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ABSTRACT Lee, J.H. and Kim, T.R., 2018. Study of High Waves caused by Slanting-fetch Effects along the Coast. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 831–835. Coconut Creek (Florida), ISSN 0749-0208. Design wave height estimation for the ports and coastal structures are mainly based on the waves from offshore wind which have long fetches enough to develop high waves. The waves generated by short fetched land wind are usually neglected because they are thought to be small and short period waves. However, in case of land wind oblique to the long coast line with short fetch, unexpected long period high waves are developed along the coast by slanting-fetch effects. These high waves can damage human lives as well as coastal structures, but are difficult to predict using offshore wave measurement system. Therefore, it is important to understand the characteristics of waves by slantingfetch and prepare countermeasures against them. This paper analyzes observed wind and wave data in the East Sea, on Feb. 6–8th and Dec. 12–14th in 2013, when waves were developed by slanting-fetch effects near the coast. During these periods, strong northwest wind of over 15 m/sec lasted more than 24 hours, but southwestward waves with significant wave height of over 1.5 m and peak period of over 10 sec were observed at Hupo Harbor in spite of land wind with short fetch. Unstructured WAVEWATCH III model is executed to simulate the waves generated by slanting-fetch effects and RDAPS/UM wind data with 12 km resolution provided by NCMS/KMA are used as forcing input data. The numerical wave model results at Hupo Harbor show relatively good agreement with in-situ measurement data explaining high waves with long period by slanting-fetch effects, and both observed and simulated wave directional spectrum at Hupo Harbor show strong energy in long period and southwestward direction. [ABSTRACT FROM AUTHOR]

ABSTRACT Kim, H.; Son, Y.B.; Jeong, J.-Y., and Jo, Y.-H., 2018. Comparison of Internal Waves in Various Ocean Fields around the Korean Peninsula. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 466–470. Coconut Creek (Florida), ISSN 0749-0208. The sea surrounding the Korean Peninsula is roughly divided into the western part (the Yellow Sea (YS) and the South Sea (SS); shallow inland sea) and the eastern part (the East Sea (ES); drastically deep). While internal wave (IW) studies have been mainly localized because of the complicated environmental conditions around the Korean Peninsula, this study determined the differences of the IWs in various ocean fields for over three years (2013–2015). First, satellite measurements with high spatial and temporal resolutions from Landsat 8 and the Geostationary Ocean Color Imager (GOCI) were used. The curvature analysis was used to define and compare the shapes of the objective factors of the IWs, such as sizes, ovalities, and maximum wavelengths. In the YS, IWs appeared at a densely spaced interval compared with the ES and the maximum wavelength of the packet was nonlinearly increased with depth, and that of the YS (1.1 km) was about 10 times larger than and ES (10.6 km). In addition, the standard deviations of the wavelengths in a packet, which can determine the irregularity of the within-packet spacings from front to rear; were 0.2 and 1.4 for the YS and ES, respectively. Second, the ocean temperature and salinity data from HYCOM and Korteweg-de Vries equation were used to calculate the theoretical phase speed of IWs. Typically, the IW phase speed increased nonlinearly with the water depth; and the mean value was approximately 0.1–0.7 m/s and 0.9–1.7 m/s for the YS and ES, respectively. [ABSTRACT FROM AUTHOR]

