.   doi: 10.1007/s13131-023-2274-7
[Abstract](143) [FullText HTML](70) [PDF 12099KB](13)
Abstract:
Studies of converted S-wave data recorded on the ocean bottom seismometer (OBS) allow for the estimation of crustal S-wave velocity, from which is further derived the Vp/Vs ratio to constrain the crustal lithology and geophysical properties. Constructing a precise S-wave velocity model is important for deep structural research, and inversion of converted S-waves provides a potential solution. However, the inversion of the converted S-wave remains a weakness because of the complexity of the seismic ray path and the inconsistent conversion interface. In this study, we introduced two travel time correction methods for the S-wave velocity inversion and imaged different S-wave velocity structures in accordance with the corresponding corrected S-wave phases using seismic data of profile EW6 in the northeastern South China Sea (SCS). The two inversion models show a similar trend in velocities, and the velocity difference is <0.15 km/s (mostly in the range of 0–0.1 km/s), indicating the accuracy of the two travel time correction methods and the reliability of the inversion results. According to simulations of seismic ray tracing based on different models, the velocity of sediments is the primary influencing factor in ray tracing for S-wave phases. If the sedimentary layer has high velocities, the near offset crustal S-wave refractions cannot be traced. In contrast, the ray tracing of Moho S-wave reflections was not significantly impacted by the velocity of the sediments. The two travel time correction methods have their own advantages, and the application of different approaches is based on additional requirements. These works provide an important reference for future improvements in converted S-wave research.
Geochemical characteristics and origins of natural gases in the eastern Cote d’Ivoire Basin, West Africa
Li Li, Quan Li, Tao Cheng, Songling Yang, Yong Rao, Xinyu Liu, Wenjing Ding
2024, 43(8): 26-36.   doi: 10.1007/s13131-024-2335-6
[Abstract](128) [FullText HTML](61) [PDF 1397KB](9)
Abstract:
The gas sources in the eastern Cote d’Ivoire Basin (Tano Basin) are seldom reported and remain controversial due to multiple sets of potential source rocks and poorly documented geochemical characteristics of natural gases. The marine source rock potential from the Upper Albian to Turonian as well as the molecular composition and the stable carbon isotope composition of natural gases in the eastern Cote d’Ivoire Basin were studied in detail to investigate the origins of natural gases. The total organic carbon (TOC), hydrogen index (HI), and generation potential (S1 + S2) of source rocks indicate that both sapropelic source rocks and humic source rocks developed during the late Albian, whereas sapropelic source rocks developed during the Cenomanian and the Turonian. The normal order of δ13CH4 < δ13C2H6 < δ13C3H8 (δ13C1 < δ13C2 < δ13C3), the relationship between C2/C3 molar ratio and δ13C2-δ13C3, and the plot of δ13C1 versus C1/(C2+C3) collectively show that the natural gases are thermogenic due to the primary cracking of kerogen, including the typical oil-associated gases from Well D-1, the mixed oil-associated gases and coal-derived gases from Well G-1 and Well L-1. Based on the plot of δ13C1 versus δ13C2 and the established relationship between δ13C1 and equivalent vitrinite reflectance (Ro), we proposed that the natural gases are in a mature stage (Ro generally varies from 1.0% to 1.3%). Combined with results of basin modelling and oil-to-source correlation, the transitional to marine source rocks during the late Albian were thought to have made a great contribution to the natural gases. Our study will make a better understanding on petroleum system in the eastern Cote d’Ivoire Basin.
