Eastern Coast Of Korea Research Articles

First report of Coolia palmyrensis in Korea: seasonal and spatial distribution of C. palmyrensis and C. malayensis in Korean coastal waters

Distribution patterns of benthic dinoflagellates that are widely observed in tropical and temperate waters and have toxic potential are changing in response to ocean climate change. Although there have been no outbreaks associated with the genus Coolia affecting humans, it is crucial to understand their changing distribution and clearly identify the species in the study area to prepare for potential toxic events. In this study, five strains of Coolia species were isolated from macroalgae samples collected from Jeju Island and the eastern coastal waters of Korea. Through morphological and molecular analysis of these isolates, one strain was identified as Coolia palmyrensis, marking the first report of this species in Korea, and four strains as C. malayensis. One of the C. malayensis strains was isolated in Pohang on the eastern coast of Korea, where it had not been previously reported. From 2021 to 2023, monitoring of Jeju Island using a quantitative polymerase chain reaction (PCR) assay revealed that C. palmyrensis cells occurred mostly in autumn, with a maximum density of 242 cells g-1, and overwintering populations were observed in 2023. However, C. malayensis cells were not observed in this area. Additionally, C. malayensis was observed in Pohang and Ulsan, located further north than Jeju Island with maximum cell densities of 537 and 201 cells g-1, respectively. These data and our decade of monitoring experience confirmed the introduction and establishment of C. palmyrensis and habitat shift of C. malayensis in Korean coastal waters. This study provides advances for understanding of the relationships between climate-driven alterations and biogeographic distribution of these species.

Evaluation of beach response due to construction of submerged detached breakwater

Submerged detached breakwaters (SDBWs) have increasingly been used in recent times as an alternative against their emergent counterpart (EDBWs) to mitigate erosion because the former do not spoil the seascape. Both of these structures are (usually) constructed using precast concrete blocks or natural granite rocks, hence becoming permeable structures. For an EDBW, a parabolic bay shape equation can be readily used to estimate the planar shape of the shoreline behind the structure, but there is still no approach to estimate how the shoreline behind the SDBW is formed. In this study, we estimated how the shoreline is balanced by examining how the dominant wave direction changes due to the diffraction of the transmitted wave generated after the installation of the SDBW from the long-term wave directional spectrum. The change in dominant wave direction was determined under the shoreline gradient condition where littoral drift does not occur, considering the diffraction phenomenon due to the difference in transmitted waves. This means that the shape of the equilibrium shoreline changes to face perpendicular to the dominant wave direction. As a meaningful result, when the transmittance is 0, it converges to the well-known empirical equation of EDBW. The present methodology is validated by comparing the observed data (wave and shoreline change) from two beaches (Anmok and Bongpo-Cheonjin Beaches) on the eastern coast of Korea. This rational approach to shoreline changes behind permeable SDBWs will help in proactive review work for coastal management as well as beach erosion mitigation.

New genus of the family Laophontidae T. Scott, 1905 (Copepoda, Harpacticoida) from Hupo on the eastern coast of Korea.

The Laophontidae is a very large and diverse family containing more than 320 species and 74 genera in the Harpacticoida. According to records published until recently, 25 species of 12 genera of Laophontidae were reported to appear in Korean waters. The most common laophontid species in Korean waters is Paralaophontecongenera (Sars, 1908). During research on the meiobenthic community in the subtidal zone near the Korean coast in the East Sea, we found an undescribed genus of the Laophontidae family. The character traits of this undescribed specimen of the Laophontidae family do not match any existing genus. Herein, a new genus of the interstitial marine benthic copepods family Laophontidae T. Scott, 1905 is described from the subtidal zone near Hupo Harbour on the east coast of Korea. This genus was named Strictlaophonte gen. nov. and has been classified into the family Laophontidae. This was based on the presence of seven segmented female antennules, reduced antennary exopod, first endopodal segments having no inner setae from the second leg to the fourth leg and P5 with a distinct exopod that is not fused at the basis. The distinguishing features of Strictlaophonte gen. nov. are P5 exopod having only four setae, the P1 exopod having two segments and the antenna exopod having four setae. In particular, this new genus has unique characteristics in that the caudal rami are very tightly attached to each other.

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.

