Coast Of Korea Research Articles

Effects of water temperature changes on the early life stages (egg and larvae) of walleye Pollock (Gadus chalcogrammus) – Laboratory experiments and field applications

The eastern coast of Korea (ECK) is the southern limit of walleye pollock (pollock) distribution in the North Pacific. Since the climate regime shift in the 1980s, pollock catch has decreased sharply, with <1 ton recorded annually since the 2000s. Pollock, a semi-demersal cold-water species, is greatly affected by sea surface temperature changes during its early life stages. This study analyzed the effect of different water temperatures (3.6, 5.1, 7.1, 10.0, 13.3, and 15.1 °C) on the survival and growth of fertilized pollock eggs and larvae to investigate whether the ECK is still suitable for the early life stages development of pollock. The hatching rate of eggs was 82%, 57%, and 4%, and the hatching period was 20.7, 11.6, and 5.6 d at 3.6, 10.0, and 15.1 °C, respectively. The larval size-at-hatch was the highest at 3.6 °C (5.14 mm) and lowest at 15.1 °C (4.24 mm). Above 10.0 °C, the hatching rate decreased rapidly, and the abnormality rate increased. Since the 1980s, the 10 °C isotherm in the ECK has been moving northward in winter, which is the pollock spawning season. Continuous warming of the ECK has thus been unfavorable for the early life stages of pollock. Overall, this study improves our understanding of changes in pollock abundance due to climate change.

해양경찰공무원의 자기효능감과 회복탄력성이 조직몰입에 미치는 영향

Korea Coast Guard officers perform diverse and dangerous tasks in the special environment of the ocean. In order for members to successfully perform their duties in this environment to achieve the organization's purpose of protecting maritime sovereignty and establishing maritime safety and public safety, Korea Coast Guard should deal with organizational commitment, which is considered an important variable representing organizational effectiveness, positively affecting the performance of the organization, such as preventing turnover, absenteeism, and job burnout in organizational management. Accordingly, this study was conducted with the purpose of exploring and verifying the factors influencing the organizational commitment of Korea Coast Guard officers.&#x0D; To achieve the purpose of the study, the study was conducted in the following manner. First, a research model and hypothesis were established through a review of previous research. Specifically, ‘self-efficacy’, which is the belief that an individual will overcome difficulties and challenging tasks, and ‘resilience’, which is the power to withstand stressful or high-risk situations, were set as independent variables, and organizational commitment was set as the dependent variable. Second, for empirical research, survey data verified at home and abroad were reorganized to suit the purpose of the study. The survey questions related to the research problem were structured on a Likert 5-point scale, and the survey questions related to socio-demographic characteristics used nominal, interval, and ratio scales. Third, a survey was conducted using all Korea Coast Guard officers as the population as of October 1, 2022. To ensure representativeness of the sample, The survey was conducted using proportional allocation sampling that comprehensively considered age, gender, class, and affiliation and 957 response sheets were used for analysis. Fourth, statistical analysis was performed to verify the research model. It was confirmed that the main variables could be used as continuous variables through normality review, and SPSS 27.0 was used to perform frequency analysis, factor analysis, reliability analysis, correlation analysis, and multiple regression analysis on the variables.&#x0D; As a result of the analysis, it was found that self-efficacy (β=.351***) and positivity (β=.182***), a sub-factor of resilience, had a statistically significant positive (+) effect on organizational commitment in the integrated model. However, it was found that self-regulation ability and interpersonal ability, other sub-factors of resilience, do not explain organizational commitment well. In addition, as a result of confirming the relative influence of variables, self-efficacy was found to best explain organizational commitment (10.8%), followed by positivity to organizational commitment at 2.3%.&#x0D; Korea Coast Guard, which must ensure the effectiveness of organizational operations with limited resources and budget, should pay attention to self-efficacy and positivity and prepare policies to improve them in order to improve organizational commitment. To this end, the level of self-efficacy and positivity must be continuously measured and managed when constructing health-related cohort data of Korea Coast Guard officers, and it is also proposed to provide psychological support, regular education, and appropriate welfare program support to improve this.

