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Ocean Science Journal
Journal Prestige (SJR): 0.262
Citation Impact (citeScore): 1
Number of Followers: 6  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1738-5261 - ISSN (Online) 2005-7172
Published by Springer-Verlag Homepage  [2467 journals]
  • Gulf of Urabá (Caribbean Colombia), a Tropical Estuary: A Review with
           Some General Lessons About How it Works

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      Abstract: Abstract Estuaries are highly diverse ecosystems that occur at the interface between land and sea and thus possess a high degree of environmental variation over short spatial and temporal scales. The Gulf of Urabá (1800 km 2; mean depth ~ 40 m) is a semiclosed estuarine area located in the southwestern part of the Caribbean Sea (South America). This large coastal–estuarine ecosystem operates as a biogeochemical reactor due to it featuring examples of high nutrient concentrations on the surface (NO 3- = 1619 μM; NO 2- = 0.505 μM; NH 4+  = 2.938 μM; PO 4 3- = 7.603 μM), high Chl α (max = 30.17; min = 0.02; mean = 9 mg m−3), as well as blooms of toxic algae, mostly Pseudo-nitzschia pseudodelicatissima. An outbreak of Tripos fusus causes bioluminescence and about 20 events of hypoxia (< 2–4 mg O 2 L−1) within a time series of 10 years. Despite this, information regarding the biological and biogeochemical oceanography (chlorophyll α, biomass, planktonic composition, nutrient cycling, mass balance of elements, and interannual variability) remains non-existent. Therefore, elucidating an ecosystem’s thresholds for various features is necessary for managing marine ecosystems, and especially for climate change projections. We here present a review of the functioning of this estuary, evaluating and reviewing each aspect of oceanographic variability.
      PubDate: 2022-12-02
       
  • Meiofauna and Nematode Community Composition in Maxwell Bay, King George
           Island, Antarctica

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      Abstract: Abstract The Antarctic Ocean hosts several species adapted to polar environments. However, the Antarctic marine environment is rapidly changing. We studied the meiofauna and nematode communities in Maxwell Bay, King George Island, Antarctica. The meiofaunal densities ranged from 174.3 ± 6.2 to 377.9 ± 7.0 individuals/10 cm2. The nematodes and harpacticoids accounted for 89.7% of the total meiofaunal density. A total of 1448 nematode individuals across 34 genera were recorded. The dominant nematode genus was Molgolaimus. This study offers guidance for future studies on polar benthic organisms and a reference to evaluate anthropogenic effects on polar ecosystems.
      PubDate: 2022-11-09
       
  • Numerical Study of Influencing Factors on Tidal Wave Propagation in the
           Persian Gulf

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      Abstract: Abstract A 2D hydrodynamic model is employed to study the characteristics of tidal wave propagation in the Persian Gulf (PG). The study indicates that tidal waves propagate from the Arabian Sea and the Gulf of Oman into the PG through the Strait of Hormuz. The numerical model is first validated using the measured water levels and current speeds around the PG and the principal tidal constituents of Admiralty tide tables. Considering the intermediate width of the PG, in comparison to the Rossby deformation radius, the tidal wave propagates like a Kelvin wave on the boundaries. Whereas the continental shelf oscillation resonance of the basin is close to the period of diurnal constituents, the results show that the tide is mixed mainly semidiurnal. A series of numerical tests is also developed to study the various effects of geometry and bathymetry of the PG, Coriolis force, and bed friction on tidal wave deformation. Numerical tests reveal that the Coriolis force, combined with the geometry of the gulf, results in the generation of different amphidromic systems of diurnal and semidiurnal constituents. The configuration of the bathymetry of the PG, with a shallow zone at the closed end of the basin that extends along its longitudinal axis in the southern half (asymmetrical cross section), results in the deformations of incoming and returning tidal Kelvin waves and consequently the shifts of amphidromic points (APs). The bed friction also results in the movements of the APs from the centerline to the south border of the gulf.
      PubDate: 2022-11-07
       
  • Sub- and Marine Mediterranean Basin Antimicrobial Resistance and
           Environmental Concerns: A Case Study of Tunisia