The East Sea (Japan Sea) ecosystem has experienced a significant warming and ever-increasing anthropogenic atmospheric deposition of nitrogen during recent decades. To understand the impacts of such environmental changes on the planktonic community, we set up a zero-dimensional European Regional Seas Ecosystem Model (ERSEM) in the Ulleung Basin, East Sea for the years 2001–2012. The model results show that as the winter maximum mixed layer depth (MMLD) changes, the growth and grazing loss of phytoplankton functional types (PFTs) are affected differently, resulting in differential success of PFTs in the upper mixed layer. Diatoms pre-empted the early spring growth by better utilization of light and nitrate. Diatoms’ advantages lessened as the MMLD decreased. Flagellates and picophytoplankton showed mixed responses to decreased MMLD. Their net primary productivity (NPP) and peak biomass decreased but their annual biomass increased due to decreased grazing. Dinoflagellates always did better when MMLD decreased. The model results also indicate that with an increase in atmospheric deposition, the picophytoplankton and the flagellates increased in summer, whereas the dinoflagellates and the diatoms decreased. For the study period, the atmospheric deposition in the Ulleung Basin increased the annual net primary production by 4.58% (mean; range 3.77–10.58%). Biological variables showed the largest responses in summer with high year-to-year variability. Picophytoplankton increased the most (summer increase mean: 23.23%; summer increase range: 9.12–42.6%) while dinoflagellates decreased the most (summer decrease mean: −2.33%; summer decrease range: −9.09 to 10.13%). The changes in flagellates and diatoms were much less. Taking the results together, it is likely that as the warming and atmospheric deposition continue to intensify into the future; the phytoplankton community in the region will shift to smaller phytoplankton with consequent changes of food web structure to follow. [ABSTRACT FROM AUTHOR]

Seismic reflection data from the Ulleung Basin, East Sea, provide extensive evidence for Plio-Quaternary mass transport deposits (MTDs). We identified 23 MTDs embedded in 7 MTD bearing seismic units (U1–U7, from oldest to youngest) and estimated their geometric characteristics and source areas. The thicknesses and volumes of these MTDs range between 25 m and 392 m, and 13 km 3 –550 km 3 , respectively. The depth of the acoustic basement below sea level varies between about 100 m in the western margins to over 5900 m in the central part of the basin and highlights eight structural highs in the central and southern parts of the basin. These structural highs had a major role in controlling the pathway and distribution of the MTDs in the basin. In general, the thickest MTD units are sourced from the southern parts of the basin and the volume of these MTDs has remained relatively constant throughout the Plio-Quaternary. The seismic reflection data also reveal about 50 m high slide/slump scars formed on the seafloor by the latest submarine landslides which mainly concentrate on the southern and western margins of the basin. High-sedimentation rates and pore pressure build-up are likely the predominant factor controlling initiation of slope failures in the southern margin. Tectonics and gas hydrates likely play a role, too. The initial water depth of submarine landslides and volume and runout of the MTDs originating from the southern margin imply significant geohazard to the region. [ABSTRACT FROM AUTHOR]

Cyclic variations of density and gamma-ray logs achieved from the two drill sites of UBGH2-1_1 and UBGH2-1_2 in the western slope of the Ulleung Basin were investigated to reveal their paleoceanographic implications and establish cyclostratigraphy of the well logs. Integration of the core, log, and seismic data from the two sites indicates that the sediments of the drilled intervals mostly consist of hemipelagic muds, with a few sporadic mass transport deposits intercalated only in the downslope site of UBGH2-1_1. Comparison with variations in sediment composition suggests that ratios of terrigeneous to biogenic materials which were modulated by orbital-scale climate changes should be responsible to the well-log variations. The established cyclostratigraphy of the well logs based on correlation with marine oxygen isotope records indicates such climatic modulation of the sedimentation in the western slope of the Ulleung Basin has persisted at least since 2.6 Ma, consistent with the variation reported from the Oki Ridge. [ABSTRACT FROM AUTHOR]

In this study the effect of underwater topography of the East Sea on the propagation of tsunamis towards the Korean Peninsula is investigated using the dispersion-correction finite difference numerical model. A series of numerical simulations are conducted for three tsunami events including the 1964 Niigata Tsunami, the 1983 Central East Sea Tsunami and the 1993 Hokkaido South-West Sea Tsunami for the cases of examining the individual or combined influence of underwater topographic features. These include the Yamato Rise, a submerged ridge connecting Yamato Rise and the Shimane Peninsula of Japan, and K-shaped submerged ridges emerging from the east coast of Korea towards the East Sea. In particular, in order to evaluate quantitatively the effects of underwater topography on the propagation of tsunamis, a new concept of energy discharge per unit width is introduced. Using this concept, the quantitative analyses of energy propagation during tsunami events are performed. The analyses show that the underwater topographies including the submerged rises and ridges capture the tsunami energy and transport it to coastal areas connected to those topographies. [ABSTRACT FROM AUTHOR]

