The Arctic is severely impacted by global warming, leading to drastic changes including marine ecosystems. Increased input of glacial and sea-ice meltwater enhances stratification, potentially altering primary production and prokaryotic degradation processes that drive the carbon cycling in Arctic waters. To better understand prokaryotic production (both heterotrophic and autotrophic) and organic matter degradation, seawater samples were collected during two field campaigns: one along inshore-offshore transects in West Greenland in 2021, and another at fjord stations off East Greenland in 2022. Concentrations of dissolved total hydrolysable amino acids (DTHAA) showed distinct differences between fjord and coastal waters, reflecting different degradation states as revealed by the Dauwe degradation index (DI; Dauwe et al., 1999). Depth-dependent DIs for dissolved free amino acids (DFAA) were observed in the waters off West Greenland. Notably, the relative abundance of Euryarchaeota was high at the East Greenland stations (up to ~4% of total prokaryotes) and correlated with DFAA concentrations, suggesting a potential role of these microbes in organic matter, particularly protein degradation. These findings highlight region-specific productivity and microbially-driven organic matter degradation across coastal Greenland waters, providing insights into biogeochemical processes in the rapidly changing coastal Arctic Ocean.

prokaryotic production,amino acids,Arctic Ocean