Korea Strait Research Articles

표영생물이 동중국해 주변 해역과 대한해협의 대형저서동물 군집에 미치는 영향 파악을 위한 선행 연구

Despite the impacts of the climate changes on the pelagic ecosystem, few studies have examined the pelagic-benthic coupling in the adjacent East China Sea and Korea Strait. Therefore, the species composition and abundance of the macrobenthic community, as well as the potential food sources of benthic fauna were investigated in the present study using stable isotope analysis (<TEX>${\delta}^{13}C\;and\;{\delta}^{15}N$</TEX>) for suspended particulate organic matter (SPOM), sedimentary organic matter (SOM), phytoplankton, and zooplankton. A total of 157 macrobenthic fauna were collected, and the density of the macrobenthic fauna ranged from 4 to 434 ind./0.25 <TEX>$m^2$</TEX>, with an average density of 149 ind./0.25 <TEX>$m^2$</TEX>. The density of the benthic fauna increased moving from offshore shelf sites to coastal sites adjacent to the Korea Strait. Cluster analysis showed that the macrobenthic communities consisted of three distinct groups: group A in the Korea Strait, group B in the East China Sea, and group C near Ieodo. The dominant species in group A were the amphipods Photis japonica and Ampelisca miharaensis, followed by the polychaete Scolotoma longifolia. Environmental variables, such as the temperature of the seawater and sediment, and oxygen, and chlorophyll a levels, appeared to affect the structure of the community, suggesting the importance of coupling with the pelagic system. The <TEX>${\delta}^{13}C$</TEX> values of SPOM and zooplankton ranged from -22.97 to -23.5% and -19.92 to -21.86%, respectively, showing a relatively narrow range(<1%) between the two components. The difference between the <TEX>${\delta}^{13}C$</TEX> values of SOM and pelagic organic matter was also within 1%, suggesting that the SOM originated from the pelagic system, which is an important factor controlling the macrobenthic community.

Effect of Thermal Stratification and Mixing on Phytoplankton Community Structure in the Western Channel of the Korea Strait

The profile of a fixed site at station M (<TEX>$34.77^{\circ}N,\;129.13^{\circ}E$</TEX>) in the Korea Strait was studied from March 2006 to February 2007. The aim was to understand the relationship between the annual thermal stratification pattern and seasonal variation in phytoplankton community structure. Physicochemical factors including temperature, salinity and nutrient concentrations, which strongly influence the proliferation and diversity of phytoplankton, were measured. The study period was divided into three due to the characteristic of thermohaline structures; mixed I (March-May 2006), stratified (June-November 2006) and mixed II(December 2006-Feburuary 2007). Diatoms dominated during the mixed I (89%) and II (48%) periods, while nanoplankton group occupied over 83% of total population during the stratified period. The dominant species during the mixed I and II was Chaetoceros socialis (47% and 29%, respectively), while during the stratified period Gyrodinium sp.(4%) was the most dominant. Averaged total chl a concentrations during the mixed I and II periods were 0.61 mg <TEX>$m^{-3}$</TEX> and 0.72 mg <TEX>$m^{-3}$</TEX>, respectively, which were at least two-fold higher than that during the stratified period (0.30 mg <TEX>$m^{-3}$</TEX>). The vertical mixing and convection process of the water column induced nutrient supply from the bottom layer to the euphotic zone. It also led to the dominance of diatoms during the mixed periods, whereas small phytoplankton prevailed over large phytoplankton as stratification blocked the upward movement of nutrients to subsurface during the stratified period. During the mixed I and II periods, microplanktonic chl a dominated concentrations (50% and 48%, respectively), while picoplanktonic chl a occupied over 37% of total chl a during the stratified period.

Satellite‐based assessment of the impact of sea‐surface winds on regional atmospheric circulations over the Korean Peninsula

In order to clarify the impact of sea‐wind satellite‐data assimilation under fair and calm weather conditions over the Korean Peninsula, several numerical experiments were carried out. The numerical model used in this study was the Fifth Mesoscale Model (MM5), verified by many previous studies; satellite data of sea winds were gathered by the QuikSCAT sensor launched on ADEOS II. During the daytime, the change in mesoscale circulations according to the assimilation of sea‐wind data increased in the coastal area and decreased deep inland. Although variations in mesoscale circulations due to satellite‐based sea‐wind data assimilation occurred near the coastal area, the mixing height far inland over the Korean Peninsula often changed according to the intensity of inflow from the surrounding seas and that of the topographic effect. In this study, a lower mixing height inland was generated by a numerical simulation using QuikSCAT sea‐wind data assimilation. The lower mixing height was caused by strong westerly and weak easterly winds from the Yellow Sea and the East Sea, respectively. The validation of the sea‐wind influence was verified quantitatively by RMSD and IOA analyses. The accuracy of weather forecasting increased at the East Sea and Korea Strait and decreased at the Yellow Sea. These different accuracy levels were caused by the inhomogeneity of sea‐wind data quality. The maintenance of the uniform quality of satellite‐based data on sea wind is an important factor in the reasonable forecasting of mesoscale circulations.

