Algal-bacterial synergy for saline-alkaline soil bioremediation: mechanisms, advances and challenges

Soil salinization severely threatens global agricultural sustainability and ecosystem stability, particularly in arid and semi-arid regions; conventional physical and chemical remediation approaches are constrained by high costs and potential ecological risks, making algal-bacterial bioremediation an eco-friendly alternative, yet the synergistic mechanisms of algal-bacterial consortia, their environmental dependence, and the long-term stability of exogenous inoculants in field environments remain poorly understood. Based on a systematic review of literature published from 2018 to 2025, this study synthesizes that saline-alkali soils contain indigenous halotolerant microbial communities with restricted functional diversity under long-term saline-alkali stress, algal-bacterial synergy achieves optimal remediation efficacy under moderate salinity and weak alkalinity driven by photosynthetic carbon input, nutrient mineralization, extracellular polymeric substance secretion, and pH buffering, and the field application of algal-bacterial consortia is hindered by the low colonization persistence of exogenous strains mainly caused by competition from indigenous microbiota and fluctuating environmental conditions. This review further emphasizes the importance of ecological compatibility, the preferential use of indigenous or locally adapted strains, and the integration of microbial inoculation with habitat improvement strategies, confirms that moderate salinity-alkalinity optimizes synergistic efficiency by promoting metabolic cross-feeding, shared stress resistance, and biofilm formation, and highlights the potential of synthetic algal-bacterial consortia and carrier-immobilized formulations to enhance the field stability and remediation outcomes of these microbial systems.