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Explorations of marine gas hydrate deposits and the signatures of hydrocarbon venting using in situ techniques
LIU Liping, CHU Fengyou, GUO Lei, LI Xiaohu
Journal of Marine Sciences    2023, 41 (1): 26-44.   DOI: 10.3969-j.issn.1001-909X.2023.01.003
Abstract413)   HTML1736)    PDF (4566KB)(1247)      

Marine gas hydrate deposits are significant temporal reservoirs for hydrocarbons migrating from deep sources. This is crucial to our understanding of ocean carbon cycling. The cold seep, a geological process regarding gas leakage from deep or shallow sources, is usually linked with gas hydrate decomposition. In this thesis, we reviewed the latest applications of in situ monitoring and detecting methods regarding the leakage plumes, migration pathways, and seafloor geomorphologies associated with gas hydrate and cold seep systems, primarily including vessel-and land-based gas plume measurements, surface ocean-lower atmosphere hydrocarbon emission detections, seafloor visualization techniques, and in situ observation networks. The integrated applications of these in situ observation methods provide a nuanced view of the temporal and spatial variability of hydrate and cold seep systems, facilitate understanding of the fate of hydrocarbons, and expand our knowledge of cold-seep biota in a watery desert.

Assessment of carbon sink potential and driving factors of island forests on national nature reserve
WU Liangxu, ZOU Huimin, CHEN Wei, XU Minghai, CAI Houcai, CHEN Shuyi, LI Xianglan
Journal of Marine Sciences    2023, 41 (1): 96-109.   DOI: 10.3969-j.issn.1001-909X.2023.01.008
Abstract375)   HTML17)    PDF (4905KB)(687)      

The monitoring of carbon flux dynamics and assessment of carbon sink functions of island forest ecosystems are rarely reported due to their special geographical location and few data sources. In this study, the forest ecosystem of the Nanji Island was used as the research object, the carbon sink potential of island forests and their driving factors were assessed. Based on eddy correlation techniques, the temporal variation characteristics and driving factors of net ecosystem productivity (NEP), gross primary productivity (GPP), and ecosystem respiration (Reco) from 2020 to 2021 were explored. Results showed that the forest ecosystem of Nanji Island was carbon sink. Net CO2 uptake in 2020 and 2021 were 516 g C·m-2·a-1 and 598 g C·m-2·a-1, Reco were 1 037 g C·m-2·a-1 and 1 646 g C·m-2·a-1, and GPP were 1 552 g C·m-2·a-1 and 2 244 g C·m-2·a-1, respectively. Total solar radiation (Rg), photosynthetically active radiation (PAR), net radiation (Rn) and sensible heat (H) were significantly and positively correlated with NEP and GPP (p≤0.001); air temperature (Tair) and soil temperature (Tsoil) were significantly and positively correlated with Reco(p≤0.001). The photosynthesis time of Nanji Island forest was longer than the carbon sink time on the daily scale. When Tair reached 10.05-27.76 ℃ and PAR reached 110.47-429.44 μmol·m-2·s-1, the photosynthesis intensity of island forest was higher than that of ecosystem respiration, which showed CO2 absorption. The monitoring and assessment of carbon fluxes in the forest ecosystems of Nanji Island will provide an important theoretical support for the establishment of a dynamic monitoring and assessment management system for blue carbon in China.

Interactions between vegetation and sediment carbon pools within coastal blue carbon ecosystems: A review and perspective
CHEN Yining, CHEN Luzhen
Journal of Marine Sciences    2023, 41 (1): 3-13.   DOI: 10.3969-j.issn.1001-909X.2023.01.001
Abstract781)   HTML301)    PDF (1348KB)(614)      

Mangroves, coastal salt marshes and seagrass beds, as the typical coastal blue carbon ecosystems, have been widely recognized for their remarkable capacity in carbon storage. Vegetation carbon pool and sediment (or soil) carbon pool were considered to be the major carbon pools within the coastal blue ecosystems and their variations determined the overall carbon sequestration of the ecosystems. From a perspective of carbon pool interactions, this study summarized the previous research work based on literature review, including the interactions within various vegetation carbon pools and within various sediment carbon pools, as well as the interactions between vegetation and sediment carbon pools. Interspecific competition, allochthonous carbon input and biogeomorphology were found to be the key to understand the carbon pool interactions. Finally, a perspective on the current state-of-the-art of blue carbon pool study is offered, with challenges and suggestions for future directions.

