Dormancy as a Signature of Microbial Community Disassembly during Hydrological Collapse in a Desert Oasis.

The Cuatro Ciénegas Basin (CCB) in Coahuila, Mexico, a Ramsar Wetland, is characterized by a unique network of pozas renowned for microbial diversity. Among them, the Churince hydrological system epitomized a delicate balance of endemic species, stable water regimes, and complex microbial assemblages. Over the last five decades, however, the Churince underwent catastrophic ~ 99% water loss, driven by intensive agricultural extraction. This desiccation caused hydrological collapse and reshaped microbial physiology. Longitudinal records from 2007 to 2025, combining satellite imagery, piezometer data, and field observations, documented progressive declines beginning in 2011 and culminating in complete desiccation by 2019. To track microbial responses, we employed a cultivation-based approach distinguishing vegetative cells from dormant spores, quantified as heat-resistant CFU, enabling direct physiological assessment of metabolic activity versus dormancy. As water diminished, spore abundance increased relative to vegetative forms, revealing a shift toward dormancy as a survival strategy under extreme desiccation. Complementary mesocosm experiments showed that reduced diversity further enriched for spores, illustrating how loss of community complexity accelerated dormancy and erosion of active assemblages. Together, these results demonstrated that habitat loss triggered microbial community change, which we frame as a microbial extension of the ecological concept of community disassembly. By combining two decades of hydrological evidence with microbial physiology, this study fills a critical gap in understanding how wetland drying selects for microbial dormancy. These findings underscore the urgent need for sustainable agriculture and integrated water management to preserve biodiversity and ecosystem function in threatened wetlands worldwide.