RESUMO
Harmful Phaeocystis blooms disrupt seawater recreation and pose serious challenges to aquatic animals. The growth performance, phenotypic traits, and antioxidant responses of Brachionus plicatilis Müller to different proportions of Phaeocystis globosa were evaluated. B. plicatilis rotifers were exposed to cultures with Chlorella sp. and P. globosa alone and in mixtures of these two algae with proportions of 25%, 50%, and 75%. The total proportions of the two algae were maintained at 100%. Results showed that P. globosa inhibited the rotifer net reproduction rate, intrinsic growth rate, and finite rate of increase (P < 0.01). It induced the formation of defense phenotypic traits in terms of the increased posterolateral spine length and the reduced body length, swimming speed, and grazing rate of B. plicatilis (P < 0.001). Superoxide dismutase and catalase activities decreased, but the reactive oxygen species levels increased as the proportions of P. globosa increased (P < 0.01). The mixture of 50% Chlorella and 50% Phaeocystis positively affected the glutathione content, glutathione peroxidase activity, and generation time of rotifers (P < 0.01). Although P. globosa released toxicants with harmful effects on the growth performance of B. plicatilis, rotifers changed their antioxidant defense system and formed defense phenotypic traits in response to eutrophic conditions.
