Occurrence and distribution of hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers(OH-GDGTs) in the Han River system, South Korea

We investigated the occurrence and distribution of terrestrial-derived hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers(OH-GDGTs) in the Han River system and their potential impact on the application of the ring index of OH-GDGTs(RI-OH) as a sea surface temperature(SST) proxy in the eastern Yellow Sea. Thereby, we analyzed various samples collected along the Han River and from its surrounding areas(South Korea, n = 34). The OHGDGTs were found in all samples investigated. OH-GDGT-0 was the dominant OH-GDGT component in the estuary and marine samples while OH-GDGT-2 was generally dominant in the soils, the lake sediments and the river suspended particulate matter(SPM). Our results thus suggests a possible warm bias of the RI-OH-derived summer SSTs in the coastal zone to which a large amount of terrestrial organic matter is being supplied. Further studies are necessary to better assess the applicability of the RI-OH proxy in the eastern Yellow Sea.

Reefs in the Early Paleozoic Taebaek Group,Korea:A Review

Various early Paleozoic （Cambrian Series 3-Middle Ordovician） reefs are found in the Taebaek Group, eastern Korea, located in the eastern margin of the Sino-Korean Block. They occur in every carbonate-dominant lithostratigraphic unit of the group, but their morphology and composition differ markedly. The Daegi Formation （middle Cambrian： Cambrian Series 3） contains siliceous sponge-Epiphyton reefs formed in a shallow subtidal environment, which is one of the earliest metazoan-bearing microbial reefs after the archaeocyath extinction. The Hwajeol Formation （upper Cambrian： Furongian） encloses sporadic dendrolites consisting of Angulocellularia, which developed in a relatively deep subtidal environment, representing a rare deeper water example. The onset of the Ordovician radiation resulted in the formation of microbialite-Archaeoscyphia-calathiid patch reefs in shallow subtidal deposits of the Lower Ordovician Dumugol Formation. Subsequent late Early Ordovician relative sea-level fall established extensive peritidal environments, forming microbial mats and stromatolites of the Lower-Middle Ordovician Makgol Formation. Ensuing Ordovician radiation resulted in one of the earliest metazoan skeletal reefs of the Middle Ordovician Duwibong Formation, constructed by stromatoporoid Cystostroma and bryozoan Nicholsonella, and developed around shallow shoals. These reefs reflect ongoing evolution and sea-level change during the early Paleozoic, and exemplify a rare glimpse of peri-Gondwanan records of reef evolution, which warrant detailed investigations and comparison with their counterparts in other regions.

Effects of Wind Fences on the Wind Environment around Jang Bogo Antarctic Research Station

This study investigated the flow characteristics altered by Jang Bogo Antarctic Research Station using computational fluid dynamics(CFD) modeling. The topography and buildings around Jang Bogo Station were constructed with computeraided-design data in the CFD model domain. We simulated 16 cases with different inflow directions, and compared the flow characteristics with and without Jang Bogo Station for each inflow direction. The wind data recorded by the site’s automatic weather station(AWS) were used for comparison. Wind rose analysis showed that the wind speed and direction after the construction of Jang Bogo Station were quite different from those before construction. We also investigated how virtual wind fences would modify the flow patterns, changing the distance of the fence from the station as well as the porosity of the fence. For westerly inflows, when the AWS was downwind of Jang Bogo Station, the decrease in wind speed was maximized(-81% for west-northwesterly). The wind speed reduction was also greater as the distance of the fence was closer to Jang Bogo Station. With the same distance, the fence with medium porosity(25%–33%) maximized the wind speed reduction.These results suggest that the location and material of the wind fence should be selected carefully, or AWS data should be interpreted cautiously, for particular prevailing wind directions.

