Nitrous oxide (N₂O), a potent greenhouse gas, is released from coastal seas & estuaries, yet we don't fully understand how it is formed and consumed. In this study we collected water from several sites in the central Baltic Sea. N₂O came from ammonia in oxic waters. Deep waters with low to no oxygen noted more active N₂O cycling. The seafloor was a source in some areas. Typically N₂O is produced by bacteria, but our results indicate possibility of other players like fungi or chemical reactions.