Spatio-temporal evolution and driving factors analysis of the coastline in Nan’ao Island from 1976 to 2021
NING Zihao, JIANG Changbo, LONG Yuannan, WU Zhiyuan, MA Yuan
Journal of Marine Sciences    2023, 41 (2): 71-82.   DOI: 10.3969/j.issn.1001-909X.2023.02.006
Abstract226)   HTML17)    PDF (3287KB)(559)      

Coastline is one of the important geographical elements to describe the boundary between land and sea. Under the dual influence of natural factors and socio-economic factors, coastline dynamic evolution of different intensities continues to occur. Based on Landsat series satellite remote sensing images, the spatial and temporal evolution of the coastline of Nan’ao Island from 1976 to 2021 was analyzed by RS and GIS technology combined with field investigation, and the driving factors were analyzed by grey correlation analysis. The results show that : (1)In the past 45 years, the coastline of Nan’ao Island has changed significantly. The coastline length has increased by 11.06 km, and the fractal dimension have generally increased.(2)During the study period, the type of coastline changed from natural coastline dominated by bedrock to artificial coastline, the comprehensive index of coastline utilization show an increasing trend, and the main structure of coastline development and utilization show a form of single to multiple.(3)The evolution of the coastline of Nan’ao Island has obvious regional differences. That of Houzhai Town is greatly affected by human factors, and its evolution is more significant. The coastlines of Yun’ao and Shen’ao Towns are mainly affected by natural factors, and their evolutions are relatively slow.(4)Typhoon(natural disasters) and population are the main driving factors of the coastline evolution of Nan’ao Island.

Carbon cycling in costal ocean and CO 2 negative emissions
YU Lei, LI Sanzhong, SUO Yanhui, WANG Xiujuan
Journal of Marine Sciences    2023, 41 (1): 14-25.   DOI: 10.3969-j.issn.1001-909X.2023.01.002
Abstract534)   HTML40)    PDF (2925KB)(516)      

Costal ocean receives a bunch of carbon materials and nutrients from terrestrial sources, relates a lot of carbon-involving interactions. Meanwhile, it is normal that sedimentary reservoir-cap systems with good trap conditions beneath coastal ocean, these entrapments have potentials to storage CO2. This review focuses on the coastal ocean as the research object, and introduces the carbon cycle processes in coastal ocean, their factors which could influence CO2 fluxes in the carbon cycle processes, and the potential carbon storage mechanisms of the coastal marine sedimentary basins. From the perspective of “carbon peaking and carbon neutrality”, the significance of coastal oceans for “Ocean Negative Carbon Emission (ONCE)”, its potential promotion paths, carbon storage potentials in sedimentary basins and the problems faced by coastal oceans are discussed. Overall, the costal ocean is one of the important blue carbon sink areas. In the coastal marine seawater system, improving the reaction efficiency of microbial carbon pump and carbonate carbon pump have positive significance for CO2 negative emissions; The suitable reservoir-cap systems for CO2 storage beneath coastal ocean can not only provide extra spaces, but also guarantee the safety for CO2 storage. In the future, the main research directions should be to inhibit the conversion process of carbon materials to CO2 in coastal oceans and ensure the safety of CO2 storage in sedimentary reservoirs, these could provide theoretical basis and technical guarantee for CO2 negative emissions.