Beach Erosion along the Eastern Coast of Korea: A Brief Review

Lim, H.S.; Lee, H.J.; Kim, D., and Hong, S., 2023. Beach erosion along the eastern coast of Korea: A brief review. Journal of Coastal Research, 39(1), 181–190. Charlotte (North Carolina), ISSN 0749-0208. Most of the beaches on the eastern coast of Korea are eroding at an alarming rate, triggered by combined natural and artificial causes. In this review, each of the major causes of beach erosion is addressed briefly. A few protection measures such as breakwaters and nourishments are also discussed, with the emphasis on the unexpected or undesirable outcomes. Finally, some of the essential requirements for the field measurements in a beach are mentioned. Global warming has induced the chief natural causes of the beach erosion in Korea, including a gradual increase in wave energies and sea level. An estimation in this review suggests the rates of shoreline of 1 m/10 yrs on the eastern coast by sea-level rise alone. By comparison, artificial beach erosion is most likely to occur upon emplacing structures nearby. A variety of the artificially erosional cases by beach developments are described in the review. Storms and typhoons play a critical role in eroding beaches and changing local morphologies in a short period of time and thus should be observed hydrodynamically. However, the diminishing run-off of rivers and streams should be regarded as the primary reason for the nationwide artificial erosion of beaches. The scanty supply of stream sands to the beaches, together with the influence of global warming, would have the beaches eroded continuously without any coastal developments.

Safety Analysis of a Nuclear Power Plant against Unexpected Tsunamis

The East Sea (Sea of Japan), surrounded by Korea, Japan, and Russia, is highly vulnerable to catastrophic tsunamis. Several nuclear power plants (NPPs) operate along the eastern coast of Korea and several more are under construction. Unexpected tsunamis can affect these power plants. The safety of NPPs has attracted worldwide attention since the Fukushima NPP accident. In this study, a coupled numerical model comprising propagation and run-up models was employed to investigate the safety of an NPP against unexpected tsunami attacks. The maximum and minimum tsunami heights and arrival times of the leading tsunami were numerically predicted to ensure the safety of the Uljin NPP, where six plants are already operational and two more are under construction. The predicted numerical results were compared with the safety guidelines proposed by relevant authorities. These results indicate that NPPs are reasonably safe from unexpected tsunamis. Additionally, we confirmed that the tsunami heights and arrival times of a leading tsunami becomes smaller and delayed as the latitude of the epicenter increased.

Seasonal Variations in the Fish Species Composition and Community Structures on the Eastern Coast of South Korea

The seasonal variations in the species composition of set net fisheries were investigated on the Eastern coast of Korea, from 2007 to 2008. In total, 51 species were found that were classified into 15 orders and 33 families. The water temperature of the study area was 0.1–1.8 °C in 2007 and 0.6–2.1 °C in 2008, which was higher than the average water temperature in the previous decade. The monthly variation in the number of species peaked twice, in May (spring) and November (autumn) when the water temperature increased and decreased, respectively, and the monthly variation in the number of individuals showed a remarkably high trend in winter and autumn and was mainly caused by large migratory species. Based on the cluster analysis of the 18 most dominant species with more than 0.4% of the total number of individuals, we divided the species composition and community structures into three groups: fishes with a temporary appearance (Group A), fishes with a long-term appearance (Group B), and dominant pelagic fishes appearing with a long-term appearance (Group C). We could conclude that the seasonal variation in the structure of the fish community was mainly caused by the pelagic migration of species under high water temperature conditions during the study period.

Development of Forecast System for the Upwelled Coastal Cold Waters in the Eastern Coast of Korea

In this study, a forecast system for the occurrence of cold waters in the eastern coast of Korea was developed by combining the ROMS ocean model and the WRF regional atmospheric model. The 1-day hindcast and 3.5-day forecasts from April 1 to August 31, 2021, successfully reproduced and forecasted the temporal and spatial changes of coastal cold waters. Three case studies with different surface boundary conditions in the ROMS model confirmed that the wind is a primary driver for the occurrence of cold waters in the region. The performance of the ROMS was improved by high-resolution WRF outputs, and through error correction using the water temperature data from the real-time stations, the average RMSE of 9 stations for Forecast Day-3 was 0.73℃, indicating a prossibility of high-precision forecast.

