Allelopathy appraisal of worm metabolites in the synergistic effect between Limnodrilus hoffmeisteri and Potamogeton malaianus on algal suppression

In Chinese Lake Taihu, the algal quantity was significantly larger in summer than late spring ( p  < 0.01). In summer, compared with the dredged area including neither zoobenthos nor submerged macrophytes, the algal biomass and density were significantly lower in the area filled with the submerged macrophytes. Interestingly, the minimum algal bloom was observed in the combined area containing submerged macrophytes and zoobenthos, which was due to the synergistic interaction between the zoobenthos and the macrophytes. The metabolite extracts from the numerically dominant zoobenthos Limnodrilus hoffmeisteri had significant algal inhibitory effects of Microcystis aeruginosa, and displayed stimulatory effects on seed germination, seedling growth, and peroxidase activity of the prevalent submerged macrophyte Potamogeton malaianus. 27 active compounds in the worm metabolites were identified by gas chromatography-mass spectrometry (GC-MS). Among these compounds three chemicals arachidonic acid, eicosapentaenoic acid, and linoleic acid with concentrations of 13.92 ± 1.11, 10.57 ± 2.52, 2.75 ± 0.73 mg/kg dry weight, respectively, were confirmed as the typical allelochemicals with algal inhibition potential. In short, the metabolites allelopathy of L. hoffmeisteri can form and assist the synergistic effect between L. hoffmeisteri and P. malaianus on algal suppression. Thus, it is feasible to simultaneously restore submerged macrophytes and zoobenthos community in the disturbed eutrophic lakes for removing harmful algae.