동열대태평양의 Kodos 지역에서의 식물플랑크톤 군집 : flow cytometry, hplc 그리고 현미경을 통한 조사

Abstract

The effects of environmental forcing on phytoplankton distribution patterns were investigated for convergence(5°N), divergence(9°N～ 10°30′N) and oligotrophic(17°N) sites in the tropical eastern Pacific during 2003 KODOS(Korea Deep Ocean Study) cruises. The distributions of picoplankton populations, Prochlorococcus, Synechococcus and picoeukaryotes were determined by flow cytometric analyses. Nano and micro phytoplankton were enumerated by LM and fluorescence microscopy. In addition, phytoplankton marker pigments were estimated using HPLC. Prochlorococcus showed consistently high abundance in the surface mixed layers of all sites at 1x105～3x105cells㎖-1 and showed declining abundance below these layers. However, these decreasing rates were not particularly sharp with considerably high abundance of 1x104cells㎖-1 or higher even at 100m depth. Vertical profiles of Synechococcus and picoeukaryotes were generally parallel to each other in all sites. A clear abundance maximum was observed at divergence site at or slightly above the pycnocline depth. Higher abundance was observed at the surface mixed layer for convergence site but a sharp decrease was observed below the pycnocline. However, there was no significant abundance fluctuation with depth at other oligotrophic sites(17°N). Integrated cell abundance of Prochlorococcus was high in the oligotrophic site at 2.17x1013cellsm-2, and low in the convergence site at 0.88x1013cellsm-2. Opposite patterns were observed for Synechococcus and picoeukaryotes where relatively high integrated cell abundances were shown in the convergence site. Diatom in the divergence site showed high abundance but showed low abundance in the oligotrophic site. Also, relatively high abundance patterns were observed in the surface layer than SCM layer. Fucoxanthin, marker pigment of diatom, also indicated a similar pattern with diatom distribution. Dinoflagellates also showed similar patterns with diatom in their cell and marker pigment(pe