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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  [2468 journals]
  • Erratum: Path Prediction for Fishing Boats Using Attention-Based
           Bidirectional Gated Recurrent Unit

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      PubDate: 2024-02-13
       
  • Monitoring Maritime Ship Characteristics Using Satellite Remote Sensing
           Data from Different Sensors

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      Abstract: Abstract Ship monitoring is important for understanding human maritime activities. Automatic identification systems are widely adopted for ship monitoring. It is not possible to extract ship information when the automatic identification system is dysfunctional due to technical problems or intentionally turned off. Satellite remote sensing is an alternative method for ship monitoring when automatic identification systems are not operational. Since McDonnell and Lewis published the first ship detection study in 1978, ship-monitoring techniques using different types of satellite sensors, such as the synthetic aperture radar, daylight and nighttime-light optical sensors, and radio frequency detectors, have been continuously improving. Despite these improvements, few studies have compared the advantages and disadvantages of each sensor-based ship-monitoring technique. In this study, we reviewed ship-monitoring techniques that used different types of sensors, including the synthetic aperture radar, day- and nighttime-light optical sensors, and radio frequency detectors. Particularly, we focused on ship detection, velocity estimation, and type classification based on these sensors. We hope that this study will contribute to the establishment of a novel maritime surveillance system in the future, supplementing ground observation methods, such as automatic identification systems.
      PubDate: 2024-01-30
       
  • Evaluation of Ecosystem Services Provided by Pacific Oyster, Crassostrea
           gigas, Farms in Hansan Bay, Korea

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      Abstract: Abstract Korea is the second highest producer of cultured Pacific oyster, Crassostrea gigas, in the world, but their potential economic values of ecosystem services have not yet been evaluated. As the first case study, we evaluated the potential values of C. gigas cultured in Hansan Bay, Korea. We utilized Gangnery’s growth model to assess the provisioning and regulating services, assuming that the nitrogen removal amount equals the difference between input and harvested oysters in terms of accumulated nitrogen. To convert these measured services into monetary values, we used the market price of C. gigas for provisioning service, and the annual operational report regarding the current state of domestic sewage treatments for regulating service. We estimated that cultivating a ha of C. gigas farms has a monetary value ranging from ca. −16.6 to 67.6 thousand US dollars, which is considerably lower than other research findings. Results suggested that the growth model applied in this study is suitable and effective, particularly in cases where other models may not be applicable. Additionally, we compared the values of coastal areas when shifting from C. gigas cultivation to another species or maintaining the status quo to assist policymakers in making decisions. Despite some limitations, our model is expected to contribute to appraising the monetary values of coastal areas and mitigating conflicts in marine spatial planning.
      PubDate: 2024-01-27
       
  • Utilizing Room-Temperature Ionic Liquids in the Analysis of Volatile
           Hazardous and Noxious Substances in Marine Sediments

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      Abstract: Abstract Hazardous and noxious substances (HNS) encompass a wide range of materials, including hazardous liquid substances, liquefied gases, and bulk or packaged solid dangerous goods. These substances are primarily generated during ship transportation or released into the water system as a result of industrial processes at marine industrial facilities, ultimately entering the marine environment. Due to the potential persistence of certain HNS in seawater and marine sediments, they pose substantial risks to both human health and marine environment. The environmental behavior may differ from conventional theories. This indicates the importance of developing a standard method to measure the accurate amount of HNS in the aquatic environment. For ten volatile HNS frequently detected in sediment using the Water Pollution Standard Method, we developed analytical method using room-temperature ionic liquids (RTIL) as extraction solvent for headspace (HS) coupled with GC–MS. Our results suggest that among NaCl and three hydrophilic RTILs, [EMIM][ESO4] is the most effective extraction solvent, showing favorable quality control results for all target analytes. To the best of our knowledge, hydrophilic RTILs have not been previously used for volatile HNS analysis in marine sediments. To confirm field applicability, ten HNS(chloroform, benzene, trichloroethylene, bromodichloromethane, toluene, tetrachloroethylene, dibromochloromethane, ethylbenzene, p,m-xylene, o,xylene) were measured by the method of this study in sediment samples near marine industrial facilities. It was confirmed that chloroform, bromodichloromethane, and p,m-xylene were detected in surrounding the marine industrial facilities. This study could provide valuable insights into the suitability and effectiveness of RTILs as solvents for HS-GC/MS analysis, potentially improving the assessment and monitoring of HNS contamination in marine environments.
      PubDate: 2024-01-26
       
