Water, ph, and temperature optima

Almost all chlorophytes, excavates and chromalveolates are limited to damp environments. A few photosynthetic species that are in lichen symbiosis are protected from desiccation and can survive extremely dry conditions. Most members are tolerant of a wide range of pH; some are specialized and can inhabit highly acidic environments like those of hot sulfur springs. In highly illuminated, oligotrophic lakes, large changes in pH can be caused by variations in dissolved CO₂ concentrations and these changes can have detrimental effects on the populations of photosynthetic species.

Some dormant stages of chlorophytes, excavates, and chromalveolates are capable of withstanding 100^?C for several hours. Other species can grow and divide at -2^?C in sea water, and specialized ‘snow algae’ have growth optima between 1 and 5^?C. Most species have a temperature optimum between 5 and 50^?C.