A piston core (EBP-3) collected from the South Korea Plateau in the East Sea (Japan Sea) preserved typical alternations of thick, dark laminated mud layers and bioturbated hemipelagic mud layers, but included several intercalated volcanic lapilli layers. The age estimate of core EBP-3 was aided by correlation of biostratigraphic radiolarian data, the abundance of microfossils (warm-water radiolarians), and geochemical properties (CaCO 3 ) with the proxies of the well-dated core MD01-2407 obtained from the Oki Ridge. A part from the Marine Isotope Stage (MIS) 11 to MIS 9 in the middle of core EBP-3 was missing, presumably because of erosion following the abrupt deposition of a volcanic lapilli layer. Despite some uncertainty, the age estimate of core EBP-3 revealed that the lower part of core EBP-3 represents MIS 13, as was also evident from a comparison with the oxygen isotope stratigraphy. Downcore biogenic opal and CaCO 3 variations in core EBP-3 exhibited less distinct orbital-scale cyclic changes than cores from other areas in the East Sea (Japan Sea). However, differences in features were discernible between MIS 2 and MIS 12 in terms of their lithology and CaCO 3 constituent, although both periods were characterized by relatively high levels of CaCO 3 (about 30% for MIS 2 and about 50% for MIS 12). MIS 2 preserved a typical thick, dark laminated mud layer, whereas MIS 12 preserved a distinctly light mud layer with thin parallel laminations. This difference of the lithologic facies between MIS 2 and MIS 12 highlighted a discrepancy among the major constituents, indicating that planktonic foraminifera were dominant in MIS 2, whereas coccolithophores were dominant in MIS 12. Our results suggest that the thinly-laminated light mud layer, which is characterized by a high CaCO 3 content primarily composed of coccolithophores in MIS 12, can be used as a reliable time marker for the establishment of chronostratigraphy in the East Sea. [ABSTRACT FROM AUTHOR]

Three species of the genus Paradoxostoma Fischer, 1855 are reported from the South Korean East Coast: Paradoxostoma flaccidum Schornikov, 1975, P. brunneum Schornikov, 1974, and one new species, P. sokchoensis, new species. The first species was previously reported from the East Sea off the Korean peninsula, with additional Paradoxostoma as part of a species list of an ecological study carried out in South Korea. Paradoxostoma sokchoensis is most closely related to P. depressum Okubo, 1977 and P. assimile Okubo, 1978. Three major differences between the new species and the other two species are: 1) the presence of an unusual group of setulae on the antennule, 2) absence of seta on first segment of L6, and 3) a more slender anterior margin of the carapace. [ABSTRACT FROM AUTHOR]

Abstract: We investigated character and distribution of the gas hydrate zone in the western part of the Ulleung Basin in the East Sea (Japan Sea) from seismic data using stochastic sparse spike deconvolution, analysis of frequencies, and acoustic-elastic coupled full-waveform inversion. The presence of gas hydrates is primarily indicated by a bottom-simulating reflector (BSR) with negative polarity at approximately 240–250 ms below the seafloor. The instantaneous frequency section defines a high-frequency anomaly above the BSR underlain by a less clear low-frequency anomaly. Sparse spike deconvolution indicates that the BSR occurs horizontally along the boundary between the high- and low-frequency anomalies. Compared to well logs obtained from the seafloor through the BSR, the high-frequency anomaly, maximally 50 ms thick (ca. 45 m), appears to outline the hydrate-bearing zone. The results from full-waveform inversion appear to delineate the hydrate-bearing zone and the underlying gas-bearing zone, although their depth ranges do not coincide accurately with those inferred from well logs. The hydrate-bearing zone is characterized by an increase in both p- and s-wave velocities, while the gas-bearing zone is marked by a decrease in p-wave velocity. The very narrow free gas zone is less than 30 m thick and appears to be concentrated immediately below the gas hydrate stability zone. The hydrate-bearing zone is also defined by decreased Poisson's ratio which suggests appreciable variations of the hydrate-bearing zone in thickness. [Copyright &y& Elsevier]