  • Substrate Characteristics Determine the Distribution and Abundance of Reef
           and Reef-Associated Fish: A Comprehensive Study in Protected and
           Non-protected Coral Ecosystems of Sri Lanka

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      Abstract: Abstract Coral reefs are one of the most productive marine ecosystems that support reefs and reef-associated fish and invertebrates. The abundance and distribution of reef and reef-associated fish species concerning substrate characteristics were empirically ascertained, evaluating protected (Bonavista) and non-protected (Trincomalee) coral reef ecosystems in Sri Lanka. Line Intercept Transect (LIT) and Underwater visual belt transect methods were employed to estimate fish and substrate diversity, distribution, and abundance during the non-monsoonal period. Shannon–Weiner index was employed to compute substrate and fish diversity, while the Similarity Index was computed to compare the similarity of the reef ecosystems. Data were analyzed using CPCe, SPSS, and MS Excel software, wherever applicable. Physicochemical parameters of seawater in the coral reef environs located on the east and southern coasts were indistinguishable (P > 0.05). Eighteen and 34 hard coral species were encountered, all of which accounted for 22.37 ± 1.27% and 68.40 ± 2.93% of the total substrate in the Bonavista and Trincomalee reefs, respectively. Merulinidae and Acroporidae were the dominant coral families and the two families of fish, Labridae and Pomacentridae accounted for the highest number of species and individuals in Bonavista and Trincomalee reefs, respectively. A total of 127 and 109 reef and reef-associated fish species were encountered at Bonavista and Trincomalee reefs, respectively. The number of fish families, species, and individuals was comparatively higher in Bonavista, albeit species diversity and evenness were higher in Trincomalee. The number of species and individuals in Bonavista and Trincomalee reef ecosystems showed a significant positive relationship (P < 0.05) with coral cover and the number of microhabitats. Species diversity at two reef ecosystems showed a positive relationship (P < 0.05) with coral cover and a negative relationship with rubble cover. Species of family Labridae showed a significant positive relationship (P < 0.05) with coral cover and the number of microhabitats, while family Pomacentridae showed strong relationships (P < 0.05) with rock cover. The present study elucidates that relationships between fish species and habitat characteristics are conspicuous and common to both reef ecosystems. And findings help authorities make policy decisions and manage species and reef environs for the long run.
      PubDate: 2024-01-26
       
  • Analysis of the Effects of Minimum Capture Size Limits on Changes in the
           Biomass and Fishing Profits of Sandfish, Arctoscopus japonicus, in Korean
           Waters

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      Abstract: Abstract Korea has implemented prohibitory regulations on fishing for particular periods (or seasons), areas, sexes, depths, and minimum lengths (or weights) for fish species, along with implementation of the Total Allowable Catch (TAC) system, for the management and protection of fishery resources in Korean waters. In this study, the ecological and economic effects of minimum capture size limits were analyzed for the sandfish Arctoscopus japonicus. Sandfish are currently mainly targeted by the East Sea Mid-sized Danish seine fishery, and the total length at first capture ( \(TL_{tc}\) ) of the fishery is 14.9 cm, which is larger than the minimum permitted total length (TL 11 cm or less). Therefore, it seems that there is little chance of growth overfishing at present. However, recruitment overfishing occurs with a spawning potential ratio (SPR) of 18%. Therefore, it is likely that this will need to be reflected in Acceptable Biological Catch (ABC) settings for TAC management. If the current \(TL_{tc}\) (14.9 cm) is considered to be a consequence of setting minimum capture size limits for the East Sea Mid-sized Danish seine fishery, the expected catch and fishing profit for cases without ( \(TL_{tc}\)  = 9 cm) and with ( \(TL_{tc}\)  = 14.9 cm) minimum capture size limits were 2204 mt (217,000 US$) and 2744 mt (270,000 US$), respectively. The establishment of the minimum capture size limit regulations showed an increase of approximately 25% in fish production and fishing profits. In addition, by testing several scenarios for the fishing intensity and the minimum capture size limits, we were able to compare the biomass of sandfish and the fishing profits of the East Sea Mid-sized Danish seine fishery after 15 years. We found that this approach was most effective in reducing the combined fishing intensities of juvenile and adult fish and more effective in reducing the fishing intensity for juveniles than for adult fish, thereby increasing the biomass and fishing profits of sandfish. These findings indicate that to recover populations and sustainably use sandfish, stocks should be managed through a holistic integrated approach that considers the ecosystem, which has been actively promoted by the Korean government in the third National Basic Plan for Fisheries Resources Management (2021–2025), rather than individually pursuing management policies such as the minimum size limit regulation, the Fisheries Resources Rebuilding Program, and the TAC management system.
      PubDate: 2024-01-18
       
