Microbial diversity and functional profiles as a signature of land-sea and land-use dynamics in west African mangrove swamp rice production systems

Mangrove ecosystems and their associated microbial communities are critical reservoirs of global biodiversity and support essential ecological functions. Within these coastal landscapes, mangrove swamp rice production systems link food production to hydrological modification of mangrove-derived soils, whose microbiomes remain poorly characterized in West Africa. Here, we present the first metagenomic study of mangrove soils in West Africa, providing an integrated characterization of microbial community composition, structure, and functional potential across 29 plots spanning natural mangroves, active and abandoned rice fields, and adjacent terrestrial tropical forests along a land-sea and land-use gradient in Guinea-Bissau. Microbial differentiation reflected compositional reorganization and selective variation in functional potential rather than generalized diversity loss. Most alpha-diversity metrics did not differ, yet ecosystem type explained 55.3 % and 16.4 % of prokaryotic and fungal compositional variation, respectively. Although 96.9 % of prokaryotic and 44.8 % of fungal taxonomic features were shared across all ecosystems, 33 fungal features detected only in active and abandoned rice fields were consistent with a potential land-use legacy. However, incomplete fungal sampling and the cross-sectional design preclude temporal inference. Mangrove soils exhibited the clearest microbial signature, with Pseudomonadota dominance (41.7 %) and predicted sulfate respiration (8.7 % versus 0.1–1.3 % elsewhere) coinciding with higher electrical conductivity and available sulfur. This work advances our understanding of West African mangrove microbiomes and identifies microbial signatures with potential to inform future monitoring of natural, cultivated, and post-cultivation ecosystem states.