Unraveling the pivotal role of microbial specialists in adapting to divergent nutrient stresses in lakes

Lakes are widely confronted with the threat of nutrient accumulation, yet less well understood is how microbial communities cope with different nutrient-level stresses in lake systems. Herein, we investigated the survival strategies of microbial communities in the three lakes with distinct nutrient levels and physicochemical conditions, i.e., the Dianchi Lake, the Erhai Lake, and the Qilu Lake, situated in the Yunnan-Guizhou Plateau of China. Our findings challenge the notion that microbial diversity and network complexity are desired reflections of nutrient levels or other physicochemical conditions across lake systems. Rather, we uncovered that specialist species, sensitive to environmental fluctuations, emerged as key indicators of the unique ecological conditions in each lake. Remarkably, microbial specialists emerged as pivotal players in sustaining community complexity and ecological functioning. Moreover, we illuminated that nutrients (TP, NH₄⁺-N, and NO₂⁻-N) and other physicochemical variables (mainly EC, TDS, and DO) jointly regulated the deterministic processes underlying microbial assembly across the three lakes, respectively towards heterogeneous selection and homogeneous selection. Overall, these findings provide novel insights into specialists in response to varying environmental disturbances within lake ecosystems, which can be of great significance for the application of specialists in maintaining lake biodiversity and ecological function.