  • Path Prediction for Fishing Boats Using Attention-Based Bidirectional
           Gated Recurrent Unit

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      Abstract: Abstract Obtaining trajectory predictions for fishing boats in complex and unpredictable seas is essential for preventing ship collisions. In this study, we propose a deep-learning model that predicts the paths of fishing boats. We choose offshore trap fishery as the fishery type for which the movement paths of fishing boats are predicted. It is because offshore trap fishing boats sail in sudden changes of 90° or more. Piecewise cubic Hermite interpolation polynomial (PCHIP) is used to interpolate regular-interval data. We focus on extracting feature variables that consider the impact of daytime and nighttime conditions on fishing operations. Trajectory windows are constructed using a sliding-window approach to create input datasets for deep learning. The framework employed is based on the sequence-to-sequence (Seq2Seq) architecture with an attention mechanism. The experimental results demonstrate the superiority of Seq2Seq with attention over Seq2Seq without attention. The performance of our proposed method has increased by at least 7.0%, 12.0% on average, compared with the GRU and LSTM. The technology developed in this study is expected to prevent collision accidents between autonomous ships and fishing boats in the future. In addition, because it is possible to predict the future path of the fishing boat, this technology can be used in the decision-making system of vessel traffic service operators.
      PubDate: 2023-12-28
       
  • The Annual Reproductive Cycle and Reproductive Effort of the Pacific
           Oyster Crassostrea gigas from a Tidal Flat in Incheon Bay on the West
           Coast of Korea

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      Abstract: Abstract Understanding temporal changes in reproductive conditions and physicochemical environmental factors governing the variation is vital in the management and ecology of oysters. This study investigated the annual gametogenesis and reproductive effort of the Pacific oyster Crassostrea gigas in Incheon Bay using histology and indirect enzyme-linked immunoassay (ELISA). Seasonal changes in the reproductive condition were closely associated with the changes in sea surface temperature (SST), as a rapid increase in SST from April (10.1 °C) to early June (18.7 °C) coincided with the growth and maturation of the eggs. Histology indicated that the spawning was synchronous, as both males and females initiated the spawning in late June, which continued until early August. Gonad-somatic index (GSI), a ratio of the egg mass to the tissue weight determined by ELISA, showed a dramatic decline from late June (47.3%) to August (3.9%), suggesting that the females discharged a substantial amount of eggs through spawning, which accounted for approximately 40% of the body weight. The condition index (CI) of oysters determined in this study was comparable to those of oysters reported from the south coast, where oysters were raised in subtidal using suspended long lines, suggesting that the off-bottom culture of the Pacific oysters near the low tide line in Incheon Bay is a promising culture technique in the tidal flat environment.
      PubDate: 2023-12-18
       
  • Spatio-Temporal Variation in Perkinsus olseni Infection Intensity in
           Manila Clam Ruditapes philippinarum in Anmyeondo and Cheonsu Bay Tidal
           Flats on the West Coast of Korea

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      Abstract: Abstract The alveolate protist Perkinsus olseni infections impose considerable stresses on the host Manila clam Ruditapes philippinarum, often reducing their tissue weight due to the drain on energy resources. However, the relationship between condition factors and P. olseni infection exhibits inconsistency in different scenarios, as it is influenced by various factors such as environmental conditions, food availability, and reproductive conditions. To gain deeper insights, we surveyed Manila clams occurring on tidal flats in Anmyeondo Island, Cheonsu Bay to assess P. olseni intensity and its effects on the fitness of Manila clams. The Ray’s fluid thioglycollate medium assay revealed that P. olseni infection in clams from inner Cheonsu Bay had considerably greater P. olseni intensities in May and September 2021 than those from outer Cheonsu Bay and reference sites (P < 0.05). Despite the high level of P. olseni infection, condition index (CI), a ratio of the flesh weight to the shell weight, in clams from inner Cheonsu Bay was also significantly higher than in clams from outer Cheonsu Bay and reference sites (P < 0.05). A noteworthy finding of this study was the positive association between P. olseni infection intensity and CI in clams, which suggests that despite the high parasite load, clams were able to maintain a higher CI, possibly due to the abundance of nutrients and organic matter present in the inner bay. The P. olseni infection intensities measured in September were significantly higher at most of the sampling sites in the inner and outer bay, which could be associated with the poor health condition of clams during a post-spawning period. These results highlight the complexity of bivalves’ ecological relationships in Cheonsu Bay and offer new insights into their adaptability accompanied by other factors to parasite stressors.
      PubDate: 2023-12-12
       
