Enhancement of community productivity and water‑air‑interface greenhouse gas uptake by plant growth-promoting rhizobacteria inoculation in submerged macrophyte communities.

Enhancing lake carbon sequestration is a vital nature-based climate solution, whereas the degradation of submerged macrophytes seriously threatens this potential. Plant growth-promoting rhizobacteria (PGPR) are capable of accelerating the stress recovery of submerged macrophytes and enhancing the greenhouse gas (GHG) absorption for single-species macrophyte. Here, four-species submerged macrophyte communities (Potamogeton wrightii, Myriophyllum spicatum, Vallisneria denseserrulata, and Hydrilla verticillata) were established under simulated underwater low-light conditions and inoculated with a high-efficiency PGPR consortium (Pseudomonas vancouverensis, Pseudomonas plecoglossicida, and Enterobacter ludwigii). Treatments included inoculation applied to 0, 1, 2, 3, and 4 species treatments, respectively. Over an annual timescale, inoculation of all four plant species resulted in the highest monthly biomass increment (19 % above control) and increased the system's CO2-equivalent sink by 336 %, yielding the lowest global warming potential (GWP, -7939.91 ± 96.73 g CO2-eq m-2 yr-1). These results indicate a strong synergy between growth promotion and carbon sink enhancement. CO2-equivalent uptake during the overwintering stage significantly exceeded that during the rapid growth stage, likely because low temperatures suppress biological metabolic activities while simultaneously enhancing physicochemical absorption, thereby enhancing net CO2 sequestration. Methodologically, the conventional 1-hour morning sampling overestimated CO2-equivalent fluxes by 3.54 to 6.28 times compared to 24-hour continuous monitoring. These findings demonstrate the dual capacity of PGPR to boost macrophyte productivity and GHG sink functions under low-light stress. The results underscore the necessity of 24-hour continuous sampling for accurate GHG flux assessment in aquatic ecosystems and provide a scientific basis for developing low-carbon lake restoration and carbon-neutral management strategies.