Recent Primary Production and Small Phytoplankton Contribution in the Yellow Sea during the Summer in 2016

장효근,강재정,이재형,김명준,안소현,정진용,윤미선,한인성,이상헌 한국해양과학기술원 2018 Ocean science journal Vol.53 No.3

The high nutrient concentration associated with the mixing dynamics of two warm and cold water masses supports high primary production in the Yellow Sea. Although various environmental changes have been reported, no recent information on small phytoplankton contribution to the total primary production as an important indicator for marine ecosystem changes is currently available in the Yellow Sea. The major objective of this study is to determine the small (< 2 μm) phytoplankton contribution to the total primary production in the Yellow Sea during August, 2016. In this study, we found relatively lower chlorophyll a concentrations in the water column than those previously reported in the central waters of the Yellow Sea. Moreover, the overall contribution of small phytoplankton (53.1%) to the total chlorophyll a concentration was considerably higher in this study than that (10.7%) observed previously. Based on the N/P ratio (67.6 ± 36.6) observed in this study, which is significantly higher than the Redfield ratio (16), we believe that phytoplankton experienced P-limiting conditions during the study period. The average daily carbon uptake rate of total phytoplankton in this study was 291.1 mg C m-2 d-1 (± 165.0 mg C m-2 d-1) and the rate of small phytoplankton was 205.7 mg C m-2 d-1 (± 116.0 mg C m-2 d-1) which is 71.9% (± 8.8%) of the total daily carbon uptake rate. This contribution of small phytoplankton observed in this study appears to be higher than that reported previously. Our recent measured primary production is approximately 50% lower than the previous values decades ago. The higher contributions of small phytoplankton to the total chlorophyll a concentration and primary production might be caused by P-limited conditions and this resulted in lower chlorophyll a concentration and total primary production in this study compared to previous studies.

동해 식물플랑크톤 군집에 대한 초미소 식물플랑크톤(< 2 ㎛) 기여도 장기 경향성 연구

장효근,이다빈,이상헌 해양환경안전학회 2023 해양환경안전학회지 Vol.29 No.6

본 연구는 2003년부터 2022년까지 동해 남서부 해역에서 초미소(0.2-2 ㎛) 식물플랑크톤의 군집, 표층 수온 상승, 그리고 무기 영양염 간의 복잡한 상호작용을 다루었다. 동해에서 관측된 표층 수온의 상승 추세는 전 지구규모의 수온 상승과 일치하며, 여름에는 최대 온도가 나타나지만 봄에는 최소 온도를 보여 일반적인 온대해역의 계절적 수온 변동과는 다른 양상을 보였다. 표층 무기 영양염의 농도는 겨울에 증가하며 봄을 거치면서 서서히 감소하는 계절적 변동성을 나타냈다. 식물플랑크톤의 생물량을 대표하는 표층 총 chlorophyll-a 농도는 온대 해역의 전형적인 쌍봉분포(bimodal distribution) 양상을 보였다. 연구 기간 동안 초미소 식물플랑크톤의 기여도는 연평균 0.5%씩 지속적으로 증가하였으나, 총 chlorophyll-a 농도는 약한 감소 추세를 보였다. 초미소 식물플랑크톤의 기여도와 영양염 간에는 강한 상관관계가 나타났으며, 이는 이러한 변동이 식물플랑크톤의 크기별 영양염의 가용성과 밀접하게 연관되어 있음을 의미한다. 이러한 분석 결과는 해양 생태계의 변화 조건에서 식물플랑크톤이 어떻게 반응할는지 예측 가능하게 하므로, 생태학적으로 중요한 의미를 갖는다. In thi study, we unveil the intricate interplay among picophytoplankton (0.2­2 μm) communities, warming surface water temperatures, and major inorganic nutrients within the southwestern East Sea from 2003­2022. The observed surface temperature rise, reflecting global climate trends, defies conventional seasonal patterns in temperate seas, with highest temperatures in summer and lowest in spring. Concurrently, concentrations of major dissolved inorganic nutrient display distinct seasonality, with peaks in winter and gradually declining thereafter during spring. The time course of chlorophyll-a concentrations, a proxy for phytoplankton biomass, reveals a typical bimodal pattern for temperate seas. Notably, contributions from picophytoplankton exhibited a steady annual increase of approximately 0.5% over the study period, although the total chlorophyll-a concentrations declined slightly. The strong correlations between picophytoplankton contributions and inorganic nutrient concentrations is noteworthy, highlighting their competitively advantageous responsiveness to the shifting nutrient regime. These findings reflect significant ecological implications for the scientific insights into the marine ecosystem responses to changing climate conditions.