Satellite retrieval algorithm of high spatial resolution sea surface partial pressure of CO 2: Application of machine learning in Xiangshan Bay in autumn
LIU Tingyu, BAI Yan, ZHU Bozhong, LI Teng, GONG Fang
Journal of Marine Sciences    2023, 41 (1): 82-95.   DOI: 10.3969-j.issn.1001-909X.2023.01.007
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Coastal bays are greatly affected by human activities and natural changes, and the influence mechanism of variation in seawater carbon source and sink patterns is extremely complex. Due to the small spatial scale of the bay, it is necessary to use wide-bands high-spatial resolution satellite remote sensing for monitoring the air-sea CO2 flux. Compared with the traditional kilometer-level ocean color satellite data, the retrieval of the sea surface partial pressure of CO2 (pCO2), the key parameter to calculate air-sea CO2 flux, is extremely challenging in small-scale bays. Taking Xiangshan Bay in Zhejiang Province in autumn as an example, a satellite retrieval algorithm for sea surface pCO2 was proposed based on the in situ pCO2 data and Sentinel-2 satellite images in the past five years, using the machine learning method of support vector machine (SVM). The algorithm validation results showed a good performance with R2 of 0.92 and RMSE of 23.23 μatm, and the satellite-derived results were consistent with the in situ values. On this basis, the satellite products of pCO2 in Xiangshan Bay in autumn from 2017 to 2021 (September to November) were produced. The results revealed that the pCO2 of Xiangshan Bay showed a decreasing trend from the top of the bay to the mouth of the bay, with an average value of 514.56 μatm, of which the average pCO2 in the inner bay was 551.94 μatm and the average pCO2 in the outer bay was 477.19 μatm, which implied that Xiangshan Bay was a source of atmospheric CO2 as a whole. There was no significant trend change of pCO2 in autumn in the past five years. Combined with the analysis of in situ data of multiple parameters, it was found that the sea surface pCO2 of autumn in Xiangshan Bay in 2021 was jointly regulated by physical mixing and biological activities. Sea surface temperature (SST) had a good positive correlation with pCO2, which was mainly reflected by the thermodynamic equilibrium of carbonate system. In addition, the normalized pCO2(NpCO2) with average temperature had a good negative correlation with seawater salinity and dissolved oxygen saturation. The relationship between NpCO2 and salinity resulted from the exchange of sea water inside the bay and offshore coastal water under tidal effect. Long-time series satellite data analysis also confirmed that sea surface pCO2 had a relatively consistent trend with the average tide height inside and outside the bay, and this trend was stronger in the outside bay than that in the inner bay. In this study, a set of pCO2 remote sensing retrieval methods in the small-scale bay was constructed, which laid a good foundation for the subsequent long-time series satellite monitoring of sea-air CO2 fluxes.

Characteristics and mechanism of ocean subsurface coherent eddies: Problems and progress
GE Yuyu, LIAO Guanghong
Journal of Marine Sciences    2023, 41 (2): 45-60.   DOI: 10.3969/j.issn.1001-909X.2023.02.004
Abstract232)   HTML26)    PDF (4529KB)(434)      

With the advancement of observation technology and the improvement of ocean numerical simulation capabilities, some stable subsurface coherent vortices have been widely observed in the ocean, which far from the formation source area. These vortices possess distinctive dynamic characteristics, such as a low potential vorticity center, lens-like structure of isopycnals, weak stratification, and anomalous temperature, salinity, or other tracer properties compared to the surrounding water mass. Their core flow is relatively stronger. These subsurface coherent vortices significantly impact ocean water mass transport, thermohaline circulation and marine biological environment. This paper comprehensively summarizes researches on subsurface coherent vortices in the ocean, including their structure, hydrological characteristics, identifying methods, global distribution, dynamic mechanisms and their important effects on ocean environment. Furthermore, the research perspectives are discussed, such as the difficulties in the research and the issues that need to be solved to comprehensively understand subsurface coherent vortices in the ocean.

Wave characteristics and their influencing factors on Nanhui tidal flats in the Changjiang Estuary
CUI Minghui, TU Junbiao, MENG Lingpeng, GUO Xingjie, SU Ni, FAN Daidu
Journal of Marine Sciences    2023, 41 (2): 28-44.   DOI: 10.3969/j.issn.1001-909X.2023.02.003
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Wave is an important factor to shape the dynamic geomorphology of the open tidal flat, but researches on tidal-flat wave characteristics are still limited. Taking Nanhui tidal flats in the Changjiang Estuary as an example, the wave characteristic parameters and wave spectrum parameters were obtained by inverting flow-velocity and water-pressure data from the Acoustic Doppler Velocimeters (ADVs) at some fixed platforms, and their changes over tidal cycles and associated influence mechanisms were discussed. The results show that both normal wave direction and prominent wave direction at three stations of Nanhui tidal flats are mainly southeast during the observation period, with long-period swells dominating. The effective wave height of the three stations is positively correlated with the water depth, but the fitting coefficients of each station are different over flood and ebb periods. Wave orbital velocities are obviously modulated by the shallow water effect and the flow directions, and their maximum values usually occur at the early flooding stage, while minimum values can be observed to occur during the current transition periods. The wave energy spectrum during ebb tides is featured by the bimodal pattern because of high influence by tidal levels and coastal topography, and the peak energy is continuously attenuated and gradually dispersed with the concurrent shift of peak frequencies.