Evaluation of Food Web Structure and Complexity in the Process of Kelp Bed Recovery Using Stable Isotope Analysis

Kelp forests have declined gradually all over the world. Understanding the trophic structure of such a productive and diverse ecosystem is crucial for its restoration and effective management. Few studies, however, have focused on the trophic structure and functional recovery of kelp forests in the process of restoration. This study was conducted in the eastern coast of Korea where kelp bed restoration was in process with the removal of sea urchins. In addition to quantitative measurement for recovery using common community parameters, we investigated how fast the stability of a food web structure could be established in the newly restored kelp beds with an initially barren condition, using stable isotope analysis, in comparison with a nearby natural bed and barren site. At the restored bed, total algal biomass and diversity reached the levels of the natural bed within 1 year. While the δ13C and δ15N values of macroalgae and organic matter were separated isotopically, they were similar among sites, excluding organic matter at the natural bed in 2019. Most consumers showed similar isotopic values among sites, with overlapping range for δ13C of producers. However, some herbivores showed higher δ15N values as predators/omnivores, particularly at barrens, which could be explained by trophic plasticity depending on the macroalgal structure. In the restored bed, for the first year, higher trophic diversity (CR, CD) and lower trophic redundancy (MNND, SDNND) showed non-overlapping &amp;gt;50% CIs among sites. However, this distinctive stage moved toward the natural bed upon entering the second year as trophic diversity decreased and trophic redundancy increased while natural bed overlapped at&amp;lt;50% CIs. The recovery speed in this system was fast (1 year for quantitative perspectives and 2 years for functional completion). After removing the sea urchins, recruitment of macroalgae quickly increased concomitantly with consumer groups, boosting the diversity and trophic structure of the restored bed. The trophic structure of the first year of restoration was not an intermediate stage toward the completion, but a transient over-shooting state. This might have been triggered by the fast introduction of diverse macroalgae to the urchin-free bare rock space, providing an interesting finding needed to be tested in other temperate marine systems.

A Study on Analysis of Freshwater-saltwater Interface in the Aquifer around Hwajinpo Lagoon on the Eastern Coast of Korea

A Study on Analysis of Freshwater-saltwater Interface in the Aquifer around Hwajinpo Lagoon on the Eastern Coast of Korea

Factors Influencing Dietary Changes of Walleye Pollock, Gadus chalcogrammus, Inhabiting the East Sea off the Korean Coast

This study examined the dietary patterns of walleye pollock, Gadus chalcogrammus, off the middle eastern coast of Korea between January 2016 and December 2017 to determine the influences of various predictors on dietary changes. Based on stomach content analyses, walleye pollock was found to be a demersal carnivore that mainly consumes carid shrimps, euphausiids, mysids, teleosts, and cephalopods. The main prey species identified in the diets of walleye pollock were Euphausia pacifica (euphausiids), Themisto japonicus (amphipods), Neomysis spp. (mysids), Neocrangon communis, Pandalus borealis (carid shrimps), Watasenia scintillans (cephalopods), and Bothrocara hollandi (teleosts), which are hyper-benthic and bentho-pelagic organisms. Dietary analyses based on the weight contributions of different prey taxa to the diets revealed significant variations in dietary composition in terms of fish size, water depth, and season, implying intraspecific dietary segregation. Euphausiids dominate the diets of smaller individuals (&lt;30 cm TL), whereas the contributions of carid shrimps, teleosts, and cephalopods increase as body size increases. Similarly, the latter three prey items are dominant food resources in deeper habitats. The PERMANOVA results revealed that the size-related spatial and temporal changes in dietary composition are all significant for the species, as well as their two- or three-way interactions among those factors, except for the size-depth interaction. The coupling effect of size and depth is indicative of depth-dependent differences in fish sizes, with the tendency for larger individuals to be distributed in deeper habitats. In addition, seasonal and interannual variations in water column structures are also evident in the diets, which may, in part, account for the diet seasonality observed in the stomach content analysis. The dietary analyses of walleye pollock will improve our understandings to seek functional role of the species in benthic food webs, and to predict the effects of environmental and anthropogenic perturbations.

Importance Aanalysis of the Environmental Management according to the Users at Recreational Beaches in the Eastern Coast of Korea

The management for the recreational beach is performed by not only central and local governments but also private organizations for various purposes in Korea. Nevertheless, with the increasing demand for diverse recreational activities based on beaches, a multifaceted and systematic management planning is urgently needed. The purpose of this study is to analysis the environment awareness factors and the importance of the environmental management in accordance with the users of the recreational beach located in the eastern coast of Korea. Likewise, some data was collected through a questionnaire survey targeted on 278 beach users (related business and leisure). Additionally, the characteristics of beach user were analyzed with regard to the environmental management significance by using T-test, ANOVA and multiple regression analysis. As a result of the points of views, it appeared that the user characteristics of the recreational beach in the eastern coast of Korea is highly related to the facility and equipment, natural environment, human resources and user factors. And the environmental awareness of recreational beaches users on the east coast of Korea partially influences the importance of environmental management. These results will be the foundation for the safer and more comfortable operation in Korean recreational beaches surrounded by the other regions as well as east area in Korea.