Cambrian Stem-group Cnidarians with a New Species from the Cambrian Series 3 of the Taebaeksan Basin, Korea

Five species, Lipopora lissa Jell and Jell, 1976, Lipopora daseia Jell and Jell, 1976, Tretocylichne perplexa Engeibretsen, 1993 from Australia, Cambroctoconus orientalis Park, Woo, Lee, Lee, Lee, Han and Chough, 2011 from China, and Cambroctoconus kyrgyzstanicus Peel, 2014 from Kyrgyzstan, belonging to the Cambrian stem-group cnidarians have been documented in the fossil record. Cambroctoconus coreaensis sp. nov., interpreted here as a stem-group cnidarian, from the Seokgaejae section in the Daegi Formation, Taebaek Group （Cambrian Series 3）, Taebaeksan Basin, central-eastern Korean Peninsula, has a slender cup-shaped skeleton. A cladistic analysis produced 21 most parsimonious trees, which invariably placed the six stem-group cnidarians below the crown-group, but their relationships within the stem-group are unresolved. Nine out of the 21 trees suggest a monophyletic relationship for the Cambrian stem-group cnidarians, whereas in six other trees a monophyly of Cambroctoconus and Tretocylichne appeared as the sister-group to the crown-group cnidarians with Lipopora at the most basal branch. This result may reflect the fact that crown-group cnidarians evolved in the Precambrian, and suggests that the diversity of stem-group cnidarians was a result of an independent radiation in the Cambrian.

Trilobite Biostratigraphy of the lower Paleozoic(Cambrian–Ordovician)Joseon Supergroup,Taebaeksan Basin,Korea

In Korea, trilobites are among the most intensively studied fossil groups in the past century and provide invaluable information about lower Paleozoic stratigraphy, paleogeography, and tectonics of the Korean Peninsula. Trilobites occur in the lower Paleozoic Joseon Supergroup of the Taebaeksan Basin which was part of the Sino-Korean Craton in the Paleozoic. The Joseon Supergroup is divided into the Taebaek, Yeongwol, and Mungyeong groups. The Taebaek and Yeongwol groups are richly fossiliferous, while the Mungyeong Group is poorly fossiliferous. Contrasting trilobite faunal contents of the Taebaek and Yeongwol groups resulted in two separate biostratigraphic schemes for the Cambrian–Ordovician of the Taebaeksan Basin. A total of 22 biozones or fossiliferous horizons were recognized in the Taebaek Group; 19 zones were established in the Yeongwol Group; and four biozones were known from the Mungyeong Group. These trilobite biozones of the Taebaeksan Basin indicate the Joseon Supergroup ranges in age from the Cambrian Series 2 to Middle Ordovician and can be correlated well with the formations of North China, South China, and Australia.

Winter distribution of diatom assemblages along the coastline of R.O.Korea in 2010

Diatoms are a globally successful and eukaryotic photosynthetic organism with an ornamented silica external wall.The relationship between their valve morphology and habitat means that diatoms can be used as bioindicators to characterize the aquatic environment.To estimate the differential distribution and diversity of diatom assemblages along the coastal line,we collected phytoplankton samples from 114 coastal sites of waters of R.O.Korea.We applied the unweighted pair-group technique using the arithmetic averages clustering method to cluster the sampling sites,apart from those where the biota consisted of other groups,such as dinoflagellates,into four regions:the Yellow Sea,South Sea,southern East Sea,and northern East Sea.Indicator species analysis in each region led to the selection of tychoplanktonic,chain-forming,attached species to substrates and psychrophilic indicator diatoms,respectively,each of which represented a planktonic lifestyle associated with one of the four regions.This study shows the diatom assemblages to serve as bioindicators of Korean coastal water in winter,and the subsequent seasonal survey will provide a starting point for the improved understanding of Korean diatom-based ecoregions,in both time and space.

High-resolution circulation forecasting of the Maenggol Channel, south coast of Korea

The Maenggol Channel and Uldolmok Strait, located on the south-west coast of Korea, have notably strong and complex currents due to tidal effects and to local geological factors. In these areas, electric power has been generated using strong tidal currents, the speed of which is more than 3 m/s during spring tides. The region also provides a shortcut for navigation. These tidal conditions are therefore sometimes useful, but may also cause terrible accidents or severe economic damage, in the absence of accurate information regarding ocean conditions. In April 2014, the passenger ferry MV Sewol capsized in the Maenggol Channel, with 295 passengers killed and 9 still missing. While this was unquestionably a man-made disaster, strong currents were one of the contributing causes. It was also difficult to conduct scuba diving rescue operations given strong current speeds,and accurate prediction of the time when the tide would turn was thus critically needed. In this research, we used the high-resolution coastal circulation forecasting system of KOOS（Korea Operational Oceanographic System） for analysis and simulation of strong tidal currents in such areas with many small islands, using measurements and modeling from this research area. For accurate prediction of tidal currents, small grid size-modeling was needed,and in this study, we identified a suitable grid size that offers efficiency as well as accuracy.