Application of C30 tetracyclic polyprenoids as effective biomarker in oil-to source rock correlation in the Zhu Ⅲ depression, Zhujiangkou Basin, northern South China
Lei Lan, Youchuan Li, Shuchun Yang, Yang Ouyang, Wenjing Ding, Qing Lin, Shanshan Zhou
2024, 43(8): 37-46.   doi: 10.1007/s13131-024-2346-3
[Abstract](116) [FullText HTML](61) [PDF 1199KB](8)
Abstract:
The northern South China Sea, including the Zhujiangkou Basin and the Beibuwan Basin, developed high-quality lacustrine source rocks during the Eocene rifting period. These source rocks are vital for hydrocarbon generation in the northern South China Sea. The Zhu Ⅰ depression in the Zhujiangkou Basin and the Beibuwan Basin typically exhibit high abundance of C30 4-methyl steranes. However, shales in the Eocene Wenchang Formation in the Zhu Ⅲ depression of the Zhujiangkou Basin contains lower quantities of high-quality lacustrine source rocks with 4-methyl steranes, which often co-elute with some pentacyclic triterpanes in gas chromatography-mass spectrometry (GC-MS). Therefore, the single 4-methylsterane parameter based on GC-MS cannot accurately distinguish organic source in the deep to semi-deep water lacustrine source rocks of the Wenchang Formation from other source rocks, thus impeding the recognition of their contributions to petroleum reservoirs. In this study, GC-MS of aliphatic hydrocarbons, palynofacies and algal identification, as well as stable carbon isotope data of organic matter were used to identify the algal species and construct the paleoclimate during deposition of the Wenchang Formation source rocks in the Zhu Ⅲ depression of the Zhujiangkou Basin. It is suggested that during the Wenchang Formation period, freshwater green algae prevailed in the lake, which is likely account for the relatively low content of 4-methyl steranes in the high-quality lacustrine source rocks. Controlled by the algal species, it is proposed that the content of C30 tetracyclic polyprenoids (TPP) can better indicate the quality of the Wenchang source rocks than C30 4-methyl steranes. Consequently, a relationship between the TPP index and the quality of the lacustrine source rocks in the Wenchang Formation of the Zhu Ⅲ depression was established. A higher TPP index indicates higher organic matter abundance and hydrogen index of the lacustrine source rocks. When applied to the origin analysis of oils in the Zhu Ⅲ depression, it is believed that the organic-rich deep lacustrine source rocks in the Wenchang Formation made great contribution to the transitional zone crude oils in the Wenchang A and Wenchang B depressions.
Diatoms as indicators of environmental change in coastal areas: a case study in Lianjiang coast of East China Sea
Tong Li, Jihui Zhang, Dongling Li, Chengxu Zhou, Chenxi Liu, Hao Xu, Bing Song, Longbin Sha
2024, 43(8): 47-57.   doi: 10.1007/s13131-024-2292-0
[Abstract](244) [FullText HTML](119) [PDF 1618KB](40)
Abstract:
Owing to the significant differences in environmental characteristics and explanatory factors among estuarine and coastal regions, research on diatom transfer functions and database establishment remains incomplete. This study analysed diatoms in surface sediment samples and a sediment core from the Lianjiang coast of the East China Sea, together with environmental variables. Principal component analysis of the environmental variables showed that sea surface salinity (SSS) and sea surface temperature were the most important factors controlling hydrological conditions in the Lianjiang coastal area, whereas canonical correspondence analysis indicated that SSS and pH were the main environmental factors affecting diatom distribution. Based on the modern diatom species–environmental variable database, we developed a diatom-based SSS transfer function to quantitatively reconstruct the variability in SSS between 1984 and 2021 for sediment core HK3 from the Lianjiang coastal area. The agreement between the reconstructed SSS and instrument SSS data from 1984 to 2021 suggests that diatom-based SSS reconstruction is reliable for studying past SSS variability in the Lianjiang coastal area. Three low SSS events in AD 2019, 2013, and 1999, together with an increased relative concentration of freshwater diatom species and coarser sediment grain sizes, corresponded to two super-typhoon events and a catastrophic flooding event in Lianjiang County. Thus, a diatom-based SSS transfer function for reconstructing past SSS variability in the estuarine and coastal areas of the East China Sea can be further used to reflect the paleoenvironmental events in this region.
