Vertical Profiles of Marine Environments and Micro-phytoplankton Community in the Continental Slope Area of the East China Sea in Early Summer 2009

Studies of the distribution of micro-phytoplankton community and chlorophyll a concentration have focused on the vertical profiles of marine environmental factors such as water temperature, salinity, sigma-t, light intensity, and dissolved oxygen in the continental slope on the east parts of East China Sea in the early summer of 2009. Water temperature showed a gradual reduction according to the depth. While the salinity was low in the surface layer showing a mixed down to the relatively subsurface layer, it was increased with an increase in the depth at the middle and bottom layers showing a maximum value at 150~200 m followed by a decreasing aspect afterwards, although the change was not large. The change of sigma-t was governed by the water temperature, and gradually increased in the surface layer with an increase in the depth, showing a value higher than in the surface layer by about 3 $kg/m^3$ at the bottom layer. Although the intensity of light was exponential reduced in the surface layer, the compensation depth was located at the depth of about 80m. The vertical profiles of chlorophyll a concentration was governed by the intensity rather than the changes in water temperature or salinity, exhibiting a maximum value at the compensation depth corresponding to 1% in the surface light intensity. The micro-phytoplankton communities consisted of 56 genera 103 species showing a relatively variety, while the standing crop was also changed to 112.0~470.0 cells/L in the pelagic environment, showing a maximum chlorophyll a concentration. Although a variety of dominant species appear at low dominance without dominant species appearing with a right-wing point in the phytoplankton communities, the silicoflagellate, Otactis otonaris at the station A and the dominance of 26% due to Leptocylindrus mediterraneus at the station C have been judged to be unusual. For community analysis of infinitesimal creatures such as phytoplankton of oligotrophic waters through the present study, ecology studies through vertical sample collection agreeing with the results of continuous observation such as identification of vertical distribution in a marine environment or of maximum chlorophyll layers have been considered rather than a survey method with intervals of a given depth such as surface, subsurface, middle and bottom layers.

이른 여름 동중국해 대륙사면의 해양환경과 소형 식물플랑크톤 군집의 연직분포 특성

2009년 이른 여름 동중국해 동부의 대륙사면을 대상으로 해양환경과 소형 식물플랑크톤 군집을 조사하였다. 수온약층은 뚜렷하지 않고 수심에 따라 완만하게 감소하였다, 염분은 표층에서 낮고 비교적 깊은 수심까지 균일한 분포를 보이나, 중간 수층이하에서는 수심과 비례하여 150~200 m에서 최댓값을 보인 다음 감소하였으나, 변화 폭은 크지 않았다. sigma-t의 변화는 수온에 의해 지배되어, 표층에서 수심과 함께 완만히 증가하여 약 500 m에서 표층보다 약 3 $kg/m^3$ 높은 값을 나타내었다. 광량은 해수 표층에서 급격히 감소하여, 보상심도는 약 100 m 수심에 위치하였다. 엽록소 a의 연직분포는 수온이나 염분보다 광량에 더욱 영향을 받는 것으로 나타났으며, 보상심도에서 최댓값을 나타내었다. 소형 식물플랑크톤 군집은 56속 103종으로 비교적 다양하였고, 세포밀도 역시 엽록소 a가 최댓값을 나타내는 수심에서 112.0~470.0 cells/L로 가장 높게 나타났다. 우점종에서 극우점하는 종은 없고, 낮은 점유율로 다양한 종이 출현하지만, 일부 정점에서 규질편모조류인 Octactis octonaria나 규조류인 Leptocylindrus mediterraneus에 의해 26%의 우점율은 나타내는 것은 이례적이다. 본 연구의 결과는 개방된 빈영양 해역의 식물플랑크톤 등 미소생물의 군집 해석은 표층, 중층 및 저층과 같은 일정 수심 간격의 조사가 아닌, 해양환경의 연직분포나 엽록소 최대층의 파악과 같은 연속관측의 결과와 연계된 생태연구가 필수적임을 지적하고 있다.