Benthic denitrification and organic matter mineralization in intertidal flats of an enclosed coastal inlet, Ago Bay, Japan

Denitrification (as N2 flux) and organic matter mineralization (as O2 uptake) were simultaneously measured in the same set of core sediments from a natural sandy and a constructed muddy tidal flat of Ago Bay, Japan. Denitrification rates at both tidal flats fluctuated between ca. 2-20 μmol N2 m−2 h−1 without showing a clear seasonal pattern, and appeared to be substrate limited as NO3- enrichment (final concentration ca. 225 μM) caused prompt and similar enhancements of ca. 10-folds. Organic matter mineralization rates were markedly higher at constructed muddy flat compared to those of natural sandy flat, especially in summer, and exhibited pronounced temperature dependent (p < 0.01) seasonality for both tidal flats. O2 uptake rates were generally ca. 2-3 order greater than respective denitrification rates indicating dominance of mineralization processes over N2 losses.