Conservation gap analysis of coastal blue carbon ecosystems: Taking Guangdong and Guangxi as examples
DONG Di, HUANG Huamei, GAO Qing, CHEN Mianrun, YANG Xi
Journal of Marine Sciences    2023, 41 (1): 110-120.   DOI: 10.3969-j.issn.1001-909X.2023.01.009
Abstract384)   HTML19)    PDF (2711KB)(404)      

Mangroves, salt marshes, and seagrass beds are known as the three major coastal blue carbon ecosystems (CBCEs), which play important roles in marine biodiversity maintenance, water purification, nutrient recycling, carbon sequestration and storage. Guangdong Province and Guangxi Zhuang Autonomous Region in China, where the CBCEs are widely distributed, were selected as the research areas, to investigate the spatial relationship between CBCEs and the marine ecological redlines (MERs). The CBCE conservation gap was analyzed, and the recommended priority conservation areas outside the MERs were proposed. The CBCE distribution data obtained from the satellite images in 2019, combined with field survey and UAV remote sensing data collected during 2020 and 2021 showed that the CBCEs in Guangdong totaled 14 481.39 hm2 (mangroves 11 928.87 hm2, salt marshes 1 258.00 hm2, seagrass beds 1 294.52 hm2), whereas the CBCEs in Guangxi totaled 11 751.30 hm2 (mangroves 10 171.70 hm2, salt marshes 1 450.36 hm2, seagrass beds 129.24 hm2). 62.13% of the CBCEs in Guangdong and 59.88% in Guangxi were covered by the MERs. The distribution areas and protection ratios of mangroves and seagrass beds in Guangdong were both larger than those in Guangxi, while the distribution area and protection ratio of salt marshes in Guangxi were larger than that in Guangdong. As to the 3 types of CBCEs in Guangdong, 62.13% of the mangroves, 38.16% of the salt marshes and 85.41% of the seagrass beds were under protection. For the CBCEs in Guangxi, 61.44% of the mangroves, 49.58% of the salt marshes and 52.99% of the seagrass beds were protected. This research suggests the coast from Rongmujiang Bay to Maowei Sea, the areas of Tieshan Bay, Leizhou Bay, Zhelin Bay and other related locations as the recommended priority conservation areas outside the MERs.

Assessment of tidal current energy resources in the significant waterways of Zhoushan sea area
CHEN Chao, BAO Min, YE Qin, YAN Yuhan, CAO Zhenyi, ZHANG Qianjiang
Journal of Marine Sciences    2023, 41 (3): 34-42.   DOI: 10.3969/j.issn.1001-909X.2023.03.004
Abstract252)   HTML19)    PDF (2578KB)(401)      

Tidal current energy is the kinetic energy carried in the horizontal movement of tidal water, which has great development prospects. Accurate simulation and characterization of regional tidal currents can help to efficiently evaluate the spatial and temporal distribution of tidal energy resources, which is the key to the development and utilization of tidal current energy resources. In this paper, a high-resolution numerical model of tidal currents is constructed by applying FVCOM ocean model in Zhoushan sea area where has rich tidal current energy, and the reliability of the model is confirmed by tidal level and current verification. According to the simulation results, six waterways with dense tidal current energy resources in the Zhoushan sea area were identified, among which the average energy density of Xihoumen waterway, Cezi waterway and Taohuagang waterway exceeds 2.0 kW/m2, and the maximum energy density exceeds 20 kW/m2, and the flow speed over 1.0 m/s of the whole month is more than 80%. During tidal current ebb and flow, the reflow is dominant, while the asymmetry and rotation of tidal current are low. The flow stability coefficient is more than 0.98, so it is more suitable for the development and utilization of tidal current energy than other three waterways. The best location for tidal current energy development in these three waterways was then determined by calculating the significant hours and available hours, and the corresponding exploitable tidal current energy resources were evaluated using the Farm method, which were 27.53 MW, 39.96 MW, and 130.26 MW, respectively.

