Abstract
Based on the hypothesis that phosphorus nutrient variation consists of linear trend and periodical fluctuation,
a mid and long-period variation model of phosphorus nutrient (PVM) is developed. The stepwise choice method
(SCM) is adopted to estimate model parameters, such as period parameters based on unequal time interval series.
The satisfactory results have been obtained by using the PVM model in fitting the observed data of phosphorous
nutrient and testing the phosphorus nutrient variation as a forecast measure. It is shown that the mean value of
phosphate increase during the mid and long-period variation has been kept at a level of minute increase at survey
station E (123°E, 30°N), and that amual seasonal change is the main factor affecting the variation of phosphate
concentration. The variation of phosphate may have a significant influence on marine primary production and
ecosystem balance in the sea area.
