What was istanbul called before he ottomans conquered the city in the 15th century

It was called Constantinople, named after the Roman Emperor Constantine.  

places of higher salinity. there are parts of the ocean where hardly any rain falls but warm dry winds cause lots of evaporation. this evaporation removes water – when water vapour rises into the atmosphere, it leaves the salt behind, so the salinity of the seawater increases. this causes the seawater to become denser.