Allelopathy and underlying mechanism of Chlorella pyrenoidosa on the bloom-causing dinoflagellate Heterocapsa bohaiensis

The dinoflagellates Heterocapsa bohaiensis caused harmful algal blooms (HABs) resulting in severe economic losses in the coastal areas of the Bohai Sea, China. A previous study revealed that the local species Chlorella pyrenoidosa, which coexists with H. bohaiensis in coastal areas, was shown to significantly inhibit H. bohaiensis. Here, we studied the physiological changes and underlying mechanisms responsible for the allelopathy of C. pyrenoidosa on H. bohaiensis. Single-cell gel electrophoresis (SCGE) and quantitative real time PCR (RT-qPCR) were used to analyze the gene-toxicity of H. bohaiensis by C. pyrenoidosa. The results showed that C. pyrenoidosa allelopathy caused growth inhibition, oxidative stress, and DNA damage in H. bohaiensis, concomitant with an up-regulation of the SSU rRNA gene expression. The concentration of C. pyrenoidosa filtrate and oxidative stress positively correlated with genotoxicity in H. bohaiensis. Overall, our data provide valuable insights into the allelopathic interactions between these two algal species, highlighting the underlying mechanisms involved. C. pyrenoidosa allelopathy has the potential to be an effective and environmentally friendly method for controlling HABs caused by H. bohaiensis. Furthermore, our study has broader implications for sustainable water management, potentially informing future environmental policies aimed at mitigating the impacts of HABs.