Research

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17 pages, 5564 KiB

Open AccessArticle

A Preliminary Study of Suspended Matters Variation Associated with Hypoxia and Shoaling Internal Tides on the Continental Shelf of the Northern Andaman Sea

by Feilong Lin, Chujin Liang, Tao Ding, Dingyong Zeng, Feng Zhou, Xiao Ma, Chenghao Yang, Hongliang Li, Beifeng Zhou, Chenggang Liu and Weifang Jin

J. Mar. Sci. Eng. 2023, 11(10), 1950; https://doi.org/10.3390/jmse11101950 - 10 Oct 2023

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Abstract

The northern Andaman Sea (AS) continental shelf is unique due to the diverse marine ecosystem and existences of both hypoxia and internal tides, but limited in situ observations restrict our understanding of the hydrographic dynamic process. Based on the turbidity, mean volumes of [...] Read more.

The northern Andaman Sea (AS) continental shelf is unique due to the diverse marine ecosystem and existences of both hypoxia and internal tides, but limited in situ observations restrict our understanding of the hydrographic dynamic process. Based on the turbidity, mean volumes of backscattering strength (MVBS), we qualitatively studied the mean distribution characteristics and temporal variation in suspended matters on the northern AS continental shelf and their relation to hypoxia and internal tides. The results of both MVBS and turbidity revealed that the suspended matters exhibited a three-layer vertical structure. The upper and lower layers exhibited high values, while the middle layer had low values. The upper boundary of the high-value region in the upper layer descended below the surface to a depth of 30 m after sunrise and returned to the surface after sunset, indicating a diel vertical migration of zooplankton and micronekton. Daytime migration depth was likely constrained by hypoxia’s upper boundary. In the lower layer, three MVBS enhancements and attenuations correlated with vertical upward and downward velocities, respectively, primarily driven by uplift or suppression. We proposed vertical velocity patterns resulted from internal bores, possibly triggered by shoaling semidiurnal internal tides. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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19 pages, 6202 KiB

Open AccessArticle

Tide-Induced Upwelling and Its Three-Dimensional Balance of the Vertical Component of Vorticity in the Wider Area of the Bohai Strait

by Yinfeng Xu, Xiaohui Liu, Feng Zhou, Xueen Chen, Ruijie Ye and Dake Chen

J. Mar. Sci. Eng. 2023, 11(9), 1839; https://doi.org/10.3390/jmse11091839 - 21 Sep 2023

Cited by 1 | Viewed by 878

Abstract

Upwelling is a widespread phenomenon in the ocean and plays key roles in the marine environment, marine fishery and air–sea carbon exchange. In coastal regions, the upwelling is usually modulated by tides and complex topography, but the dynamical mechanism is still unclear and [...] Read more.

Upwelling is a widespread phenomenon in the ocean and plays key roles in the marine environment, marine fishery and air–sea carbon exchange. In coastal regions, the upwelling is usually modulated by tides and complex topography, but the dynamical mechanism is still unclear and yet to be quantified. In this study, a three-dimensional (3D) regional ocean model is used to investigate tide-induced upwelling and its mechanisms quantitatively in the mouth of a semi-closed bay, the Bohai Strait, which is a tide-dominated coastal region. The results show that the upwelling mainly occurs near the tidal front in the north of the Laotieshan Channel and the southern region of the front, with the most active upwelling existing off promontories and small islands. Numerical sensitivity experiments indicate that the upwelling in the study area is mainly caused by tides, accounting for approximately 86% of the total. The 3D balance of the vertical component of the vorticity based on the model results quantifies the dynamic processes of the upwelling and reveals that tides induce the upwelling through tidal mixing and nonlinear effects. In the tidal front zone, the upwelling is mainly caused by baroclinic processes related to tidal mixing. Off promontories and small islands, we first reveal that the upwelling is driven by both the tidal mixing and nonlinear effect related to centrifugal force rather than just one of the two mechanisms, and the latter plays a dominant role in producing the upwelling. The strong nonlinear effect is attributed to the periodic movement of barotropic tidal currents rather than the mean flow. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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26 pages, 11532 KiB

