The Biogeochemistry, an interdisciplinary science founded by Vladimir Vernadsky in 1926, provides the basic knowledge for understanding the physicochemical and biologic processes which govern the component composition of the natural environ at the different spheres of the earth. This science is related with the atmosphere sciences, biology, environmental chemistry, geology, ecology, soil sciences and oceanography. In this work, some examples of biogeochemical processes which occur at the hydrosphere in extreme conditions as hydrothermal systems, saline lagoon and coastal saline with the participation of saprophytic bacteria and micro alga are shown. [ABSTRACT FROM AUTHOR]