West Coast Of Korea Research Articles

Detection and Quantification of Tetrodotoxin in Marine Mud Snails, Nassarius sinarum from a Tidal Flat on the West Coast of Korea

Detection and Quantification of Tetrodotoxin in Marine Mud Snails, Nassarius sinarum from a Tidal Flat on the West Coast of Korea

Airborne Bathymetric Light Detection and Ranging Waveform Processing for Digital Elevation Model Construction of Tidal Flats on the West Coast of Korea

Airborne Bathymetric Light Detection and Ranging Waveform Processing for Digital Elevation Model Construction of Tidal Flats on the West Coast of Korea

Genetic Variability and Population Genetic Structure of Marbled Flounder Pseudopleuronectes yokohamae in Korea and Japan Inferred from mtDNA Control Region Sequences

The marbled flounder (Pseudopleuronectes yokohamae) is a demersal flatfish species, widely distributed in the northwestern Pacific region. In the present study, the mitochondrial DNA (mtDNA) control region was used to determine the genetic diversity and population genetic structure of this species. We obtained a 380 bp segment of the mtDNA control region after the alignment of 78 individual sequences from P. yokohamae collected from two locations in Korea (Biungdo and Mukho) and one location in Japan (Tohoku) and 103 individual sequences from a previous study (Yokjido and Namhae). The overall haplotype diversity and nucleotide diversity were 0.983 ± 0.003 and 0.016 ± 0.008, respectively. The genealogical relationships of the mtDNA control region did not exhibit any specific genealogical association according to sampling location. The pairwise FST value indicated that the Biungdo (west coast of Korea) and Tohoku (Japan) populations showed genetically differentiated structures (but the Tohoku and Mukho populations did not). However, there was no discernible difference between the Mukho population from Korea’s eastern coast and the Yokjido and Namhae populations from the southern coast. The biological characteristics of P. yokohamae and oceanographic barriers may have contributed to producing genetically distinct populations.

First report of Perkinsus marinus occurrence associated with wild Pacific oysters Crassostrea gigas from the west coast of Korea

This study reports the occurrence of Perkinsus marinus associated with wild Pacific oyster (Crassostrea gigas) specimens collected along the west coast of Korea. Confirmation of P. marinus presence was achieved by conventional PCR using World Organization of Animal Health (WOAH)-recommended primers that specifically targeted regions of the rDNA locus (ITS1, 5.8S, and ITS2). Sequencing of 10 samples revealed two distinct sequences differing by a single base pair, indicating potential haplotype variability. One sequence closely resembled the P. marinus strain found in Maryland, USA, whereas the other exhibited divergence, indicative of species diversity in the Korean strain, as was evident from the haplotype network analysis. Further validation involved the Ray’s Fluid Thioglycollate Medium (RFTM) assay, which initially yielded inconclusive results, possibly due to low infection intensity. Subsequently, RFTM and 2 M NaOH assays conducted on the isolates in the present study, cultured P. marinus cells in standard DMEM/F12 medium, and a positive P. marinus strain (ATCC 50509), revealed characteristic hypnospores of P. marinus upon Lugol’s iodine staining. These comprehensive investigations underscore the conclusive confirmation of P. marinus in Korean waters and mark a significant milestone in our understanding of the distribution and characteristics of this parasite in previously unreported regions.

Enhancing Seed Harvest of Wild Manila Clam (Ruditapes philippinarum) through Fiberglass Mesh Installation in the Tidal Flat of Jugyo, West Coast of Korea

Enhancing Seed Harvest of Wild Manila Clam (Ruditapes philippinarum) through Fiberglass Mesh Installation in the Tidal Flat of Jugyo, West 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.

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

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.

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

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.

