• 한국해양학회지:바다
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• 제7권2호
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• pp.60-67
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• 2002

황해 대륙붕 해역의 전 수주(whole water column)의 질소 섭취율 중 무광대(aphotic zone)내 식물플랑크톤에 의한 질소 섭취율의 기여도를 파악하기 위하여 상부의 유광대(euphotic zone)와 하부의 무광대에서 식물플랑크톤에 의한 질소 섭취율의 크기를 측정하였다. 1997년 5월과 11월에 유광대와 무광대에서 일정량의 해수를 채취하여 선상에서 식물플랑크톤의 질산염과 암모늄 섭취율 측정을 $^{15}N$으로 표지하여 추적하였다. 전 유광대내의 질산염 및 암모늄 섭취율은 각각 1.8${\sim}$15.3 mg N $m^{-2}$ $d^{-1}$과 5.0${\sim}$132.2 mg N $m^{-2}$ $d^{-1}$의 범위이며, 대체로 암모늄 섭취율이 질산염 섭취율보다 우세하였다(1.9${\sim}$19.4배). 전 수주내의 질산염 및 암모늄 섭취율은 각각 2.9${\sim}$22.0 mg N$m^{-2}$ $d^{-1}$과 15.7${\sim}$175.5 mg N$m^{-2}$ $d^{-1}$의 범위를 나타냈다. 전 수주내의 총 질소 섭취율 중 무광대의 식물플랑크톤에 의한 질소 섭취율이 차지하는 비율은 질산염의 경우에 13.0${\sim}$86.2%, 암모늄의 경우에는 13.8${\sim}$67.8%로서, 무광대에서 식물플랑크톤에 의한 질소 섭취가 상당함이 발견되었다. 본 연구의 결과는 무광대내에서 상당한 양으로 활발하게 질소를 섭취하는 식물플랑크톤이 물리적 작용들(예를 들면, 와류 혼합, 수온약층의 수직이동 등)에 의해 유광대로 다시 편입(entrainment)될 경우 유광대의 물질 순환에 크게 기여할 가능성이 있음을 시사한다. 그리고, 본 연구 결과는 황해에서 신생산(new production)의 크기가 질산염 섭취로만 추정될 경우 과소평가될 가능성이 있으며, 암모늄 섭취에 기초한 재생산(regenerated production)의 일부가 신생산에 포함되어야 함을 제시한다.

• 한국물환경학회지
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• 제34권6호
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• pp.632-641
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• 2018

Algal dynamics is controlled by multiple environmental factors such as flow dynamics, water temperature, trophic level, and irradiance. Underwater irradiance penetrating from the atmosphere is exponentially decreased in water column due to absorption and scattering by water molecule and suspended particles including phytoplankton. As the exponential decrease in underwater irradiance affects algal photosynthesis, regulating their spatial distribution, it is critical to understand the light extinction characteristics to find out the mechanisms of algal dynamics more systematically. Despite the significance, the recent data have been rarely reported in the main stream areas of large rivers, Korea. In this study, the euphotic depths and light extinction coefficients were determined by monitoring the vertical variation of underwater irradiance and water quality in the main channel of Nakdong River near Dodong Seowon once a week during summer of 2016. The average values of euphotic depth and light extinction coefficient were 4.0 m and $1.3m^{-1}$, respectively. The degree of light extinction increased in turbid water due to flooding, causing an approximate 50 % decrease in euphotic depth. Also, the impact was greater than the self-shading effect during the periods of cyanobacterial bloom. The individual light extinction coefficients for background, total suspended solid and algal levels, frequently used in surface water quality modeling, were determined as $0.305m^{-1}$, $0.090m^{-1}/mg{\cdot}L^{-1}$, $0.013m^{-1}/{\mu}g{\cdot}L^{-1}$, respectively. The values estimated in this study were within or close to the ranges reported in literatures.

