Trace elements in the ocean can be broadly classified by their vertical distribution profiles: 'nutrient-type' elements (such as cadmium, copper, and zinc) show depletion in surface waters due to biological uptake and enrichment at depth due to regeneration from sinking organic matter, closely tracking the profiles of major nutrients like phosphate and nitrate; in contrast, 'scavenged-type' elements (such as aluminium) show the opposite pattern, with relatively high concentrations near the surface (often from atmospheric dust/aeolian input) that decrease with depth as the element is rapidly removed (scavenged) by adsorption onto sinking particles.