Open AccessArticle

Deep Learning-Based Time Series Forecasting Models Evaluation for the Forecast of Chlorophyll a and Dissolved Oxygen in the Mar Menor

by Francisco Javier López-Andreu, Juan Antonio López-Morales, Zaida Hernández-Guillen, Juan Antonio Carrero-Rodrigo, Marta Sánchez-Alcaraz, Joaquín Francisco Atenza-Juárez and Manuel Erena

J. Mar. Sci. Eng. 2023, 11(7), 1473; https://doi.org/10.3390/jmse11071473 - 24 Jul 2023

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Abstract

The Mar Menor is a coastal lagoon of great socio-ecological and environmental value; in recent years, different localized episodes of hypoxia and eutrophication have modified the quality of its waters. The episodes are due to a drop in dissolved oxygen levels below 4 [...] Read more.

The Mar Menor is a coastal lagoon of great socio-ecological and environmental value; in recent years, different localized episodes of hypoxia and eutrophication have modified the quality of its waters. The episodes are due to a drop in dissolved oxygen levels below 4 mg/L in some parts of the lagoon and a rise in chlorophyll a to over 1.8 mg/L. Considering that monitoring the Mar Menor and its watershed is essential to understand the environmental dynamics that cause these dramatic episodes, in recent years, efforts have focused on carrying out periodic measurements of different biophysical parameters of the water. Taking advantage of the data collected and the versatility offered by neural networks, this paper evaluates the performance of a dozen advanced neural networks oriented to time series forecasted for the estimation of dissolved oxygen and chlorophyll a parameters. The data used are obtained in the water body by means of sensors carried by a multiparameter oceanographic probe and two agro-climatic stations located near the Mar Menor. For the dissolved oxygen forecast, the models based on the Time2Vec architecture, accompanied by BiLSTM and Transformer, offer an R2 greater than 0.95. In the case of chlorophyll a, three models offer an R2 above 0.92. These metrics are corroborated by forecasting these two parameters for the first time step out of the data set used. Given the satisfactory results obtained, this work is integrated as a new biophysical parameter forecast component in the monitoring platform of the Mar Menor Observatory developed by IMIDA. The results demonstrate that it is feasible to forecast the concentration of chlorophyll a and dissolved oxygen using neural networks specialized in time series forecasts. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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19 pages, 4079 KiB

Open AccessArticle

Study of Phytoplankton Biomass and Environmental Drivers in and around the Ross Sea Marine Protected Area

by Yangjinan Song and Xianqing Lv

J. Mar. Sci. Eng. 2023, 11(4), 747; https://doi.org/10.3390/jmse11040747 - 30 Mar 2023

Viewed by 1332

Abstract

The Southern Ocean plays a vital role in the global climate system and the life cycle of high-latitude marine life. Phytoplankton is an important source of primary productivity in this ecosystem. Its future changes could affect Southern Ocean geochemistry, carbon export, and higher [...] Read more.

The Southern Ocean plays a vital role in the global climate system and the life cycle of high-latitude marine life. Phytoplankton is an important source of primary productivity in this ecosystem. Its future changes could affect Southern Ocean geochemistry, carbon export, and higher trophic organisms. To better protect Antarctica, three different marine protected areas (MPA) have been established in the Ross Sea region. Because time-continuous and regionally complete data are difficult to obtain in this region, we obtained data from ocean model outputs to understand the spatiotemporal variability of phytoplankton biomass in this region. This study explored the correlation between phytoplankton biomass and key environmental factors. Phytoplankton biomass peaks in February as temperatures rise and sea ice melts. Correlations also vary between different protected areas. The correlation between biomass, nitrate, and salinity in the Krill Research Zone (KRZ) area was significantly different from other protected areas. In addition, in the context of global warming, Antarctica lacks temperature perception. The model results show a downward trend in temperature and an increase in sea ice coverage in the western Ross Sea that other studies have also pointed to. How phytoplankton biomass will change in protected areas in the future is a question worth considering. Finally, the study simply simulates future regional trends by comparing the biomass distribution in hot years to average years. This will increase our knowledge of the polar system. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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13 pages, 3516 KiB

Open AccessArticle

Ecological Response to the Diluted Water in Guangxi during the Spring Monsoon Transition in 2021

by Yang Yang, Tinglong Yang, Zhen Zhang, Zuhao Zhu, Li Zhang and Dewei Cheng

J. Mar. Sci. Eng. 2023, 11(2), 387; https://doi.org/10.3390/jmse11020387 - 09 Feb 2023

Viewed by 926

Abstract

Based on the field survey data of the Guangxi offshore voyage in May 2021, the distribution characteristics of the wind field during the spring monsoon transition period, the temporal and spatial changes in the diluted water path, and the corresponding ecological responses were [...] Read more.