Identifying the external N and Hg inputs to the estuary ecosystem based on the triple isotopic information (δ15NNO3, Δ17ONO3 and δ18ONO3)

The supply and sources of N and Hg in the Geum estuary of the western coast of Korea were evaluated. Triple isotope proxies (δ15NNO3, Δ17ONO3 and δ18ONO3) of NO3− combined with conservative mixing between river and ocean waters were used to improve isotope finger-printing methods. The N pool in the Geum estuary was primarily influenced by the Yellow Sea water, followed by riverine discharge (821 × 106 mol yr−1) and atmospheric deposition (51 × 106 mol yr−1). The influence of the river was found to be greater for Hg than that of the atmosphere. The triple isotope proxies revealed that the riverine and atmospheric inputs of N have been affected by septic wastes and fossil fuel burning, respectively. From the inner estuary towards offshore region, the influence of the river diminishes, thus increasing the relative impact of the atmosphere. Moreover, the isotope proxies showed a significant influence of N assimilation in February and nitrification in May.

Feeding habits of Pacific anchovy, Engraulis japonicus (Actinopterygii: Clupeiformes: Engraulidae), captured off the southern coasts of Korea

Understanding the feeding ecology of anchovies in the southern waters of Korea is crucial for improving ecosystem management. However, to date, few studies have examined seasonal changes in the diet of Pacific anchovy, Engraulis japonicus Temminck et Schlegel, 1846, in Korean waters, with the majority of these focusing on the larval and adult stages. The presently reported study provides updates on the feeding habits of E. japonicus off the southern coast of Korea. We analyzed 347 individuals. One-way analysis of similarity was performed to evaluate the differences in diet composition among size classes and seasons of E. japonicus, and correspondence analysis was conducted using the matrix of the percentage by number (%N) data for prey with occurrence of less than 10% to determine the distribution of prey across all size classes and each season. The diet of E. japonicus was investigated according to season and four size classes. The fork length of these specimens ranged from 5.4 to 14.1 cm. A total of 55 prey taxa of varying sizes between 0.33 mm (diatom Coscinodiscus spp.) and 5.8 mm (fish larvae) were recorded. Anchovies were exclusively planktivorous, and copepods were the most common prey, comprising 82.1% of the identified food items and 84.3% of anchovy stomach contents analyzed. However, their occurrence and abundance varied according to season and Pacific anchovy size class. According to the percentage of the index of relative importance (%IRI), the most important prey items were the copepods Calanus sinicus (48.0%), Paracalanus orientalis (31.7%), bivalve larvae (5.8%), Ditrichocorycaeus affinis (4.2%), and calanoid copepods (2.4%). Analysis of similarities and similarity percentage analysis indicated that a distinct diet of Pacific anchovy in the southern waters of Korea is potentially driven by differences in hydrological conditions. Correspondence analysis revealed that anchovies had the most significant impact on the differences between size classes. The results deepen our understanding of prey species diversity and intraspecific food competition off the southern coast of Korea.

Morphology, phylogeny, and host range of the novel early-diverging oomycete Sirolpidium dinoletiferum sp. nov. parasitizing marine dinoflagellates

Oomycetes are fungus-like heterotrophic organisms with a broad environmental distribution, including marine, freshwater, and terrestrial habitats. They function as saprotrophs that use the remains of other organisms or as parasites of a variety of eukaryotes, including protists, diatoms, dinoflagellates, macroalgae, plants, fungi, animals, and even other oomycetes. Among the protist hosts, the taxonomy, morphology, and phylogenetic positions of the oomycete parasitoids of diatoms have been well studied; however, this information concerning the oomycete parasitoids of dinoflagellates is poorly understood. During intensive sampling along the east and west coasts of Korea in May and October 2019, a new species of oomycetes was discovered and two strains of the new parasitoid were successfully established in cultures. The new oomycete parasitoid penetrated the dinoflagellate host cell and developed to form a sporangium, which was very similar to the perkinsozoan parasitoids that infect marine dinoflagellates. The most distinctive morphological feature of the new parasitoid was a central large vacuole forming several long discharge tubes. The molecular phylogenetic tree inferred based on the small subunit (SSU) ribosomal DNA (rDNA) revealed that the new parasitoid forms a distinct branch unrelated to other described species belonging to early-diverging oomycetes. It clustered with species belonging to the genus Sirolpidium with strong support values in the cytochrome c oxidase subunit 2 (cox2) tree. Cross-infection experiments showed that infections by the new parasitoid occurred in only six genera belonging to dinoflagellates among the protists tested in this study. Based on the morphological and molecular data obtained in this study, we propose to introduce a new species, Sirolpidium dinoletiferum sp. nov., for this novel parasitoid, conservatively within the genus Sirolpidium.