달기 탄산광천수의 수리화학적 특성 및 영족기체 기원

정찬호 ( Jeong Chan Ho ),장효근 ( Jang Hyo Geun ),김규한 ( Kyu Han Kim ),( Nagao Keisuke ) 대한지질공학회 2010 대한지질공학회 학술발표회논문집 Vol.2010 No.1

A Review on Marine N2 Fixation: Mechanism, Evolution of Methodologies, Rates, and Future Concerns

P. S. Bhavya,이상헌,민준오,김민섭,장효근,김관우,강재중,이재형,이다빈,조나은,김명준,김예진,이준범,이창화,배현지,유혜주,박상훈,윤미선 한국해양과학기술원 2019 Ocean science journal Vol.54 No.4

Investigations on marine N2 fixation have gained momentum since 1960s with eventual establishments of relevant methodologies to identify species involved and quantify the rates. The evolution of various methodologies to understand N2 fixation and to estimate its rates were underpinned by the constant efforts of pioneers in the ocean biogeochemical research field. Those efforts succeeded in introducing various methodologies that include experimental (15N2 bubble method and acetylene reduction method), geochemical (N* and P* method), mathematical modelling, and remote sensing techniques. However, the construction of an accurate N budget is still under progress due to inseparable issues associated with each method and difficulties in conducting the experiments onboard on a larger scale. Nevertheless, the contributions by each of the methodologies are significant and helped in forming basic ideas about N2 fixation activities on a global scale. It is not only important to recognize the contributions made by the formation of various methodologies by marine research pioneers, but also vital to summarize what we have achieved in the marine N2 fixation research area so far. Hence, this review is an attempt to brief on the various milestones achieved in research on the N2 fixation mechanism, species involved, evolution of methodologies to estimate N2 fixation rates, species identification, budgets, and future concerns.

청원지역 시추공 지하수의 수리화학 및 자연방사성물질 산출 특성

정찬호 ( Chan Ho Jeong ),김문수 ( Moon Su Kim ),이영준 ( Young Joon Lee ),한진석 ( Jin Seok Han ),장효근 ( Hyo Geun Jang ),조병욱 ( Byung Uk Jo ) 대한지질공학회 2011 지질공학 Vol.21 No.2

이 연구에서는 지하수내 존재하는 우라늄과 라돈-222와 같은 자연방사성물질 산출과 지화학적 상관관계를 알아보기 위하여 연구용 부지(충북 청원군 부용면 갈산리)에 120 m 심도로 시추하고, 심도별로 채취된 지하수의 화학적 특성과 시추코어의 암석화학적 특성을 분석하였다. 시추코어상 주요 암종은 흑운모편암과 흑운모화강암이며 일부 구간에서 반상화강암과 염기성암맥이 확인되었다. 더블패커 시스템으로 채취한 6개 구간에서 지하수의 pH는 5.66∼8.34 범위를 보이고, 화학적 유형은 Ca-HCO3 형으로 속한다. 심도별 및 시기별로 수리화학적 특성 차이를 보인다. 지하수내 우라늄과 라돈-222의 함량은 최고 683 ppb와 7,600 pCi/L를 각각 보이며, 심도 50~70 m구간에서 가장 높은 값을 보인다. 암석 및 광물내 우라늄과 토륨의 함량은 각각 0.51~23.4 ppm과 0.89~62.6 ppm의 범위를 보이며, 흑운모편암에서 가장 많은 방사성포유물(radioactive inclusion)이 관찰되었고, 현미경관찰과 EPMA 분석결과 방사성원소를 함유하는 광물로는 흑운모내 함유된 소량광물인 모나자이트, 일메나이트로 확인되었다. 우라늄은 이들 광물의 주요 구성원소를 치환하여 존재하며, 일부 석영과 장석 입자내에도 우라늄의 산출이 확인되었다. 시추공 심도 -50~-70 m 구간 지하수에서 높은 방사성물질 함량을 보이는 것은 이 구간의 지하수의 화학적 특성, 즉, 약알칼리성의 pH와 산화환경이고, 중탄산의 함량이 높아 우라늄의 용존에 좋은 조건이 된 것으로 보인다. 지하수내 라돈가스의 함량은 우라늄 농도와 대체로 비례하므로 우라늄의 붕괴와 관련된 것으로 보이며, 라돈가스의 기원에 대한 하나의 해석방법으로 헬륨과 네온등 영족기체 동위원소비를 이용한 간접적인 추적방법을 적용할 필요가 있을 것이다. A test borehole was drilled in the Cheongwon area to investigate the relationship between geochemical environment and the natural occurrence of radioactive materials (uranium and Rn-222) in borehole groundwater. The borehole encountered mainly biotite schist and biotite granite, with minor porphyritic granite and basic dykes. Six groundwater samples were collected at different depths in the borehole using the double-packed system. The groundwater pH ranges from 5.66 to 8.34, and the chemical type of the groundwater is Ca-HCO3. The contents of uranium and Rn-222 in the groundwater are 0.03-683 ppb and 1,290-7,600 pCi/L, respectively. The contents of uranium and thorium in the rocks within the borehole are 0.51-23.4 ppm and 0.89-62.6 ppm, respectively. Microscope observations of the rock core and analyses by electron probe microanalyzer (EPMA) show that most of the radioactive elements occur in the biotite schist, within accessory minerals such as monazite and limenite in biotite, and in feldspar and quartz. The high uranium content of groundwater at depths of -50 to -70 m is due to groundwater chemistry (weakly alkaline pH, an oxidizing environment, and high concentrations of bicarbonate). The origin of Rn-222 could be determined by analyzing noble gas isotopes (e.g., 3He/4He and 4He/20Ne).

구두발표 : 국내 지하수중 자연방사성 물질 산출과 지질과의 연관성

정찬호 ( Chan Ho Jeong ),김문수 ( Moon Su Kim ),김태승 ( Tae Seung Kim ),조병욱 ( Byung Uk Jo ),유근석 ( Kun Seok Ryu ),장효근 ( Hyo Kun Jang ),김동욱 ( Dong Uk Kim ) 대한지질공학회 2013 대한지질공학회 학술발표회논문집 Vol.2013 No.1