Hydrogyaphic Observations In The Eastern Equatorial Pacific In November 1999

In November 1999 a hydrographic survey was carried out in a section from $5\\\\\\\\deg$N to $3\\\\\\\\deg$S in the eastern along $125\\\\\\\\deg$W. Velocity profiles showed four zonal and three meridional flow cores, indicating the equatorial zonal currents and the flow associated with the tropical instability waves. Water property sections showed that the warm and fresh surface water moving southward from the northern part formed a sharp thermal front at $2.1-2.2\\\\\\\\deg$N. The cold and saline water subducted beneath the front and continued to the north to $4.5\\\\\\\\deg$N, deepening to the thermocline depth. The speed of the saline water subduction reached up to 55 cm/s at 80 m depth at $3.2\\\\\\\\deg$N and the northward meridional flow at this location appeared down to 300 m depth below the thermocline. Dissolved oxygen (DO) data agreed well with the observations from T-S and velocity fields. This suggests that DO can be a good tracer to distinguish water masses in this complicated region. The features of Chlorophyll {\\\\\\\\it a} and other biochemical materials will be also presented.1

Apparent Dominance of Regenerated Primary Production in the Yellow Sea

The Yellow Sea is known to be a very productive region in terms of fisheries. However, its trophic status seems to be highly variable, ranging from oligotrophic to eutrophic, based on new production (NP) values. The NP and regenerated production (RP) values estimated from 15N -labelled nitrate and ammonium uptake in spring (April 1996) and winter (February 1997) during this study ranged from 0.05 to 19.8 mg Nm−2d−1 and from 0.1 to 22.8 mg Nm−2d−1 , respectively. Our measurements and earlier observations suggested that NP in the Yellow Sea varied over the four orders of magnitude (range 0.05-180.9 mg Nm−2d−1 ) temporally and spatially, and that RP (range 0.1-507.5 mg Nm−2d−l ) based on ammonium predominated during most period of the year, except in winter when both productions were low. The significant nitrogen uptake by phytoplankton below the euphotic zone and episodic entrainment of phytoplankton from below the euphotic zone into the euphotic zone, and nitrite excretion and dissolved organic nitrogen release during nitrate uptake might explain the apparent dominance of RP in the Yellow Sea.33Nkciothe

생물검정실험에 의한 섬진강 하구역 식물플랑크톤 성장의 제한영양염 평가

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Is Nitrogen Uptake Rate by Phytoplankton below the Euphotic Zone in the Yellow Sea Considerable?

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 15N 으로 표지하여 추적하였다. 전 유광대내의 질산염 및 암모늄 섭취율은 각각 1.8 ∼ 15.3 mg N m−2 d−1 과 5.0 ∼ 132.2 mg N m−2 d−1 의 범위이며, 대체로 암모늄 섭취율이 질산염 섭취율보다 우세하였다(1.9 ∼ 19.4배). 전 수주내의 질산염 및 암모늄 섭취율은 각각 2.9 ∼ 22.0 mg N m−2 d−1 과 15.7 ∼ 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 ∼ 86.2%, 암모늄의 경우에는 13.8 ∼ 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. To determine whether nitrogen (N) uptake by phytoplankton below the euphotic zone in the Yellow Sea is considerable, we measured the uptake rates of nitrate and ammonium using 15N -labeled stable isotope K15NO3 and 15NH4Cl , in May and November 1997 at total 10 stations. Depth-integrated uptake rates of nitrate and ammonium over the euphotic zone during this study ranged from 1.8 to 15.3 mg N m−2 d−1 and from 5.0 to 132.2 mg N m−2 d−1 , respectively, and ammonium uptake predominated at 9 of 10 stations (1.9-19.4 fold). Depth-integrated uptake rates of nitrate and ammonium over the whole water column ranged from 2.9 to 22.0 mg N m−2 d−1 and from 15.7 to 175.5 mg N m−2 d−1 , respectively. The significant proportion of whole water column N uptake was attributed to uptake by phytoplankton below the euphotic zone, ranging from 13.0 to 86.2% for nitrate and from 13.8 to 67.8% for ammonium, indicating that phytoplankton N uptake below the euphotic zone is at times considerable in the study area. The results suggest that when phytoplankton below the euphotic zone in the Yellow Sea are again entrained into the euphotic zone by a certain physical forcing such as turbulent mixing and the vertical movement of thermocline, these episodic events may significantly affect the material fluxes within the euphotic zone. Furthermore, the results suggest that a portion of regenerated production estimated from 15N -ammonium uptake should be included in new production estimates, which otherwise could be underestimated in the Yellow Sea.33Nkciothe