Analysis of measured wave characteristics in the coastal waters of Cangnan, Zhejiang Province
ZHOU Yiming, YANG Lihua, HUAN Caiyun, LIU Rong
Journal of Marine Sciences    2023, 41 (3): 43-55.   DOI: 10.3969/j.issn.1001-909X.2023.03.005
Abstract178)   HTML11)    PDF (4079KB)(393)      

Based on the one-year measured wave data in the coastal area of Cangnan, Zhejiang Province, the characteristics of wave parameters were statistically analyzed, the correlation between wave parameters was analyzed by using the least square method, the relationship between the average wave duration and wave height was studied, the wave energy was estimated, and the characteristics of typical typhoon waves during typhoon “Lekima” were analyzed.The results show that the study area is mainly composed of light waves with spectral peak period of 5-9 s, the annual average significant wave height of 1.22 m, the normal wave direction is E, the strong wave direction is ENE.There is a significant linear relationship between the characteristic wave heights, which conforms to the typical Rayleigh Distribution.In typhoon free period and cold wave free period with significant wave height below 2.7 m and typhoon period with significant wave height above 4.1 m, the average duration of wave decreases exponential decays with the increase of wave height, and the attenuation rate of typhoon period with significant wave height above 4.1 m is higher than that of typhoon free period and cold wave free period with significant wave height below 2.7 m.During the impact of typhoon “Lekima”, the maximum wave height, spectral peak period, and spectral peak density show a basically synchronous process of first increasing and then decreasing, with a maximum spectral peak density of 55.10 m2/Hz;the typhoon wave spectrum before and after the impact of the typhoon show a bimodal spectrum, while the wave spectrum during the most significant period of typhoon impact show a unimodal spectrum.

Clay mineral characteristics of sediments in the seamount basin of the Western Pacific and its indicative significance
DENG Tao, XU Dong, XIAO Tinglu, YE Liming, ZHANG Weiyan
Journal of Marine Sciences    2023, 41 (3): 56-72.   DOI: 10.3969/j.issn.1001-909X.2023.03.006
Abstract159)   HTML12)    PDF (4269KB)(390)      

The clay mineral assemblage in abyssal sediments can reflect the paleoclimate and paleoenvironment changes of the provenance area. Predecessors have many studies about the characteristics of clay mineral assemblages in the Pacific sediments west of the Mariana Trench, but the less research on the characteristics of clay mineral assemblages in the east of the Mariana Trench limits a deeper understanding of the relationship between the Asian aeolian dust input and the Pacific deep-sea sedimentary environment. In this study, 31 surface samples and 1 core sample collected in the Malkus-Wake Seamount area of the Western Pacific during the 2019 DY54 cruise were analyzed for clay minerals, combined with the data collected in the Western Pacific and nearby areas, we discussed the characteristics of composition, distribution and the provenance of clay minerals. The results showed that illite was the main clay mineral in surface sediments of the study area, with an average value of 69%; the content of chlorite and kaolinite were the second, with an average of 16% and 11% respectively; that of smectite was the least, with an average of 3%. In the core P04, the assemblage of the clay mineral was basically the same as surface samples, but below 250 cm depth, the content of smectite increased significantly, while the content of illite decreased relatively. Provenance analysis showed that Asian aeolian dust was the main source of illite in the study area, and kaolinite and chlorite might also be from Asian aeolian dust, and the East Asian winter monsoon was the main transport force of these clay minerals. The smectite in sediments could be mainly formed by weathering of submarine volcanic materials. The increase of illite content while the decrease of smectite content in the upper layer of core P04 sediment was responded to the increase of Asian aeolian dust input since the Middle Pleistocene.

The seasonal blooming characteristics of phytoplankton and POC export flux in the waters around South Georgia Island: Based on BGC-Argo and satellite remote sensing observations
ZHAO Yueran, FAN Gaojing, WU Jiaqi, SUN Weiping, PAN Jianming, HAN Zhengbing
Journal of Marine Sciences    2023, 41 (4): 1-11.   DOI: 10.3969/j.issn.1001-909X.2023.04.001
Abstract218)   HTML40)    PDF (2882KB)(373)      

