Li-Gong Zou1, Yu-Feng Yang1 & Hong-Ye Li1
1College of Life Science and Technology, Jinan University, Guangzhou 510632, China
Correspondence: Li-gong Zou. zlg007@126.com
Allelopathy has been proposed as a key mechanism mediating macroalgae–microalgal interactions. In this study, we examined the effects of leaching solution extracts from the marine macroalga Gracilaria salicornia on microalga Phaeodactylum tricornutum under various exposure conditions. G. salicornia inhibits growth and biomass accumulation of P. tricornutum in a dose-dependent manner. Gracilaria has a markedly impacts on photosynthesis efficiency of P. tricornutum. Cell mortality of P. tricornutum increased considerably with increasing concentrations of Gracilaria extracts. Further, the lipid content declined continuously with increasing exposure time, with the maximum decrease up to 93.6%. Reactive oxygen species (ROS) was also found to mediate the allelopathy, which mostly destroyed membranous structures of organelle, and broke cellular homeostasis, further suppressed the resilience of cell viability. The results indicate that macroalgal allelopathy effects are highly dependent on macroalgal dose. Oxidative stress caused by ROS mediates the allelopathy. Endomembrane system injury disrupts cellular homeostasis which potentially affects photosynthesis and metabolic network, thereby limiting the growth of P. tricornutum.