Phosphorus accounts for only about 0.1 percent of Earth’s crust, but it is an essential nutrient for all life forms. It is a key component of cell membranes, DNA, RNA, and ATP. Unlike the other biogeochemical cycles discussed thus far, the phosphorus cycle does not have a significant atmospheric component, although some phosphorus is transported by dust particles. Most of Earth’s phosphorus is in the form of phosphate in rocks and deep-sea sediments, and it cycles very slowly through the geological system because it requires sedimentary rock formation, uplift, and weathering. In contrast, phosphorus in organisms cycles rapidly, and it is often a limiting factor for their growth, particularly for plants. As you learned in Key Concept 57.2, runoff of phosphorus from fertilizers and detergents into aquatic systems can result in eutrophication.