Vertical distribution of the salt marsh invader Spartina alterniflora and native halophytes on the west coast of Korea in relation to tidal regimes

Smooth cordgrass (Spartina alterniflora Loisel.), an aggressive non-native species worldwide, colonized tidal flats on the west coast of Korea in two regions differing in tidal amplitude between 1990–2004. By the time of our study in 2015, expansion had occurred both clonally and through formation of new patches, providing an opportunity to determine intertidal range, which is a key component of understanding the threat posed by S. alterniflora through competition with native halophytes or transformation of unstructured mudflat. At Ganghwa (5.69 m tidal range), S. alterniflora ranged from 3.52 to 1.34 m above Mean Sea Level (MSL). At Jindo (2.02 m tidal range), S. alterniflora ranged from 1.57 to -0.18 m relative to MSL. Thus, a wider absolute intertidal range was occupied by S. alterniflora at the megatidal vs mesotidal region, but the lower limit of S. alterniflora did not extend below MSL under megatidal conditions, a pattern that now appears to emerge consistently in both the native and introduced range. In both study regions, S. alterniflora occurred at the same elevations as other salt marsh plants, occupying an upper zone with Phragmites australis (non-native) and middle zone with several native species including Suaeda japonica. S. alterniflora occurred below native marsh vegetation at all sites, which would result in transformation of the extensive mudflats along the Korean coast.

Roles of Exposure Time and Geochemical Factors in the Characteristics of the Surface Sediments of the Hwangdo Tidal Flat, Taean, Cheonsu Bay, West Coast of Korea

The Hwangdo tidal flat is an intertidal landform located in Cheonsu Bay, Taean-gun, Chungcheongnam-do, on the west coast of Korea. The topographical characteristics of the semi-enclosed bay on the eastern side of the study area include waterways, sandbars, small islands, and tidal flats. In this study, data were acquired from tide gauges installed on the Hwangdo Bridge, and the height of the ellipsoid was measured using a real-time kinematics global positioning system (RTK-GPS). Digital elevation model (DEM) using Matrice 300 drone data were also acquired after processing. The geochemical sediment characteristics in the study area were analyzed, together with tidal-flat exposure-time characteristics based on environmental factors. Sediment data (n = 107) collected from October 25 to 28, 2022 (Korean local time) were used to classify sediment particles according to Folk and Ward (1957). Sedimentary facies ranged from coarse sand (sand:mud ratio = 9:1) to sandy silt (sZ) followed by muddy sand (mS) and slightly gravelly sandy mud ((g)sM). Total organic carbon (TOC) in the surface sediments was also characterized based on a particle-size analysis. The mean change in tidal height measured at Hwangdo Bridge during the sampling period was ~7.53 m (minimum: −3.86 m, maximum: +3.67 m). Based on the Boryeong’s sea level measurement tide data in 2022, the tidal area in the drone images ranged from 6.362 m2 (0.006 km2) at DEM +4.0 to 4,841,078 m2 (4.841 km2) at DEM −4.0 m, indicating an increase in the tidal-flat area according to the tidal level of up to ~800-fold. The daily average exposure time was 9.0 h (minimum: 1.5 h, maximum: 17.9 h). Based on the results of multivariate analysis using exposure times and a geochemical dataset, four groups were identified: upper, middle, and lower intertidal zones and regions with a relatively high organic-matter concentration. A determination of the main characteristics of the Hwangdo tidal flat according to their spatial distribution showed that, among various environmental factors, changes in the sand or clay sediment composition were determined by community factors. The results of this study demonstrate the four statistically processed groups of marine environmental characteristics in the Hwangdo tidal flats. Changes in sedimentary patterns, rather than in the exposure time, accounted for the differences in the sediment compositions of the upper, middle, and lower stations, a response that is expected to continue.

Novel morphological and molecular data for Nasitrema spp. (Digenea: Brachycladiidae) in the East Asian finless porpoise (Neophocaena asiaeorientalis sunameri)

The East Asian finless porpoise, Neophocaena asiaeorientalis sunameri, ranks among the most endangered species with rapidly decreasing population in the Northwest Pacific. Trematode parasites of the genus Nasitrema that inhabit the air sinuses, inner ear, and the central nervous system of cetaceans frequently cause equilibrium dysfunction, disorientation, interference with echolocation, incoordination, and nervous system degeneration. Due to their specific location and associated pathologies, they have been recognized as one of the causes of cetacean strandings. Stranding data provides crucial information on the species’ biology, population health, and on the status of entire marine ecosystem. However, published data on parasite-induced standings that include information on the causative parasite pathogens are scarce. As part of a wider survey on the causes of East Asian finless porpoise strandings along the west coast of Korea, herein, we provide novel morphological and molecular data on two sympatric species of Nasitrema, namely, Nasitrema spathulatum and Nasitrema sunameri based on newly collected specimens from a stranded alive East Asian finless porpoise at the West coast of Korea. Our study adds a new distribution record for important parasite pathogens in cetaceans and provides the first molecular data for the parasite species recovered, which enabled us to re-evaluate the species relationships within the family Brachycladiidae, a group of important parasite pathogens of marine mammals.