The waters surrounding South Georgia Island are one of the highest primary productivity regions in the Southern Ocean with enormous carbon sequestration potential. However, the strength of the biological pump efficiency in this area is still uncertain due to the lack of continuous upper ocean observation data.In this study, the hydrological and biogeochemical parameters obtained from the Biogeochemical Argo (BGC-Argo) floats deployed in the South Georgia Island vicinity during the period of 2017-2020 were utilized to investigate the impacts of physical processes on biogeochemical processes and to estimate the carbon export flux in the Antarctic summer. Results indicated that both upstream (northeast of the Antarctic Peninsula) and downstream (Georgia Basin) regions of South Georgia Island exhibited strong seasonal characteristics in Chl-a, with the latter area having a 4-month sustained period of phytoplankton bloom, suggesting a stable and continuous supply of iron. Using the temporal variability of the seasonal particulate organic carbon (POC) export, the summer POC export fluxes of the upstream and downstream regions were estimated to be 7.12±3.90 mmol·m-2·d-1 and 45.29±5.40 mmol·m-2·d-1, respectively, indicating that the difference might be due to enhanced downward export of organic carbon after the deepening of the mixed layer. The study found that the region maintained a high biological pump efficiency, contrary to the previous conclusion that the Georgia Basin had “high productivity low export efficiency”, which might have been caused by the limited “real-time” representation of the entire seasonal characteristics during ship-based surveys. BGC-Argo provides high spatiotemporal resolution of multi-parameter observation data, and this study demonstrates that it can more accurately quantify and evaluate marine biogeochemical processes and carbon sequestration potential.

Variations in water and sediment fluxes in Oujiang River during flooding and non-flooding seasons
ZHANG Wanying, LU Shasha, XIA Xiaoming, LIU Jingui
Journal of Marine Sciences    2023, 41 (2): 61-70.   DOI: 10.3969/j.issn.1001-909X.2023.02.005
Abstract204)   HTML14)    PDF (4251KB)(359)      

Oujiang River is a typical mountain river whose water and sediment fluxes are characterized by a great disparity between flood and dry seasons. Based on the measured data of water discharge and sediment load at the mainstream control hydrological station of Oujiang River in the past 71 years (1950—2020) and 43 years (1956—1998), respectively, the coefficient of nonuniformity, Mann-Kendall non-parametric statistical test and double mass curve were used to analyze the variations of runoff and sediment load during the flood seasons (including plum rain season from April to June and typhoon season from July to September) and dry seasons (non-flooding season from October to March in next year) in the Oujiang River. The results showed that: (1) The peak and valley month of runoff were the same as sediment load. The peak month of both runoff and sediment load appeared in June, while their valley month appeared in December. The plum rain season was the most important period of water and sediment transporting to sea from Oujiang River. (2) The runoff showed significant decreasing trend in the plum rain season, significant increasing trend in non-flooding season, and non-significant trend in typhoon season during 1950—2020 in Oujiang River. The nonuniformity of intra-annual distribution for runoff had become more uniform obviously, resulting from the regulation of reservoirs. (3) The sediment load showed significant decreasing trend in the plum rain season due to the interception of reservoirs, and no significant trend in typhoon season and non-flooding season during 1956—1998 in Oujiang River. The nonuniformity of intra-annual distribution for sediment load showed little change, which might relate to the nonuniformity of intra-annual distribution for precipitation. (4) The relationship between sediment load and runoff during typhoon and non-flooding season changed in 1975 and 1959, respectively, both of which were related to the heavy rainfall within the river basins.

Seasonal variation in coastal saltmarsh carbon stocks, south bank of Hangzhou Bay
CHEN Yining, ZHANG Ziyan, CHEN Luzhen, ZHANG Jialin, LIU Bing, XIA Xiaoming, WANG Xinkai, CAI Tinglu
Journal of Marine Sciences    2023, 41 (1): 55-67.   DOI: 10.3969-j.issn.1001-909X.2023.01.005
Abstract519)   HTML31)    PDF (6011KB)(348)      