Abstract: During drilling in 2010 in the Ulleung Basin, East Sea, Logging-While-Drilling (LWD) was conducted for thirteen sites. LWD data shows various characteristics indicating presence of gas hydrate-bearing sediments. In particular, a series seismic chimney sites are characterized by anomalous log data (i.e. high resistivity and velocity values), compared to surrounding marine sediments. At chimney sites, the resistivity and velocity log values are over 200 Ω-m and 3000 m/s, respectively. Moreover, log values of low density (less than 1.1 g/cm3) indicating the presence of massive hydrates also correlate with intervals with the highest resistivity and velocity. Gas hydrates at the seismic inferred chimney sites occurred within inclined fractures in the mud dominated sediments. These gas hydrate-filled fractures were identified on LWD resistivity images and X-ray images of pressure cores. The gas hydrate-filled fracture intervals coincide with high measured resistivity intervals at three sites (Sites UBGH2-3, UBGH2-7, UBGH2-11). In most cases, high measured resistivity translated into high hydrate saturations via Archie's relationship; but the high saturations derived from the Archie's relationship appear to overestimate gas hydrate saturations when compared to pressure core samples and acoustic log measurements. Also, in intervals with inclined gas hydrate-filled fractures (e.g., UBGH2-3), there is notable separation between phase-shift and attenuation resistivity logs, with 2 MHz resistivity measurements being significantly higher than 400 kHz resistivity measurements. In this study, the analysis of fractures with dip angles greater than 30° on the resistivity log-images show dip angles between 43 and 63° in average for the three sites examined. The dip azimuth of the fractures at Sites UBGH2-3 and UBGH2-7 dominate westerly to southwestern direction, while the fractures at Site UBGH2-11 are characterized by no preferred orientation. This fracture pattern indicates that maximum horizontal stress direction at the time of fracture formation was not constant. In addition, the differential compaction of the sediments after deposited may be contributed to the development of fracture. [Copyright &y& Elsevier]

Examinations of core and well-log data from the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) drill sites suggest that Sites UBGH2-2_2 and UBGH2-6 have relatively good gas hydrate reservoir quality in terms of individual and total cumulative thicknesses of gas-hydrate-bearing sand (HYBS) beds. In both of the sites, core sediments are generally dominated by hemipelagic muds which are intercalated with turbidite sands. The turbidite sands are usually thin-to-medium bedded and mainly consist of well sorted coarse silt to fine sand. Anomalies in infrared core temperatures and porewater chlorinity data and pressure core measurements indicate that “gas hydrate occurrence zones” (GHOZ) are present about 68–155 mbsf at Site UBGH2-2_2 and 110–155 mbsf at Site UBGH2-6. In both the GHOZ, gas hydrates are preferentially associated with many of the turbidite sands as “pore-filling” type hydrates. The HYBS identified in the cores from Site UBGH2-6 are medium-to-thick bedded particularly in the lower part of the GHOZ and well coincident with significant high excursions in all of the resistivity, density, and velocity logs. Gas-hydrate saturations in the HYBS range from 12% to 79% with an average of 52% based on pore-water chlorinity. In contrast, the HYBS from Site UBGH2-2_2 are usually thin-bedded and show poor correlations with both of the resistivity and velocity logs owing to volume averaging effects of the logging tools on the thin HYBS beds. Gas-hydrate saturations in the HYBS range from 15% to 65% with an average of 37% based on pore-water chlorinity. In both of the sites, large fluctuations in biogenic opal contents have significant effects on the sediment physical properties, resulting in limited usage of gamma ray and density logs in discriminating sand reservoirs. [ABSTRACT FROM AUTHOR]