The occurrence phases and enrichment mechanism of rare earth elements in cobalt-rich crusts from Marcus-Wake Seamounts
Jingjing Gao, Jihua Liu, Hui Zhang, Shijuan Yan, Xiangwen Ren, Quanshu Yan
2024, 43(8): 58-68.   doi: 10.1007/s13131-023-2276-5
[Abstract](25) [FullText HTML](13) [PDF 4720KB](3)
Abstract:
To explore the occurrence phases and enrichment mechanism of rare earth elements (REEs) in cobalt-rich crusts, this study analyzes the mineral composition and REE contents of the samples from Marcus-Wake Seamounts by XRD, ICP-OES and ICP-MS. The results show that, (1) the cobalt-rich crusts contain the major crystalline mineral (vernadite), the secondary minerals (quartz, plagioclase and carbonate fluorapatite), and a large amount of amorphous ferric oxyhydroxides (FeOOH). (2) The cobalt-rich crusts contains higher Mn (10.83% to 28.76%) and Fe (6.14% to 18.86%) relative to other elements, and are enriched in REEs, with total REE contents of 1 563−3 238 µg/g and Ce contents of 790−1 722 µg/g. Rare earth element contents of the old crusts are higher than those of the new crusts. Moreover, the non-phosphatized crusts have positive Ce and negative Y anomalies, and yet the phosphatized crusts have positive Ce and positive Y anomalies, indicating that cobalt-rich crusts is hydrogenetic and REEs mainly come from seawater. (3) Analytical data also show that the occurrence phases of elements in cobalt-rich crusts are closely related to their mineral phases. In the non-phosphatized crusts, REEs are adsorbed by colloidal particles into the crusts (about 67% of REEs in the Fe oxide phase, and about 17% of REEs in the Mn oxide phase). In contrast, in the phosphatized crusts (affected by the phosphatization), REEs may combine with phosphate to form rare earth phosphate minerals, and about 64% of REEs are enriched in the residual phase containing carbonate fluorapatite, but correspondingly the influence of Fe and Mn oxide phases on REEs enrichment is greatly reduced. In addition, the oxidizing environment of seawater, high marine productivity, phosphatization, and slow growth rate can promote the REE enrichment. This study provides a reference for the metallogenesis of cobalt-rich crusts in the Pacific.
Acoustical imaging of the nearshore seafloor depositions and deformations, a key study for Western Istanbul, Türkiye
ÖZGAN Sinan, ALP Hakan, BAYAT Oğuz, VARDAR Denizhan
2024, 43(8): 69-78.   doi: 10.1007/s13131-023-2197-3
[Abstract](362) [FullText HTML](161) [PDF 7847KB](32)
Abstract:
To protect the sustainability of the benefits from seas and near coastal areas, which have under the effect of the very complex hydrodynamic conditions and intensive human activities, without disrupting the balance of nature, it is necessary to image the status of the seafloor features. Therefore, this study presents the deformations, depositional conditions, underwater constructions, and the other non-natural impacts on the seafloor of the nearshore area at western Istanbul (between Küçükçekmece and Büyükçekmece lagoons) where it intensely used by the citizens. The results of the study may provide some guidance for understanding the impacts and risk factors of uses that are or will be conducted in coastal and/or near-coastal areas. Construction planning for civil coastal structures and areas should be done in great harmony with nature, minimizing negative environmental impacts. Although sediment distribution in the area is generally quite complex, the current state of the region, wave action, hydrodynamic conditions, the amount of material transported from the land, and bathymetry are important influencing factors. The seafloor has been damaged primarily by anchor deformation and associated bottom scanning, as well as disturbing trawl tracks. The seafloor was observed as partially shallowing near the constructions (such as natural gas pipelines, fishermen’s shelter, and port piles) of coastal areas and associated with sand deposits. Therefore, scanning the seafloor using side-scan sonar may provide valuable frequency data to prevent future disruptions.
Articles$Marine Biology
Temporal variations of food web in a marine bay ecosystem based on LIM-MCMC model
Pengcheng Li, Hu Zhang, Chongliang Zhang, Binduo Xu, Yupeng Ji, Yiping Ren, Ying Xue
2024, 43(8): 79-88.   doi: 10.1007/s13131-023-2273-8
[Abstract](141) [FullText HTML](55) [PDF 7509KB](9)
Abstract:
Climate change has led to significant fluctuations in marine ecosystems, including alterations in the structure and function of food webs and ecosystem status. Coastal ecosystems are critical to the functioning of the earth’s life-supporting systems. However, temporal variations in most of these ecosystems have remained unclear so far. In this study, we employed a linear inverse model with Markov Chain Monte Carlo (LIM-MCMC) combined with ecological network analysis to reveal the temporal variations of the food web in Haizhou Bay of China. Food webs were constructed based on diet composition data in this ecosystem during the year of 2011 and 2018. Results indicated that there were obvious temporal variations in the composition of food webs in autumn of 2011 and 2018. The number of prey and predators for most species in food web decreased in 2018 compared with 2011, especially for Trichiurus lepturus, zooplankton, Amblychaeturichthys hexanema, and Loligo sp. Ecological network analysis showed that the complexity of food web structure could be reflected by comprehensive analysis of compartmentalized indicators. Haizhou Bay ecosystem was more mature and stable in 2011, while the ecosystem’s self-sustainability and recovery from disturbances were accelerated from 2011 to 2018. These findings contribute to our understanding of the dynamics of marine ecosystems and highlight the importance of comprehensive analysis of marine food webs. This work provides a framework for assessing and comparing temporal variations in marine ecosystems, which provides essential information and scientific guidance for the Ecosystem-based Fisheries Management.
