Duckweed growth as a function of nitrogen and phosphorus availability
Duckweed, Lemna minor, has the ability to fundamentally alter pond composition through it surface cover and interactions with nutrients in the system. Total surface cover create dark, anoxic conditions, leading to duckweed dominance and soil nutrient release. Duckweed takes up nutrients directly through its roots and tissues and benefits from high phosphorus availability in water. Using greenhouse conditions, the growth of duckweed as a result of varying phosphorus and nitrogen conditions was measured across 10 weeks using spiked artificial pond water. At the end of the growth period, phosphorus analyses were done on the water and plant tissue. Relative growth rates of duckweed tissue were only significantly affected by nitrogen levels, with a slight phosphorus interaction where higher levels in one nutrient offset a deficiency in the other. In measurements of water and tissue phosphorus content after the growth period, only starting phosphorus conditions were significant. The uptake of soluble reactive phosphorus (SRP) from the water into duckweed tissue was observed more at higher phosphorus conditions, indicating a luxury uptake of nutrients by the duckweed dependent on environmental conditions. This project worked to parse out the complex interactions between nutrients in water systems as a predictor for duckweed growth, and an attempt to characterize the interactions between water and duckweed nutrient compositions.