Though the oceans are, by far, the largest saline body of water, hypersaline environments are generally defined as those containing salt concentrations in excess of sea water (3.5% total dissolved salts). Many hypersaline bodies derive from the evaporation of sea water and are called thalassic. A great diversity of microbial life is observed in tharassic brine from marine salinity up to about 3-3.5mol L-1NaCl, at which point only a few extreme halophlies can grow, e.g. Halobacterium, dunaliella, and a few bacterial species. Athalastic waters are those in which the salts are of nonmarine proportion, found for example after the concentration of sea water leads to precipitation of NaCl, leaving a high concentration of potassium and magnesium salts. This point marks the upper limit of resistance of all biological forms.