Fig. 1.

Effect of the acidification by HCl (a–e) and the ocean acidification conditions by elevating pCO₂ (f–j) on the cell growth of the coccolithophore E. huxleyi. Before experiments, all cells had been grown at pH 8.2 under the bubbling of air containing 400 ppm CO₂. Temperature was 20 °C. a, f, Change in turbidity; b, g change in cell number; c, h H in the medium. Initial pHs were set at 8.2 in a (closed circles), 7.7 in closed squares and 7.2 in closed triangles by HCl (a–c) and at 7.9 in closed circles, 7.6 in closed squares and 7.5 closed triangles by elevating pCO₂ (f–h). d, i Specific growth rates (μ) calculated on the basis of cell number; e, j inorganic carbon concentrations in the medium at each pH and the elevated pCO₂ concentration at 1 day. CO₂ concentration was set at 15 μmol L⁻¹ in all the conditions (right column). Solid (left) and stripe (middle) columns indicate total DIC and HCO₃ ⁻ concentrations, respectively. DIC, bicarbonate and CO₂ concentrations were calculated by a kind help of Dr. Midorikawa according to Leuker et al. (2000)