The dissolved organic matter (DOM) pool and microbial communities are highly diverse in the aquatic environment, and their interactions play critical roles in regulating biogeochemical cycles. Heterotrophic bacteria are the important conduit for shaping the marine DOM pool via assimilation, transformation and release of organic molecules. Meanwhile the changes in bioavailable organic substrates can also affect the composition of bacterial community. Both microbial communities and organic substrates could influence the microbial produced DOM, and the experiments reveal that the microbial complexity was more important than the substrate in shaping the molecular composition of DOM. Further, the DOM composition played a larger role in shaping the microbial compositions than the concentrations of DOM and inorganic nutrients. The co-occurrence network analysis revealed that complex substrates resulted in higher molecular diversity of the microbial produced DOM, sustained a higher microbial diversity, and maintained a more diverse association between microbial communities and DOM molecules. In addition, the chemical composition of microbial produced DOM demonstrated that CHO, CHON and CHOS containing molecules were enriched in the glucose, GBT and DMSP experiments, respectively. The spatiotemporal signatures of microbial communities and DOM composition suggested microorganisms likely transformed the DOM from a relatively high (>400 Da) to a low (<400 Da) molecular weight, corresponding to an apparent increase in overall aromaticity. K- and r-strategists exhibited different correlations with two-size categories of DOM molecules owing to their different lifestyles and responses to environmental nutrient conditions. A comparison of the environmental variables and DOM composition with the microbial communities showed that the environmental/DOM variations played a more important role in shaping the microbial communities than vice versa. These results shed light on the interactions between microbial populations and DOM compounds at the molecular scale, improving our understanding of microbial roles in marine biogeochemical cycles.

Primary Presenter: Qiang Zheng, Xiamen University (zhengqiang@xmu.edu.cn)

Authors:

Qi Chen, Xiamen University  ()

Jinxin Xu, Xiamen University,  ()

Christian Lønborg, Aarhus University  ()

Chen He, China University of Petroleum  ()

Quan Shi, China University of Petroleum  ()

Nianzhi Jiao, Xiamen University  ()

Yu Wang, Xiamen University,  ()