Minor elements in seawater
Most of the other elements of the Periodic Table are also present in seawater. They are called minor and trace elements. Among them, the micronutrient elements N, P, Si, and Fe are essential for biological production in the ocean. Their abundance is controlled by horizontal and vertical circulation and by biogeochemical processes of utilization and regeneration. Of other elements, even dissolved gold is found in the water of all oceans. Although present in very small concentrations (0.000004 mg/litre), there is 5.6 million t of gold in all the Earth’s oceans, but the dilution is such that it cannot be extracted economically.