These three factors (density, salinity and temperature) are somehow connected to each other in terms of affecting each other when you change the value of each one of them.
Density is relatively dependent on the temperature and the amount of substance present in water. As temperature increases, the volume increases. When the volume increases, the density decreases. However, as the temperature continually rises, the water evaporates thus increasing the concentration of the salt in the water (salinity).
Salinity is the degree of saltiness that a body of water have. As you increase the salinity, you increase the concentration of salt in the water and you decrease the density of the solution. Remember that salts are more compact and denser than liquids thus when you add salt to water, the density decreases.