Dissolved organic matter characteristics and nitrogen transformation rates in sediments of Pojo Bay, Finland

However, gradual mixing of fresh and saline water masses alters the availability nitrate and bioavailable carbon from near-shore to offshore, which may alter the function of "coastal filter". Here, we combine stable isotope analysis, N2O measurements and organic carbon characterization, and show that a significant amount of the N removed in estuary is released as greenhouse gas nitrous oxide (N2O), while archipelago areas are characterized by efficient recycling of N in coastal Baltic Sea, challenging the current understanding on role of these regions as filters of land-to-sea transfer of N.