What does the speaker say about the ocean’s level of saltiness? [originaltext]

Scientists believe that when the oceans were young, they contained only a trace of salt, and that the level of salinity has been going up gradually. Over the years, rains have been wearing away the reek mantle of the continent. Minerals released by these erosion have been carded to the sea by the flow of river water. This water adds several billions tons of salt to the ocean annually. There are other sources of oceanic salinity too; one source is underwater volcanic action. These eruptions occurred along the mid-ocean ridge and release great amount of salt into the sea each year. However, these sources don’t increase the actual mineral composition of the water by much because the enormous chemical requirements of marine life. Oysters, clams, snails and other mollusk use salt to build shells and skeletons. Coral reefs also consume large amount of salt. Also, some salt leaves the ocean through the process of evaporation. As salts escape into the atmosphere, they go into the creation of rain drops, this is why the coast receives more rain. Salt exists in the atmosphere near the ocean, thereby attracting the increased moisture and producing rain.