FIG 5.

Cellular carbon and nitrogen mass scaling to volume. (a) A significant (chi-square ANOVA, P < 0.005) nonlinear relationship exists between cellular volume and carbon mass ($R^2=0.95$). (b) A significant (chi-square ANOVA, P < 0.05) nonlinear relationship also exists between cellular volume and carbon mass density (carbon mass per unit cell volume, $R^2=0.63$). Significant (chi-square ANOVA, P < 0.05) nonlinear relationships also exist between between cellular volume and nitrogen mass ($R^2=0.59$) (c) and cellular volume and nitrogen mass density (nitrogen mass per unit cell volume, $R^2=0.49$) (d). Gray lines represent best fits, described by the equations $m_{\mathit{carbon}}=197\times V^{0.46}$ for panel a, ${\rho }_{m\_\mathit{carbon}}=326\times V^{-0.35}$ for panel b, $m_{\mathit{nitrogen}}=39\times V^{0.38}$ for panel c, and ${\rho }_{m\_\mathit{nitrogen}}=78\times V^{-0.33}$ for panel d, where $m_{\mathit{dry}}$ and $m_{\mathit{nitrogen}}$ are carbon and nitrogen masses in femtograms, ${\rho }_{m\_\mathit{carbon}}$ and ${\rho }_{m\_\mathit{nitrogen}}$ are carbon and nitrogen mass densities in femtograms per cubic micrometer, and V is cell volume in cubic micrometers. Error bars indicate SEs. Color coding of the individual data points corresponds to the color coding of the investigated species outlined for Fig. 2.