Cell size variation of Anoplosolenia brasiliensis(calcareous nannoplankton) in the central equatorial Pacific Ocean

Abstract

A morphometric analysis on Anoplosolenia brasiliensis(calcareous nannoplankton) was conducted employing samples obtained from 0 to 120 m water depths in the central equatorial Pacific Ocean along the equator ranging from 166.3°E to 170.1°W. Measured cell length of A. brasiliensis showed the minimum of 39 μm to the maximum of 165 μm. The cell width ranged from the minimum of 1 μm to the maximum of 10 μm. Measured cell volumes ranged from the minimum of 28.3 μm3 to the maximum of 2,741 μm3. In addition, length/width ratios ranged from the minimum of 6.8 to the maximum of 37.5. The cell size of this taxon is very large compared to that of other calcareous nannoplankton taxa such as Emiliania huxleyi. Related factors for such a large cell size appears to be: (1)population density of the own taxon; (2)ambient temperature; (3)ambient dissolved oxygen concentration; and (4)other phytoplankton population density such as that of E. huxleyi. The life adaptation of A. brasiliensis is interpreted as fundamentally pursuing a K-strategy, but this taxon is also pursuing an r-strategy when appropriate situation arises. The population density of this taxon may be related to ambient nutrient concentrations, intricate balance among several species of nutrients, and competitions with other coccolithophore taxa such as E. huxleyi.