Abstract: The Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) recovered various forms of gas-hydrate bearing sediments from 10 drill sites in the lower slope and basin floor of the Ulleung Basin. To characterize the gas-hydrate occurrences and the properties of the host sediments, whole-round core samples were taken from portions of recovered cores determined to be hydrate-bearing based on infrared (IR) scanning. These samples were further characterized by a variety of shipboard experiments such as imaging of the sediments with hand-held IR and visual cameras, measurements of pore water chlorinity within and around IR inferred cold regions in the core and grain-size analysis of pore-water squeeze cakes. Sediment compositions of selected samples were further characterized by X-ray diffraction and scanning electron microscopes during post-cruise analysis. The shipboard and post-cruise analysis results collectively indicate that the recovered gas hydrates mainly occur as 1) “pore-filling” type bounded by discrete silty sand to sandy silt layers, 2) “fracture-filling” veins and nodules, or 3) “disseminated” type in silt. In addition, minor but significant variation in gas hydrate concentrations were observed in diatomaceous silt where gas hydrates occur as “pore-filling” material in layers dominated by intact diatom frustules. Gas hydrate accumulations of “fracture-filling” type occur predominantly in regions where acoustic blanking features in the seismic record suggest gas migration from below the gas hydrate stability zone. Results from the UBGH2 core studies along with the analysis of similar samples from other expeditions, including those executed by the Ocean Drilling Program, the Integrated Ocean Drilling Program, and the First Ulleung Basin Gas Hydrate Drilling Expedition, greatly improved our understanding of lithologic controls on marine gas hydrate occurrences. [Copyright &y& Elsevier]

The effects of the thermal discharge from a coastal nuclear power plant on the spatial and seasonal variability of nematode assemblages were investigated in the Gori coastal waters of the southern East Sea. Taxonomic and functional approaches were taken to describe the assemblage structure and relate it to the abiotic environment based on a sampling scheme involving three stations and four seasons. The analysis of the nematode communities suggested that heated effluent influenced the assemblage structure or the spatial distribution of the taxa studied. The abundance of the nematodes differed significantly among seasons and stations and the numbers of species also differed significantly between stations. The seasonal variation was greater in winter and summer than in spring and autumn. The numbers of species and their abundances were highest at station 3 (impact station), attributable to the increased bottom temperature. However, the functional diversity of the assemblages did not change notably between stations or seasons. Species such asSabatieriasp. (34%),Linhysterasp. (18%) andParodontophorasp.(11%) were usually dominant in all seasons and at all stations.Parodontophorasp.displayed a significantly negative correlation with the bottom temperature (P<0.05). These results indicate that the nematode species composition was significantly affected by the bottom temperature. [ABSTRACT FROM AUTHOR]

Heo, K.-Y., Shim, J.-S., Kwon, J.-I., Jeong, J.-Y., Park, K.-S. and Choi, J.-W., 2013. Abnormal storm waves around the Korean Peninsula: A case study of an extratropical explosive cyclone over East Sea. On April 3, 2012, an extratropical explosive cyclone developed over East Sea, producing heavy rainfall and strong winds. This cyclone produced maximum wind speeds of up to around 21 m s−1 over the ocean around Korea. As the explosive cyclone developed rapidly from 00 UTC April 3, 2012, it began to affect the coastal areas, and abnormal storm waves were generated by the strong wind. The observed maximum wave heights and periods around Korea were 11.1 m and 9.1 s at Chilbaldo, 12.0 m and 9.1 s at Marado, and 13.7 m, and 5.8 s at Ulleungdo in the period 04-10 UTC April 3, 2012. The objectives of this study are to investigate the mechanisms and conditions favorable for the development of the explosive cyclone, and to investigate the influence of the cyclone on the abnormal storm waves. To achieve the above objectives, numerical studies are conducted using the Weather Research and Forecasting (WRF) model as an atmospheric model and the open ocean wave model WAM. The explosive cyclone is amplified by latent heat release as well as the formation of an upper-level cut-off low, which resulted in the rapid intensification of the cyclone; while surface heat fluxes had a lesser contribution to the explosion of the cyclone. In situ meteorological observation data and wave data from buoy measurements for this event are available for comparison and validation. The comparisons show that the WRF and WAM models can accurately predict the wind speed and wave height. [ABSTRACT FROM AUTHOR]