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      Abstract: Abstract Antibiotics are a growing contaminant of substantial concern, principally in the aquatic environment, because of their pseudo-persistence and biological activity, and they have received a lot of attention in the recent decade. The spread of antibiotic-resistant bacteria and their antibiotic-resistant genes have showed expansion in most natural surroundings, including water, soil, and sediments, causing and presenting health problems for humans and animals. The ecological impact and environmental concerns of antibioresistance in aquatic and littoral habitats are highlighted in this review. Antibiotic pollution levels in marine, coastal water lakes, and river water flowing into the Mediterranean Sea were reported in all gathered data. Likewise, this paper showed that there was a significant lack of data and information about this pollution in seawater and general aquatic environments, revealing a substantial difficulty in following and studying these new qualities of pollutants and their main fates in natural environments. Also, their impact on the marine and lake environment in terms of the emergence of drug-resistant bacteria and drug-resistant genes was described.
      PubDate: 2022-10-25
       
  • Influence of the Cape Angle and Flow Speed on Eddy Formation and
           Detachment: Experimental Results and Comparison with North Brazil Current
           Eddies

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      Abstract: Abstract The quasi-periodic formation of eddies during retroflection of an initially steady surface current is addressed by experimental modeling and observations. The retroflection process was simulated for various conditions, corresponding to different combinations of a cape angle and surface current speed. The simulations were conducted on a stratified domain under rotation. Results indicate that eddy size and shape, and detaching frequency depend on cape angle, not on upstream speed. Eddies detach at a higher rate for 40 \(^\circ\) and 80 \(^\circ\) cape angles. Other configurations did not show either a regular eddy formation nor detaching. Eddy size was related to the internal Rossby radius of deformation ( \(R_{d}\) ) as predicted by theory. Current displacement toward the rotation axis in our experiments prior to eddy detachment was from 3.1 to 3.5 \(R_{d}\) . Retroflection angle was proportional to detachment T for each cape angle: 6T for 80 \(^\circ\) , and 3T for 40 \(^\circ\) , where T is the rotation period of the turn table. We conclude that eddy detachment is a result of eddy angular momentum increase from the momentum flux of the steady current. Similarity was analyzed with retroflection present in the North Brazil Current. Eddy vorticity profile and dimensionless quantities related to moving speed and eddy size in the oceanic flow agree with our results.
      PubDate: 2022-09-15
      DOI: 10.1007/s12601-022-00087-7
       
  • Study of Shoreline Changes Through Digital Shoreline Analysis System and
           Wave Modeling: Case of the Sandy Coast of Bou-Ismail Bay, Algeria

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      Abstract: Abstract This work aims to analyze the evolution of Bou-Ismail coastline in Algeria using aerial photographs and quick-bird satellite image during the elapsed period from 1959 to 2017 combined with a numerical modeling of waves, currents and sediments transport. The digital shoreline analysis system (DSAS) was used to quantify shoreline changes. Furthermore, the end point rate (EPR) and the net shoreline movement (NSM) approaches were used to study the evolution of this sandy coast. In addition, numerical modeling of waves, currents and sediment transport using SWAN and Mike 21 FM models were performed to better understand the longshore dynamic process and identify the waves characteristics that contributed to the evolution of the study area's shoreline. The shoreline change results show that the study area was in a moderate accretion state between 1959 and 1984 with an average end point rate of 0.13 m/year. This state turned negative and became alarming from 1984 to 1999 when EPR decreased to − 0.554 m/year. Nevertheless, the period between 1999 and 2017 is characterized by a stabilization state or even moderate accretion that translates into equivalent EPR of 0.02 m/year. The numerical simulation results show that the sandy coast of Bou-Ismail is directly exposed to waves coming from north and northwest with possible induced return currents which could be responsible for the coastal erosion observed in the study area, while northeast and northwest waves can produce a littoral drift contributing to the nourishment of some beaches of Bou-Ismail bay.
      PubDate: 2022-09-14
      DOI: 10.1007/s12601-022-00083-x
       