Intercomparison of Air–Sea Interface Fluxes over the Yellow Sea and Korea Strait: Impact of Tsushima Warm Current

Surface-layer meteorological observations obtained from oceanic buoys over the Korean Strait and the Yellow Sea are used to estimate surface-layer turbulent fluxes of heat, moisture and momentum over the East-Asian Marginal Seas. Special emphasis is paid towards explanation of the impact of the Tsushima warm current flowing through the Korean Strait on air–sea interface fluxes. During the active phase of the Tsushima warm current, when the difference in sea surface temperature and air temperature becomes as large as 8°C, the sensible heat flux increases to a value of about 135 W m−2, while the latent heat flux is around 200 W m−2. The study attempts to broaden our understanding on the air-sea interaction processes over the Yellow Sea and Korean Strait.

동해남부해역과 울릉분지의 퇴적상과 퇴적작용

The coarse deposit with a lower mud content adjacent to the shelf of the southern East Sea is probably a "relict" sediment deposited in response to a lower stand of sea level during the Pleistocene. The sediment that developed on the slope and in the deep sea was river-borne primarily and was secondarily reworked or redistributed by the Tsushima Warm Current from the East China Sea. The clay mineralogy of the area suggests various sources of fine-grained sediment from adjacent rivers, the Korea Strait, volcanic material from Ulleung Island, and the Japan coast. Massive sand, bioturbated mud, homogeneous mud, and laminated mud were the dominant facies found in the core sediments from the study area. The massive sand was mainly volcanic ash from an eruption on Ulleung Island (9300 yr BP) and consisted of colorless pumiceous glass and a black scoriaceous type. The sedimentation rates on the slope, based on the Ulleung-Oki ash layer, were about 10cm/ky higher than in the basin. Other than the coarse-grain sediment, the mean size of the fine sediment dominating the bioturbated and homogeneous muds in the basin and the laminated mud on the slope was 6-10 phi. This indicates a difference in the major sedimentary process: hemipelagic sedimentation in the Ulleung Basin and mass flow deposition, such as turbidite, on the slope of the southern East Sea.

The influence of geochemical processes in the near-bottom layer on the hydrochemical characteristics of the waters of the Sea of Japan

According to the results of the international expedition aboard the R/Vs Roger Revelle and Professor Khromov in the summer 1999, areas with low oxygen contents (below 210 μM/kg) and those with increased contents of dissolved inorganic carbon and phosphates were found that roughly coincided with one another. These areas are located near the bottom on the southwestern slope of the Tsushima Basin in the region of the Korea Strait and on the continental slope in the region of the Tatar Strait in the northern part of the sea at about 46° N. The set of hydrochemical data points to a high geochemical activity in the near-bottom layer of the areas noted. This activity is confirmed by direct observations of the composition of the interstitial water in the sediments collected in the northern part of the sea during the expedition of R/V Akademik M.A. Lavrent’ev in 2003. It was supposed that the main cause of the increased geochemical activity is the runoff of suspended and dissolved matter from the Korea and Tatar straits. In the areas mentioned, the near-bottom waters are characterized by low values of the nitrogen-phosphorus ratio (below 10), which is geochemical proof of the denitrification process occurring under the conditions of high oxygen concentrations characteristic of the Sea of Japan. Based on the value of the annual production in the Sea of Japan, a rate of denitrification equal to 3.4 × 1012 gN/year was calculated. Hence, it is confirmed that the geochemical processes in the near-bottom layer have a direct influence on the spatiotemporal characteristics of the hydrochemical properties of the waters of the Sea of Japan.