  • Characteristics of Plastic Debris Ingested by Sea Turtles: A Comprehensive
           Review

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      Abstract: Abstract Sea turtles, an ecologically vital marine species, face the mounting threat of plastic ingestion. To devise effective mitigation strategies, a nuanced understanding of the characteristics of ingested plastics is essential. Previous reviews have predominantly concentrated on the frequency of occurrence (%FO) and quantity of ingested plastics. In this study, we present an update to the literature on %FO and quantity of ingested plastics and also introduce a novel review of the morphology, color, and polymer composition of ingested plastics. This analysis draws upon 110 scholarly articles on plastic ingestion by sea turtles. Additionally, we explore geographical variations in both the quantity and characteristics of ingested plastics. Most of the analyzed studies were conducted in the Americas and Europe. We found that approximately 54% of examined sea turtles had ingested plastic debris. Loggerhead sea turtles ingested more foams than green sea turtles (Wilcoxon rank-sum test, p < 0.05). By contrast, green sea turtles exhibited a higher ingestion on films (Wilcoxon rank-sum test, p > 0.05). Our study also underscored the paucity of data regarding the original usage of ingested plastics. White and transparent plastics were most commonly ingested. Additionally, polymers with a lower density than seawater, such as polyethylene, polypropylene, and their copolymers, were frequently found. We strongly advocate for future studies to furnish more comprehensive data regarding the ingested plastics, including quantities, morphological and chemical properties, and origins. Such detailed information is indispensable for shaping well-informed and effective strategies to combat plastic ingestion in marine life.
      PubDate: 2023-11-09
      DOI: 10.1007/s12601-023-00124-z
       
  • Movability Number as the Parameter of Sediment Incipient Motion: A
           Mathematical Approach

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      Abstract: Abstract In fluvial sediment transport, the sediment threshold parameter Movability Number, which is the ratio of the shear velocity and the settling velocity of a sediment particle, is seen as a potential replacement for the traditional Shields parameter. Until now, the studies carried out on Movability Number have been mostly empirical or crudely analytical. In the current study, a mathematical modeling approach is attempted. Steady unidirectional flow is considered and the mode of entrainment is taken as that of rolling, with a compact sediment bed. The mathematical relationships developed here express the Movability Number as a function of either shear Reynolds number or dimensionless grain diameter. Comparisons are made with both experimental data and previous empirical formulae. The developed model is a novel approach to study the Movability Number, which bears satisfactory nearness to the previous studies. The deviation produced in terms of underestimation is due to the rolling mode of motion, which requires the least disturbing energy. The developed model can be improved by the consideration of turbulence in future studies.
      PubDate: 2023-10-11
      DOI: 10.1007/s12601-023-00112-3
       
  • Distribution and Abundance of Intertidal Sponge (Porifera) Communities in
           Coral Reefs of Singapore

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      Abstract: Abstract Given the important functional roles of sponges in the coral reef community, few studies have looked at sponge community assemblages in Singapore. This study was conducted to assess the sponge diversity, species richness, and species abundance of intertidal sponge communities in Singapore’s coral reefs, including Pulau Hantu, P. Subar Laut, Tanjong Rimau, and Labrador Park. Belt transects measuring 10 m by 1 m were established to survey the sponge communities at these reef sites. Based on sponge morphology, a total of 28 morphospecies were identified, belonging to eight different sponge orders, namely Chondrillida, Clionaida, Dictyoceratida, Haplosclerida, Poecilosclerida, Suberitida, Tetractinellida, and Verongiida. Univariate statistical analyses revealed that sponge diversity, species richness, and abundance at P. Hantu site 2 were significantly higher than that in Labrador Park. In addition, multivariate statistical analyses showed that in terms of community structure, there were three distinct clusters found at P. Hantu site 2, Labrador Park, and P. Subar Laut. The formation of these distinct clusters was sponge species specific and shaped by environmental factors and anthropogenic stresses. Preliminary sponge data presented in this study contribute to the regional biogeography of sponges and could serve as baseline data for future studies, including ecological research and biomonitoring of marine invertebrates, and support marine conservation efforts in Singapore.
      PubDate: 2023-10-11
      DOI: 10.1007/s12601-023-00123-0
       
