We characterize community level uptake kinetics of GBT and homarine using uptake kinetics experiments, identify competitive inhibitors to homarine uptake in marine microbial communities using uptake competition experiments, and quantify the fluxes of these compounds through the DOM pool by combining uptake kinetics with dissolved metabolomics measurements. This dataset provides the raw targeted mass spectrometry data collected for this experiment for targeted uptake measurments (TQS_Uptake_Data.xlsx), in situ particulate measurments (QE_Particualte_GBT_Homarine_Data.xlsx), and in situ dissolved measurements (QE_Dissolved_Metabolomics_Data.xlsx). Meta data is provided in Metadata.docx. All data and code used in these analyses and data visualizations are available on GitHub at https://github.com/jssacks/Marine_Betaine_Flux.