Pollution arises when toxic or poisonous substances enters the sea. In many cases Marine pollution comes from the land itself. Few ships discharges the waste materials directly into the water, deep sea mining, atmospheric pollution are the causes of marine pollution. Marine pollution will cause a lot of loss of the lives of the marine organisms, because of the polluted area the organisms cannot receive the sufficient amount of oxygen and proper and sufficient food and at last they leads to the damage of the complete marine biodiversity and marine ecosystem.
Pollution can differ depending on the context and the purpose for which seawater is being used. Such as normal sea water has some tiny particles of plants or sand in it, and when the sea is considered as habitat of marine animals, one would not think of these particles as a pollutant, whereas one would define toxic chemicals as pollutants. Still, if somebody wanted to use this brine for cooking, they might see the sand and plants as polluting our cooking water.