  • A Comprehensive Investigation of Coastal and Shelf Sediment Sources in the
           South Sea of Korea: A Marginal Sea of the Northwestern Pacific

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      Abstract: Abstract To identify and quantify the sediment sources in the South Sea of Korea, a marginal sea of the northwestern Pacific, we analyzed a comprehensive aluminum–magnesium dataset comprising 121 surface sediment samples and two sediment cores. The findings demonstrate pronounced spatial variation in sediment sources, with Korean river sediments dominating in embayment bays and Chinese river sediments prevailing in the shelf area. In the coastal zone, Korean river sediments account for over 60–70%, but their proportion decreased to 10–20% in the shelf zone. This reveals that most of the sediments from Korean rivers are mainly confined to the coastal embayments, with limited transport to the shelf area. Notably, the central South Sea mud (CSSM) deposits are primarily govern by the sediment influx from Chinese rivers (CR), rather than the Seomjin River discharge. The prevalence of CR-sourced sediments in the shelf region is closely linked to the Tsushima Warm Current and Cheju Warm Current, transporting sediments from the East China Sea shelf northwards and the southwestern Korean coastal zone eastwards, respectively. This driving mechanism for the widespread deposition of CR sediments is further supported by an abrupt shift from KR to CR dominance in sediment sources around 8 kyr BP, coinciding with the establishment of the modern current systems in the northwestern Pacific marginal seas. Our study provides a new perspective on the source-to-sink pathways, particularly of Chinese river sediments, in the formation of the Korean coastal mud deposits.
      PubDate: 2023-10-06
      DOI: 10.1007/s12601-023-00121-2
       
  • Development and Benchmarking of the Shallow Shelf Approximation Ice Sheet
           Dynamics Module

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      Abstract: Abstract Numerical simulation of ice sheet dynamics is crucial for improved assessment and prediction of glacier mass balance and grounding line migration. For the quantitative simulation of continental-scale ice sheets in Antarctica and Greenland, ice flow models have been described using the Shallow Shelf Approximation (SSA), Shallow Ice Approximation (SIA), and combinations thereof. Here, we developed the COM-SSA, a finite element SSA module implemented in COMSOL Multiphysics® via the Weak Form module. To verify the applicability of the COM-SSA to ice sheet dynamics, five independent cases were modeled and compared with the Ice Sheet System Model (ISSM), which is a widely used ice sheet dynamics package. In Cases 1 and 2, which considered the nonlinearity problems of Glen’s viscosity and Weertman-type friction laws, we confirmed that the COM-SSA successfully handled the convergence of viscosity and basal friction with an increasing number of iterations. In Case 3, we tested the ice thickness evolution computed by solving the equation of mass conservation. Grounding line migration in response to ice thickness changes was investigated in Case 4. The COM-SSA showed a similar pattern of glacier geometry evolution compared to ISSM in Cases 3 and 4, indicating that the COM-SSA could precisely calculate ice sheet dynamics in a time-dependent manner. We demonstrated the capabilities of the COM-SSA in Case 5, to which the Pine Island Glacier in Antarctica was subjected. Similar to the ISSM, the COM-SSA predicted the velocity field, ice thickness, and grounding line for the Pine Island Glacier after 300 years of ablation.
      PubDate: 2023-09-27
      DOI: 10.1007/s12601-023-00120-3
       
  • Assessing the Potential Marine Environmental Impacts of Heavy Metal
           Leaching from Ship Cleaning Residues

