Tracking\nthe Changes of DOM Composition, Transformation,\nand Cycling Mechanism Triggered by the Priming Effect: Insights from\nIncubation Experiments

The priming effect (PE) is recognized\nas an important mechanism\ninfluencing organic matter transformation in aquatic systems. The\nland-ocean aquatic continuum (LOAC) has received large quantities\nof dissolved organic matter (DOM) from various sources, which is an\nideal interface for PE research. Here, we investigated the PE process\nby utilizing such a coastal environment to explore the turnover of\nDOM in the LOAC system. Suwannee River natural organic matter was\nselected as the background, and various external environmental samples\nwere introduced to track the changes of organic carbon. The PE process\ntogether with the variations of DOM sources, compositions, and structures\nwas characterized. Generally, river and estuary environments exhibited\na positive PE, while the offshore zone showed a negative effect. Additionally,\nnutrients, salinity, and DOM composition all contributed to the PE.\nAfter the incubation, the feature of carbon sources transferred from\nterrestrial to autochthonous. The carbonyl and alcohol functional\ngroups significantly decomposed, while the methyl and methylene groups\nincreased and heteroatoms further accelerated the PE process. The\ndata also shows that special parameters and molecular markers can\nbe utilized to track the carbon response to the PE. This research\nindicates that the change of carbon flux and the imbalance of its\nbudget in aquatic systems could be partially explained from the perspective\nof the PE.