When excessive plant nutrients enter bodies of water, algae overgrow. Phosphorus is naturally found in soil and and is an ingredient in fertilizers. As weathering, runoff and erosion occurs, increased amounts of phosphates are added to bodies of water resulting in an overgrowth of algae or eutrophication. This can wreak havoc on the aquatic biome. Normally, phosphorus in the form of PO4, is taken up by plants and animals that consume the plants. Rain acts as an agent of weathering and causes phosphates to be removed from rocks and allows its entry into the soil and water. Phosphorus can end up on the ocean floor. This phosphorus is not available to the cycle. Phosphate is even excreted in feces. Phosphorus only gets into the soil by weathering of rocks. Phosphorus in dead plants returns to the soil by decomposition. However, when people farm and ship the crops elsewhere, the land becomes deficient of phosphorus. It must artificially be added by the use of fertilizers.