Size-scaling of macromolecules and chemical energy content in the eukaryotic microalgae

Abstract

The macromolecular composition and cell size of microalgae can influence their competitive interactions for nutrients and food quality for predators. Here we quantify the cell volume and dry weight based size-scaling of protein, lipid, carbohydrate and chemical energy content of eukaryotic microalgae from data extracted from the scientific literature. Across all the microalgae examined, cell size is an excellent predictor of macromolecular and chemical energy content with size-scaling exponents ranging from 0.8 to 0.93 for cell volume and 0.96 to 1.1 for dry weight. There are secondorder taxonomic differences in the size scaling of macromolecular and chemical energy content. Relative to the green algae and dinoflagellates, the diatoms have lower cell volume size-scaling exponents for protein, lipid and chemical energy content due to their larger increase in vacuole volume with increasing cell volume. The dinoflagellates have a lower size-scaling exponent for carbohydrate relative to the diatoms and green algae and the green algae have a relatively high size-scaling exponent for protein as compared to the diatoms. Differences in the size-scaling of macromolecular and chemical energy content across the diatoms, green algae and dinoflagellates appear to reflect fundamental differences in cellular architecture and growth and storage allocation strategies across these microalgal phyla. KEYWORDS: carbohydrate; cell size; lipid; phytoplankton; protein