Based on the field survey data of the Guangxi offshore voyage in May 2021, the distribution characteristics of the wind field during the spring monsoon transition period, the temporal and spatial changes in the diluted water path, and the corresponding ecological responses were analyzed. The results show the following: the core region of diluted water is located along the coast of Guangxi, and the diluted water expands to the east and west at the same time, where the thickness of the diluted water reaches 20 m. Under the combined action of the easterly wind and westward current, the westward expansion trend was stronger than the eastward expansion trend. The surface distribution of suspended solids, chlorophyll a, dissolved oxygen, and active silicon is similar to the dispersion range of the diluted water, and the high-value areas all appear near the estuary, which is basically consistent with the salinity distribution in the core region of the diluted water. Under the mixing caused by the wind and tide in the estuary area, the difference in dissolved oxygen between the surface and bottom layer is small, while in the nearshore area, the stratification of seawater hinders the dissolved oxygen’s downward transmission, resulting in a large difference in dissolved oxygen between the bottom and the surface. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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12 pages, 4452 KiB

Open AccessArticle

Characteristics of Mesoscale Eddies in the Vicinity of the Kuroshio: Statistics from Satellite Altimeter Observations and OFES Model Data

by Yiyun Shi, Xiaohui Liu, Tongya Liu and Dake Chen

J. Mar. Sci. Eng. 2022, 10(12), 1975; https://doi.org/10.3390/jmse10121975 - 12 Dec 2022

Cited by 1 | Viewed by 1448

Abstract

Mesoscale eddies propagate westward in the northwestern Pacific Ocean and interact with the Kuroshio in the vicinity of the western boundary of the ocean. However, the processes affecting the eddy properties and the detailed structure of the eddies when they encounter the Kuroshio [...] Read more.

Mesoscale eddies propagate westward in the northwestern Pacific Ocean and interact with the Kuroshio in the vicinity of the western boundary of the ocean. However, the processes affecting the eddy properties and the detailed structure of the eddies when they encounter the Kuroshio remain unclear. In this study, we analyze the statistics of the eddy properties around the Kuroshio using 25 years of satellite altimeter data and the eddy-resolving OFES model product. The spatial compositions of the eddies in the northwestern Pacific show that, as the eddies propagate westward, their radius and amplitude decrease sharply when they approach the Kuroshio region. The radius, amplitude, and kinetic energy of the eddies reaching the Kuroshio region decay much faster during their lifespan compared with the eddies in the interior of the Pacific Ocean. Furthermore, the three-dimensional structure of the eddies obtained from the OFES model data shows that the maximum temperature anomalies in the cyclonic and anticyclonic eddies occur at ~300 m, and the maximum depth reduces as a result of the interaction between the eddies and the main Kuroshio current. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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12 pages, 3063 KiB

Open AccessArticle

Mycoplanktonic Community Structure and Their Roles in Monitoring Environmental Changes in a Subtropical Estuary in the Beibu Gulf

by Jiongqing Huang, Huaxian Zhao, Shu Yang, Xinyi Qin, Nengjian Liao, Xiaoli Li, Qiuyan Wei, Wenjing Li, Gonglingxia Jiang, Nan Li and Pengbin Wang

J. Mar. Sci. Eng. 2022, 10(12), 1940; https://doi.org/10.3390/jmse10121940 - 07 Dec 2022

Cited by 1 | Viewed by 1071

Abstract

Mycoplankton are an important component of marine ecosystems and play a key role in material cycling and energy flow in marine ecosystems. In this study, high-throughput sequencing of the 18S rDNA gene was employed to investigate the community structure of mycoplankton during summer [...] Read more.