• Journal of the korean society of oceanography
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• 제35권1호
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• pp.16-33
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• 2000

In order to measure the vertical fluxes of particles and reactive radionuclides such as thorium and polonium isotopes, Dunbar-type sediment traps were freely deployed at the Ulleung Basin and in warm and cold water masses around the polar front of the East Sea. We estimated the ratios of the catched (F) to the predicted $^234$Th fluxes (P) using natural tracers pair $^234$Th-$^238$U. The F/P ratios are decreased with increasing water depth. Whereas the concentrations of suspended particles are homogeneous in water column, the mass fluxes are also decreased with increasing water depth like the F/P ratios. These facts indicate that organic matters of settling particles are destructed within the euphotic layer due to decomposition. Whereas regenerations of sinking particles are negligible in the cold water mass, about 80% of them are regenerated in the warm water mass during falling of large particles. These downward mass fluxes are closely correlated with their primary productions in euphotic zone. The activities of $^234$Th, $^228$Th and $^210$Po in the sinking material were increased with water depth. Because $^234$Th steadily produced in the water column are cumulatively adsorbed on the surface of sinking particles, vertical $^234$Th fluxes were observed to increase with water depth. Therefore, these sinking particles play important roles in transporting the particle reactive elements like thorium from surface to the deep sea. The scavenging processes including adsorption and settling reactions generate radio-disequilibrium between daughter and parent nuclides in water column. The activity ratios of $^234$Th/$^238$U and $^228$Th/$^228$Ra were observed to be < 1.0 in the surface water and approached to be equilibrium below the thermocline. The extent of the deficiency of daughter nuclides compared to the parents nuclide was highly correlated with the vertical particle flux. Because most of the $^210$Po in the surface water are scavenged on a labile phase and are recycled at sub-surface depths (< 200 m), the $^210$Po are always observed to be excess activities compared to $^226$Ra in surface water.

• ALGAE
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• 제35권2호
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• pp.167-176
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• 2020

Iodine exists as a trace element in seawater, with total iodine being generally constant at about 0.45-0.55 μM. Almost all of this iodine occurs in two main forms: iodate and iodide. Iodate is the thermodynamically stable form under normal seawater conditions, and thus should be the only iodine-containing species in the water column. However, iodate concentrations are found to vary considerably, being generally greater at depth and lower at the surface, while iodide concentrations follow the reverse pattern, being anomalously accumulated in the euphotic zone and decreasing with depth. The fact that iodide concentrations follow a depth dependence corresponding to the euphotic zone suggests that biological activity is the source of the reduced iodine. Nonetheless, the nature and source of iodate reduction activity remains controversial. Here, using a combination of field and laboratory studies, we examine some of the questions raised in our and other previous studies, and seek further correlations between changes in iodine speciation and the presence of marine macro- and microalgae. The present results indicate that microalgal growth per se does not seem to be responsible for the reduction of iodate to iodide. However, there is some support for the hypothesis that iodate reduction can occur due to release of cellular reducing agents that accompany cell senescence during phytoplankton bloom declines. In addition, support is given to the concept that macroalgal species such as giant kelp (Macrocystis pyrifera) can take up both iodide and iodate from seawater (albeit on a slower time scale). We propose a mechanism whereby iodate is reduced to iodide at the cell surface by cell surface reductases and is taken up directly as such without reentering the bulk solution.

• 한국수산과학회지
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• 제28권2호
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• pp.174-182
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• 1995

Using the optical data from the EUMELI 3 and 4 missions, the optical properties are discussed in relation to primary production in the oligotrophic zone of the Eastern Atlantic Ocean. The depth of euphotic layer $(Z_{eu})$, the total accumulated concentration of pigment $(C_{TOT})$ and the concentration of pigment (C) are 88m, $12.4mgm^{-2}\;and\;0.14mgm^{-3}$, respectively for the EUMELI 3 mission and 101.7m, $10.0mgm^{-2}\;and\;0.10mgm^{-3}$, respectively for the EUMELI 4 mission. The concentration of pigment is higher in autumn (EUMELI 3) than in spring (EUMELI 4). This indicates that the concentration of photosynthetic pigment has a close correlation with vertical attenuation coefficient $(K(\lambda))$ that changes seasonally in the euphotic layer. While the spectral distributions of downward Irradiance$(E_d)$ for the wave length of 470nm increase with depth, those of upward irradiance $(E_u)$ for the wave length range between 410nm and 490nm are constant, because the study area is covered with the blue and clear oceanic deep waters. The vertical attenuation coefficients of downward irradiance $(K_d)$ and upward irradiance $(K_u)$ have low values between 0.02 and $0.06m^{-1}$ due to the low absorption and scattering by the photosynthetic pigment of phytoplankton. Therefore this zone has the characteristics of the case 1 waters with low concentrations of photosynthetic pigment, and can be classifed into IB.