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      Abstract: Abstract Antifouling paint is periodically applied to prevent the fouling of marine organisms that increase friction on the ship operations and fuel consumption. However, the process of cleaning the surface of ships in coastal areas results in the introduction of alien species, and a large amount of heavy metals, such as Cu and Zn, which are toxic substances in antifouling paints, are discharged. Mixed antifouling sludge paint obtained from the cleaning process of various ships was used for the experiment. The leaching rates of copper (Cu) and zinc (Zn) discharged from sludge paint and powdered paint were measured and their impact on the marine environment was predicted. The concentrations of Cu and Zn in the dried sludge paint were 15.5% and 31.7%, respectively. The leaching rates of Cu and Zn were found to decrease rapidly over time, and the predicted environmental concentrations (PECs) of Cu and Zn were calculated to be 0.099 μg/L and 0.822 μg/L, respectively. Although the PEC values for both metals were well below the long-term standard for the protection of marine ecosystems, Cu had a PEC value similar to the predicted no effect concentration (PNEC), suggesting that it may be environmentally harmful under certain conditions. The physicochemical and behavioral properties of antifouling toxic chemicals, as well as the hydraulic characteristics of the cleaning area, should be considered for a more accurate prediction of ecological impacts and to provide treatment standards for ship cleaning.
      PubDate: 2023-09-21
      DOI: 10.1007/s12601-023-00122-1
       
  • Phase Shift in Vertical Distribution of Macroalgal Assemblages on Udo
           Islet, Jeju, Korea, After a Decade of Revisiting

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      Abstract: Abstract We investigated seasonal macroalgal assemblages using virtual transect lines and 0.25 m−2 quadrats from the upper intertidal zone to subtidal 15 m depth during the period from May 2019 to February 2020 at Udo Islet, Jeju Island. A total of 191 species (15 Chlorophyta, 36 Ocrophyta, and 140 Rhodophyta) were observed among the quadrats, with annual mean biomass of 1998.8 g wet wt m−2. To confirm the decadal variation of the macroalgal assemblage in Udo, we compared our data with previous observations during 2009–2010 at the same locations reported by Kang et al. We were able to confirm that species diversity did not decrease, although subtidal biomass showed a considerable decrease. Notably, the biomass of non-calcareous macroalgae was considerably reduced, whereas calcareous algal biomass doubled despite maintaining the distribution of dominant species. This changing pattern of macroalgal assemblage is similar with the early process of sea-barrenness reported by previous studies on the Jeju coast. In this study, it was not possible to identify the cause of the decrease in abundance of non-calcareous algae, as the survey focused on only macroalgal assemblage without verifying any environmental factors. Further studies identifying additional factors that might be directly connected to marine deforestation, including physiological, chemical, and biological factors, are essential to recovering or at least maintaining the macroalgal community of Udo Islet.
      PubDate: 2023-09-07
      DOI: 10.1007/s12601-023-00119-w
       
  • Exploring Rearing Water Temperature Conditions for Inducing Body Growth
           without Water Temperature Stress in Red-Spotted Grouper (Epinephelus
           akaara)

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      Abstract: Abstract This study explored appropriate rearing water temperatures that can minimize water temperature stress and induce body growth in the farmed red-spotted grouper (Epinephelus akaara). An examination of annual growth performance showed that body growth (body weight and total length) was induced faster from July to September 2020 than during other periods. Weight gain (WG), specific growth rate (SGR), and feed efficiency (FF) were highest in August 2020. The hepatocyte diameter increased significantly in June and October 2020. It was observed that the body weight and total length were significantly induced under the conditions of 26 °C and 32 °C. WG and SGR were highest at 26 °C and 32 °C, respectively, and FCR was highest at 26 °C. The expression of Cu/Zn-Superoxide dismutase (SOD) and Mn-SOD mRNA in the brain was significantly higher in the 32 °C group than that in the 26 °C group after 12 weeks. Expression of catalase (CAT) mRNA was significantly higher in the natural group than in the 26 °C group. The expression of Cu/Zn-SOD and CAT mRNA in the liver was significantly higher at a natural temperature at 8 weeks. The expression of Mn-SOD mRNA was significantly higher in the natural temperature group than that in the 32 °C group. The hepatosomatic index values and hepatocyte diameter tended to decrease more significantly at 26 °C and 32 °C. Our findings are based on growth performance and physiological indicators, and it is considered that a water temperature of 26 °C is suitable for farmed red-spotted groupers.
      PubDate: 2023-09-07
      DOI: 10.1007/s12601-023-00117-y
       
  • Trace-Metal-Clean Sampling System: Application to Ice-Breaking Research
           Vessel Araon