Mycoplankton are an important component of marine ecosystems and play a key role in material cycling and energy flow in marine ecosystems. In this study, high-throughput sequencing of the 18S rDNA gene was employed to investigate the community structure of mycoplankton during summer and winter and their response to environmental changes in the Dafengjiang River estuary in the Beibu Gulf, Guangxi. The mycoplanktonic community was generally dominated by Ascomycota, Basidiomycota, and Cryptomycota. However, there were significant seasonal differences in the α-diversity of the mycoplanktonic community (p < 0.05). Random forest modeling also revealed that Paramicrosporidium, Parengyodontium, Arthrinium, Paramycosphaerella, Pestalotia, and Talaromyces were the most effective bioindicators of environmental changes. Spearman’s correlation analysis and distance-based redundancy analysis suggested that the trophic status, chemical oxygen demand, dissolved oxygen, and salinity were the key environmental factors regulating the mycoplanktonic community structure. Variation partitioning analysis also found that nutrient levels were the main driver of the β-diversity of the mycoplanktonic community, showing a greater effect than the water quality parameters. In conclusion, this study revealed the mycoplanktonic community structure and its key drivers in the Dafengjiang River estuary, thus providing a theoretical reference for ecological environmental monitoring and resource management in the Beibu Gulf. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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17 pages, 3130 KiB

Open AccessArticle

Long-Term Benefits of Coastline Ecological Restoration in China

by Yaowen Zhang, Haoli Lin and Guanqiong Ye

J. Mar. Sci. Eng. 2022, 10(4), 541; https://doi.org/10.3390/jmse10040541 - 14 Apr 2022

Cited by 4 | Viewed by 2135

Abstract

Coastline ecological restoration is a critical approach for improving the coastal ecological environment and natural disaster mitigation capacity. Zhejiang Province, with the longest coastline in China, has carried out a three-year action of coastline remediation and restoration, expecting to complete the 300-km coastline [...] Read more.

Coastline ecological restoration is a critical approach for improving the coastal ecological environment and natural disaster mitigation capacity. Zhejiang Province, with the longest coastline in China, has carried out a three-year action of coastline remediation and restoration, expecting to complete the 300-km coastline restoration by 2020 as part of China’s coastline restoration project. We developed a cost–benefit framework synthesizing the ecosystem services (ES) analysis pattern and input-output approach to evaluate Zhejiang’s coastline ecological restoration projects. The results showed that the average value of ecosystem services (VES) of coastline restoration in Zhejiang was approximately 11,829 yuan/m, which was lower than the average VES of natural coastline. Obviously, damaged natural coastline could cause VES degradation, which cannot make up for the loss in a short time. In an optimistic scenario, coastline ecological restoration projects would deliver enormous well-being to Zhejiang and even China. Our results suggested that making decisions should be based on the net value after accounting for costs (NES), because ignoring costs might mislead planners to overstate the perceived benefits. The study provided a realistic data basis and method for coastline restoration projects in terms of the design, implementation and effectiveness evaluation to achieve sustainable development. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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15 pages, 3758 KiB

Open AccessArticle

Spatial and Temporal Variations of Chlorophyll a and Primary Productivity in the Hangzhou Bay

by Yiheng Wang, Jianfang Chen, Feng Zhou, Wei Zhang and Qiang Hao

J. Mar. Sci. Eng. 2022, 10(3), 356; https://doi.org/10.3390/jmse10030356 - 03 Mar 2022

Cited by 4 | Viewed by 1789

Abstract

The Hangzhou Bay (HZB) is an important part of the Zhoushan fishing ground, the most productive region in the Eastern China Seas. Although HZB remains eutrophication all year round, its chlorophyll a (Chl) and primary productivity (PP) are usually significantly lower than those [...] Read more.

The Hangzhou Bay (HZB) is an important part of the Zhoushan fishing ground, the most productive region in the Eastern China Seas. Although HZB remains eutrophication all year round, its chlorophyll a (Chl) and primary productivity (PP) are usually significantly lower than those in the adjacent waters. In the present study, we presented the Chl and PP distributions in the HZB and analyzed their correlations with environmental factors in four seasons. The field observation showed that Chl and PP had significant seasonal variations, and was highest in the summer (1.66 ± 0.61 mg·m⁻³ and 12.11 ± 12.25 mg C·m⁻³·h⁻¹, respectively). Total suspended matters (TSM) concentration was the key environmental factor that constrains PP in the study area. High concentration of TSM reduced light exposure (LE, the annual mean value was 0.92 ± 0.81 Einstein·m⁻²·day⁻¹) in the mixed layer of the HZB, which was much lower than the saturated light intensity of phytoplankton growth, and thus caused a strong light limitation in the HZB. However, the seasonal variations in the photosynthesis rates (P^B) and Chl did not coincide. This fact suggested that the growth rate was not the only factor controlling seasonal variations of phytoplankton biomass. In winter, the very high TSM and strong mixing might reduce the zooplankton grazing rate, and lead to a relatively high concentration of Chl during the very low LE and P^B period. These results implied that, in the HZB, the extremely turbid water could affect both phytoplankton growth and loss, which was probably the major mechanism responsible for the complex phytoplankton spatial and temporal variations. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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22 pages, 11797 KiB

