Would you expect the salinity of the ocean to be high or low near the mouth of the river in a rainy region or in a dry region

Near the mouth of a river, the salinity would be lower because river water is always freshwater.  In a rainy region, it would also be lower because rainwater is always freshwater.  Finally, in a dry region, it would be higher, because when water evaporates, it does not bring the salt with it.  Slowly, there would be less and less water with higher and higher salt content.  Hope this helps!!!

Reduction in overall biodiversity