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      Abstract: Abstract Trace metals generally exist at very low concentrations (pM–nM) in seawater, and could function as nutrients, contaminants, and tracers of various oceanographic processes. However, collection of seawater samples for a trace metal analysis without contamination is difficult because they exist ubiquitously. We present a detailed trace-metal-clean seawater sampling system that has been constructed on the ice-breaking research vessel (IBR/V) Araon. This sampling system consists of commercially available components without custom fabrication to minimize costs. The system consists of a polyurethane-coated aluminum rosette frame, 12-L Teflon-coated Niskin-X samplers, nonmetallic rope, and autofiring module that enables an automatic bottle firing. Using this system, seawater samples were collected in the Ulleung Basin, East Sea (Japan Sea), and the concentrations of dissolved trace metals (Mn, Fe, Cu, Zn, Cd, and Pb) were analyzed. Comparisons of trace metal concentrations to those obtained from the normal sampling system and previous data showed that our clean seawater sampling system could be utilized without metal contamination.
      PubDate: 2023-08-24
      DOI: 10.1007/s12601-023-00118-x
       
  • Spatial Patterns of the Primorye Current in the Northwestern East/Japan
           Sea on Satellite Images and Standard Sections

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      Abstract: Abstract Spatial patterns of the Primorye Current, as a band of cold water along the coast of Primorye (northwestern East/Japan Sea), are considered on the data of satellite images and standard sections obtained in 2000–2020. The data of AVHRR and MODIS scanners mounted on the satellites NOAA, Terra and Aqua are used with spatial resolution of 1.0–1.1 km. Temperature and salinity profiles in the upper 500 m layer were measured at the standard sections directed southward and east-southeastward from Vladivostok. The new data contradict a false supposition about the current origin from the Okhotsk Sea that is preserved in the name of “Liman Current”, still used sometimes. The cold-water area prolongs from the southern Tatar Strait to Peter the Great Bay but is definitely separated from the Amur Liman. Its core with the lowest SST is usually located on the external shelf of Primorye, outside of the Tatar Strait. Shape of the cold-water area is complicated and highly variable; it looks seldom as an alongshore flow, but more frequently as chains of eddies or filaments. In winter, the Primorye Current is presented usually as a wide uninterrupted alongshore belt with many intrusions to the warmer waters. This belt is distorted in spring by mesoscale eddies. In summer, the cold-water zone is narrowed and sometimes interrupted between 43 and 45°N; the cold waters interact with large anticyclonic eddies which transport the warm subtropic water close to the shore. The cold-water zone begins to extend again in fall season: large eddies and cold intrusions spread offshore, and upwellings appear at the coast. In November–December, summer stratification is destroyed and the warm water advection is weakened, so the solid band of cold water mixed by convection occupies a vast area of the northwestern East/Japan Sea off the coast of Primorye. Observed structural patterns show that the cold water at the sea surface along the coast of Primorye is produced on the shelf by upwellings or tidal mixing. Possible mechanisms of the cold spot inducing are discussed.
      PubDate: 2023-08-08
      DOI: 10.1007/s12601-023-00116-z
       
  • Short-Term Exposure to Combined Condition of Low Salinity and pH Affects
           ROS-Mediated Stress in Disk Abalone (Haliotis discus hannai)

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      Abstract: Abstract Climate change due to global warming can alter the salinity and pH in aquatic ecosystems. Low salinity (LS) and ocean acidification (OA) are stressors involved in osmotic regulation and can alter the antioxidant capacity of the body. In this study, we observed Na+/K+-ATPase (NKA) expression and activity in disk abalone gill tissue and changes in hemolymph osmolarity in relation to osmotic regulation over a short period (5 days). To confirm the degree of oxidative stress caused by changes in salinity and pH, changes in H2O2 levels, reactive oxygen species (ROS) levels, antioxidant enzyme (superoxide dismutase [SOD] and catalase [CAT]) expression, and caspase-7 expression were investigated at the molecular level. The degree of DNA damage was evaluated using the comet assay. mRNA expression, activity of gill NKA, and osmolarity of the hemolymph were significantly decreased in the LS group. Nonetheless, no noteworthy distinction was observed in mRNA expression or NKA activity between the control group and OA group. Hemolymph H2O2 levels and mRNA expression of SOD, CAT, and caspase-7 were significantly higher under the LS + OA condition than under single conditions of LS and OA. Further, caspase-7 mRNA expression and DNA damage increased with increasing exposure time. The group exposed to LS + OA showed the highest levels of caspase-7 expression and DNA damage. These results indicate that a combination of low salinity and pH induces more stress than a single condition does. Unmanageable ROS-mediated stress caused by environmental changes can lead to cell death and DNA damage.
      PubDate: 2023-07-25
      DOI: 10.1007/s12601-023-00115-0
       
 
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