• Journal of Microbiology and Biotechnology
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• 제24권5호
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• pp.592-596
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• 2014

HMO-2011, a recently isolated lytic phage that infects the SAR116 bacterial clade, represents one of the most abundant phage types in the oceans. In this study, the HMO-2011 genome sequence was compared with virome sequences obtained from various depths of the Pacific Ocean regions using metagenome binning. HMO-2011 was confirmed to be one of the most highly assigned viruses, with a maximum of 7.6% of total reads assigned. The HMO-2011-type phages demonstrated a depth-specific distribution, showing more abundance in the euphotic zone of coastal, transition, and open ocean regions as compared with the dark ocean.

• 한국환경과학회지
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• 제6권6호
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• pp.595-604
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• 1997

To investigate characteristics of biogeochemical environment of the Korea Deep Ocean Study(KODOSI area in the northeast Pacific Ocean, we preferentially measured Inorganic nutrients and fluorescent organic matters. Typically. the permanent thermocline was well developed at the depth of 200~1000m In the study area. Nitrate. phosphate and silicate were low In the surface mixed layer and Increased with depth. N/P and N/Si showed 15 and 0.2 respectively In the deeper layer. Two fluorophores, biomacromolecule(protein-like) and geomacromolecule (humid-like) , were observed by three dimensional fluorescence excltatlon/ emission spectra matrix. Biomacromolecule(maximum fluorescence at $Ex_{280m}/Em_{330nm}$) ranged from 41.9 to 147.0 TU with its maximum In the surface mixed layer and minimum in deeper water, This is a same trend that has been reported for DOC in the equatorial Pacific. This suggests that biomacromolecule might be labile and converted to refractory humic substance after bacterial degradation In the deeper layer. On the contrary, geomacromolecule(maximum fluorescence at $Ex_{330m}/Em_{430m}$), ranged from 7.6 to 46.5 QSU, showed minimum in the surface nixed layer(euphotic zone) Implying photodegradation and then increased with depth at all stations. In the characteristics of vertical profiles, the relationship between biomacromolecule and geomacromolecule showed negative correlation. Such trend can be attributed to biochemical regeneration or formation of fluorescent materials accompanying oxidation and rennnerallzation of settling organic matter.

• 한국해양학회지:바다
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• 제4권4호
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• pp.275-288
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• 1999

유기물 투기에 대한 박테리아의 반응을 이해하기 위해 동해의 비투기해역과 투기해역의 유광대에서 1996년 4월부터 1997년 9월까지 총 5회에 걸쳐 박테리아 개체수, 박테리아 생산력, 아미노펠티다제(aminopeptidase; AMPase) 가수분해능, 베타글로코시다제(${\beta}$-g1ucosidase; ${\beta}$-GLCase) 가수분해능을 측정하였다. 비투기해역과 투기해역에서 유광대 수심으로 적분한 식물플랑크톤 생물량 및 박테리아 변수들을 비교해 본 결과, 전 시기에 걸쳐 일관되게 외양의 투기 정점에서 외양의 비투기 정점보다 ${\beta}$-GLCase 가수분해능이 항상 높았다. 또한 thymidine과 leucine 고정율로부터 추정된 박테리아 생산력도 계절에 관계없이 투기해역에서는 유의한 상관관계(균형성장)를 나타내었으나 비투기해역에서는 무관한 관계(불균형성장)를 나타내었다. 이러한 결과들은 투기해역에서 유기성 투기물의 지속적인 공급에 대해 박테리아 군집이 반응하고 있는 양상으로 보인다. 또한 계절에 관계없이 투기해역에서는 박테리아 개체수와 생산력이 양의 상관관계를 나타내었으나 비투기해역에서는 무관한 관계를 나타내어, 투기해역에서 박테리아 개체수의 조절 기작이 비투기 해역과 다름을 시사하였다. 그 밖의 변수들의 관계들은 연구 해역과 계절에 따라 변화하는 양상을 나타내어 봄과 여름에 박테리아 조절 요인들이 달라짐을 보여주었다. 이러한 변화가 수온, 수온과 관련된 현상, 또는 투기물 특성의 변화와 연관된 것인지에 대한 추가적인 연구가 필요하다.