Adaptive Momentum-Backpropagation Algorithm for Flood Prediction and Management in the Internet of Things

Flooding is a hazardous natural calamity that causes significant damage to lives and infrastructure in the real world.Therefore,timely and accurate decision-making is essential for mitigating flood-related damages.The traditional flood prediction techniques often encounter challenges in accuracy,timeliness,complexity in handling dynamic flood patterns and leading to substandard flood management strategies.To address these challenges,there is a need for advanced machine learning models that can effectively analyze Internet of Things(IoT)-generated flood data and provide timely and accurate flood predictions.This paper proposes a novel approach-the Adaptive Momentum and Backpropagation(AM-BP)algorithm-for flood prediction and management in IoT networks.The AM-BP model combines the advantages of an adaptive momentum technique with the backpropagation algorithm to enhance flood prediction accuracy and efficiency.Real-world flood data is used for validation,demonstrating the superior performance of the AM-BP algorithm compared to traditional methods.In addition,multilayer high-end computing architecture(MLCA)is used to handle weather data such as rainfall,river water level,soil moisture,etc.The AM-BP’s real-time abilities enable proactive flood management,facilitating timely responses and effective disaster mitigation.Furthermore,the AM-BP algorithm can analyze large and complex datasets,integrating environmental and climatic factors for more accurate flood prediction.The evaluation result shows that the AM-BP algorithm outperforms traditional approaches with an accuracy rate of 96%,96.4%F1-Measure,97%Precision,and 95.9%Recall.The proposed AM-BP model presents a promising solution for flood prediction and management in IoT networks,contributing to more resilient and efficient flood control strategies,and ensuring the safety and well-being of communities at risk of flooding.

Characteristics of Atmospheric Circulation Associated with Cold Surge Occurrences in East Asia:A Case Study During 2005/06 Winter

The characteristics of the upper-level circulation and thermodynamical properties for the period when two distinct cold surges broke out over East Asia during the 2005/06 winter are investigated. From early December 2005 to early January 2006, exceptionally cold weather lasted for approximately one month due to two successive cold surges that took place on 2 December 2005 and 2 January 2006, respectively. This study reveals that both involve the upper-tropospheric circulation, which induces the amplification and expansion of the surface Siberian high toward East Asia, but arose from different causes： the former is caused by the upper-level blocking originated from the North Pacific and the latter is caused by the upper-level wave train across the Eurasian Continent. In particular, it is suggested that the lower-tropospheric anomalous wind caused by upper-level circulation anomalies and a steep meridional temperature gradient amplified by phase-locked annual cycle combined to induce very strong cold advection in East Asia, which resulted in exceptionally cold weather that lasted for several weeks. The present results emphasize that the characteristics of the upper-tropospheric circulation can be considered as important precursors to cold surge occurrences in East Asia.

Marine ciliate community in relation to eutrophication of coastal waters in the Yellow Sea

We assessed the potential of marine ciliate community as an indicator to coastal water quality using water samples collected from four stations in the Yellow Sea in the summer 2000. The four stations were characterized by different levels of pollution. The ciliate communities consisted primarily of tintinnids and aloricate ciliates that were <30 μm. A total of 78 species were classified: 55 species at Station 2, 51 species each at Stations 1 and 4, and 47 species at Station 3. The mean number of species at each site was 29.2±2.0 (Station 1), 28.5±2.9 (Station 2), 27.8±1.7 (Station 3), and 24.5±2.3 (Station 4). The abundance was highly variable: 19 331±11 187 ind./L at Station 1, 7 960±5 639 ind./L at Station 2, 29 015±12 999 ind./L at Station 3, and 8 190±4 658 ind./L at Station 4. Our results suggest that neither the simple chemical analysis (e.g. chemical oxygen demand, dissolved inorganic nitrogen, and phosphate) nor the eutrophication/pollution index adequately described the water quality at the four stations. The same was true of the number of species and their abundance, both of which had no correlation with the chemical indices. In contrast, Margalef’s diversity index values (3.12 at Station 2, 2.89 at Station 1, and 2.64 at Stations 3 and 4) generally discriminated the water quality status of the four stations. The difference in water quality among the stations was strongly supported by the pattern of species richness (i.e. the total number of species) of ciliates at each station. Our evaluation was consistent with the results of long-term water quality monitoring at the four stations. With increasing eutrophication, we observed also a compositional and functional shift in the ciliate assemblages from algivorous oligotrich/choreotrich to nonselective-omnivorous gymnostomatids to bacterivorous-detrivorous scuticociliatids. Thus, ciliates may be used to indicate the coastal water quality status of a given site.