Paleo-Tsushima Water and its effect on surface water properties in the East Sea during the last glacial maximum: Revisited

The semi-enclosed deep marginal East Sea is known by limited sill flow and low sea-surface salinity during the last glacial maximum (LGM) when sea level was about 130 m lower than the present level. Although three straits (the Tsugaru, the Soya and the Tartar) with shallower than 130 m sills were completely closed, the Korea Strait with a maximum sill depth of 140 m seems to have persisted as a partial connection to the East Sea, allowing a sill flow. The volume transport at the Korea Strait during the LGM is estimated at approximately 0.3–1.1×10 12 m 3/yr, by using bathymetry, seismic reflection profiles and current data. The low sea-surface salinity has been explained by the East China Sea Coast Water (ECSCW) and high precipitation. However, the existing geological observations indicate that precipitation was reduced in the glacial East Sea. The high-resolution numerical simulation results predict that evaporation (2.16 mm/day) exceeded precipitation (1.43 mm/day), further suggesting net evaporation (evaporation minus precipitation) rates (0.2×10 12 m 3/yr) over the LGM East Sea. This signifies that the precipitation was not the factor lowering surface paleosalinity and that the paleo-Tsushima Water carried a huge amount of freshwater from the ECSCW than previously expected. The calculated surplus evaporation (0.2×10 12 m 3/yr) and sill flow (0.3–1.1×10 12 m 3/yr) are not identical, but they could be oceanographically considered as similar. The comparison between both values implies that most of the throughflow ultimately escaped the East Sea through the evaporation process during the LGM. The regional sea level in the almost isolated East Sea might be largely maintained by a rough balance between incoming throughflow and outgoing evaporation during the LGM. The geographic restriction due to lowered sea level and lower surface salinity by limited vertical mixing in the glacial East Sea are analogous to modern oceanographic features in the Black Sea.

Fundamental‐mode basin oscillations in the Japan/East Sea

We present observational evidence from coastal tide station and bottom pressure data that basin‐mode oscillations are frequently excited in the Japan/East Sea (JES). The fundamental basin‐mode is a Kelvin‐wave‐like oscillation consisting of a single amphidromic system around which the high water propagates counter‐clockwise. Its period is about 6.7 hours and its coastal wavelength is equivalent to the circumference of the JES. The relative amplitudes of the observed oscillations agree with Rikiishi's 1986 model results except for stations near the Korea Strait where the closed boundary in the model produces unrealistically high amplitudes. The basin oscillation amplitude varies on synoptic time scales (2–17 days) and exhibits seasonal variations. The optimal wind direction to generate basin‐mode oscillations is along 60°/240° T.

Surface water changes recorded in Late Quaternary marine sediments of the Ulleung Basin, East Sea (Japan Sea)

In order to reconstruct past sea surface temperature (SST) and salinity (SSS) in the East Sea (Japan Sea), this study investigated the oxygen isotopic composition of the planktonic foraminifer Globigerina bulloides, and the degree of unsaturation of alkenones in bulk sediments of core TY99PC18 recovered from the southeastern part of the Ulleung Basin, East Sea. Between 11 and 15 cal kyr BP, the surface waters were 2–4 °C cooler than today. The surface salinity was 12‰ lower during 14–15 cal kyr BP than today, then increased after 14 cal kyr BP, but remained lower during 11–14 cal kyr BP than present values. Between 14 and 15 cal kyr BP, the northern East China Sea surface waters were likely to be greatly diluted by fresh water discharge from land, and coastal waters would have flowed into the East Sea through the Korea Strait. During 11–14 cal kyr BP, the southern input waters most likely changed from fresh water-influenced coastal water to open ocean water. The increased salinity probably enhanced active deep water convection at that time. During 7–11 cal kyr BP, the surface waters were warmer (∼ 1 °C) and more saline (1–3‰) than today, indicating that the warm and saline Kuroshio Current became stronger, and that one of its branches flowed into the East Sea during this time interval. The cold (∼ 2 °C) and less saline waters (∼ 1‰) at 3–6 cal kyr BP may indicate a suppression of the Kuroshio Current. The SST and SSS values are close to the present values at about 3 cal kyr BP, suggesting that the physiological conditions of the East Sea approached that of the present at this time.

