Media phosphorus was quantified using Hach PhosVer reagent and Hach method 8048. Briefly, samples were diluted in sterile filtered water 50-fold to a final volume of 10mL, ensuring that all glassware was free of residual phosphate with an acid wash. To each sample one sachet of PhosVer 3 was added and mixed by inversion for 15 seconds. Samples were incubated for 2 minutes at room temperature, then measured via UV-Vis spectrophotometer for absorbance at 880nm. Samples were quantified using a 4 point standard curve and discarded if outside the linear range. Samples were quantified within 8 minutes of reagent addition.