  • Erratum to: Spatio-Temporal Variation of the M2 Tidal Current from Field
           Observations in the Jeju Strait

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      PubDate: 2022-09-13
      DOI: 10.1007/s12601-022-00088-6
       
  • Reproductive and Growth Parameters of the Razor Clam, Cultellus maximus
           (Gmelin, 1791), in Southern Vietnam

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      Abstract: Abstract This study aimed to analyze the sex ratio, spawning seasons, length at first maturity, length distribution, length–weight relationship, and relative condition factor of Cultellus maximus (Gmelin, 1791) in Southern Vietnam. A total of 1037 individuals of C. maximus were collected at 3 sampling sites from June, 2019 to June, 2020. The sex ratio was found to be female biased in Can Gio and male biased in Phu Tan and Ngoc Hien. The clam spawns throughout the year, peaking at Q2 and Q3 during the rainy season. Pooled length at first maturity was 10.12 cm (9.65–10.49 cm CI 95%, P-value < 2.2·10–16). The length–weight relationship indicates positive allometric growth. This study suggests that imposing a minimum harvest size limit on C. maximus using the length at first maturity as reference and with harvest seasons in Q1 in Ngoc Hien and Can Gio and Q2 or Q3 in Phu Tan would be ideal for consumption of this species.
      PubDate: 2022-09-02
      DOI: 10.1007/s12601-022-00089-5
       
  • The First Recorded Occurrences and the Distribution of Physalia physalis
           (Hydrozoa: Physaliidae) in Algerian Waters

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      Abstract: Abstract Recently, there have been recorded findings of the pleustonic siphonophore Physalia physalis Linnæus, 1758, in different regions of Algeria. Several colonies washed ashore during March and May 2021 along the Algerian coast. Thirty colonies were observed on surface water and stranded on the beach between March and May from Beni Saf (35.30182° N;-1.40293° W) to Skikda (36.916557° N;7.162915° E). The highest number of such strandings of this species was recorded in Tipaza and Algiers. This is the first record of P. physalis in Algeria, extending the previously known distributions from the tropical and sub-tropical latitudes of Atlantic, Pacific and Indian oceans and may represent a danger to human health and the coastal economy. Strandings of P. physalis were notably associated with sea surface current and wind forces pushing P. physalis to become stranded on beaches. Our findings highlight the need for a monitoring program to be developed to understand more about trends associated with changes in the distribution and impact of this species. This work provides an update on the spatial distribution of P. physalis in the Mediterranean Sea.
      PubDate: 2022-09-01
       
  • Abandoned, Lost and Discarded Fishing Gear from the Fishing Sector of
           Kerala, India

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      Abstract: Abstract Abandoned, lost or otherwise discarded fishing gear (ALDFG) is rapidly becoming a major global environmental problem. In the present study, a survey of 390 fishermen operating ten different types of fishing gear was conducted, to get a quantitative estimate of ALDFG generated in the fishing intense coastal state of India (Kerala). On average, the total gear loss from 10 selected marine fishing gears operated in Kerala was estimated to be 167.5 ± 251.7 kg.vessel−1 year−1. Fishing crews reported that each year, 11.6% of the total gear used is lost, 7.5% is abandoned, and 2.3% is discarded. There was significant variation in the ALDFG incurred regarding different types of fishing gears. Motorized large mesh ring seine recorded the highest gear loss (35.5%), followed by motorized small mesh ring seine (29.7%), mini trawl (27.4%), trammel net (24.4%), motorized gillnet (18.75%), non-motorized gillnet (16.3%), small trawl (14.6%), large trawl (12.07%), medium trawl (11.25%) and shore seine (0.32%). The ALDFG estimates and associated trends worked out in the current study can assist filling in data gaps about fishing gear loss and aid in the design of strategies to manage marine debris from the fishing industry.
      PubDate: 2022-09-01
       
  • Dissolved Pb Concentrations and Stable Pb Isotope Ratios in the Ulleung
           Basin, East/Japan Sea