Distribution, compositional characteristics, and historical pollution records of microplastics in tidal flats of South Korea

Studies on distribution of microplastics (MPs) in sediments of tidal flats are relatively scarce compared to other coastal areas. In this study, spatial and vertical distributions and compositions of MPs in tidal flat sediments along the west coast of Korea were investigated. The abundance of MPs in surface and core sediments ranged from 20 to 325 and 14 to 483 particles per 50 g dry weight, respectively. Polypropylene (51%) and polyethylene (36%) were the most dominant MPs; the size was <0.3 mm, and the shape was mostly fragments followed by fibers. The abundance of MPs in sediments has increased rapidly since the 1970s, and recently showed a slight decrease. Surface morphology of MPs analyzed using a scanning electron microscope revealed that the MPs in tidal flats were highly weathered mechanically and/or oxidatively. The results of this study provide valid baseline data on distributions of MPs in tidal flats.

Description of Fervidibacillus gen. nov. with Two Species, Fervidibacillus albus sp. nov., and Fervidibacillus halotolerans sp. nov., Isolated from Tidal Flat Sediments and Emendation of Misclassificed Taxa in the Genus Caldibacillus.

Two Gram-stain-positive, motile, endospore-forming, facultatively anaerobic strains, designated MEBiC13591T and MEBiC13594T, were isolated from tidal flat sediment of the Incheon City on the west coast of Korea. Growth of both novel strains was observed at pH 5-9 (optimum, pH 7-7.5), and in 0-8% NaCl (optimum, 2% for MEBiC13591T and 3% for MEBiC13594T). Strains MEBiC13591T and MEBiC13594T grew optimally at 50°C, (37.5-56.1°C) and 44°C (20.7-50.7°C), respectively. The main cellular fatty acids of strain MEBiC13591T were iso-C15: 0, anteiso-C15: 0, iso-C16: 0, iso-C17: 0 and anteiso-C17: 0, while those for strain MEBiC13594T were C14: 0, iso-C14: 0, iso-C15: 0, anteiso-C15: 0 and C16: 0. In both taxa, the major isoprenoid was MK-7. The genomic DNA G + C contents were 34.1 and 37.0mol% for MEBiC13591T and MEBiC13594T, respectively. A 16S rRNA gene sequence analysis revealed that the novel strains showed high similarity with members of the genera Aeribacillus (95.0%) and Caldibacillus (93.5-94.5%); however, showed lower than 90% with Caldibacillus debilis TfT. Phylogenetic and Phylogenomic analysis revealed that two novel strains comprised distinct phyletic line with members formerly assigned to Caldibacillus. Based on genomic indices, such as AAI and ANI, members formerly affiliated with Caldibacillus and Bacillus as well as the novel strains should be classified into five independent genera. Based on the phenotypic, genomic and biochemical data, strains MEBiC13591T and MEBiC13594T represent two novel species in the novel genus, for which the names Fervidibacillus albus gen. nov., sp. nov. (MEBiC13591T [= KCCM 43317T = KCTC 43181T = JCM 33662T = MCCC 1K04565T]), and Fervidibacillus halotolerans sp. nov. (MEBiC13594T [= KCTC 43182T = JCM 34001T]) are proposed. Three additional genera Caldifermentibacillus, Palidibacillus, and Perspicuibacillus are also proposed by reclassification of the several species with valid names that formerly affiliated with the genera Caldibacillus.