Distribution of dinoflagellate cysts in Yellow Sea sediments

To investigate the distribution, abundance, and species composition of dinoflagellate cysts in the Yellow Sea, surface sediment samples were collected at 37 sites, including the Korean dump site. Twenty-one di- noflagellate cyst taxa were identified, with the assemblages dominated mainly by Spiniferites bulloideus, Operculodinium centrocarpum, and cyst of Alexandrium catenella/tarnarense type. A high frequency of O. centrocarpum in the Yellow Sea was observed for the first time, and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water Mass and the Changjiang （Yangtze） River runoff. Total cyst concentrations ranged from 23 to 48 442 cysts/g dry weight, and high cyst concentrations were recorded adjacent to the dumping site. This result suggests that anthropogenic activities such as ocean dumping s- timulate the growth of dinoflagellates in the Yellow Sea, which in turn leads to high levels of dinoflagellate cyst production.

Glacier Extent and Volume Change(1966～2000) on the Su-lo Mountain in Northeastern Tibetan Plateau,China

The topographic maps of 1:50,000 scales,aerial photographs taken in 1966,one Landsat image taken in 1999,and SRTM data from 2000 were used to quantify the losses in area and volume of the glaciers on the Su-lo Mountain,in the northeastern Tibetan Plateau,China in the past 30 years.The total glacier area decreased from 492.9km2 in 1966 to 458.2km2 in 1999.The volume loss of the studied glaciers reached 1.4 km3 from 1966 to 2000.This agrees with documented changes in other mountain glaciers of the whole Tibetan Plateau.

Analysis of recent climate change over the Arctic using ERA-Interim reanalysis data

This study investigates recent climate change over the Arctic and its link to the mid-latitudes using the ERA-Interim global atmospheric reanalysis data from the European Center for Medium-Range Weather Forecast （ECMWF）. Since 1979, sub- stantial surface warming, associated with the increase in anthropogenic greenhouse gases, has occurred over the Arctic. The great- est warming in winter has taken place offshore in the Kara-Barents Sea, and is associated with the increase in turbulent heat fluxes from the marginal ice zone. In contrast to the marked warming over the Arctic Ocean in winter, substantial cooling appears over Siberia and eastern Asia, linked to the reduction of Arctic sea ice during the freezing season （September-March）. However, in summer, very little change is observed in surface air temperature over the Arctic because increased radiative heat melts the sea ice and the amount of turbulent heat gain from the ocean is relatively small. The heat stored in the upper ocean mixed layer in summer with the opening of the Arctic Ocean is released back to the atmosphere as turbulent heat fluxes during the autumn and through to the following spring. This warming of the Arctic and the reduced sea ice amplifies surface cooling over Siberia and eastern Asia in winter.