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      Abstract: Abstract The spatial distributions of dissolved lead (Pb) concentrations and stable Pb isotope ratios in the Ulleung Basin, East/Japan Sea, were investigated to identify the Pb source, the behavior of Pb in seawater, and the relationship between Pb isotopes and water masses. The Pb concentrations showed a surface maximum and rapidly decreased with increasing water depth. In the slope area, Pb concentrations increased near the seafloor due to diffusive flux from the sediments. The Pb concentrations in the surface layer were higher than in the Northwest Pacific Ocean and western Philippine Sea due to the proximity and downwind location of the sampling site from a Pb source area. The bottom Pb concentrations were lower in the study area than in the open ocean, indicating a higher scavenging rate due to the presence of well-developed bottom boundary layers from the continental slope to the basin. The Pb isotope ratios obtained from the continental slope and basin area were relatively constant among water masses. The Pb isotope ratios in the surface layer were similar to those of coal from northern China, which may indicate Pb supply from coal combustion in China. Meanwhile, Pb in the bottom water had a similar isotopic signature to Russian ore deposits and coal, indicating that bottom Pb is associated with thermohaline circulation in the East/Japan Sea. The Pb isotope ratios of the intermediate layer were constant across the depths of East Sea Central Water (ESCW) and were similar to aerosols measured previously (in 2003–2004) around Ulleung Island, which may indicate the timing of ESCW formation.
      PubDate: 2022-09-01
       
  • Evolution and Sedimentation Mechanisms of Estuarine Beach in the Nakdong
           River Estuary, Korea: Natural and Human Impact

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      Abstract: Abstract Dadae Beach located in the Nakdong River estuary has been continuously evolving as the result of natural and anthropogenetic activities. Due to the geographic characteristics of an estuarine beach, in which the estuary, ocean, and human activities converge, it is very difficult to identify the factors shaping changes in the sedimentary environment and present quantitative results. Nevertheless, this study presents a survey of hydrological characteristics that reveals major depositional mechanisms and the factors impacting the sedimentary environment by analyzing morphological variations over the last five decades. We found that Dadae Beach has transformed from a marine system to an estuarine system through three major stages of evolution over the last five decades and has now reached a quasi-equilibrium state. The depositional mechanism contributing to the deposition of Dadae Beach is mainly driven by rainfall during the wet season. In addition, the strengthening of ocean energy during the dry season causes erosion. By proposing a new evolutionary history of Dadae Beach which had previously been considered a byproduct of the barrier island generation process of the Nakdong River, we suggest a novel conceptual model for estuarine beach evolution.
      PubDate: 2022-09-01
       
  • Estimation of Seasonal Representation of the Sea Water Temperature Profile
           Using Machine Learning and Its Effect on the Prediction of Underwater
           Acoustic Detection Performance

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      Abstract: Abstract Seawater temperature and salinity profiles are important physical properties that represent oceanic environments and affect underwater acoustic detection prediction performance. Average ocean data can be used to predict the SONAR detection area in areas where obtaining real-time ocean data or instantly predicting the SONAR detection area is difficult. However, it can yield distorted results. In this study, representative temperature profiles reflecting properties of the vertical structure at various temperatures in the study area were obtained using K-means clustering, an unsupervised machine learning technique. K-means clustering was applied to the temperature profiles obtained from the three stations of the Ulleung Basin in the East Sea. In addition, the physical characteristics of the representative profiles obtained were compared, and the representativeness of the acoustic detection area obtained from the representative profiles was evaluated. In summer, when the mixed layer was thin, each cluster was classified according to the vertical temperature gradient of the thermocline. In winter, the clusters were classified according to the mixed layer and thermocline depths, rather than the vertical temperature gradient of the thermocline. For each obtained cluster, the acoustic detection area was calculated using all the profiles and displayed as a histogram. The acoustic detection area calculated from the representative profile of the cluster was generally close to the average of the acoustic detection area. Thus, K-means clustering can effectively classify temperature profiles physically and acoustically and can potentially be applied in other regions for the classification and analysis of seawater temperature and salinity profiles.
      PubDate: 2022-08-12
      DOI: 10.1007/s12601-022-00086-8
       
  • Estimation of Potential Habitats for Three Species of Bivalves Using the
           Habitat Variables in Gomso Bay Tidal Flat, Korea