Open AccessArticle

Short-Term Variations in Water Temperature of the Antarctic Surface Layer

by Yuyi Hu, Weizeng Shao, Jun Li, Chunling Zhang, Lingqiao Cheng and Qiyan Ji

J. Mar. Sci. Eng. 2022, 10(2), 287; https://doi.org/10.3390/jmse10020287 - 18 Feb 2022

Cited by 6 | Viewed by 1630

Abstract

Against the background of global climate change, the warming water temperature of Antarctic surface water (<500 m) is worthy of study. Therefore, the purpose of this study was to investigate short-term variations in the water temperature of Antarctic surface water from January 2000 [...] Read more.

Against the background of global climate change, the warming water temperature of Antarctic surface water (<500 m) is worthy of study. Therefore, the purpose of this study was to investigate short-term variations in the water temperature of Antarctic surface water from January 2000 to December 2016, using offline coupled ocean models, i.e., the WAVEWATCH-III (WW3) model and the Stony Brook Parallel Ocean Model (sbPOM). The validation of the WW3-simulated significant wave height (SWH) against the measurements from the Jason-2 altimeter produced a root mean square error (RMSE) of 0.39 m with a 0.30-m bias. Moreover, the sbPOM-simulated water temperatures were compared with the collocated measurements from Argo buoys, yielding, and RMSE for water temperatures of less than 1.0 °C and a correlation coefficient (COR) of 0.92. The annual variation in the sbPOM-simulated water temperatures of the Antarctic surface water layer showed that the sea surface temperatures (SSTs) of the Pacific Ocean and Atlantic Ocean were greater than the SST of the Indian Ocean. Moreover, the SST rapidly increased to 2 °C in the Pacific Ocean in specific years due to El Nino and La Nina events. The vertical profile of the water temperature showed that the depth of the cool water in the Indian Ocean has decreased to 100 m since 2008, while the depth in the Pacific Ocean and Atlantic Ocean is about 200 m. It was also found that the seasonal variations in the water temperature at depths of 0 m, 50 m, and 100 m in the Pacific Ocean were more sensitive to El Nino events between January and June. However, it was revealed in this work that the increasing intensity of El Nino and La Nina events could reduce water warming in the Pacific Ocean. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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Review

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14 pages, 8038 KiB

Open AccessReview

The Need for an Environmental Notification System in the Lithuanian Coastal Area

by Ilona Šakurova, Vitalijus Kondrat, Eglė Baltranaitė and Vita Gardauskė

J. Mar. Sci. Eng. 2023, 11(8), 1561; https://doi.org/10.3390/jmse11081561 - 07 Aug 2023

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Abstract

The Lithuanian coastal area is divided by the jetties of the Port of Klaipėda and represents two geomorphologically distinct parts. Local companies and institutions contribute to shaping the coastal area through infrastructure development. Awareness of the changes in the coastal zone can play [...] Read more.

The Lithuanian coastal area is divided by the jetties of the Port of Klaipėda and represents two geomorphologically distinct parts. Local companies and institutions contribute to shaping the coastal area through infrastructure development. Awareness of the changes in the coastal zone can play an important role in the planning and economic feasibility of activities in the Klaipėda coastal region. Therefore, developing a notification system that provides long– and short–term monitoring data for the Lithuanian coastal zone is necessary. In order to do so, the authors intend to create a system that should provide a link between long– and short–term observation and monitoring data for stakeholders, such as wind speed and direction, wave direction and significant height, water and air temperature, atmospheric pressure, sediment size, and distribution, height above sea level, shoreline position, beach width, change in beach protection measures, beach wreckage, and marine debris management, in order to provide timely notifications to end users. Full article

(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)

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