Effects of triazine herbicide terbutryn on physiological responses and gene expression in Alexandrium catenella

Herbicides enter the ocean through surface runoff and have become a serious pollution threat in the coastal areas. As photosynthetic inhibitors, triazine herbicides are more harmful to marine photosynthetic organisms, especially phytoplankton, than to marine animals. Herbicide pollution may also cause other environmental issues such as algal blooms by altering the structure of phytoplankton community and toxin production in bloom-forming species. To explore whether triazine herbicides will cause similar effects, we analyzed the effects of a common triazine herbicide pollutant, terbutryn, on the physiological responses and gene expression of Alexandrium catenella , a harmful algal bloom forming dinoflagellate. Our results show that A. catenella maintained a normal growth rate when exposed to terbutryn at the concentrations of 0.1 and 1 μg L −1 . Treatment with terbutryn at 10 μg L −1 significantly reduced the growth rate by inhibiting photosynthesis in A. catenella , which may also affect the repair of photosystem II by repressing the expression of the D1 protein gene. Exposure to terbutryn at 1 μg L −1 also impacted the photosystem II, but no changes were observed on the maximum relative electron transport rate of photosynthesis. Additionally, expression of genes involved in saxitoxin was also analyzed in this study, which were not affected by the terbutryn treatment. Our study provides critical information about the potential threat of a herbicide in affecting a harmful algal bloom species.