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      Abstract: Abstract The gradual changes in the habitat of Gomso Bay negative impacted the intertidal flat aquaculture of the Manila clam Ruditapes philippinarum. The habitat evaluation of the Manila clam in Gomso Bay tidal flat that should be preceded to identify this negative impact in clam culture was conducted using the habitat variables chlorophyll-a, hydrodynamics, sediment sand, exposure time, dissolved oxygen, and salinity. Additionally, to utilize the unsuitable sites of Manila clam culture, we used the habitat suitability index by subdividing substrate variables (sorting coefficient, silt content, and mean grain size) for two species (Cyclina sinensis and Mactra veneriformis). As a result, the lower flat was chosen as the optimal habitat for Manila clam, with a habitat suitability index mean score of 0.62 and the upper flat was deemed to be the potential habitat for C. sinensis, while the middle flat was chosen for M. veneriformis. Therefore, the possibility of using unsuitable sites for Manila clam farming as alternative species was identified. These findings can be used as a reference for optimal site selection for the diversification of commercial species and decentralization of clam culture farms in the Gomso Bay tidal flat.
      PubDate: 2022-08-04
      DOI: 10.1007/s12601-022-00085-9
       
  • Spatio-Temporal Variation of the M2 Tidal Current from Field Observations
           in the Jeju Strait

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      Abstract: Abstract The variability in the tidal current in the Jeju Strait was investigated based on sea surface current fields observed by a high-frequency (HF) radar and vertical current profiles observed by three bottom-moored acoustic Doppler current profilers (ADCPs). The monthly M2 tidal current, the most dominant constituent in the study area, had significant temporal variability, and there were spatial changes in the temporal variation trend. While the semi-major axis of the M2 tidal current in winter was stronger than that in summer in some parts of the HF radar observation range, the summertime semi-major axis was stronger than that in wintertime in other parts of the observation range. Both opposite trend areas coexisted within the HF radar coverage area of several tens of kilometers. The vertical structure of the tidal currents in winter was similar to the theoretical structure in which Ekman dynamics was applied under depth-independent vertical eddy viscosity, and the year-to-year change was weak. In contrast, the vertical structure of the tidal currents in summer significantly varies over depth and years. Furthermore, the seasonal variation patterns at the three ADCP stations differed spatially. The temporal and spatial variability of tidal currents could be explained as a result of the strengthening stratification and, consequently, semidiurnal internal tides in summer. In summer, an internal tide with a wavelength of tens of kilometers could be generated in the vicinity of and propagate into the study area. The overlapping and offsetting of the barotropic and internal tidal components within the HF radar observation range caused complex spatial variations.
      PubDate: 2022-08-01
      DOI: 10.1007/s12601-022-00084-w
       
  • Effects of Light, Salinity and Temperature on Germination Characteristics
           of Surfgrass, Phyllospadix japonicus and P. iwatensis Seeds

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      Abstract: Abstract Surfgrass (Phyllospadix spp.) is a marine flowering plant that attaches to the bedrock of the Pacific Ocean, where the tide is fast and the waves are strong. In Korea, two species of surfgrass are mainly found on the east coast. Phyllospadix japonicus is present throughout the east coast, whereas P. iwatensis is mainly present on the central east coast. The germination requirements of these two surfgrass species were studied in relation to the light, salinity, and temperature treatments. In the light test, both species showed significantly higher percentage germination (PG), faster daily germination rate (DGR), and shorter mean time-to-germinate (MTG) under light conditions than those under dark conditions. In the salinity and temperature experiments, the highest PGs for P. japonicus and P. iwatensis were 95.6 ± 4.4% and 82.2 ± 1.1%, respectively, at 30 psu and 7 °C. The maximum DGRs of P. japonicus and P. iwatensis were 1.95 ± 0.04 seeds d−1 and 1.43 ± 0.05 seeds d−1, respectively, at 15 psu and 17 °C. MTGs of both species were the shortest at 15 psu at all temperatures, and increased as salinity increased. The two surfgrass species showed a similar germination tendency, but P. japonicus showed a higher PG, faster DGR, and shorter MTG than P. iwatensis. Owing to these differences in germination characteristics, P. japonicus may have an advantage for occupying a wider bedrock area in the East Sea coast of the Korean Peninsula.
      PubDate: 2022-07-29
      DOI: 10.1007/s12601-022-00077-9
       