Holocene sedimentation in the Hupo Trough of the southwestern East Sea (Japan Sea) and development of the East Korea Warm Current

Various sediment properties, such as mean grain size, total organic carbon, total nitrogen, C/N ratio, CaCO3, and biogenic opal content, were analyzed for a box core (BC02; 45 cm long) and a gravity core (GC02; 628 cm long), which were collected from the western margin of the Hupo Trough located off the eastern coast of Korea. The study area has been affected by the East Korea Warm Current (EKWC), a branch of the Tsushima Warm Current (TWC). The analytical results obtained for BC02 and the upper part of GC02 were in agreement, affirming the core-top preservation of GC02. Based on the corrected calibrated AMS 14C dates, the sedimentation rate of GC02 changed abruptly at ~8.2 ka from ~4.0–10.2 cm/kyr in the lower part to ~56.6–91.0 cm/kyr in the middle to upper part. This corresponds to the lithologic change from sandy mud to mud sediments showing the mean grain size change from 6.9 to 46.0 μm. Diverse paleoceanographic proxies representing the surface water condition exhibited varying degree of change at ~8.2 ka, after which all the properties remain almost unchanged, implying stable and continuous depositional conditions following the complete development of the EKWC. Furthermore, it indicated that the sediment depositional conditions in the Hupo Trough in response to the EKWC might have stabilized at ~8.2 ka since the opening of the Korea Strait during the Holocene sea level rise. Moreover, microfossil data from previous studies on the establishment of the TWC in the East Sea (Japan Sea) support our interpretation that the sediment properties revealed the Holocene development of the EKWC in the Hupo Trough.

Estimation of Extreme Significant Wave Height in the Northwest Pacific Using Satellite Altimeter Data Focused on Typhoons (1992–2016)

The estimation of extreme ocean wave heights is important for understanding the ocean’s response to long-term changes in the ocean environment and for the effective coastal management of potential disasters in coastal areas. In order to estimate extreme wave height values in the Northwest Pacific Ocean, a 100-year return period were calculated by applying a Peak over Threshold (PoT) method to satellite altimeter SWH data from 1992 to 2016. Satellite altimeter SWH data were validated using in situ measurements from the Ieodo Ocean Research Station (IORS) south of Korea and the Donghae buoy of the Korea Meteorological Administration (KMA) off the eastern coast of Korea. The spatial distribution and seasonal variations of the estimated 100-year return period SWHs in the Northwest Pacific Ocean were presented. To quantitatively analyze the suitability of the PoT method in the Northwest Pacific, where typhoons frequently occur, the estimated 100-year return period SWHs were compared by classifying the regions as containing negligible or significant typhoon effects. Seasonal variations of extreme SWHs within the upper limit of 0.1% and the PoT-based extreme SWHs indicated the effect of typhoons on the high SWHs in the East China Sea and the southern part of the Northwest Pacific during summer and fall. In addition, this study discusses the limitations of satellite altimeter SWH data in the estimation of 100-year extreme SWHs.

Sex of Mussel Mytilus coruscus (Bivalvia: Mytilidae) : Sequential Hermaphroditism.

Samples were collected from the subtidal region of Jumunjin on the eastern coast of Korea in July 2020. A total of 338 mussels of shell height (SH) 20.8-149.8 mm were used for sex ratio analysis. The sex ratio (F:M) in the same population of mussel Mytilus coruscus was approximately 1:0.7. The sex ratio according to the class of SH was different. The sex reversal pattern of M. coruscus appears to go from male → female → male → female, and as such is determined to be sequential hermaphrodites.

Simulation of Bay-Shaped Shorelines after the Construction of Large-Scale Structures by Using a Parabolic Bay Shape Equation

Among the various causes of coastal erosion, the installation of offshore breakwaters is considered the main cause that influences the most serious changes in shorelines. However, without a proper means for predicting such terrain changes, countries and regions continue to suffer from the aftermath of development projects on coastal land. It has been confirmed that the parabolic bay shape equation (PBSE) can accurately predict shoreline changes under the wave climate diffracted as a result of such development projects. This study developed a shoreline change model that has enhanced the previous shoreline change models by applying PBSE to shoreline changes into bay-shaped features. As an analytical comparison with the second term of the GENESIS model, which is an existing and well-known shoreline change model, a similar beach erosion width was obtained for a small beach slope. However, as the beach slope became larger, the result became smaller than that of the GENESIS model. The validity of the model was verified by applying it to satellite images that demonstrated the occurrence of shoreline changes caused by breakwaters for seaports on the eastern coast of Korea; Wonpyeong beach, Yeongrang beach, and Wolcheon beach. As a result, each studied site converged on the static equilibrium planform within several years. Simultaneously, the model enabled the coastal management of the arrangement of seaports to evaluate how the construction of structures causes serious shoreline changes by creating changes to wavefields.