First record of a cylindrical Dipterocladia (Ceramiales, Delesseriaceae), D. cylindrica sp. nov., from Korea based on morphological and molecular analyses

Abstract We describe a new species, Dipterocladia cylindrica, found in the subtidal zone of the eastern and southern coasts of Korea. This species has cylindrical branches with numerous sub-dichotomously branching monosiphonous determinate branchlets without adventitious filaments, heavy cortication throughout the thallus, and alternating clockwise periaxial cell formation. The external features of the new species are closer to those of the genus Dasya than to those of Dipterocladia, which have flattened thalli with pairwise distichously arranged monosiphonous pseudolateral and polysiphonous determinate laterals. However, based on the combined results of plastid rbcL and mitochondrial COI–5P sequences, the molecular phylogenetic relationships clearly indicate that our specimens belong to the genus Dipterocladia. We also detected more meaningful morphological characters for delineating the genus within the subfamily Dasyoideae by comparing the morphology and phylogeny, but we could not find unique characters for each clade. Further studies based on reproductive morphology and molecular phylogeny for delimiting the generic boundaries are needed.

Evaluation of Spatiotemporal Variations in Water Quality Along the Chungnam Province Coast and Inner Estuary (West Coast of Korea)

Evaluation of Spatiotemporal Variations in Water Quality Along the Chungnam Province Coast and Inner Estuary (West Coast of Korea)

Effect of Freshwater Discharge on the Water Quality in Cheonsu Bay, West Coast of Korea

Effect of Freshwater Discharge on the Water Quality in Cheonsu Bay, West Coast of Korea

Morphology of Hobagella saltata n. gen. and n. sp. (Syndiniophyceae, Miozoa) infecting the marine dinoflagellate Cucumeridinium coeruleum (Dinophyceae, Miozoa) and its potential onshore advection

Over the past decade, molecular phylogenies have placed endoparasites of the genus Euduboscquella in a distinct subclade within clade 4 of the Marine Alveolate (MALV) Group I. Recently, however, rRNA gene sequences have become available for four novel Euduboscquella-like species that infect dinoflagellates, with phylogenies including these sequences indicating that the genus Euduboscquella is paraphyletic. Here, we provide a morphological characterization of the intracellular and extracellular life-cycle stages of a novel species that infects Cucumeridinium coeruleum, a warm water pelagic species sometimes found in coastal environments. We formally describe the novel parasite, Hobagella saltata n. gen, n. sp., and identify a constellation of morphological and developmental characters that distinguish it, as well as Euduboscquella melo and E. nucleocola, both parasites of dinoflagellates, from Euduboscquella species that infect ciliates. We recommend the reassignment of E. melo and E. nucleocola as Hobagella melo n. comb. and H. nucleocola n. comb., respectively. We also propose the family Hobagellidae for these three congeners. We anticipate that the character set developed for distinguishing species of Euduboscquella and Hobagella will be valuable for sorting other Euduboscquella-Hobagella-like taxa scattered across the Group I phylogeny and will provide insight into morphological evolutionary patterns within Group I. Lastly, we consider the potential influence of summer-fall typhoons on the occurrence of H. saltata and its host C. coeruleum in near-shore waters along the southeastern coast of Korea and propose a hypothesis regarding the northward transport and onshore advection of host and parasite populations. If future research supports the hypothesized mechanisms, it could help us better understand parasite distribution and potential changes in biogeography associated with ongoing global changes in surface seawater temperature.

Spatiotemporal variations in migratory bird diversity and abundance along the coast of Gochang getbol.

