Standing crops of planktonic ciliates and nanoplankton in oceanic waters of the western Pacific

Abstract

The vertical distribution of planktonic ciliates and nanoplankton was investigated in 3 types of oceanic waters in the western Pacific. Ranges of their standing crops, in abundance and biomass, were 50 to 2540 cells l-1 and 4.89 × 104 to 6.32 × 106 pg C l-1 for ciliates and 7.2 × 104 to 1.97 × 106 cells l-1 and 2.45 × 105 to 4.92 × 107 pg C l-1 for nanoplankton in the spring subarctic water, <1080 cells l-1 and <1.27 × 106 pg C l-1 for ciliates and 7.5 × 106 to 2.76 × 106 cells l-1 and 1.01 × 105 to 1.03 × 107 pg C l-1 for nanoplankton in the fall subarctic water, and <570 cells l-1 and <1.59 × 106 pg C l-1 for ciliates and 1.45 × 105 to 3.18 × 106 cells l-1 and 3.05 × 105 to 2.62 × 107 pg C l-1 for nanoplankton in the subtropical water. The standing crop of ciliates, as a whole, was positively correlated to that of nanoplankton especially in biomass: Bc = 0.211 × Bn0.994, r = 0.81, p < 0.001, where Bc and Bn are biomass of ciliates and nanoplankton, respectively. This suggests that nanoplankton and ciliate stocks are tightly linked in oceanic waters.