Chapter 6 - Salinity tolerance of inhabitants in thalassic and athalassic saline and hypersaline waters & salt flats

Abstract

Organisms that live in “thalassic” (inhabiting in the sea) and athalassic saline and hypersaline habitats (waters associated with lands which are not joined to the sea) are of great interest to ecologists and physiologists. These unusual ecosystems act as reservoirs of unique microbial life. Naturally, this chapter begins with a description of salinities in thalassic and athalassic water bodies. In terms of salinity, organisms living in water bodies are classified into osmo-regulators and osmo-conformers. This is followed by a description of all types of lives in thalassic seawater bodies, thalassic brackish water bodies, athalassic brackish water bodies, and athalassic hypersaline water bodies. Special attention is given to the topic of life in lithium chloride-dominated hypersaline salt flats & ponds belonging to the Lithium Triangle Zone (Argentina, Bolivia, and Chile) of South America. The inhabitants of hypersaline water, through the evolution of special mechanisms, have achieved a remarkable degree of osmotic independence from, or tolerance of, their unusual environment. Organisms that can live in such hostile habitats are typically microbes, and are commonly known as extremophile or extremotolerant taxa. Investigations have shown that concentrated brines support life and are dominated by hundreds of species of microorganisms. Due to saline stress, these extremophiles have developed very special strategies to survive even in lithium soup. These findings have implications beyond Earth: they have marked implications for our understanding of the potential for life on planets (e.g., Mars) and other celestial bodies with salt-lakes or brines that provide a potential niche for microbial life. Results of the studies carried out on microbial life in high salinity environments can be used to further the understanding of salt tolerance, and likely have value as models for the understanding of putative extra-terrestrial (e.g., Martian) life. Interestingly, experimental exclusion of the Andean flamingo from shallow water areas of a Salt Lake in the Bolivian Andes caused large increases in the biomass of microorganisms inhabiting the surface sediments, demonstrating the influences that water birds in general exert on the structure of aquatic ecosystems. This chapter winds up with a discussion of the importance of Atacama Desert in astrobiological study of Mars.