Year-to-year variation of cold waters around the korea strait

Year-to-year variation of bottom cold waters around the Korea Strait was investigated based on bottom temperatures measured by submarine telephone cable between Pusan, Korea and Hamada, Japan from 1982 to 1992. The characteristics of bottom temperatures could be divided into three different groups: the Korean side, the middle, and the Japanese side. Temperature drops in summer appeared in all the three regions implying the intrusion of cold waters into the Korea Strait. Significant decreases in the Korean side were observed in 1983, 1986, 1990, 1991, and 1992 when bottom temperatures were high in the middle. In contrast, bottom temperatures significantly decreased in the middle in 1985, 1988, and 1989 when the temperature drops in the Korean side were relatively small. This tendency for a negative relationship was also shown in the second mode of an EOF analysis. In the years when bottom temperatures significantly decreased in the Korean side, the cold water along the east coast of Korea expanded offshore and its temperature was low. On the contrary, cold water in the southern region of the Ulleung Basin developed in the years when bottom temperatures decreased considerably in the middle.

Seasonal variation of the Korea Strait Bottom Cold Water and its relation to the bottom current

Analysis of high resolution hydrographic and current data revealed that the Korea Strait Bottom Cold Water (KSBCW) flowed into the Korea Strait from May to January and contained two temperature minimums, one in August/September and another in December/January. With the main current flows confined within 70 km of the Korean coast, maximum southwestward bottom currents corresponded with the temperature minimums. Time‐series of bottom current and temperature near the Korean coast clearly showed that the bottom temperature decreased as the bottom current strengthened. Seasonal variation of the KSBCW was linked to the combined effects of the barotropic and baroclinic current variations in the Korea Strait. The annual minimum bottom temperature of the KSBCW was associated with the maximum southwestward baroclinic component. The KSBCW had a secondary maximum southwestward bottom current and secondary minimum temperature in December/January when the Tsushima Warm Current (TWC), flowing into the East/Japan Sea (EJS), had the minimum volume transport.

Southwestward intrusion of korea strait bottom cold water observed in 2003 and 2004

Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in June and November 2004. The bottom cold water, which was lower than 10°C, appeared in the channel trough except in March 2003. It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed of the intrusion current were about 20 km and approximately 25 cm s-1, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv (Sv≡106 m3 s-1) in August 2003 and 0.026 Sv in November 2004.

Late Quaternary sediments on the outer shelf of the Korea Strait and their paleoceanographic implications

Sedimentological and micropaleontological characteristics of core sediments from the outer shelf of the Korea Strait, which connects the northern East China Sea and the East Sea (Sea of Japan), were investigated to elucidate the paleoceanographic environment, especially the timing of the Kuroshio inflow, since the last glacial maximum. The core sediments, containing continuous records of the last 15,000 years, are characterized by a relatively high mud content (more than 50%, on average) and well-developed tide-influenced sedimentary structures. Their mineralogy suggests that the material originated from the paleo-Nakdong River system, which extended across the shelf of the Korea Strait during low sea-level periods. Planktonic foraminifers reveal a series of well-defined changes in paleoceanographic conditions during the late Pleistocene–Holocene. Down-core variations in the abundance of four foraminiferal assemblages, i.e., cold, coastal, tropical–subtropical, and Kuroshio water groups comprising characteristic planktonic species, suggest the occurrence of a distinct paleoenvironmental change in the surface water at 7,000 years b.p., i.e., from 15,000 to 7,000 years b.p., the area was influenced by coastal waters whereas since ca. 7,000 years b.p., it has been under the influence of open-sea water related to the Kuroshio Current flow, associated with both higher temperature and higher salinity. In particular, Pulleniatina obliquiloculata increased markedly in abundance at this time, documenting the inflow of the Kuroshio into the study area. These data indicate that the coastal water stage terminated at ca. 7,000 years b.p. when the warm Kuroshio and its major branch, the Tsushima Current, began to flow into the East Sea, as is the case today. The intrusion of the Tsushima Current through the Korea Strait after ca. 7,000 years b.p. resulted in abrupt changes in sedimentation rates and a dramatic increase in abundance of the Kuroshio indicator species, P. obliquiloculata.

Suspended Sediment Transport in the Coastal Area of Jinhae Bay—Nakdong Estuary, Korea Strait

Abstract Hydrodynamic measurements and analysis of suspended sediments were conducted in the coastal area to reveal the source and dispersal processes of muds accumulating in Jinhae Bay, one of the largest bays in the Korea Strait. A number of hydrographic stations in the bay were occupied in order to obtain time series of suspended sediment concentrations, currents, water level, temperature, and salinity for one or two tidal cycles. The results, measured in May through October, suggest that a slight net influx of suspended sediments into the bay occurs consistently under low-wave, microtidal conditions. They also show a passageway of suspended sediments selectively through an entrance facing the open sea. The hydrodynamic measurements, together with tidal current pattern and landsat image of the suspended plume in the Korea Strait, indicate that the mud in Jinhae Bay has been fed largely by the adjacent Nakdong River, rather than by offshore sources.