Carbon stock variation observation forms the basis for coastal saltmarsh blue carbon sink accounting. In order to accurately estimate the carbon sequestration rate of coastal saltmarshes over a short-term scale (seasonal to annual), this study carried out field observations and sample collections within a coastal saltmarsh on the south bank of Hangzhou Bay, covering different seasons of 2022. This study was primarily based on high-resolution surface monitoring by Surface Elevation Table (SET) systems. The results revealed a seasonal plant growth pattern between March and September for both the native species Scirpus mariqueter and the exotic species Spartina alterniflora. In terms of belowground biotic carbon stock changes, over the growing season, the carbon stock increase for Scirpus mariqueter reached 11 g C·m-2 whilst this value was 56 g C·m-2 for Spartina alterniflora. The SET data indicated a sedimentation rate of 13.02 cm·a-1 within the Spartina alterniflora saltmarsh, higher than that of the Scirpus mariqueter saltmarsh, 12.30 cm·a-1. Calculating the sedimentation rate data with sediment bulk density and organic carbon content, the sediment carbon accumulation rate of Scirpus mariqueter saltmarsh was estimated to be 460 g C·m-2·a-1, lower than 588 g C·m-2·a-1 of the Spartina alterniflora saltmarsh. Combining the biotic carbon stock increase and sediment carbon stock increase, the carbon sequestration rate for the Spartina alterniflora saltmarsh was found to be 644 g C·m-2·a-1, higher than the value of Scirpus mariqueter saltmarsh, 471 g C·m-2·a-1. Thus, the difference in carbon sequestration abilities of native and exotic species should be considered for future coastal blue carbon management.

Application of two-phase leaching method in the study of ferromanganese nodule mineralization
ZHU Feiyang, LI Huaiming, YAO Pengfei, WANG Xiao, ZHU Jihao, LÜ Shihui, LUO Yi, ZHOU Li’na, LIU Yuwei, TANG Yutong
Journal of Marine Sciences    2023, 41 (2): 83-93.   DOI: 10.3969/j.issn.1001-909X.2023.02.007
Abstract196)   HTML10)    PDF (3754KB)(328)      

Two-phase leaching method can separate hydrogenetic and residual mineral phases of ferromanganese nodules, which will provide valuable information with the research of ferromanganese nodule mineralization and pale-environment. In order to study the applicability of the two-phase leaching method in the nodule mineralization research for different types of nodules compared to the bulk sample results, the ferromanganese nodules samples from six stations were selected, which were collected on the seamounts area of western Pacific Ocean and CC Zone of eastern Pacific Ocean, respectively. Geochemical and mineralogical compositions of the bulk samples were analyzed, and elements compositions of the hydrogenetic and residual mineral phases were analyzed, which were obtained using the two-phase leaching method. The results indicated that the mass ration variation of the residual mineral phases was not obvious with about 14.0%-17.6%, which had high contents of Nb, Rb, Ta, Ti, Zr. Contents and relevant rations of elements such as Co, Ni, Cu, Zn, Sr, REY in the hydrogenetic mineral phase showed similar features with those in the bulk samples. Proportion of elements contents like Ti, Nb, Sr between hydrogenetic and residual mineral phases showed well negative correlation with Mn/Fe values, which probably could be regarded as index for ferromanganese nodule mineralized environment research in the future.

Upper ocean response to super typhoon Rammasun(2014) based on Argo data in the South China Sea
YU Jie, ZHANG Han, CHEN Dake
Journal of Marine Sciences    2023, 41 (2): 14-27.   DOI: 10.3969/j.issn.1001-909X.2023.02.002
Abstract264)   HTML29)    PDF (6711KB)(323)      

Using Argo measured data combined with satellite remote sensing data and moored buoy data, the upper ocean temperature and salinity response caused by super typhoon Rammasun in 2014 was analyzed and studied. The result shows that super typhoon Rammasun resulted in cooling of sea surface temperature and deepening of mixing layer. Meanwhile, mixing length and vertical velocity induced by typhoon were calculated in this research, which explained the causes of temperature changes in the subsurface layer. Strong mixing and weak upwelling led to warming of the subsurface layer, whereas weak mixing and strong upwelling led to cooling of the subsurface layer. Compared with the change of temperature, the response of salinity was more complex. Precipitation first caused the decrease of surface salinity, and then vertical mixing led to a large increase of surface salinity. However, the effect of precipitation could greatly inhibit this process. After the typhoon departed, the vertical mixing was weakened, and the salinity was greatly reduced because of the heavy precipitation, it was even lower than that before the typhoon.

