|
Small size phytoplankton are dominated in the western and central equatorial Pacific. Our study of HPLC measurements, size fractions of chlorophyll (alpha) and flow cytometric measurements indicate that phytoplankton communities in the equatorial Pacific are dominated by prokaryotic picophytoplankton with Prochlorococcus and Synechococcus, and small size autotrophic eukaryotes. Phytoplankton populations and the distribution were showed to differ from oligotrophic warm water region of the western equatorial Pacific and mesotrophic upwelling region of the central equatorial Pacific. In the oligotrophic region, phytoplankton distribution forms maximum layer around the nitracline. Prochlorococcus is most abundant in there. In the mesotrophic region, chlorophyll maximum layer is not found clearly. The population of autotrophic eukaryotes represented as prymnesiophytes were increased in there. Specific spectral absorption coefficients of phytoplankton [(alpha) *ph((lambda) )] were measured throughout the euphotic zone in the two different regions. The (alpha) *ph((lambda) ) were also reconstructed from HPLC results as the total of specific spectral absorption coefficients of chlorophyll (alpha) [(alpha) *chla((lambda) )], chlorophyll b [(alpha) *chlb((lambda) )], chlorophyll c [(alpha) *chlc((lambda) )], photosynthetically active carotenoids [(alpha) *psc((lambda) )] and photoprotective carotenoids [(alpha) *ppc((lambda) )]. Reconstructed (alpha) *ph((lambda) ) were compared with measured (alpha) *ph((lambda) ). Reconstructed (alpha) *ph((lambda) ) were overestimated at the field of (alpha) *psc((lambda) ), especially in the mesotrophic region. The (alpha) *psc((lambda) ) were considered as high contribution of prymnesiophytes. It was assumed that the package effect of prymnesiophytes was a cause of the overestimate of reconstructed (alpha) *ph((lambda) ).
|
