Inputs for photosynthesis are water (H2O) and carbon dioxide (CO2) plus light. Oxygen is released as a byproduct.
Cells of a plant, like an animal are mostly water.
An interesting side-note: Contrary to conventional assumptions, the O2 released during plant photosynthesis isn't sourced from the CO2 input. Instead, the released O2 originates from the H2O input.
So, the plants get their mass from everywhere. I can get that, but any idea how much, ratio-wise, comes from the pond water. I guess that I am trying to generate an idea of how much plant-life is needed to reduce "X" amount of nutrients. IF, for example, it takes 1000 pounds of plants to "suck up" 5 pound of nutrients from the pond...why bother?! My back does not have it in it.
As referenced by Vortex, a plant's live-weight mass is largely comprised of water. When assessing or quantifying a plant's nutrient reduction efficiency, dry-mass (after desiccation) is the measure upon which to focus.