• 한국해양학회지:바다
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• 제19권2호
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• pp.109-124
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• 2014

남극 아문젠해의 탄소순환을 이해하기 위해서 표층에서 심층으로의 입자상 유기탄소 침강플럭스를 ${\psi}$/${\psi}$ 비평형법을 이용하여 추정하였다. 2012년 2월과 3월에 걸쳐 남극 아문젠해의 총 14개 정점에서 깊이별로 해수시료를 채취하였고, 총 ${\psi}$, 용존 ${\psi}$ 및 입자상 유기탄소를 분석하였다. 수심에 따라 총 ${\psi}$의 활동도 농도는 ${\psi}$에 비하여 결핍과 과잉을 나타내었다. 유광대에서 총 ${\psi}$의 결핍 정도는 엽록소 및 형광도와 거울상을 나타내고, 질산염 제거와 수반되어 나타나므로 생물 활동의 영향으로 파악되었다. 심층에서 일어나는 총 ${\psi}$ 결핍은 Fe/Mn 산화물에 의해 이루어지는 것으로 해석되었다. 유광대 바로 아래의 수층에서 나타나는 총 ${\psi}$ 과잉은 재광물화 작용보다는 이 깊이에 집적된 입자상 ${\psi}$에 기인하였다. 정상상태 모델로 추정한 ${\psi}$의 침강플럭스는 평균 $867{\pm}246dpmm^{-2}day^{-1}$이었으며, 유광대에서 질소와 인의 결핍 총량과 밀접한 관련성을 보였다. 입자상 유기탄소와 ${\psi}$의 비율($7.08{\pm}4.27{\mu}molCdpm^{-1}$)을 이용하여 추정한 입자상 유기탄소의 침강플럭스는 평균 $5.9{\pm}3.9mmolCm^{-2}day^{-1}$으로 나타났는데 이 값은 2-3월의 웨델해와 유사한 수준이었다. 입자상 유기탄소 플럭스와 일차생산력의 비율로 나타낸 생물 펌프의 효율(ThE)은 3-54%(평균 28%) 범위였다.

• ALGAE
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• 제21권4호
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• pp.445-452
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• 2006

The morphometry and distribution of the unarmoured dinoflagellates Brachidinium capitatum F.J.R. Taylor, Asterodinium gracile Sournia, Microceratium orstomii Sournia and the toxic species Karenia papilionacea Haywood et Steidinger have been investigated in open waters of the SE Pacific Ocean. The genus Microceratium Sournia is recorded for the first time since the initial description. These taxa showed a high morphological similarity and they may correspond to life stages of a highly versatile single species that is able to project body extensions. Karenia papilionacea showed the higher abundance in the surface waters of the more productive areas (the Marquesas Archipelago and the Perú-Chile Current). Brachidinium capitatum and K. papilionacea often co-occurred, predominating B. capitatum in offshore surface waters. Asterodinium gracile was recorded at the bottom of the euphotic zone (down to 210 m depth), with a shallower distribution in more productive areas. Intermediate specimens of Asterodinium-Brachidinium-Karenia, with variable disposition and size of the body extensions were illustrated.