Diversity and Assemblage Structure of Marine Fish Species Collected by Set Net in Korean Peninsula During 2009–2013

Assemblage structure analysis was conducted based on seasonal fish species composition data collected four times a year during 2009–2013 from 10 stations around Korea (except the western coast of Korea) using set nets. A total of 154 fish species were identified, of which Trachurus japonicus (22.1%) was the most dominant, followed by Konosirus punctatus (9.2%) and Scomber japonicus (8.7%). Species richness was highest in Jumunjin (in the mid-eastern coast of Korea) and lowest in Gijang (in the east-southern coast of Korea), and species diversity was highest in Gangjeong (southern Jejudo Island) and lowest in Hanrim (northern Jejudo Island). Based on a Bray-Curtis similarity index value of 38%, the 10 stations were divided into three groups: group A comprised four stations in the eastern coast of Korea, group B comprised four stations in the east-southern coast of Korea and Jejudo Island, and group C comprised two stations in the westsouthern coast of Korea. One-way analysis of similarities showed significant differences among groups (global R: 0.822, p = 0.001). The characteristics of the sea currents (e.g., Tsushima Warm Current, North Korea Cold Current) and water masses (e.g., Yellow Sea Bottom Cold Water) might have influenced this grouping.

Grain size distribution and chemistry of the brackish Lake sediment in Korea

To determine the grain size distribution and chemical characteristics of bottom surface sediments in shallow brackish lagoons, we studied sediment samples collected from the entire horizontal lake area and in vertical profiles from three stations in Lakes Youngrang and Hwajinpo, on the eastern coast of Korea. Vertical and horizontal grain size distributions of the bottom sediments indicated predominantly sand- and silt in both lakes. The vertical distribution of C/N ratios ranged from 6.14 to 11.92 in Lake Youngrang, and 6.74 to 12.34 in Lake Hwajinpo. The horizontal distribution of C/N ratios in Lake Youngrang ranged from 6.1 to 17.6, whereas they ranged from 4.4 to 12.1 in Lake Hwajinpo. C/N ratios showed locally different responses to the origin of allochthonous (partial region) and autochthonous (entire region) organic materials. Horizontally, bottom sediment with low δ&lt;sup&gt;13&lt;/sup&gt;C and high δ&lt;sup&gt;15&lt;/sup&gt;N in Lake Youngrang were likely to be influenced by autochthonous organic material derived from primary production, and would be affected by N inputs from sources. In contrast, high δ&lt;sup&gt;13&lt;/sup&gt;C and low δ&lt;sup&gt;15&lt;/sup&gt;N sediments in Lake Hwajinpo were likely to be influenced by cyanobacteria.

동해 중부 연안 환경 변화에 따른 명태 개체 크기 및 분포의 시공간적 변화

동해 중부 연안 환경 변화에 따른 명태 개체 크기 및 분포의 시공간적 변화

Holocene Transgressive Sands on the Nearshore of a Micro-tidal Shelf

Lee, H.J.; Lee, S.H.; Baek, Y.S., and Lim, H.S., 2020. Holocene transgressive sands on the nearshore of a micro-tidal shelf. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 553-557. Coconut Creek (Florida), ISSN 0749-0208.A beach retreat by the Holocene sea-level rise is commonly observed in shelf environments. To investigate into a consequence of the beach retreat in a micro-tidal shelf, surface and cored sediments were sampled from a coastal area around a stream in the eastern coast of Korea and were analyzed texturally. A coastal stratigraphy is constructed with three units representing fluvial sediments, eolian sands and beach sands in an ascending order. This stratigraphy results from the Holocene transgression. The textural characteristics of the units are compared with those of the surficial samples to determine the origin of surficial sands. As a result, the nearshore sands in the study area are most probably the erosional remnants of the antecedent eolian and beach sands. This study exemplifies the Holocene transgression over a narrow, steep shelf whereby active shoreface erosion left portions of beach sediments behind in small estuarine environments.