Adaptation in Algae to Environmental Stress and Ecological Conditions

Algae (including Cyanobacteria) are aquatic organism and ubiquitous in distribution. They are found not only in fresh and marine waterbodies but also on terrestrial habitats such as soil, tree trunk and man-made substrates. As they heavily depend on water, it becomes a limiting factor for their survival. However, algae are found growing abundantly in extreme habitats indicating their adaptation to the harsh environment which we try to explore in this chapter. The response of algae to desiccation stress is widely studied. They produce specialized spores that would remain dormant during harsh period and revive once the favourable conditions return. Their thick cell walls would have further protective layers of chemical substances and also mucilage sheath which helps in the delay of desiccation. Algae produce and accumulate varieties of organic osmolytes that protect them from desiccation, high irradiation and UV light. Algae also have de novo biosynthesis mechanism to manage the damage occurred due to desiccation. Algae occurring in colder habitats have substances in their cells that would withstand sub-zero temperatures. Algae growing in saline habitats accumulate salt and maintain ionic balance with the cellular concentration. Although algae are also found in hot springs, not many studies are available to explain their adaptive strategies.