Thiosulfate oxidation and autotrophy potential by marine prevalent heterotrophic bacteria of genus Marinobacter
Fei Xu, Xiang Zeng, Yadong Gong, Zongze Shao
2024, 43(8): 89-97.   doi: 10.1007/s13131-023-2263-x
[Abstract](154) [FullText HTML](75) [PDF 3408KB](6)
Abstract:
The genus Marinobacter is very broadly distributed in global environments and is considered as aerobic heterotroph. In this study, six Marinobacter strains were identified with autotrophic thiosulfate oxidation capacity. These strains, namely Marinobacter guineae M3BT, Marinobacter aromaticivorans D15-8PT, Marinobacter vulgaris F01T, Marinobacter profundi PWS21T, Marinobacter denitrificans JB02H27T, and Marinobacter sp. ST-1M (with a 99.93% similarity to the 16S rDNA sequences of Marinobacter salsuginis SD-14BT), were screened out of 32 Marinobacter strains by autotrophic thiosulfate oxidization medium. The population of cells grew in a chemolithotrophic medium, increasing from 105 cells/mL to 107 cells/mL within 5 d. This growth was accompanied by the consumption of thiosulfate 3.59 mmol/L to 9.64 mmol/L and the accumulation of sulfate up to 0.96 mmol/L, and occasionally produced sulfur containing complex particles. Among these Marinobacter strains, it was also found their capability of oxidizing thiosulfate to sulfate in a heterotrophic medium. Notably, M. vulgaris F01T and M. antarcticus ZS2-30T showed highly significant production of sulfate at 9.45 mmol/L and 3.10 mmol/L. Genome annotation indicated that these Marinobacter strains possess a complete Sox cluster for thiosulfate oxidation. Further phylogenetic analysis of the soxB gene revealed that six Marinobacter strains formed a separate lineage within Gammaproteobacteria and close to obligate chemolithoautotroph Thiomicrorhabdus arctica. The results indicated that thiosulfate oxidizing and chemolithoautotrophic potential in Marinobacter genus, which may contribute to the widespread of Marinobacter in the global ocean.
Frequent recombination in Cynoglossus abbreviatus (Pleuronectiformes: Cynoglossidae) ribosomal 18S rDNA
Li Gong, Tingqi Jiang, Bilin Hu, Kaixin Wang, Nannan Zhang, Zengliang Miao
2024, 43(8): 98-103.   doi: 10.1007/s13131-024-2291-1
[Abstract](126) [FullText HTML](64) [PDF 657KB](2)
Abstract:
The conventional theory of concerted evolution has been used to explain the lack of sequence variation in ribosomal RNA (rRNA) genes across diverse eukaryotic species. However, recent investigations into rRNA genes in flatfish genome have resulted in controversial findings. This study focuses on 18S rRNA genes of the widely distributed tongue sole, Cynoglossus abbreviatus (Pleuronectiformes: Cynoglossidae), aiming to explore sequence polymorphism. Five distinct 18S rDNA sequence types (Type A, B, R1, R2, and R3) were identified, suggesting a departure from concerted evolution. A combination of general criteria and variations in highly conserved regions were employed to detect pseudogenes. The results pinpointed Type A sequences as potential pseudogenes due to significant sequence variations and deviations in secondary structure within highly conserved regions. Three types (Type R1, R2, and R3) were identified as recombinants between Type A and B sequences, with simple crossing over and gene conversion as the most likely recombination mechanisms. These findings not only contribute to rRNA pseudogene identification but also shed light on the evolutionary dynamics of rRNA genes in teleost genomes.
