한강기수역에서의 암모늄 제거율 변화 및 질산화의 잠재적 역할

현정호,정경호,박용철,최중기,Hyun, Jung-Ho,Chung, Kyung-Ho,Park, Yong-Chul,Choi, Joong-Ki 한국해양학회 1999 바다 Vol.4 No.1

In order to understand the importance of tidal action and $NH_4{^+}$ -nitrification in the removal of dissolved oxygen (DO) and $NH_4{^+}$, concentrations of DO, $NH_4{^+}$, $NO_2{^-}$ and $NO_3{^-}$ were measured with time for water samples collected at different tidal state in the eutrophic macrotidal Han River estuary. Field measurements indicated that most environmental parameters, except for the water temperature and DO concentration, were tightly controlled by the eutrophic freshwater runoff and large-scale tidal action. Dark incubation of the water sample at $25^{\circ}C$ showed that the removal rates of DO and $NH_4{^+}$ in high tide sample were 2.76 ${\mu}M\;O_2\;d^{-1}$ and 1.76 ${\mu}M\;N\;d^{-1}$ respectively, and increased to 5.66 ${\mu}M\;O_2\;d^{-1}$ and 3.36 ${\mu}M\;N\;d^{-1}$ respectively, in low tide sample. These changes indicated that microbial degradation and uptake of organic matter and inorganic nutrients were more active during low tide. $NH_4{^+}$-nitrification responsible for total DO removal in low tide (23.81%) and $NH_4{^+}$ turnover rates due to $NH_4{^+}$-nitrification in low tide (0.18 $d^{-1}$) were approximately 3.7 times and 3 times, respectively, higher than those in high tide. These results indicated that $NH_4{^+}$ -nitrifying bacteria introduced into the Han River estuary during low tide played a significant role in the removal of DO and $NH_4{^+}$. The decreasing removal rates in DO and $NH_4{^+}$ with the increasing tidal level seemed to be associated with the salinity impact on the halophobic freshwater $NH_4{^+}$-nitrifying bacteria. The results implied that anthropogenic $NH_4{^+}$ sources should be treated prior to the freshwater runoff into the estuary for the effective control of $NH_4{^+}$ in the Han River estuary. These results also suggest that parallel ecological studies on the chemoautotrophic nitrifying bacteria are essential for the elucidation of nitrogen cycles in the eutrophic Han River estuary.

Molecular tools for recording and intervention of neuronal activity

현정호,Kisang Eom,Jinhwan Jung,Byungsoo Kim 한국분자세포생물학회 2024 Molecules and cells Vol.47 No.1

Observing the activity of neural networks is critical for the identification of learning and memory processes, as well as abnormal activities of neural circuits in disease, particularly for the purpose of tracking disease progression. Methodologies for describing the activity history of neural networks using molecular biology techniques first utilized genes expressed by active neurons, followed by the application of recently developed techniques including optogenetics and incorporation of insights garnered from other disciplines, including chemistry and physics. In this review, we will discuss ways in which molecular biological techniques used to describe the activity of neural networks have evolved along with the potential for future development.

북동적도 태평양 KODOS 97-2 해역 심해저 퇴적물 내의 ATP 분포양상

현정호,김경홍,지상범,문재운,Hyun, Jung-Ho,Kim, Kyeong-Hong,Chi, Sang-Bum,Moon, Jai-Woon 한국해양학회 1998 바다 Vol.3 No.3

Environmental baseline information is necessary in order to assess the potential environmental impact of future manganese-nodule mining on the deep-seabed ecosystem. Total ATP (T-ATP), dissolved ATP (D-ATP) and particulate ATP (P-ATP) were measured to estimate total microbial biomass and to elucidate their vertical distribution patterns in the seabed of KODOS (Korea Deep Ocean Study) area, northeast equatorial Pacific Ocean. Within the upper 6 cm depth of sediment, the concentrations of T-ATP, D-ATP and P-ATP ranged from 4.4 to 40.6, from 0.6 to 16.1, and from 3.0 to 29.2 ng/g dry sediment, respectively. Approximately 84% of T-ATP, 81% of D-ATP, and 74% of P-ATP were present within the topmost 2 cm depth of sediment, and the distributions of ATP were well correlated with water content in the sediment. These results indicate that the distribution of total microbial biomass was largely determined by the supply of organic matter from surface water column. Fine-scale vertical variations of ATP were detected within 1-cm thick veneer of the sediment samples collected by multiple corer, while no apparent vertical changes were observed in the box-cored samples. It is evident that the box-core samples were disturbed extensively during sampling, which suggests that the multiple corer is a more appropriate sampling gear for measuring fine-scale vertical distribution pattern of ATP within thin sediment veneer. Overall results suggest that the concentrations of ATP, given their clear changes in vertical distribution pattern within 6 cm depth of sediment, are a suitable environmental baseline parameter in evaluating the variations of benthic microbial biomass that are likely to be caused by deep-seabed mining operation.

