Controlling Factors of Algae
Knowledge of the ecological factors that control algae is based very largely on field observations with all the uncertainty which that implies. Nevertheless, it is possible to make general statements, some of which may be true and almost all of which are in need of more study.
Many algae seem to be opportunistic, which appear and flourish when conditions are right for them, and then give way to other species. This enables us at least to observe their optimum conditions, but, rare species sometimes appear in great numbers for short periods or in very limited places, so their ecological requirements are probably a complex of conditions.
Moreover, from studies made in still water and in cultures, many algae interact with one another by the production of metabolites which they release into the water.
Certain algae normally occur in particular types of habitat, coupling this with water quality data and observations on seasonal cycles and altitudinal occurrences, some general conditions become apparent controlling factors. The growth or types of algae are influenced by temperature, sunlight, current, substrate, alkalinity, nutrients, scour and to some extent by grazing animals such as aquatic insects.