인도양 중앙 해령의 열수 plume 추적: 탁도 아노말리 및 메탄 분포

인도양 중앙 해령에서 CTD-TOYO 및 심해저 카메라(deep-sea camera, DSC) 운영 시 광케이블에 MAPR(miniature autonomous plume recorder, NOAA)을 장착해 수층 내 부유물질의 변화 양상을 연속적으로 관측하였다. 또한 CTD system(Model 911 plus, carousel-24, Sea-Bird Inc.)을 이용한 정점 조사에서도 MAPR을 장착해 자료를 획득하였으며, 수심 별로 채취한 해수 시료에서는 메탄(CH4) 분석을 수행하였다. 부유물질은 일차적으로 해저 열수 환경에서 열수 plume의 분포를 파악하는데 유용하며, 메탄은 해저 열수 활동을 지시해주는 화학적 추적자이다. 연구 지역은 인도양의 남위 약 8°~ 17°, 동경 약 65.5°~ 68.5°구간에 위치한 중앙 해령으로, 해령확장축과 변환단층을 하나의 확장구간(Segment)으로 구분해 총 7개의 확장구간에서 연구를 수행하였다. 연구결과, MAPR의 탁도 아노말리(dNTU) 분석을 통해 인도양 중앙 해령의 전반적인 열수 plume 분포를 파악하였으며, 화학적 추적자와의 비교를 통해 일부 구간에서는 활동성 열수분출 근원지 위치가 추정되었다. 향후 ATP(adenosine triphosphate), pH, 무기영양염, 중금속 등의 생지화학적 추적자 자료와 해저면의 기반암/암석 자료 등을 종합적으로 고려해 인도양 중앙 해령의 열수 활동 특성을 이해하기 위한 연구를 수행할 예정이다.2

Characterization of microbial structure and function in the sulfate-methane transition zone(SMTZ) of the gas hydrate-bearing sediment in the Ulleung Basin in the East Sea

We investigated microbiological parameters (diversity and abundance of dsrAB gene and mcrA gene, and prokaryotic composition based on 16S rRNA gene) to characterize microbial communities associated with biogeochemical parameters (sulfate reduction rate (SRR) and the distribution of CH4, SO4 2-, CO, and H2) in the sulfate-methane transition zone (SMTZ) of the gas hydrate-bearing sediment in the southwestern continental slope of the Ulleung Basin (UB) in the East Sea. From the profiles of SO4 2-and CH4, the SMTZ was clearly defined between 0.6 and 1.4 mbsf. Highest peaks in sulfate reduction rate (12.6 nmol cm-3d-1 at 0.65 mbsf), carbon monoxide (83 μM), gene copies of dsrA (6.2 x 106 copies cm-3 at 0.5 mbsf) and mcrA (11.6 x 106 copies cm-3 at 0.8 mbsf) were appeared within the SMTZ. We suggest that CO in the SMTZ might be one of intermediate metabolic products of AOM independent sulfate reduction, which is rapidly consumed by CO oxidizer coupling to sulfate reducer. Bacterial communities were dominated by members of the uncultured candidate division JS1 (59-66.7%) group and Chloroflexi (9.2-21%) of total bacterial clones. The uncultured candidate division JS1 group might be responsible for breakdown of organic matter in the SMTZ of the UB. Both Deep-Sea Archaeal Group (10-45%, DSAG/MBGB) and Marine Benthic GroupD (40-52%, MBGD) appeared to be dominant archaeal groups associated with the Ae reduction rate (SRR) and the distribution of CH4, SO4 2-, CO, and H2) in the sulfate-methane transition zone (SMTZ) of the gas hydrate-bearing sediment in the southwestern continental slope of the Ulleung Basin (UB) in the East Sea. From the profiles of SO4 2-and CH4, the SMTZ was clearly defined between 0.6 and 1.4 mbsf. Highest peaks in sulfate reduction rate (12.6 nmol cm-3d-1 at 0.65 mbsf), carbon monoxide (83 μM), gene copies of dsrA (6.2 x 106 copies cm-3 at 0.5 mbsf) and mcrA (11.6 x 106 copies cm-3 at 0.8 mbsf) were appeared within the SMTZ. We suggest that CO in the SMTZ might be one of intermediate metabolic products of AOM independent sulfate reduction, which is rapidly consumed by CO oxidizer coupling to sulfate reducer. Bacterial communities were dominated by members of the uncultured candidate division JS1 (59-66.7%) group and Chloroflexi (9.2-21%) of total bacterial clones. The uncultured candidate division JS1 group might be responsible for breakdown of organic matter in the SMTZ of the UB. Both Deep-Sea Archaeal Group (10-45%, DSAG/MBGB) and Marine Benthic GroupD (40-52%, MBGD) appeared to be dominant archaeal groups associated with the A2

Effects of bioturbation on mineralization of organic materials by sulfate and ion reduction