최적라인 설계 및 자동 분석을 위한 e-FEED 시스템 적용 효과

현정호,최상수,이범기,장용,성낙윤,신연식 (사)한국CDE학회 2014 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2014 No.2

북동태평양 심해 퇴적물에 서식하는 중형 저서 생물군집의 위도별 특징

현정호,최진우,이경용,김동성,Hyun, Jung-Ho,Choi, Jin-Woo,Lee, Kyeong-Yong,Kim, Dong-Sung 한국해양학회 2000 바다 Vol.5 No.3

This study was conducted to investigate the community structure and distributional pattern of meiobenthos in the deep sea bottoms of northeastern Pacific during July 1998. The faunal samples were collected using the multiple corer at ten stations; eight stations along the transects from 5$^{\circ}$N to 12$^{\circ}$N, and two stations in the Preservation Zone and Impact Zone of the KODOS (Korea Deep Ocean Study) area. The organic carbon content in sediments ranged from 0.79 to 1.76 mg cm$^{-3}$, and higher concentration appeared at stations in lower latitudes than 8$^{\circ}$N. The most abundant meiobenthos was nematodes and followed by foraminiferans; these two taxa comprised more than 70% of the total abundance at all stations. The most abundant meiobenthos occurred with mesh size of 0.063 nm. The maximum density of meiobenthos was 442 ind./10 cm$^2$ at station N5, and the density gradually decreased toward station N8 where the minimum density of 92 md./10 cm$^2$ was found. More than 60% of meiobenthos were distributed at surface sediment layer within 1.0 cm, and the peak abundance was found at 0-0.25 cm layer. The latitudinal distribution pattern of meiobenthos in the study area seemed to be related with the primary productivity of the surface water that is also connected to the water circulation pattern of the Pacific Ocean near the Equator, diverging at latitude of 8$^{\circ}$N and conversing at 5$^{\circ}$N.

아데노신 3인산(ATP; Adenosine-5′ triphosphate)을 이용한 심해저 및 연안퇴적토의 총 미생물 생체량 측정

현정호,김경홍,권개경,이정현,이홍금,김상진,김기현 한국미생물학회 2002 미생물학회지 Vol.38 No.2

심해와 연안의 서로 다른 해양퇴적토 환경에서 ATP농도를 이용한 총 미생물 생체량을 측정하였다. 표층 ATP의 분포는 연안역에서 가장 높았으며, 육지로부터 멀어질수록 감소하였다. 또한 수직적으로는 깊이에 따라 급격히 감소하는 양상을 나타내, 저층의 생태계가 수층으로 부터의 영양원 공급에 의해 일차적으로 조절되고 있는 것으로 나타났다. 한편, 유기물은 퇴적물로의 흡착으로 인해 환경 내 체류시간이 길어짐으로 인해, 유기탄소의 함량 변화가 ATP에 비해 급격히 일어나지 않았으며, 특히, 연안퇴적토의 경우 유기탄소의 함량 변화에 비해 ATP의 농도변화가 일정하게 나타나 두 변수간의 유의성 이 없는 것으로 나타났다. 이러한 결과는 분해가능한 유기물의 공급이 많은 연안퇴적토의 경우, 영양원에 의한 조절보다는 상위영양단계의 포식활동이 미생물의 생체량을 최종적으로 조절하는 요인으로 작용하기 때문 인 것으로 사료된다. 지역분포 특성 및 수직적 분포 특성으로부터 ATP는 서로 다른 저서 생태환경의 생체량 분석을 위한 일차적 인 도구로 유용하게 쓰일 수 있는 것으로 나타났다.

