Defense strategies of algae and cyanobacteria against solar ultraviolet radiation

Abstract

Ultraviolet radiation (UVR) is a natural fraction of the solar radiation, and therefore has always influenced life in aquatic ecosystems. The development of oxygenic photosynthesis 2.5-2.7 billion years ago (Holland 1984) led to drastic chemical changes in the Earth's oceans and atmosphere. The gradual increase in photosynthetically produced oxygen over millions of years was accompanied by a strong enrichment of it in the atmosphere, which ultimately acted as precursor for the ozone (O3) layer in the stratosphere.