Environmental variability and its control of productivity

Aquatic oxygenic photosynthesis occurs in incredibly diverse groups of cyanobacteria, eukaryotic phytoplankton, macroalgae and macrophytes (see Chapters 2 and 3). It is modulated by abiotic (e.g., nutrient availability, light, temperature) and biotic (e.g., interspecific competition, prey–predator interactions, infection with pathogenic organisms) factors linked to the environment. Here, focusing on the cyanobacteria and microalgae which globally are responsible for the bulk of aquatic photosynthesis, we address the main abiotic factors controlling biosynthetic processes within cells and therefore the elemental and macromolecular composition of photoautotrophs in balance with the environment.