The same process occurs within the aquatic ecosystem. Phosphorus is not highly soluble, binding tightly to molecules in soil.
Phosphates also enter waterways through fertilizer runoff, sewage seepage, natural mineral deposits, and wastes from other industrial processes.
These phosphates tend to settle on ocean floors and lake bottoms. As sediments are stirred up, phosphates may reenter the phosphorus cycle, but they are more commonly made available to aquatic organisms by being exposed through erosion.
Water plants take up the waterborne phosphate which then travels up through successive stages of the aquatic food chain.