Coastal switching of dominant depositional processes driven by decreasing rates of Holocene sea-level rise along the macrotidal coast of Gochang, SW Korea

ABSTRACTDecreasing rates of eustatic sea-level rise during the Holocene accompanied the deposition of transgressive coastal deposits worldwide. However, unraveling how transgressive deposition varies in response to different rates of relative sea-level (RSL) rise is limited by the scarcity of long (10+ m) well-dated cores spanning the entire middle to late Holocene record along macrotidal coasts. To investigate the sedimentary response of this macrotidal coast to decreasing rates of RSL rise, we acquired four cores up to 32 m in length and Chirp seismic profiles along the west coast of Korea. Core sediments were analyzed in terms of sedimentary texture, structure, and facies. Nineteen optically stimulated luminescence (OSL) and fourteen 14C accelerated mass spectrometry (AMS) ages constrain the timing of deposition of the sandy sediments. This relatively dense distribution of ages is used to determine how deposition rates changed through time. We also use a compilation of previously published RSL indices for the southwestern Korean coast in order to better constrain RSL changes through time. Results show that the evolution of the Gochang coastline switched from a tide-dominated environment to a wave-dominated environment during the latter stage of transgression as the rate of the sea-level rise decreased. Rugged antecedent topography likely led to the development of tidal currents and the formation of a tide-dominated tidal flat during rapid RSL rise from 10 to 6 ka. As the tidal channels filled with fine-grained sediments from 6 to 1 ka, tidal amplification likely waned leading to a greater role of wave energy in shaping the formation of the sandy open-coast tidal flat. Since 1 ka, wave-dominated environments formed sand-rich tidal beaches and flats. Decreasing changes in rates of the RSL rise resulted in changes in depositional environments from a tide-dominated intertidal flat to an open-coast tidal flat and finally a wave-dominated tidal beach. This study highlights the important role that rates of RSL rise play on not only sedimentation rates in a shelf setting but also playing a role in the switch from a tide-dominated to a wave-dominated setting.

Characterization of the lesser known Korean seerfishScomberomorus koreanus(Kishinouye, 1915) (Scombriformes: Scombridae) in Indian waters

AbstractScomberomorus koreanuswas originally described from a single specimen from the west coast of Korea. In 1964 the species was synonymized withS. guttatusduring the systematic review of the scombroid fishes of India. Subsequently,S. koreanuswas discovered in Palk Bay in 1976, confirming its first record from India and the Indian Ocean. Since then, no such detailed taxonomic studies have been undertaken for the species along the Indian coast. Although the species is distributed in the Indo-West Pacific region and forms a commercially important fishery in part of its range,S. koreanusis poorly known and very limited taxonomic studies have been carried out in detail which usually results in misidentifications at field level. The present morpho-genetic investigation and previous molecular study by the authors confirmed the occurrence of the species in the coastal waters of both the Bay of Bengal and the Arabian Sea. The exact characteristics ofS. koreanusare detailed here, and their comparison was made here with the related speciesS. guttatusfound in the northern part of the east coast of India, based on a thorough morphological study, including the radiographs of 13 fresh specimens (334–588 mm FL), colour photographs ofS. koreanuscollected in 2019–2021 and DNA barcoding.

한국 서해안 곰소만에서 곰소옆새우 Sinocorophium homoceratum (Yu, 1938)의 계절별 현존량 변동 및 염분 내성

The physiochemical factors and seasonal variation in abundance of Sinocorophium homoceratum were examined at the intertidal flat in Gomso Bay, west coast of Korea, for one year. The salt tolerance of S. homoceratum was also investigated in the laboratory. S. homoceratum showed relatively high density in spring and summer, which were relatively high temperature (12 - 28°C) and low salinity (20.0 - 22.0 psu), and the lowest density in winter, which was low temperature (5°C or less) and high salinity (30-32 psu). Although immature individuals appeared throughout the year and juveniles did in all seasons except winter, ovigerous females were only collected from April to June. Relative growth of the head length and head width against the body length was best described by the primary regression equation. In experiments on salt tolerance in S. homoceratum, all individuals died after 24 hours at 0 psu. Six days after the start of the experiment, its survival rates (20.0 - 22.2%) at 28 - 35 psu were significantly lower than those (80.0 -82.3%) at 7 - 21 psu. The results of this study suggest that S. homoceratum is a species well adapted to estuarine mudflat by digging burrows in a silt mudflat and maintaining a relatively high density in all seasons except winter.