The TAPAS project (Degradation of Terrigenous Dissolved organic matter in Arctic coastal waters: the importance of priming effect and identification of microbial ActorS) aims to monitor the degradation of terrestrial dissolved organic matter (tDOM) from melting permafrost in the Arctic by microbial communities in the Mackenzie Delta (Canada). The second objective of this project is to describe changes in the structure and function of Arctic microbial communities following the addition of tDOM. A third objective is to study the priming effect hypothesis in the case of the addition of labile dissolved organic matter in the form of exudates from an Arctic diatom Chaetoceros neogracilis.