Salinity
The number one determining factor in the types of organisms that can live in a body of water is salinity.
Salinity is the concentration of salt in a body of water. Salinity is a significant ecological factor that influences the types of organisms that live in a body of water. Aquatic organisms such as fish and crabs have different tolerable salt ranges, hence salinity have a great effect on their distribution and abundance in water. Aquatic organisms that are unable to tolerate or adapt to high salinity levels may die.