갯벌의 생태적 건전성 평가와 생지화학적 물질순환을 이해하기 위해서는 유기물 분해능 및 분해 경로와 함께 이에 영향을 미치는 요인들에 대하여 인식하여야 한다. 저서동물의 활동에 의한 생물교란이 표층에서 저층으로 유기물과 산소를 동시에 공급함으로서 퇴적물의 표층 뿐만 아니라 저층에서도 유기물 분해가 활발히 진행되고, Fe(III)의 재순환이 원할 해짐에 따라 유기물 분해과정에서 철환원작용이 증대되었다.2

Concentration and stable carbon isotopic composition of dissolved methane in hydrothermal plumes at the Central Indian Ridge

The concentration and stable carbon isotopic composition (δ13C) of dissolved methane were measured to trace hydrothermal plume and to identify the source and behavior of methane in the Central Indian Ridge, 11 - 13°S. We observed significant hydrothermal plumes in the depth of 2500 - 3500 m. The concentration and δ13C of methane in the plumes (Stn. IR02 and IR03) ranged from 3.34 to 42.33 nmol kg-1 and from -30.0 to -15.4 ‰, respectively. The concentration and δ13C of methane in the background seawater (Stn. IR01) ranged from 0.52 to 1.15 nmol kg-1 and from -35.1 to -28.9 ‰, respectively. The δ13C of methane was the heaviest in the center of plumes at Stn. IR02 (-15.4 ‰) and IR03 (-17.8 ‰). The estimated δ13C of methane in hydrothermal vents was around -20 ‰. The results indicated that methane was most likely derived from magmatic outgassing or chemical synthesis of inorganic matters. The behavior of methane was explained by the relationship between δ13C of methane and 1/[CH4]. The behavior of methane was mainly controlled by the physical mixing and diffusion at Stn. IR03, whereas the behavior of methane at Stn. IR02 was controlled by the microbial oxidation as well as by the physical mixing and diffusion. The topography of Stn. IR02 was the form of basin, unlike Stn. IR03. Thus, at Stn. IR02, because the methane could not be quickly mixing and diffusion with ambient seawater,ificant hydrothermal plumes in the depth of 2500 - 3500 m. The concentration and δ13C of methane in the plumes (Stn. IR02 and IR03) ranged from 3.34 to 42.33 nmol kg-1 and from -30.0 to -15.4 ‰, respectively. The concentration and δ13C of methane in the background seawater (Stn. IR01) ranged from 0.52 to 1.15 nmol kg-1 and from -35.1 to -28.9 ‰, respectively. The δ13C of methane was the heaviest in the center of plumes at Stn. IR02 (-15.4 ‰) and IR03 (-17.8 ‰). The estimated δ13C of methane in hydrothermal vents was around -20 ‰. The1

Stable carbon isotope ratios of dissolved methane in hydrothermal plumes in the central Indian Ridge

Stable carbon isotopic composition (δ13C) of dissolved methane, along with its vertical distributions, were measured to trace the hydrothermal plume and identify the source and behavior of methane in the Central Indian Ridge (11 - 13°S). Significant hydrothermal plumes were observed at depths of 2500 - 3500 m. The concentration and δ13C of methane in the plumes (Sts. IR02 and IR03) ranged from 3.3 to 42.3 nmol kg-1 and -30.0 to -15.4 ‰, respectively. The concentration and δ13C of methane in the background seawater (St. IR01) ranged from 0.52 to 1.15 nmol kg-1 and -35.1 to -28.9 ‰, respectively. The δ13C of methane was highest in the center of the plumes at St. IR02 (-15.4 ‰) and St. IR03 (-17.8 ‰). The δ13C of methane in the source hydrothermal vents estimated using methane distribution and its stable isotopic composition was approximately -22 ‰. The results indicated that the methane was most likely derived from magmatic outgassing or the chemical synthesis of inorganic matter. The behavior of the methane can be explained by the relationship between the δ13C of methane and 1/[CH4]. If the behavior of methane was controlled by simple mixing with ambient seawater, the measured stable carbon isotope ratios of methane would fall on the mixing line between vent and ambient methane. However, if the behavior of methane was influenced by microbial oxidation, the measured stable carbon isotope ratios wou Significant hydrothermal plumes were observed at depths of 2500 - 3500 m. The concentration and δ13C of methane in the plumes (Sts. IR02 and IR03) ranged from 3.3 to 42.3 nmol kg-1 and -30.0 to -15.4 ‰, respectively. The concentration and δ13C of methane in the background seawater (St. IR01) ranged from 0.52 to 1.15 nmol kg-1 and -35.1 to -28.9 ‰, respectively. The δ13C of methane was highest in the center of the plumes at St. IR02 (-15.4 ‰) and St. IR03 (-17.8 ‰). The δ13C of methane in the source hydrothermal vents estimated using methane distribution and its stable isotopic composition was approximately -22 ‰. The results indicated that the methane was most likely derived from magmatic outgassing or the chemical synthesis of inorganic matter. The behavior of the methane can be explained by the relationship between the δ13C of methane and 1/[CH4]. If the behavior of methane was controlled by simple mixing with ambient seawater, the measured stable carbon isotope ratios of methane would fall on the mixing line between vent and ambient methane. However, if the behavior of methane was influenced by microbial oxidation, the measured stable carbon isotope ratios wou1