Seasonal dynamics and interaction of shallow groundwater geochemical properties and microbial community patterns

Characterizing the temporal variation of microbial community is essential to better understand the biogeochemical cycles in groundwater systems. So far, the roles of microbial metabolisms in affecting the seasonal variation of shallow groundwater biogeochemistry remains largely unknown. In this study, shallow groundwater was sampled during rainy season (RS) and dry season (DS) at Yuncheng Basin, a semi-arid region in northern China. Based on results of hydrogeochemical, environmental isotopic (& delta;18O, & delta;2H and & delta;13C) and high-throughput sequencing analysis, we found that 1) the seasonal variation of groundwater geochemistry is closely related to the stronger evaporation, mineral dissolution, and anthropogenic activities in DS and enhanced cation exchange and stronger recharge in RS; 2) the seasonal dynamics of microbial community were mostly driven by groundwater temperature (T) and total organic carbon (TOC); 3) potential functional consequences indicated stronger microbial carbon fixation and denitrification in RS; 4) the microbial contribution to SO42 in ground water may increase when gypsum dissolution was weaker while sulfur oxidation was stronger during RS. Our findings suggest that the seasonal variation of microbial metabolisms play important roles in the dynamic characteristics of