Tidal flats provide critical habitat for migratory waterbird species; however, populations of migratory waterbirds have significantly declined due to tidal flat loss and degradation caused by human activities, particularly in Asia. Gochang getbol is one of tidal flats located on the southwest coast of South Korea and a center of clam production. Using bird monitoring data collected at five zones (zone1 to zone5) established across Gochang getbol and near coastal area, we examined distribution patterns of migratory bird diversity and conservation-related species along the coast of Gochang getbol. The intensity of human activity ‒ mudflat culture (mostly bivalve) and aquaculture was relatively high at zone2 and zone3, occupying > 30% of 2km circular area surrounding most sample points of these zones. Zone1 and particularly zone4 contained more natural/semi-natural habitats (less disturbed mudflats and wetlands) and zone5 had smallest mudflat than others. Shannon diversity, species richness, and abundance of migratory birds differed between zones (Anova test, P ≤ 0.02) except Shannon diversity in winter. In fall, all values were higher at zone4 than zone3 and zone5. In winter, zone1 showed greatest species richness and higher abundance than zone2, zone3, and zone5. In spring, while most differences were found between zone4 and zone5, abundance at zone4 was somewhat higher than zone2. The results from the fourth corner analysis indicated that abundance of species foraging at mudflat level was positively associated with zone1 (winter) but negatively with zone3 (fall). Sandpipers were positively associated with zone4. Abundance distribution maps of conservation-related species, created by inverse distance-weighted interpolation modeling, also showed high abundance of most conservation-related species at zone4 and 1. The findings of our study suggest the importance of natural/semi-natural habitat, and the possible link between human activity and distribution patterns of migratory birds in Gochang getbol. While we need further investigation on direct response of migratory birds to human activity, areas with low human activity with more natural/semi-natural habitat, e.g., zone4 and zone1 may be crucial for the conservation of migratory birds.

Optimizing CO2 Injection in Depleted Gas Fields Off the East Coast of Korea: A Comprehensive Approach to Flow Assurance

Optimizing CO2 Injection in Depleted Gas Fields Off the East Coast of Korea: A Comprehensive Approach to Flow Assurance

Marine oil spill analyses based on Korea Coast Guard big data from 2017 to 2022 and application of data-driven Bayesian Network

Oil spills have a large after-effect on maritime environment. Oil spills occur worldwide, and their accident histories provide a rich data. In this study, oil spill data collected over six years from Korea Coast Guard (KCG) formed the basis for statistical analysis, using the Bayesian Network (BN) model. In the analysis, map-based ship distribution and accident scale were analyzed, along with the time of accident occurrence, region, oil and ship types, accident causes, and accident sources. The BN model for predicting whether the oil spill amount was low or high was constructed using the K2 and counting learning algorithms, with an accuracy of 71.43% and an area under the curve (AUC) of 75.85%. Five analyses based on the BN model were performed, and the probability distribution, effect of other nodes on a specific target node, the condition according to the amount of oil spill, effect of attribute variables on class variables, and most probable configuration for a specific class variable “Ship_type” was analyzed. Finally, a policy based on the results was proposed to support in-depth decision-making by government agencies.

Population genetic patterns across the native and invasive range of a widely distributed seagrass: Phylogeographic structure, invasive history and conservation implications.

The seagrass Zostera japonica is a dramatically declined endemic species in the Northwestern Pacific from the (sub)tropical to temperate areas, however, it is also an introduced species along the Pacific coast of North America from British Columbia to northern California. Understanding the population's genetic patterns can inform the conservation and management of this species. North Pacific. We used sequences of the nuclear rDNA internal transcribed spacer (ITS) and chloroplast trnK intron maturase (matK), and 24 microsatellite loci to survey 34 native and nonnative populations (>1000 individuals) of Z. japonica throughout the entire biogeographic range. We analysed the phylogeographic relationship, population genetic structure and genetic diversity of all populations and inferred possible origins and invasion pathways of the nonnative ones. All markers revealed a surprising and significant deep divergence between northern and southern populations of Z. japonica in the native region separated by a well-established biogeographical boundary. A secondary contact zone was found along the coasts of South Korea and Japan. Nonnative populations were found to originate from the central Pacific coast of Japan with multiple introductions from at least two different source populations, and secondary spread was likely aided by waterfowl. The divergence of the two distinct clades was likely due to the combined effects of historical isolation, adaptation to distinct environments and a contemporary physical barrier created by the Yangtze River, and the warm northward Kuroshio Current led to secondary contact after glacial separation. Existing exchanges among the nonnative populations indicate the potential for persistence and further expansion. This study not only helps to understand the underlying evolutionary potential of a widespread seagrass species following global climate change but also provides valuable insights for conservation and restoration.

