Effect of allelopathic potential from selected aquatic macrophytes on algal interaction in the polluted water

• Algal interaction is related to algae, aquatic macrophyte, and pollutants.
• Macrophyte allelopathy will modify algal interaction.
• Allelopathic macrophytes can enhance the negative feedback between algae.
• Allelochemicals shows stronger allelopathy than macrophyte exudates.
• Allelopathy in the aquatic macrophytes will control harmful algal bloom.

Pollutants and macrophyte allelopathy can drive the change of algal interactions in aquatic ecosystems. Eutrophication, Pb and Polychlorinated biphenyls could induce a positive interaction between two green algae or blue algae in the stationary and death phases, as well as a negative interaction between these algae in the lag and exponential phases. Similarly, the negative interaction between a green alga and a blue alga always occurred in whether polluted conditions or the control. These results demonstrate that alga species identify and life history stage influences if the interactions are negative or positive. In polluted water, macrophytes or their representative allelochemicals enhance the negative interaction, or weaken the positive interaction between two algae species. Allelochemicals displayed a stronger effect on algal interaction than macrophytes' exudates. The effect was synergistic in that increasing the number of macrophytes or allelochemicals increased their effect on alga species interactions. Overall, macrophytes can inhibit harmful algae by affecting algal interaction. The present study offers an alternative for treating harmful algal blooms.