Carbon to volume relationship of Isochrysis galbana (Prymnesiophyceae) during cell divisions

Abstract

Dependency of carbon cell quota (C) on cell volume (V) was studied for the Prymnesiophyte Isochrysis galbana. Changes in the cell volume and carbon quota during cell divisions were examined at 25°C in a continuous culture with an enriched f/2 medium under a 12/12 h light/dark cycle at an irradiance of 45, 150, and 365 μmol m 2 sec 1 . Carbon quota estimates followed the relation log C=b log V+log a, where b is the slope and log a is the intercept of the relationship. Significant relationships between carbon quota and cell volume during cell divisions were obtained at the three irradiances tested. The value of the slope and the intercept ranged from 0.59 to 0.98 and from 0.22 to 0.64, respectively, however, they were not significantly different between the three irradiances. The relationship between carbon quota to cell volume during cell divisions also corresponded well to previously published carbon quota to cell volume relationship values within the size range of nanophytoplankton ranging from 2 to 20 μm, even though the irradiances used in the experiments differed from those studied previously. Due to the close similarity in cell size and division manner between the majority of nanophytoplankton communities and I. galbana, the results of the present study can be applied to natural assemblages of nanophytoplankton to estimate their carbon biomass in the euphotic layer regardless of sampling time on a given day.

Diel variation in motility of prymnesiophyte <i>Isochrysis galbana</i> under different irradiance

“…where u is the motility rate (µm s −1 ), and ESD is the equivalent spherical diameter of a cell (µm). The ESD values were estimated every 6 h from published data for Isochrysis galbana (Ishiwata et al 2013) to calculate the motility. Time courses of Sh under the 2 light regimes in each 6-h time interval were calculated as follows by using a value of 10 3 µm 2 s −1 for the diffusion coefficient, D (Karp-Boss et al 1996):…”