Deciphering linkages between microbial communities and priming effects in lake sediments with different salinity

Priming effects (PEs) and their associated microbial drivers are not well studied in lake sediments. Here, we investigated PEs and underlying potential microbial drivers in the sediments of lakes on the Qinghai-Tibetan Plateau (QTP). Sediments were collected from three QTP lakes with different salinity, followed by microcosm construction and subsequent incubation at in-situ temperature. The sediment microcosms were amended with 13C-labeled glucose, on which PE intensities were evaluated in the incubations on the 7th and 42nd day. Positive PEs were observed in all the studied lake sediment microcosms. PE intensities exhibited significantly (P < 0.05) linear correlations with most of the measured physicochemical factors (e.g., salinity, sediment total nitrogen/phosphorus and ratios of carbon: nitrogen), and such linear correlations were inverse for the early (i.e., on the 7th day) and late (i.e., on the 42nd day) PEs. Prokaryotic and fungal community compositions significantly changed owing to glucose addition in the studied lake microcosms, suggesting that both prokaryotes and fungi may contribute to the observed PEs. Network analysis showed that the numbers of positive correlations between fungal taxa and other microorganisms increased with the enhancement of the late PE intensity, suggesting that fungi and associated co-metabolisms may play key roles in late PEs in this study. Collectively, this study gives new insights into PE intensity and underlying microbial drivers of PE in lake sediments, and such knowledge is of great importance to understanding organic matter mineralization in lake ecosystems.