Hydrodynamics and Sediment Transport at Socheongcho Ocean Research Station, Korea, in the Yellow Sea

A seasonal variability in flow and sediment flux at the Socheongcho Ocean Research Station (SORS) on the west coast of Korea in 2018 was investigated to elucidate the formation of a two-layered flow structure and changes in sediment transport during stratification. An analysis of SORS data revealed stable temperatures (5–10 °C) in deeper waters, while surface temperatures rose from 6 °C in April to a peak of 30 °C in late August, gradually declining and leading to full water column mixing by late November. This temperature variation induced stratification, influencing the development of a two-layered flow structure. In winter, a singular flow structure was observed, contrasting with the emergence of a two-layered structure as stratification progressed. In the surface layer, residual currents flowed northward in summer and southward in winter, consistent with previous studies. In deeper layers, a southward residual current persisted, irrespective of the season. Sediment flux consistently moved southward, regardless of the season or water depth, with notably higher cumulative sediment flux in the deeper layer (1300 kg·m−2s−1) compared to the surface layer (300 kg·m−2s−1). These findings diverge notably from previous studies, providing new insights into ocean currents and material transport in the Yellow Sea.

Remote impacts of low-latitude oceanic climate on coastal upwelling in a marginal sea of the Northwestern Pacific

Upwelling plays an important role in the physical processes and biological variability of coastal regions. Using 40-year-long hydrographic and climate data, the remote impacts of low-latitude oceanic climate on the upwelling along the east coast of Korea were investigated. During El Niño, the development of anomalously enhanced anti-cyclonic circulation over Northwestern Pacific resulted in relatively strong (∼1.1 m s−1) southerly winds, compared to La Niña. During El Niño, the mean upwelling index was 402 ± 106 kg m−1 s−1, and 10 °C isotherm was located at a depth of 32.7 m. During La Niña, they were 368 ± 95 kg m−1 s−1 and 39.9 m, respectively. During El Niño, in the approximation, the offshore Ekman transport by wind-induced upwelling and the vertical transport by isotherm were higher than those during La Niña. This finding can be explained by the increased sea surface height gradient, the subsequent enhanced geostrophic current, the decrease in onshore sea surface temperature, and the increase in chl-a concentration during El Niño. The intensity of upwelling tended to be stronger (weaker) during periods when El Niño (La Niña) and the PDO (Pacific Decadal Oscillation) were in phase than those when they were out of phase. These results suggest that low-latitude climate change could affect the coastal upwelling in the mid-latitude marginal sea through the teleconnection.

Environmental Parameters Related to Hypoxia Development and Persistence in Jinhae Bay from 2011 to 2016 and Their Potential for Hypoxia Prediction

