Multi‐species assemblages promote community recovery of submerged macrophytes and enhance the absorption of greenhouse gases across the water–air interface

Introduction Restoration of submerged macrophyte communities is critical for maintaining clear‐water states and enhancing carbon sequestration in shallow lakes. However, the restoration of submerged macrophytes often faces challenges such as low‐light stress and species simplification. Objectives We assessed how species assemblage influences community recovery of submerged macrophytes and greenhouse gas (GHG) fluxes under low‐light conditions. Methods We established single‐, three‐, and four‐species configurations of Vallisneria denseserrulata , Potamogeton wrightii , Hydrilla verticillata , and Myriophyllum spicatum under a low‐light treatment (10% of natural light intensity). Biomass, plant recovery from herbivory, GHG fluxes, and carbon sink capacity were measured. Notably, herbivory was caused by a sudden outbreak of Parapoynx diminutalis (late July–late September). By late September, plant biomass approached zero, marking the onset of the plant recovery phase. Results The four‐species assemblage consistently outperformed monoculture. The four‐species assemblage ( V. denseserrulata + P. wrightii + H. verticillata + M. spicatum ) achieved a total biomass of 9292.11 ± 1442.81 g/m 2 , 2.30 times the monoculture mean (4034.74 ± 740.63 g/m 2 ). Furthermore, its cumulative carbon sequestration reached −5.28 ± 0.48 kg CO 2 ‐eq/m 2 , 3.02 times the monoculture mean (−1.75 ± 0.17 kg CO 2 ‐eq/m 2 ). This enhancement arose from functional complementarity: M. spicatum and P. wrightii drove carbon dioxide uptake, and V. denseserrulata suppressed methane and nitrous oxide emissions at the community level. Moreover, H. verticillata and P. wrightii showed superior herbivory resistance in polycultures, with P. wrightii buffering grazing impacts on co‐occurring species. Conclusions Multi‐species assemblages enhanced both community recovery and GHG mitigation through functional complementarity and keystone species effects.