Detailed analysis of core sediments and acoustic characteristics of Chirp sub-bottom profiles from a submarine ridge in the southern slope of the Ulleung Basin, East Sea, Korea, reveals changes in sedimentary processes and deformation of sedimentary sequence induced by seafloor mound formation since the Last Glacial Maximum (LGM). The core sediments consist generally of four sedimentary facies which represent hemipelagic sedimentation under a poorly-oxygenated bottom-water condition during the LGM (crudely laminated mud), shoreface erosion and seaward transport off the shelf break during the post-glacial transgression (bioturbated sandy mud or muddy sand), hemipelagic sedimentation under generally well-oxygenated bottom-water condition after the sea-level rise (bioturbated mud), and episodic precipitation of authigenic carbonates by methane venting since the LGM (authigenic carbonate-bearing mud), respectively. The formation of authigenic carbonate-bearing mud facies and associated accumulation of near-seafloor gas hydrates might have led to up-warping of the sediment cover since the LGM that resulted in the seafloor mounds protruding along the crest line of the ridge. The effects of up-warping by expansion of the subsurface gas hydrates are firstly manifested in this paper by the abrupt lateral changes in the sedimentary facies distribution and uplifted acoustic reflectors between the mounds and the background seafloor. [ABSTRACT FROM AUTHOR]

The objective of the study was to investigate if reproductive characteristics of Pandalus eous affect the depth distribution in the East Sea of Korea. P. eous was found at depths of 500–900 m in the East Sea of Korea, with the highest percentage occurrence (34%) at 500 m. A negative correlation was observed between the number of individuals and the depth. The overall sex ratio also turned out to be significantly correlated with depth. On average, the larger individuals (bigger than 26.37 cm), which included transitional, female, and ovigerous females, were mostly distributed at 700 m depth. The percentage of males increased by depth and ovigerous females were mainly distributed in the shallow water (300 m) during winter. Ovigerous females were not found at 900 m, which is the deepest depth range in this study. The percentage of transitional individuals was greatest at 500 m and decreased gradually with depth. All ovigerous female individuals were of the spent ovarian stage in winter. Female numbers in the ripe ovarian stage increased with depth and immature females rarely appeared. The gonadosomatic indices of the nonovigerous females and ovigerous females were highest at 700 m in depth. The mean egg size of P. eous was 0.83±0.11 mm3 in the non–eyed stage and 0.93±0.17 mm3 in the eyed stage. [ABSTRACT FROM AUTHOR]

Abstract: The Gas Hydrate Research and Development Organization (GHDO) of Korea successfully accomplished both coring (hydraulic piston and pressure coring) and logging (logging-while-drilling, LWD, and wireline logging) to investigate the presence of gas hydrate during the first deep drilling expedition in the Ulleung Basin, East Sea of Korea (referred to as UBGH1) in 2007. The LWD data from two sites (UBGH1-9, UBGH1-10) showed elevated electrical resistivity (>80 Ω-m) and P-wave velocity (>2000 m/s) values indicating the presence of gas hydrate. During the coring period, the richest gas hydrate accumulation was discovered at these intervals. Based on log data, the occurrence of gas hydrate is primarily controlled by the presence of fractures. The gas hydrate saturation calculated using Archie’s relation shows greater than 60% (as high as ∼90%) of the pore space, although Archie’s equation typically overestimates gas hydrate saturation in near-vertical fractures. The saturation of gas hydrate is also estimated using the modified Biot-Gassmann theory (BGTL) by . The saturation values estimated rom BGTL are much lower than those calculated from Archie’s equation. Based on log data, the hydrate-bearing sediment section is approximately 70 m (UBGH1-9) to 130 m (UBGH1-10) in thickness at these two sites. This was further directly confirmed by the recovery of gas hydrate samples and pore water freshening collected from deep drilling core during the expedition. LWD data also strongly support the interpretation of the seismic gas hydrate indicators (e.g., vent or chimney structures and bottom-simulating reflectors), which imply the probability of widespread gas hydrate presence in the Ulleung Basin. [Copyright &y& Elsevier]