Prospect of artificial intelligence in oceanography
DONG Changming, WANG Ziyun, XIE Huarong, XU Guangjun, HAN Guoqing, ZHOU Shuyi, XIE Wenhong, SHEN Xiangyu, HAN Lei
Journal of Marine Sciences    2024, 42 (3): 2-27.   DOI: 10.3969/j.issn.1001-909X.2024.03.001
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Artificial intelligence in oceanography has demonstrated a great potential with the explosive growth of ocean observation data and numerical model products. This article first reviews the history of ocean big data development, and then introduces in detail the current status of artificial intelligence in oceanography applications including identifying ocean phenomenon, forecasting ocean variables and phenomenon, estimating dynamic parameters, correcting forecast errors, and solving dynamic equations. Specifically, this article elaborates the research on the intelligent identification of ocean eddies, internal waves and sea ice, the intelligent prediction of sea surface temperatures, El Ni?o-Southern Oscillation, storm surges, waves and currents, the intelligent estimation of ocean turbulence parameterization for numerical models, and the intelligent correction of waves and current forecast errors. In addition, it discusses the recent progress of applying physical mechanism fusion and Fourier neural operator for solving ocean dynamic equations. This article is based on the current status of artificial intelligence in oceanography and aims to provide a comprehensive demonstration of the advantages and potential of applying artificial intelligence methods in the field of oceanography. With the two emerging research hotspots: digital twin oceans and artificial intelligence large models, the future development direction of artificial intelligence provides enlightenment and reference for interested scientists and researchers.

Macrobenthos community and living organic carbon pools on muddy tidal flat: Implications from Aiwan Bay of Wenling in summer
TIAN Sujie, TANG Yanbin, YU Peisong, LIU Chenggang, LIU Qinghe, ZHANG Rongliang, SHOU Lu, ZENG Jiangning, LIAO Yibo
Journal of Marine Sciences    2023, 41 (4): 102-112.   DOI: 10.3969/j.issn.1001-909X.2023.04.010
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The intertidal zone is a key area connecting terrestrial ecosystems and marine ecosystems, among which muddy tidal flat is an important and easily overlooked CO2 collection habitat, and the macrobenthos play a central role in the input, transport and preservation of carbon. Macrobenthos community and living organic carbon pools of muddy tidal flat were analyzed in Aiwan Bay, eastern coast of Zhejiang Province in summer. The average abundance of macrobenthos was 105.2 ±37.2 ind/m2, and the average biomass was 46.9 ±6.4 g/m2. The major taxa components within the habitat were crustaceans and mollusks, and the ecosystem health status was excellent. The organic carbon contents of macrobenthos at Aiwan Bay from highest to lowest were other animals including fish and nemertinea (40.95%), polychaetas (22.98%), crustaceans (17.24%), echinoderms (15.90%), mollusks (10.76%), and estimated the macrobenthos carbon pool was 163.90 Mg, of which crustaceans have the largest contribution rate, accounting for 59.80%. The exploration of macrobenthos community structure and living organic carbon pools size in muddy tidal flat can provide scientific suggestion for constructing the blue carbon survey system and supply fundamental data to further quantify the overall carbon pool size in coastal habitats.

Paleoenvironmental indication of n-alkanes composition: A case study of sediments from the Pearl River Estuary since the mid-Holocene
CHEN Guosheng, QIU Zihui, KONG Deming
Journal of Marine Sciences    2023, 41 (1): 121-130.   DOI: 10.3969-j.issn.1001-909X.2023.01.010
Abstract195)   HTML14)    PDF (2731KB)(289)      

The multiple indices of n-alkanes including ∑oddC25-33, CPI, ACL, C31/C27 and Pmar-aq from a sediment core HKUV16 retrieved in the Pearl River Estuary were analyzed to explore their sources and environmental changes since the mid-Holocene. The distribution features of n-alkanes of core HKUV16 indicated that they were mainly from terrestrial higher vegetation. From 8.0 to 7.0 ka BP, ∑oddC25-33, CPI, and Pmar-aq increased, while ACL and C31/C27 were low, which showed that terrestrial organic matter input increased and woody vegetation increased. The decrease of ∑oddC25-33 during 7.0~3.2 ka BP indicated that the input of terrestrial organic matter decreased, while the ACL and C31/C27 showed an increase-decrease-increase trend, suggesting that the Pearl River Basin might have experienced dry-wet-dry climate change. From 3.2 to 2.2 ka BP, high ACL and C31/C27 indicated that herbaceous plants expanded and the climate was relatively arid. The multi-indices showed that the input of n-alkanes to the Pearl River Estuary before 2.2 ka BP was mainly affected by East Asian summer monsoon. However, increasing human activities since 2.2 ka BP might have become the dominant factor for the ecological environment of the Pearl River Basin.