Surface chlorophyll a variability near the Dokdo Islets, East Sea (Japan Sea) observed from a moored buoy: Possible consequences of eddy-driven vertical mixing

As part of the Dokdo East Sea Time Series Studies (DETS) of the East Sea (Sea of Japan), a DETSbuoy system equipped with a set of meteorological sensors (wind, temperature, humidity,pressure, and wave height) 2 m above sea level, a conductivity-temperature-depth (CTD) sensorwith a fluorescence detector 1 m below the sea surface, and CTD sensors at 20-, 40-, 60-, 80-,100-, and 120-m depths was deployed on the 130-m-deep continental shelf of the Dokdo Islets inthe center of the East Sea. Sensor observations have been taken every 10 min since February2009 and transmitted to an onshore laboratory in Uljin on the east coast of the Korean Peninsula.Chlorophyll a concentrations in surface water at the DETS buoy exhibited frequentlow-concentration maxima in addition to low-frequency bimodal annual chlorophyll aconcentration variations due to a spring phytoplankton bloom and a smaller fall bloom. Thesesmaller frequent blooms appear to have been triggered by injection of nutrient-rich deepsubsurface water to sunlit surface water. This eddy-pumping mechanism was hypothesizedbased on cross-correlation analyses among daily mean water temperature and salinity at variousdepths (2–120 m below sea surface) and wind speed, wave height, and in vivo chlorophyll a atthe sea surface using a one-year data set from 30 March to 7 February retrieved from the DETSbuoy. This mechanism is also responsible for uctivity-temperature-depth (CTD) sensorwith a fluorescence detector 1 m below the sea surface, and CTD sensors at 20-, 40-, 60-, 80-,100-, and 120-m depths was deployed on the 130-m-deep continental shelf of the Dokdo Islets inthe center of the East Sea. Sensor observations have been taken every 10 min since February2009 and transmitted to an onshore laboratory in Uljin on the east coast of the Korean Peninsula.Chlorophyll a concentrations in surface water at the DETS buoy exhibited frequentlow-concentration maxima in addition to low-frequenc1

Surface chlorophyll a variability near the Dokdo Islets, East Sea (Japan Sea) observed from a moored buoy: Possible consequences of eddy-driven vertical mixing

As part of the Dokdo East Sea Time Series Studies (DETS) of the East Sea (Sea of Japan), a DETS buoy system equipped with a set of meteorological sensors 2 m above sea level, a conductivity-temperature-depth (CTD) sensor with a fluorescence detector was deployed on the 130-m-deep continental shelf of the Dokdo Islets. Chlorophyll a concentrations in surface water at the DETS buoy exhibited frequent low-concentration maxima in addition to low-frequency bimodal annual chlorophyll a concentration variations. These smaller frequent blooms appear to have been triggered by injection of nutrient-rich deep subsurface water to sunlit surface water. This eddy-pumping mechanism was hypothesized based on cross-correlation analyses among daily mean water temperature and salinity at various depths and wind speed, wave height, and in vivo chlorophyll a at the sea surface using a one-year data set retrieved from the DETS buoy.ence detector was deployed on the 130-m-deep continental shelf of the Dokdo Islets. Chlorophyll a concentrations in surface water at the DETS buoy exhibited frequent low-concentration maxima in addition to low-frequency bimodal annual chlorophyll a concentration variations. These smaller frequent blooms appear to have been triggered by injection of nutrient-rich deep subsurface water to sunlit surface water. This eddy-pumping mechanism was hypothesized based on cross-correlation analyses among daily mean water temperature and salinity at various depths and wind speed, wave height, and in vivo chlorophyll a at the sea surface using a one-year data set retrieved from the DETS buoy.1