Algal shift from Chlorella vulgaris to Microcystis aeruginosa influenced the bioaccumulation and trophic transfer of polycyclic aromatic hydrocarbons in plankton food chain

Eutrophication has led to algal shift from Chlorophyta dominance to Cyanobacteria dominance in many aquatic systems, resulting in mismatch between phytoplankton and zooplankton. How algal shift affects the fate and risk of contaminants in aquatic food chains is largely unknown. We simulated algal shift by a controlled community-composition gradient from Chlorella vulgaris to Microcystis aeruginosa to investigate how it affected the bioaccumulation and trophic transfer of polycyclic aromatic hydrocarbons (PAHs) in the Algae - Daphnia magna food chain. Algal shift from C. vulgaris to M. aeruginosa enhanced the bioaccumulation of the PAHs by both algae and D. magna. The initial proportion of M. aeruginosa significantly affected their bioconcentration by algae and biomagnification in the food chain. The logarithmic biomagnification factor (log BMF) of the PAHs showed an increasing trend when the initial proportion of M. aeruginosa was less than 40%. The increase in the initial proportion of M. aeruginosa further inhibited the growth and feeding of the D. magna with severe oxidative stress, which reduced the log BMF when it was greater than 40%. Our results suggest algal shift from C. vulgaris to M. aeruginosa enhances the risk of PAHs in the plankton food chain, and the initial proportion of M. aeruginosa plays crucial roles in these processes. It advances the knowledge of the fate of hydrophobic organic contaminants in waters with blooms of M. aeruginosa.