Dietary exposure to sulfamethazine, nanoplastics and their binary mixture disrupts the spermatogenesis of marine medaka (Oryzias melastigma)
Yuting Zhang, Ruanni Chen, Zhiqiang Chen, Xiaoyu Fu, Ziyi Wu, Jinwan Chen, Lingtian Xie, Humin Zong, Jingli Mu
2024, 43(8): 104-110.   doi: 10.1007/s13131-024-2289-8
[Abstract](147) [FullText HTML](60) [PDF 10117KB](9)
Abstract:
In the coastal environment, the co-occurrence of antibiotic and nanoplastic pollution is common. Investigating their individual and combined toxicity to marine organisms is of great necessity. In the present study, the reproductive toxicity of sulfamethazine (SMZ) and nanoplastics (polystyrene, PS) via the dietary route on the spermatogenesis of marine medaka (Oryzias melastigma) was examined. After 30 d of dietary exposure, SMZ alone decreased the gonadosomatic index (GSI) value (~35%) and the proportion of undifferentiated type A spermatogonia (Aund) (~40%), probably by disrupting the testicular sex hormone production, the spermatogenesis-related growth factor network and the balance of apoptosis. Individual exposure to PS did not affect the GSI value or the proportions of germ cells at different developmental stages, but dysregulated the expression of several spermatogenesis-related genes. Interestingly, the presence of PS alleviated the decreased GSI value caused by SMZ. This alleviation effect was achieved by enhancing the spermatogonia differentiation instead of reversing the suppressed self-renewal of Aund, suggesting that the mixture of PS and SMZ could cause reproductive effects in a different way. These findings expand our knowledge of threats of ubiquitous antibiotic and nanoplastic pollution to fish reproduction and population.
Impacts of Early Pleistocene glacial vicariance among refugial lineages and Mid-Late Pleistocene interglacial dispersal and expansion on forging population genetic structure of the giant clam Tridacna squamosa (Bivalvia: Cardiidae: Tridacninae) across the Red Sea and Indo-West Pacific oceans
Temim Deli
2024, 43(8): 111-127.   doi: 10.1007/s13131-023-2265-8
[Abstract](147) [FullText HTML](71) [PDF 2134KB](8)
Abstract:
This study aims at identifying the microevolutionary processes responsible for the onset of the remarkable phylogeographic structure already recorded for the endangered giant clam Tridacna squamosa across its distribution range. For this purpose, the evolutionary, biogeographic and demographic histories of the species were comprehensively reconstructed in a mitochondrial dataset comprising nearly the whole available published cytochrome c oxidase 1 gene sequences of T. squamosa. Relatively higher level of genetic diversification was unveiled within T. squamosa, in comparison to earlier macro-geographic investigations, whereby five mitochondrial clusters were delineated. The resulting divergent gene pools in the Red Sea, western Indian Ocean, Indo-Malay Archipelago and western Pacific were found to be driven by Early Pleistocene glacial vicariance events among refugial lineages. Accentuated genetic diversification of the species across the Indo-Malay Archipelago was successively triggered by historical dispersal event during the Mid-Pleistocene MIS19c interglacial. This latter historical event might have also enabled genetically distinct giant clams from the Indo-Malay Archipelago to subsequently colonize the western Pacific, accounting for the genetic diversity hotspot detected within this region (comprising three divergent mitochondrial clusters). Late Pleistocene demographic expansion of T. squamosa, during the Last Interglacial period, could have contributed to forging spatial distribution of the so far delineated genetic entities across the Indo-Western Pacific. Overall, being resilient to major climate shifts during the Pleistocene through adaptation and consequent diversification, T. squamosa could be used as a model species to track the impact of climate change on genetic variability and structure of marine species. In particular, the new information, provided in this investigation, may help with understanding and/or predicting the consequences of ongoing global warming on genetic polymorphism of endangered coral reef species among which Tridacna sp. are listed as ecologically important.