Portable NMR/MRI용 소형 영구자석에 특화된 Shim/Gradient 코일의 설계

현정호,서증훈,조영승,한상덕,문동민,김경한,오창현 대한전기학회 2011 정보 및 제어 심포지엄 논문집 Vol.2011 No.4

Cognition and control using optogenetic approach

현정호 한국공업화학회 2021 한국공업화학회 연구논문 초록집 Vol.2021 No.1

혐기성 해양환경에서 철 환원세균에 의한 유기물 분해 및 생물정화

현정호,Hyun Junc-Ho 한국해양학회 2005 바다 Vol.10 No.3

I reviewed an ecological and environmental significance of microbial carbon respiration coupled to dis-similatory reduction of fe(III) to Fe(II) which is one of the major processes controlling mineralization of organic matter and behavior of metals and nutrients in various anaerobic environments. Relative significance of Fe(III) reduction in the mineralization of organic matter in diverse marine environments appeared to be extremely variable, ranging from negligible up to $100\%$. Cenerally, Fe(III) reduction dominated anaerobic car-bon mineralization when concentrations of reactive Fe(III) were higher, indicating that availability of reactive Fe(III) was a major factor determining the relative significance of Fe(III) reduction in anaerobic carbon mineralization. In anaerobic coastal sediments where $O_2$ supply is limited, tidal flushing, bioturbation and vegetation were most likely responsible for regulating the availability of Fe(III) for Fe(III) reducing bacteria (FeRB). Capabilities of FeRB in mineralization of organic matter and conversion of metals implied that FeRB may function as a useful eco-technological tool for the bioremediation of anoxic coastal environments contaminated by toxic organic and metal pollutants.

하계 강화도 갯벌의 혐기성 유기물 분해능 및 황산염 환원력

현정호,목진숙,조혜연,조병철,최중기 한국습지학회 2004 한국습지학회지 Vol.6 No.1

갯벌이나 연안습지의 생태구조 및 생지화학적 물질 순환을 이해하기 위해서는 유기물 분해기능 평가 및 분해경로에 대한 연구가 필수적으로 진행되어야 함에도 불구하고 국내에는 이에 대한 연구가 거의 없다. 본 논문에서는 하계 강화도 남단의 갯벌에서 미생물에 의한 혐기성 유기물 분해정도를 파악하고, 황산염 환원을 통한 유기물 분해경로의 정량적 중요성을 평가하고자 하였다. 유기물 분해율은 깊이 6 cm 이내에서 41.9~89.4 mmol m-2 d-1의 범위로 나타났으며, 이를 강화도 갯벌의 전체 면적(약 300 km2)으로 환산할 경우, 하루에 216 ton의 유기물이 혐기적 과정을 통해 분해되는 것으로 계산되었다. 이러한 결과는 하구갯벌인 강화도 갯벌의 유기물 분해능이 생산력이 높은 염습지의 유기물 분해능에 비해 결코 뒤지지 않음을 보여주는 결과이다. 한편, 인위적으로 유기물(acetate)을 공급하였을 경우 유기물 분해율이 약 2배~5배의 증가율을 나타냈다. 이러한 결과는 미생물의 유기물 분해가 이용 가능한 유기물의 공급 부족에 의해 제한되고 있음을 의미한다. 한편 깊이 6 cm 이내에서 적분한 황산염 환원율은 20.7~45.1 mmol SO42- m-2 d-1의 범위로 나타났으며, 전체 혐기성 유기물 분해의 대부분을 차지하였다. 이러한 연구결과는 황산염 환원력의 과도한 증대가 향후 갯벌 주변 생태계의 생물 다양성 감소로 이어질 수 있음을 시사하는 것이다. Despite its significance in understanding ecological structure and biogeochemical element cycles, there have been few studies on the microbial mineralization of organic matter and mineralization pathway in the intertidal flat of Korea. We measured anaerobic mineralization of organic matter and sulfate reduction rate, and evaluated the significance of sulfate reduction in total anaerobic carbon respiration at the southern part of Ganghwa Island. Depth-integrated carbon mineralization rate down to 6 cm depth ranged from 41.9 to 89.4 mmol m-2 d-1, which accounted for approximately 216 tons of organic matter mineralization in entire intertidal flat area of Ganghwa(300 km2). The results indicated that capacity for the organic matter mineralization in the Ganghwa tidal flat is comparable to highly productive salt marsh environments. Mineralization rates in the sediment amended with acetate were 2~5 times higher than in unamended sediment. The results implied that microbial mineralization was limited by the availability of organic substrates, and the organic matter mineralization capacity seems to be higher than estimated at ambient organic substrate level. Depth-integrated sulfate reduction rates within 6 cm depth of the sediment ranged from 20.7 to 45.1 mmol SO4 2- m-2 d-1, and sulfate reduction was mostly responsible for organic matter remineralization. It should be noticed that the increase of H2S in the sulfate reduction dominated tidal flat may result in the decrease of biological diversity.