Ex situ echo sounder target strengths of ice krill Euphausia crystallorophias

Ice krill is the keystone species in the neritic ecosystem in the Southern Ocean,where it replaces the more oceanic Antarctic krill. It is essential to understand the variation of target strength(TS in d B re 1 m 2) with the different body size to accurately estimate ice krill stocks. However,there is comparatively little knowledge of the acoustic backscatter of ice krill. The TS of individual,formalin-preserved,tethered ice krill was measured in a freshwater test tank at 38,120,and 200 k Hz with a calibrated split-beam echo sounder system. Mean TS was obtained from 21 individual ice krill with a broad range of body lengths(L :13–36 mm). The length( L,mm) to wet weight( W; mg) relationship for ice krill was W =0.001 218×103 × L 3.53( R 2= 0.96). The mean TS-to-length relationship were TS3 8 k Hz =-177.4+57log 10( L),( R 2 = 0.86); TS 120 k Hz =-129.9+31.56 log 10( L),( R 2 =0.87); and TS 200 k Hz =-117.6+24.66log1 0( L),( R 2 =0.84). Empirical estimates of the relationship between the TS and body length of ice krill were established at 38,120,and 200 k Hz and compared with predictions obtained from both the linear regression model of Greene et al.(1991) and the Stochastic Distorted Wave Born Approximation(SDWBA) model. This result might be applied to improve acoustic detection and density estimation of ice krill in the Southern Ocean. Further comparative studies are needed with in situ target strength including various body lengths of ice krill.

Strategy of photo-protection in phytoplankton assemblages in the Kongsfjorden, Svalbard, Arctic

Photo-protective functions were investigated in phytoplankton assemblages at Kongsfjorden,Svalbard in spring,using their UV-absorbing compounds(mycosporine-like amino acids(MAAs)),xanthophyll pigments(diadinoxanthin(DD) and diatoxanthin(DT)) and < beta >- dimethylsulphoniopropionate(<beta>- DMSP). The dominant phytoplankton species in the inner bay were dominated by Phaeocystis spp. and nanoflagellates,while the offshore waters were dominated by Thalassiosira spp. In the inner bay,UVabsorbing compounds and xanthophyll pigments exhibited higher ratios of MAA to chlorophyll a(MAA:chl a ratio),and both DD and DT to chlorophyll a(DD:chl a ratio and DT:chl a ratio),respectively.Thus,the photoprotective-pigments such as DD and DT appear to complement MAAs in the natural phytoplankton assemblage. However,the ratio of<beta>- DMSP to chlorophyll a(<beta>-DMSP:chl a ratio) did not show a distinct spatial distribution according to environmental factors or interspecies differences. In this study,we found that photoprotective compounds occurred in a manner dependent on the phytoplankton species composition in Kongsfjorden Bay,where Phaeocystis is the dominant species.

The Southern Annular Mode(SAM) in PMIP2 Simulations of the Last Glacial Maximum

The increasing trend of the Southern Annular Mode （SAM） in recent decades has influenced climate change in the Southem Hemisphere （SH）.How the SAM will respond increased greenhouse gas concentrations in the future remains uncertain.Understanding the variability of the SAM in the past under a colder climate such as during the Last Glacial Maximum （LGM） might provide some understanding of the response of the SAM under a future warmer climate.We analyzed the changes in the SAM during the LGM in comparison to pre-industrial （PI） simulations using five coupled ocean-atmosphere models （CCSM,FGOALS,IPSL,MIROC,HadCM） from the second phase of the Paleoclimate Modelling Intercomparison Project （PMIP2）.In CCSM,MIROC,IPSL,and FGOALS,the variability of the simulated SAM appears to be reduced in the LGM compared to the PI simulations,with a decrease in the standard deviation of the SAM index.Overall,four out of the five models suggest a weaker SAM amplitude in the LGM consistent with a weaker SH polar vortex and westerly winds found in some proxy records and model analyses.The weakening of the SAM in the LGM was associated with an increase in the vertical propagation of Rossby waves in southern high latitudes.

Effects of ocean acidifi cation driven by elevated CO_2 on larval shell growth and abnormal rates of the venerid clam, Mactra veneriformis

A bstract The venerid clam(M actra veneriformis Reeve 1854) is one of the main cultured bivalve species in intertidal and shallow subtidal ecosystems along the west coast of Korea. To understand the effects of ocean acidifi cation on the early life stages of Korean clams, we investigated shell growth and abnormality rates and types in the D-shaped, umbonate veliger, and pediveliger stages of the venerid clam M. veneriformis during exposure to elevated seawater pCO_2. In particular, we examined abnormal types of larval shell morphology categorized as shell deformations, shell distortions, and shell fi ssures. Specimens were incubated in seawater equilibrated with bubbled CO_2-enriched air at(400±25)×10^(-6)(ambient control),(800±25)×10^(-6)(high pCO_2), or(1 200±28)×10^(-6)(extremely high pCO_2), the atmospheric CO_2 concentrations predicted for the years 2014, 2084, and 2154(70-year intervals; two human generations), respectively, in the Representative Concentration Pathway(RCP) 8.5 scenario. The mean shell lengths of larvae were signifi cantly decreased in the high and extremely high pCO_2 groups compared with the ambient control groups. Furthermore, under high and extremely high pCO_2 conditions, the cultures exhibited signifi cantly increased abundances of abnormal larvae and increased severity of abnormalities compared with the ambient control. In the umbonate veliger stage of the experimental larvae, the most common abnormalities were shell deformations, distortions, and fi ssures; on the other hand, convex hinges and mantle protuberances were absent. These results suggest that elevated CO_2 exerts an additional burden on the health of M. veneriformis larvae by impairing early development.

