No abstract

The ecological amplitude of nitrate of algae can be defined in terms of the range of nitrate conditions under which it is able to grow and reproduce. It usually consists of the optimum nitrate concentrations, the optimum growth range of nitrate concentrations and the tolerance range of nitrate concentrations. In order to calculate the ecological amplitude of nitrate during algal growth, the relationship between nitrate concentration and the cell density, and that between nitrate concentration and maximum specific growth rate of Alexandrium tamarense were analyzed at three different fixed initial phosphate concentrations [0. 48 滋mol / L ( low鄄P) , 0. 97 滋mol / L ( medium鄄P) and 1. 45 滋mol / L ( high鄄P) ] in laboratory cultures. The experiments were carried out in three independent batch cultures respectively. The cell density and the specific growth rate were assessed as the response parameters. A nitrate tolerance model of algal growth was established following Shelford忆s law of tolerance and using the experimental data. The results show that: (1) in low鄄P, medium鄄P, and high鄄P鄄grown cultures, both the cell density and the specific growth rate of A. tamarense increased when C N 臆 C Nopt and then decreased when C N 逸 C Nopt ; (2) the nitrate tolerance model was consistent with Shelford忆s law of tolerance; (3) the optimum nitrate concentrations in low鄄P, medium鄄P, and high鄄P grown cultures were 30. 36, 62.