Neoporphyra haitanensis is an important economic alga. A 3 × 2 factorial layout containing three nitrogen levels (1, 5, 10 mg L −1 ) and two phosphorus levels (1, 5 mg L −1 ) were designed to examine the effect of nitrogen and phosphorus levels on physiological responses of N. haitanensis conchocelis during growth phase (trial I) and development phase (trial II). In trial I, a higher phosphorus concentration inhibited the rela...