The variation of photoperiod affects the photosynthesis of primary producer algae in the ocean, leading to fluctuations in algal abundance. The changes in photoperiod and algal abundance may have complex integrated effects on primary consumer herbivorous zooplankton. Therefore, in this study, we exposed two clones of rotifer Brachionus plicatilis to the combinations of five photoperiods (0 L: 24 D, 6 L: 18 D, 14 L: 10 D, 18 L: 6 D, and 24 L: 0 D) and three algal abundances (3 × 10