Jinhae Bay, a semi-enclosed bay on the southern coast of Korea, is a major aquaculture area that forms a spawning ground and nursery for commercially important fishes. Since the late 1960s, industrial and domestic waste from adjacent cities and industrial complexes has been released into the region, resulting in chronic hypoxia and red tides. As a central site of environmental monitoring efforts for aquaculture and fisheries in southeastern Korea, Jinhae Bay was surveyed every 2 months usually, and every 2–3 weeks during the hypoxia season, with the seawater properties observed at approximately 31–34 stations. The maximum area and duration of hypoxia in Jinhae Bay occurred in 2016 (316 km2 and 26 weeks, respectively), with minima of area in 2013 (213 km2) and duration in 2011 (15 weeks). Correlation analyses of the seawater properties, weather parameters, and hypoxia indices showed that the hypoxic area was positively correlated with the surface-water temperature, air temperature, and rainfall; the minimum dissolved oxygen concentrations were negatively correlated with the air and water temperatures and bottom-water nutrient levels; and the water stability was negatively correlated with the surface-water salinity and positively correlated with both the surface- and bottom-water nitrate and silicate concentrations. These findings imply that the air temperature and precipitation may be important factors in the development and persistence of hypoxia in Jinhae Bay via the control of the stratification intensity and eutrophication of the water column. Therefore, we tested these parameters for their potential to predict hypoxia. Based on our results, we propose the following trends of hypoxia in Jinhae Bay: the initial hypoxia development generally depends on the criteria of an air temperature ≥ 19.5 °C for 1 week and total precipitation &gt; 100 mm over 4 weeks, and it becomes more severe (≥50% coverage) under strong eutrophication, mainly due to organic matter discharge following heavy rainfall, based on the logarithmic correlation with the 4-week rainfall (R2 = 0.6). Therefore, the hypoxic area index can be predicted using its linear regression relationships with the 1-week air temperature and 4-week precipitation (R2 = 0.56). This study tested the prediction of the hypoxic area based on a simple calculation method and weather parameter criteria, and it demonstrated the potential of this method for precisely forecasting hypoxia in combination with biogeochemical models or other mathematical solutions to prevent massive fishery damage.

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

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

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

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

An ancient genome perspective on the dynamic history of the prehistoric Jomon people in and around the Japanese archipelago

The Jomon people were prehistoric residents of the Japanese archipelago who occupied the region from ca. 16,500 to 2,300 years before present (BP). While recent accumulation of ancient genomes and genome-wide data of the Jomons has substantially enhanced our understanding of their genetic profiles and contribution to present-day populations, their genetic history in the Jomon-period archipelago, spanning over 14,000 years in time and 2,000 km in distance, remains scarcely investigated. Here we report multiple findings illuminating the Jomon genetic history based on the analysis of the genetic relationship between published ancient genome-wide data of 23 Jomon and Jomon-like individuals. First, the Initial Jomon individual from Shikoku, dated to ca. 9,000 BP, forms a common outgroup to the remaining later Jomon individuals, suggesting a population turnover in western Japan. Second, genetically Jomon-like individuals outside the Jomon archaeological context, found in the Miyako Island in Ryukyu and the Yokjido island in the southern coast of Korea, show the closest genetic affinity with the Late Jomon individual from Shikoku, narrowing down their sources in space and time. This study highlights a dynamic history of the Jomon people in and out of the Japanese archipelago and calls for a large-scale investigation of the ancient Jomon genomes.

Population Characteristics of the Mud Shrimp Upogebia major (De Haan, 1841) (Decapoda: Gebiidea: Upogebiidae) on Korean Tidal Flats in the Eastern Yellow Sea

The population parameters of the ecologically important mud shrimp Upogebia major (De Haan, 1841) were analyzed from 2012 to 2015 in tidal flats in Seonjaedo and Jugyo on the west coast of Korea. The shrimp density averaged 265/m2 in Seonjaedo and 118/m2 in Jugyo. The sex ratio varied monthly, often male-biased, and, by size, males were significantly dominant, with a carapace length (CL) over 30 mm. Although the shrimp settled almost annually, only a single size-group was observed from 2012 to 2014. The recruitment in Jugyo in 2014 was notably successful, resulting in two cohorts persisting until 2015. Many shrimp were parasitized at varying local rates: 6.0% in Seonjaedo and 37.1% in Jugyo. The growth curves revealed that the shrimp grew annually after settlement, reaching CLs of 11.90, 18.24, and 23.02 mm in Seonjaedo and 13.73, 20.86, and 25.82 mm in Jugyo. Annual mortality was 77.2% in Seonjaedo and 67.4% in Jugyo. The estimated lifespan (tmax) was 10 years in Seonjaedo and 8 years in Jugyo, whereas the 2010 cohort in Jugyo largely disappeared in 5 years. Ovigerous females appeared from November to June and benthic juveniles between June and September. The shrimps’ growth was slower relative to other East Asian populations, likely due to colder sea water temperatures and altered food conditions from a higher shrimp density.