  • Monsoon-Driven Geomorphological Changes Along the West Coast of Sri Lanka:
           A Combined Approach Utilizing ‘CoastSat’ and Google Earth Engine

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      Abstract: Abstract Long-term field monitoring of shoreline changes is time-consuming, expensive, and labor-intensive. Instead, satellite images can be used as an alternative method to collect field data. The time-series satellite images are available at any location in the world that can be processed with the Google Earth Engine cloud environment. This study primarily focuses on shoreline change detection and describing the coastal geomorphology of three urban beaches on the west coast of Sri Lanka. The study extended from 2015 to 2021 during which large-scale coastal development projects were carried out in the study area. The ‘CoastSat’ toolkit was used to extract the time-series of shoreline positions. Time-series shoreline position obtained through ‘CoastSat’ was compared with the field measurements carried out using the Global Navigation Satellite System technique with a horizontal accuracy of 7 mm. The results indicate that the average horizontal difference of shoreline positions obtained by ‘CoastSat’ and field observation was 7.5 ± 1 m in Agulana-Ratmalana on 19 August 2019, and was 8.3 ± 1 m in Kalutara on 29 July 2020. The extracted shoreline changes show erosion and deposition patterns affected by monsoon seasonality and anthropogenic events. The results further show that North of Mount Lavinia Beach was accreted from 18 to 27 m, while South of Mount Lavinia Beach was eroded from 12 to 17 m. Accretion was mainly due to sand nourishment in the area during the 1st quarter of 2020. Furthermore, Agulana-Ratmalana Beach predominantly accreted from 22 to 30 m, while the northernmost transect (AR1) had a steady-state beach condition. This was again due to nourished sand during the 1st quarter of 2020. In contrast, accretion and erosion trends in Kalutara Beach are mainly due to the breakup of the river mouth sand bar to control flooding by the artificial cutting open of the sand spit bar in 2017. The transect (KL2) near the broken sand spit bar at the north of Kalutara shows severe erosion (56 m), since northward longshore transport of sediment has stopped with the breakage of the sand spit bar. In contrast, Kalutara south transects show an accretion to steady-state condition due to the existing hard engineering structures. Consequently, the study suggests that the CoastSat: A Google Earth Engine-enabled Python toolkit can be used to extract shoreline positions and to detect medium-to-large-scale coastline changes with appropriate tidal corrections, when and where there are no long-term coastal field measurements available. This method could be adapted to any coastal area in the world for acceptable shoreline detection that would be very useful for planning and evaluating coastal management strategies.
      PubDate: 2022-07-07
      DOI: 10.1007/s12601-022-00081-z
       
  • Multi-proxy Stratigraphy and Paleoceanographic Variations in Sediment from
           the Korea Plateau, East Sea (Japan Sea), Over the Last 500 kyr

