Elimination of cyanobacteria and cyanobacterial microcystin with increase in heterogeneity

Cyanobacterial blooms and their corresponding toxins have resulted in the reduction of heterogeneity within aquatic ecosystems, and vice versa. Yet much remain to be known whether high heterogeneity can lead to effective elimination of cyanobacteria and microcystin (MC). In this work, by introducing biota (macrophyte and bivalve) and abiota (artificial substrate) to increase heterogeneity, cyanobacterial and MC elimination were enhanced. With increasing heterogeneity, the mean removal efficiencies of cyanobacteria increased from 58.86% to 79.11%. Correspondingly, the mean MC removal efficiencies enhanced from 42.38% to 74.16%. The biofilm was shown to be the most efficient for removing cyanobacteria and MC, whereas the bivalve was less efficient for cyanobacterial removal than the macrophyte and had no effect on MC removal. Furthermore, crustaceans were significantly enriched in all the heterogeneous systems; the introduced bivalve increased respiratory activity in the substrate biofilm. Conclusively, increasing heterogeneity appears to be a not only viable solution for improving the quality of water in protected sources but also potential criterion for restoring and managing aquatic ecosystems.