Lake Mazandaran is one of the largest and most interesting lakes in the world and the most important fish and oil-rich mass of water in the world. The area of the lake is about 436,000 square kilometers and its volume is equivalent to 77,000 cubic km. Its form and level of salinity have changed many times in the history of geology, and it has finally become isolated and independent from other seas and gained the present form at the end of the Pliocene period.
The Flora and Fauna study of this sea and examination of its biological, physical and chemical conditions have begun since the end of the eighteenth century in terms of heat and salinity changes and the amount of food products; these studies reached their climax in the late nineteenth century and numerous articles on this case have been published by Russian researchers.
The animals and plants of this sea have different origins and patterns of dispersion; its endemic animals are the remains of organisms that lived in the Tethys Sea, and after the separation of the Caspian Sea from that sea they were confined there, but the great part of migratory beings came to this sea from the northern frozen seas or adjacent freshwater areas by rivers, and added to its limited aspects. Eventually a large number of the Black Sea and the Azov Sea creatures arrived and, gradually adapted to the new environment.
Some of the plants of this sea live in the lower reaches of the sea, and some are suspended in water either motionless or with independent movements. Among the plants, especially those that are small and simple, there are many that have organs specifically for swimming, and can swim independently. Generally, three kinds of animals and plants live in this sea as follows:
-Benthos: animals and plant that live at the bottom of the sea.
- Nekton: animals with full swimming organs, such as fish.
- Plankton: animals and small plants suspended in water.
What follows in this summary is a glimpse into the origin of the plants and animals of this sea and how they evolved during the Pliocene and the fourth period.