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      Abstract: Abstract High-resolution geochemical measurements were performed on core E09-08, which was taken from the top flat area of the Korea Plateau in the East Sea (Japan Sea). Based on analyses of sedimentary lamination, high-resolution oxygen isotopes, alkenone sea surface temperature (SST) variations, and comparison with previous results from the eastern part of the East Sea, a detailed multi-proxy-based stratigraphy was reconstructed. The results demonstrated that the core bottom dates approximately 500 kyr in the late marine isotope stage (MIS) 13, and provides high-resolution data on the paleoceanographic regime in the study area. Biogenic components of total organic carbon (TOC), carbon and nitrogen isotopes of organic matter (δ13Corg and δ15Norg), and alkenone concentrations indicate a paleoceanographic regime shift within the last 500 kyr. The excursion of proxies of δ18O, δ13Corg and δ15Norg and alkenone-based SST indicate two modes of oceanographic conditions: strong negative coupled mode (SNCM) during MIS 2, 10, and 12, and normal oceanographic decoupled mode (NODM) during other MIS. These two modes were interpreted as the terrestrial organic matter source domain and high-productivity oceanographic domain, respectively. The SNCM is characterized by relatively low δ13Corg and δ15Norg, and a high C/N ratio (> 12), whereas the NODM is characterized by relatively high δ13Corg and high δ15Norg, implying that larger amounts of terrestrial material were supplied during MIS 2, 10 and 12, with enhanced productivity during other MIS. The SNCM and NODM mode are also strongly associated with eustatic sea-level changes. The δ13Corg and δ15Norg values and alkenone-based SST excursions over glacial-interglacial periods were generally consistent with global-scale paleoclimate variation, as well as local paleoclimate. This study employed multi-proxy-based stratigraphy to demonstrate dramatic oceanographic variations since MIS 13, indicating that the local oceanographic setting was superimposed on global glacial-interglacial variations.
      PubDate: 2022-06-14
      DOI: 10.1007/s12601-022-00076-w
       
  • Seasonal Growth Dynamics of Posidonia oceanica in a Pristine Mediterranean
           Gulf

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      Abstract: Abstract Seasonal growth dynamics and ecology of Posidonia oceanica were studied in a space alongshore a pristine Mediterranean gulf in 2011–2012. About one-third of the present study surface area was occupied meadows where only calcite rocks were found on bottoms between 0.5 and 29 m. Shoot density was not significantly different among seasons, and was above 364 ± 27 shoots m−2, but was different among the depths. The density variables decreased along the bottom depth gradient along which the number of leaves per shoot, inter shoot distance and the morphometrical variables tended to increase. Inferring the dynamics of biometrics (length and width of leaf, orthotropic rhizomes and leaf sheath) and density (LAI, leaf biomass and the number of leaves per shoot), the biometrics of the meadow grew seasonally between growth by March and mortality by August–September, regardless of the coverage area. Mortality occurred due to the highest annual salinity in late summer. A transition depth in space and month in time was assessed as 15 m and as August for variation of the biometrics, respectively. Rhizome related-biometrics (length, thickness, weight, sheath length and width) were dynamically initialized mainly by water nitrogen content which was high by winter-spring. A PAR in the range of 10–32%, and surface water temperature up to 28.8–29.3 °C corresponding to up to ~ 40 PSU were critical limiting factors for P. oceanica to survive in space. Water physics, chemistry, and optical properties governed the annual course of biometrics. Total organic carbon was also negatively affecting the seasonal dynamics of the rhizome.
      PubDate: 2022-06-13
      DOI: 10.1007/s12601-022-00078-8
       
  • Current Structure and Volume Transport in the Jeju Strait Observed for a
           Year with Multiple ADCP Moorings

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      Abstract: Abstract The seasonal and spatial variation of the current structure and volume transport across the Jeju Strait (JS) is described based on an analysis of the data from five bottom mounted acoustic Doppler current profilers from February 13, 2020 to February 23, 2021. The current was weak and the mixed layer was well developed in winter, so the vertical current shear was not large. Whereas in summer, the inflow of high-temperature and low-salinity surface water built up the stratification, and the surface current velocity increased, resulting in a large vertical current shear. One salient feature to be found was that a westward flowing counter current in the lower layer appeared from June to December near the bottom trough of the JS. We named this seasonal counter current in the lower layer the Jeju Strait Under Current. The eastward net volume transport passing through the JS was large in summer–autumn and small in winter-spring, but did not follow a simple sinusoidal pattern. The annual mean net volume transport was 0.48 Sv (Sv ≡ 106 m3 s−1), with a minimum (0.27 Sv) in December and a maximum (0.79 Sv) in October 2020. When there were strong northerly winds in winter, a net volume transport to the west was temporarily caused by Ekman transport, but the direction reverted to the east as soon as the northerly winds lessened. When there were strong northwesterly (southeasterly) winds due to typhoons, the volume transport decreased (increased) sharply and then recovered rapidly.
      PubDate: 2022-06-08
      DOI: 10.1007/s12601-022-00079-7
       
 
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