Morphological, phylogenetic and metabolite profile of Prorocentrum clipeus, a newly recorded epiphytic dinoflagellate in the northern Yellow Sea
Ruifang Wang, Mengmeng Tong, Shiwen Zhou, Junjie Zheng, Wenguang Zhang, Xinfeng Dai, Douding Lu, Jiarong Hu, Tianze Leng, Qinglin Mu, Zhongyong Yan, Jiangning Zeng, Pengbin Wang
2024, 43(8): 128-141.   doi: 10.1007/s13131-024-2302-2
[Abstract](216) [FullText HTML](94) [PDF 6398KB](67)
Abstract:
More than 30 species of benthic Prorocentrum have been identified, some of which produce okadaic acid (OA) and its derivatives, dinophysistoxins (DTXs), which cause diarrhetic shellfish poisoning (DSP). Increasing numbers of benthic Prorocentrum species have been reported in tropical and subtropical waters of China. In contrast, only a few benthic Prorocentrum species have been reported in temperate waters. In this study, morphological descriptions obtained using light microscopy, scanning electron microscopy and molecular characterization of one Prorocentrum clipeus strain isolated from the Yellow Sea are presented. Prorocentrum clipeus cells were nearly circular in shape, with a collar, ridge, and one protrusion. The periflagellar area was wide U-shaped, with two curved projections on platelet 1a. Nine periflagellar platelets of different sizes were observed. The morphology closely fits that of the species isolated from other locations. Phylogenetic analysis based on the molecular sequences of the small subunit (SSU) rDNA, internal transcribed spacer (ITS), and large subunit (LSU) rDNA was performed. A comprehensive metabolomic analysis incorporating target, suspect and non-target screenings was first applied to investigate the intracellular and extracellular metabolite profiles of the current isolate of P. clipeus. According to the results of the target and suspect screenings, 179 metabolites or toxins produced by DSP-related algal species, including OA, dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2) and pectenotoxin-2 (PTX2), were not detected. Non-target screening involving feature-based molecular networking (FBMN) provided a global view of major metabolites produced by the P. clipeus DF128 strain and revealed 23 clusters belonging to at least 13 compound classes, with organometallic compounds, lipids and lipid-like molecules, phenylpropanoids and polyketides, and benzenoids as major types. To date, this is the first record of the characterization of P. clipeus in samples from Chinese waters. Our results support the wide distribution of epibenthic Prorocentrum species.
A review on the parasitic isopod genus Notophryxus G. O. Sars, 1883 (Crustacea: Isopoda), and first report of Notophryxus globularis G. O. Sars, 1885 from Lakshadweep Sea (Amini Island)
Mukkattu Nazar Suhaana, Jaime Gómez-Gutiérrez, Paravanparambil Rajakumar Jayachandran, Punnakkal Hari Praved, Sivasankaran Bijoy Nandan
2024, 43(8): 142-153.   doi: 10.1007/s13131-023-2217-3
[Abstract](250) [FullText HTML](117) [PDF 1727KB](48)
Abstract:
Isopod crustaceans of the family Dajidae are exclusively marine ectoparasites. The genus Notophryxus G. O. Sars, 1883 currently includes nine nominal species, which are very rarely reported as the chances for encountering these specimens are unpredictable. Our comprehension of the taxonomy, biology, ecology, and life cycle of species belonging to the Notophryxus genus is notably lacking. All nominal species of Notophryxus genus are reviewed here to obtain a comprehensive and integrative taxonomic understanding of this genus, in an attempt to address the lacunae. This paper also documents the rediscovery of an ectoparasitic isopod from the genus Notophryxus in Indian waters, after 55 years. Adult isopod specimens obtained from the outer reefs of Amini Island in the Lakshadweep archipelago, Southeastern Arabian Sea, display morphological congruence to Notophryxus globularis G. O. Sars, 1885. The only previous report on this species dates back to 1885 from G.O. Sars' description of N. globularis as an ectoparasite on the euphausiid Thysanoessa gregaria G. O. Sars, 1883 in the North Pacific. This discovery represents a range extension of N. globularis from the North Pacific to the Arabian Sea. Two cryptoniscid larvae and three adult females of N. globularis (with dwarf males) were found attached to four adult mysid specimens of Siriella aequiremis Hansen, 1910. The present study provides an improved diagnosis of N. globularis with the aid of light microscopy images and line drawings which was not given in the original G. O. Sars, 1885 report. This research also provides a concise description of cryptoniscid larvae from the same sampling location and same host which is most likely to be N. globularis larvae.

Latest Issues