The gases come from the atmosphere. As water is a universal solvent, many different compounds are dissolved in it. A 1kg sample of saltwater contains 35 g of dissolved compounds, including inorganic salts, organic compounds from living organisms, and dissolved gasses. Oceanic salinities generally range from 34 to 37 parts per thousand. Variations from place to place are due to factors such as rainfall, evaporation, biological activity and radioactive decay.
Salinities are higher in the tropics due to high evaporation rates.
Fresh supplies of salts are now being added to the oceans from the rivers at roughly the same rate that they are being removed by various physical, chemical and biological processes. I n contrast to the other salts, the nitrates and phosphates vary in concentration due to biological activity. In surface waters, where plants are actively in the process of photosynthesis, the nitrates and phosphates can be in short supply, limiting the amount of biological activity that can take place. T emperature Temperature is a very important physical parameter in the marine environment. It limits the distribution and ranges of ocean life by affecting the density, salinity, and concentration of dissolved gasses in the oceans, as well as influencing the metabolic rates and reproductive cycles of marine organisms.