Currents, Eddies, and a "Fish Story" in the Southwestern Japan/East Sea

Abstract : As part of the Japan/East Sea (JES) initiative supported by the U.S. Office of Naval Research, we conducted an observational experiment to understand the physics of the mesoscale circulation in the Ulleung Basin, located in the south-western corner of the JES. The current passing through the Korea Strait divides upon entering the JES, with portions of the current flowing along the Korean and Japanese coasts. The variability of these currents is especially energetic in our study region. Our objectives were to measure the time-varying currents in the upper and deep levels of the JES. We relate the population density of vertically migrating fish or squid to the time-varying locations of fronts. We moored a two-dimensional array of pressure-gauge-equipped inverted echo sounders (PIES) and deep-recording current meters for 24 months starting June 1999. Figure 1 shows the study region, which spanned roughly a 250-km square between the Republic of Korea and Japan. The inverted echo sounder is a bottom-moored instrument that measures the time required for an acoustic pulse to travel from the seafloor to the sea surface and back. Travel-time variations arise primarily from temperature changes in the overlying water column caused by meandering fronts and eddies. The PIES array was used to map the temperature field at a suite of depth levels and the dynamic method was used to calculate profiles of geostrophic current. Bottom pressure and deep current meters moored 25 m above the seafloor were used together to map the deep circulation.

Geochemistry of surface sediments in the southwestern East/Japan Sea

We analyzed 77 surface sediment samples collected in the southwestern East/Japan Sea from the Korea Strait through the Ulleung Basin and the Korea Plateau for grain size, calcium carbonate, organic carbon, and major (Na, Mg, Al, Fe, K, Ca, and Ti) and trace elements (P, Mn, Sr, Li, Sc, V, Cr, Co, Ni, Zn, Cu, and Pb). The chemical composition of the surface sediments was found to be highly variable spatially. Cluster analysis of surface sediment chemical compositions indicated five major geochemical sedimentary environments: basin, lower slope, coast and upper slope, inner shelf, and outer shelf. Continental-shelf sediments were rich in shell fragments and had relict and coarse-grained characteristics. Recent fine-grained sediments were only distributed in coastal, slope, and basin areas. Concentrations of Al, K, Ca, Ti, Cr, and Sc were highest in the coastal and upper slope areas and decreased with water depth. Elemental ratios using major and trace elements indicated that coastal and upper slope detrital sediments were mixtures of sediments derived from the Changjiang (Yangtze) and Nakdong Rivers. Although the concentrations of organic carbon, P, Mn, V, Co, Ni, Cu, and Pb increased with water depth, their distribution patterns indicated authigenic (V, Cu, and Pb) and diagenetic (Fe, P, Mn, Co, and Ni) origins. The distribution pattern with water depth suggested that the chemical composition of surface sediment was determined by sedimentologic and geochemical processes, such as the supply of detrital and biogenic materials, and authigenic and post-depositional diagenetic processes in sediments.

Paleoenvironmental changes and depositional history of the Korea (Tsushima) Strait since the LGM

Two deep cores (SSDP 102 and SSDP 105) from the southeastern inner shelves of Korea were examined in order to reconstruct the paleoenvironmental history of the Korea Strait during postglacial sea-level fluctuations. The results of the lithofaces, organic geochemical components, foraminiferal assemblages, and stable isotopes show that the Korea Strait was influenced in different ways by river discharges and open-ocean currents, according to their temporal and spatial variability. The results of core SSDP 105 indicate that the southeastern coast of Korea was probably a shallow coastal environment, such as a shoreface or beach, by about 17.5 cal ka. The area remained a coastal environment that was affected by high energy conditions and partly by freshwater input during the transgressive period of 17.5–8.1 cal ka. The area has changed to a modern-type shelf environment influenced by the inflow of the Tsushima Current and by the high supply of fine-grained sediments derived from the Nakdong River since 8.1 cal ka. Meanwhile, the results of core SSDP 102 taken from the Nakdong River mouth reveal that the river mouth area was most likely a terrestrial or fluvial environment at least before 13.9 cal ka. It then changed to the estuarine (deltaic) environment that was directly affected by the Nakdong River between 13.9 and 7.0 cal ka, and established a modern-type shelf (prodeltaic) environment, which is similar in many respects to the southeastern coast of Korea after temporarily undergoing erosion between 7.0 and 6.1 cal ka.