Abstract: The East Sea, with an average depth of 1700m, has long been subject to heavy fishing pressure, resulting in derelict fishing gear. Most derelict fishing gears, such as fishing nets, fishing ropes, and crab pots, sink to the seabed and do not degrade. This gear results in “ghost fishing,” which has adverse impacts on deep benthic habitats. Recently, the Korean government has started to remove derelict fishing gears from the deep seabed of the East Sea by bottom trawling with heavy hooks (50–80kg) and ropes. A total of 207.8 and 252.2tons of marine debris in 2009 and 2010, respectively, were removed from the seabed, most of which were derelict fishing gears. Contrary to monitoring surveys and clean-up in shallow waters, removal of marine debris from remote deep habitats is much more difficult and dangerous for removal crews. [Copyright &y& Elsevier]

Entanglement of marine mammals in fishing gear is a global issue. It is considered a significant threat to minke whales ( Balaenoptera acutorostrata) in the East Sea of Korea. A total of 214 entanglements of minke whales in this area between 2004 and 2007 were used to investigate types and parts of fishing gears involved in entanglements. The majority of entanglements were mainly caused by three types of fishing gears: set nets, pots, and gill nets ( n= 207, 96.7%). Other entanglements were associated with bottom trawls, purse seines, and trawls. A total of 65 entanglements were attributed to the main and branch lines of fishing gears. The most common body part of minke whales which attached to fishing gears was the mouth ( n= 63, 30.4%). Most entanglements took place within 10 nmi from land ( n= 179, 86.5%), and between 10 and 220 m of water depth. The mean length of entangled minke whales in set nets was significantly smaller than that of whales in pots and gill nets samples ( P < 0.001). Also, the mean body length of minke whales that entangled in the coastal area and shallow waters was significantly shorter than that of whales in the offshore area and deep waters ( P < 0.001). This information can be used as fundamental data to conserve and manage this population of minke whales in the East Sea of Korea, and also to modify fishing gear to reduce entanglements. Future studies should focus on investigating the impact of these entanglements on the population and the effectiveness of mitigation measures to reduce entanglements of minke whales in this area. [ABSTRACT FROM AUTHOR]

Abstract: Six piston cores (95PC-1, MB97PC-19, TY99-PC18, 95PC-3, 95PC-4 and 96EBP-4) from the East Sea (Japan Sea) were examined to assess the fluctuations in carbonate and biogenic silica sedimentation. Data from four of these cores (95PC-1, MB97PC-19, TY99-PC18 and 96EBP-4), collected from depths above the present carbonate compensation depth (CCD), clearly show that carbonate content increased during glacial periods and decreased during interglacial periods, whereas biogenic silica content shows the opposite pattern. The two cores collected below the CCD also show glacial/interglacial variations in carbonate and biogenic opal contents with patterns similar to the cores collected above the CCD. This study provides strong evidence for cyclic variations of biogenic components corresponding to interglacial–glacial cycles, even though variations in carbonate and opal contents seem to be affected by dissolution and dilution. The inverse correlation between carbonate and biogenic silica contents suggests that two mutually exclusive oceanic modes affected the biogenic sedimentation. These modes may have resulted from sea level changes that led to water column stratification during glacial low stands and breakdown of water column stratification, and consequent active vertical mixing during interglacial high stands. [Copyright &y& Elsevier]