Spatial variations of size-fractionated Chlorophyll, Cyanobacteria and Heterotrophic bacteria in the central and western Pacific

摘要

Geographic and vertical variations of size-fractionated (0.2-1 #mu#m, 1-10 #mu#m, and > 10 #mu#m) Chlorophyll a (Chl.a) concentration, cyanobacteria abundance and heterotrophic bacteria abundance were investigated at 13 stations from 4 deg S, 160 deg W to 30 deg N, 140 deg E in November 1993. The results indicated a geographic distribution pattern of these parameters with instances of high values occurring in the equatorial region and offshore areas, and with instance of low values occurring in the oligotrophic regions where nutrients were almost undetectable. Cyanobacteria showed the highest geographic variation (ranging from 27 x 10~3 cell 1~-1), followed by Chl.a (ranging from 0.048 to 0.178 #mu#g 1~-1), and heterotrophic bacteria (ranging from 2.84 x 10~3 to 6.50 x 10~5 cell 1~-1). Positive correlations were observed between nutrients and Chl.a abundance. Correspondences of cyanobacteria and heterotrophic bacteria abundances to nutrients were less significant than that of Chl.a. The total Chl.a was accounted for 1.0-30.9