Robust processing against uncertain reverberation spectra in shallow-water broadband active sonars

Broadband low-frequency active sonars operating in shallow water must work against reverberation having uncertain spectral color. Under these conditions prewhitening of the background is appropriate for detection and estimation processing. To assess the importance of prefiltering, in this talk signal-to-background performances of energy detected data subjected to no prewhitening, prewhitening, and Eckart filtering are compared for typical observed shallow-water reverberation spectral shapes. Adaptive prewhitening algorithms are described and their performances analyzed in terms of loss associated with spectral estimation errors. Modeled detection performance is compared with measured results obtained from Area Characterization Test III performed in the Korea Strait. Finally, the relevance of adaptive prewhitening to estimation for classification is also described. [Work supported by ONR and DARPA.]

Yeosuana aromativorans gen. nov., sp. nov., a mesophilic marine bacterium belonging to the family Flavobacteriaceae, isolated from estuarine sediment of the South Sea, Korea

A marine bacterium, GW1-1T, capable of degrading benzo[a]pyrene (BaP), was isolated from estuarine sediments of the South Sea (the Korea Strait), Korea, after an enrichment culture maintained for 2 years in a medium supplemented with a mixture of BaP and pyrene. The strain formed yellowish-brown colonies on marine agar 2216. Cells were strictly aerobic, non-motile, Gram-negative rods and produced non-diffusible carotenoid pigments. Optimal growth occurred in the presence of 1 % (w/v) NaCl and at pH 7 and 33-36 degrees C. No growth occurred without supplementation with either CaCl2 or MgCl2, even in the presence of NaCl. Phylogenetic analysis based on the nearly complete sequence of the 16S rRNA gene revealed that the isolate formed a phyletic lineage with the genera Gelidibacter (93.9-94.7 % gene sequence similarity), Subsaximicrobium (93.3 %) and Subsaxibacter (93.9 %). The isolate also showed high sequence similarities to Gaetbulibacter saemankumensis (94.5 %), Algibacter lectus (94.2 %), members of the genus Bizionia (93.6-94.3 %) and Formosa algae (93.2 %), even though it belonged to a different phyletic line. The major respiratory quinones of the isolate were menaquinones MK-5 and MK-6. The DNA G+C content was 51.4 mol%. Dominant fatty acids were i-15 : 0, a-15 : 0, i-15 : 1omega10c and 16 : 1. On the basis of this polyphasic taxonomic evidence, strain GW1-1T is classified as a member of a novel genus and species in the family Flavobacteriaceae, for which the name Yeosuana aromativorans gen. nov., sp. nov. is proposed. The type strain of the type species is GW1-1T (=KCCM 42019T = JCM 12862T).

Marinimicrobium koreense gen. nov., sp. nov. and Marinimicrobium agarilyticum sp. nov., novel moderately halotolerant bacteria isolated from tidal flat sediment in Korea

Two moderately halotolerant Gram-negative bacteria were isolated from tidal flat sediment of the South Sea in Korea (the Korea Strait). The strains, designated M9T and M18T, were strictly aerobic, rod-shaped and non-spore-forming and motile with a flagellum and their major fatty acids were C(16:0) and C(19:0) cyclo omega8c. Strains M9T and M18T could grow in the presence of up to 13-15% (w/v) NaCl, but their optimum salt concentrations were relatively low (0-3%, w/v). The major predominant isoprenoid quinone was Q-8 and the G + C content of the genomic DNA was 57-58 mol%. Phylogenetic analyses and comparative 16S rRNA gene sequence studies revealed that strains M9T and M18T formed a phylogenetic lineage distinct from the genus Teredinibacter within the class Gammaproteobacteria and were most closely related to the genera Microbulbifer, Saccharophagus and Teredinibacter, with less than 92.5% 16S rRNA gene sequence similarity. The level of 16S rRNA gene sequence similarity between the two strains was 96.7%. On the basis of physiological and phylogenetic properties, strains M9T and M18T represent separate species within a novel genus of the class Gammaproteobacteria, for which the names Marinimicrobium koreense gen. nov., sp. nov. (type species) and Marinimicrobium agarilyticum sp. nov. are proposed. The type strains of Marinimicrobium koreense and Marinimicrobium agarilyticum are M9T (= KCTC 12356T = DSM 16974T) and M18T (= KCTC 12357T = DSM 16975T), respectively.