VHF meteor radar at King Sejong Station,Antarctica

Since 2002, we have been observing the mesosphere and lower thermosphere （MLT） region over King Sejong Station （KSS; 62.22°S, 58.78°W）, Antarctica, using various instruments such as the Spectral Airglow Temperature Imager （SATI）, All Sky Camera （ASC） and VHF meteor radar. The meteor radar, installed in March 2007, continuously measures neutral winds in the alti- tude region 70-110 km and neutral temperature near the mesopause 24 h.d-1, regardless of weather conditions. In this study, we present results of an analysis of the neutral wind data for gravity wave activity over the tip of the Antarctic Peninsula, where such activity is known to be very high. Also presented is temperature estimation from measurement of the decay times of meteor trails, which is compared with other temperature measurements from SATI and the Sounding of the Atmosphere using Broadband Emis- sion Radiometry （SABER） instrument onboard the Thermosphere Ionosphere Mesosphere Energy and Dynamics （TIMED） satel- lite.

Transposon mutagenesis of Psychrobacter cryohalolentis PAMC 21807 by tri-parental conjugation

Random mutagenesis is commonly used to study gene function. The screening of mutants exhibiting specific pheno- types assists in the identification of phenotype-related genes. In the current study, we isolated Antarctic bacteria, and developed a transposon Tn5 mutagenesis system. A total of 26 strains were isolated from seawater and freshwater near Antarctic King Sejong Research Station, King George Island. Six Psychrobacter strains were identified as psychrophilic, with optimal growth tempera- tures of 10~C or 15~C Psychrobacter cryohalolentis PAMC 21807 with a high growth rate at 4~C was selected for transposon mutagenesis. Tri-parental conjugation with a plasmid containing Tn5 produced 13 putative recombinants containing the selectable marker. Genomic Southern hybridization confirmed Tn5 existed as episomes for seven recombinants, and for a single recombinant, Tn5 was integrated into the genome of Psychrobacter cryohalolentis PAMC 21807. The result indicates that the mutagenesis method, although successful, has a relatively low rate. The psychrophilic bacteria isolated in this study may be a useful resource for studying cold adaptation mechanisms, and the mutagenesis method can be applied to genetic analysis.

Systematic Revision of Trilobites from the Middle Ordovician(Darriwilian) Klimoli Formation of the Zhuozishan Area,Inner Mongolia,China

New morphologic information permits systematic revision of trilobites from the Middle Ordovician Klimoli Formation of the Zhuozishan area, Ordos Basin, Inner Mongolia. The new assemblage is composed of 10 species of the Raphiophoridae, Nileidae, Asaphidae, and Telephinidae.？ An asaphid, aff. Mioptychopyge lashachungensis （previously Paraptychopyge lashachungensis） displays an intermediate morphology between the Chinese nobiliasaphine genera Mioptychopyge and Zhenganites. The pygidial doublure is regarded as the most significant character to differentiate Symphysurus klimoliensis （previously Nileus klimoliensis） of the Nileidae from such closely allied taxa as Poronileus. A nileid, cf. Peraspis kujandensis displays typical nileid morphology, unlike the type species, Peraspis lineolata, which might turn out to be an asaphid. Ampyx gongwusuensis sp. nov. of the Raphiophoridae is the first record of the genus in the Zhuozishan area and reveals morphologic details that might be employed to resolve Ampyx taxonomy in China. Morphologic differences between A. gongwusuensis and Abulbaspis ordosensis might represent a case of sexual dimorphism.