The kinetics of PO4—P and NO3—N uptake by Ulva prolifera

Abstract:

This paper mainly studied the uptake kinetics of NO₃—N and PO₄—P by Ulva prolifera in laboratory. The results showed that: (1) The higher the density of algae, the higher removal efficiency on the NO₃—N and PO₄—P in Ulva prolifera is. When the algae density is 10g/L, the concentration of PO₄—P in the culture medium are 94.27 percent lower than the starting time after 6 h; (2) The absorption rates of U. prolifera on nitrogen and phosphorus can be described by the MihcaelsiMenton equation (R2> 0.95); The absorption rates of U. prolifera on nitrogen and phosphorus had a relationship with their contents in the medium. With increasing of NO₃ —N and PO₄—P concentrations in the medium, the absorption rates are at higher levels and eventually leveling off balance. When the concentrations of PO₄—P rise to 20 μmol/L, or NO₃—N rise to 45 μmol/L in the medium, the uptake rates both reached the maximum. (3) With the extension of time, there were three different stages for U. prolifera uptaking NO₃—N and PO₄—P: the first 60 min ,called rapid uptake stage , within the the maximum uptake rate of 250.43 and 5.82 μmol/(gh), respectively, while in the subsequent 60-320 min the changes of uptake rates are relatively slow, and with the maximum absorption rate of 155.12 and 2.36 μmol/(gh), respectively. After 320-720 min, the uptake rates are close to flat, the maximum absorption rates of U. prolifera are 36.72 and 1.32 μmol/(gh), respectively. This study provided a theoretical basis for exploring the mechanism of U. prolifera outbreak and its marine ecological effects assessment.