『Abstract
　Wetland ecosystems in agricultural areas often become progressively more isolated from main water bodies. Stagnation favors the accumulation of organic matter as the supply of electron acceptors with water renewal is limited. In this context it is expected that nitrogen recycling prevails over nitrogen dissipation. To test this hypothesis, denitrification rates, fluxes of dissolved oxygen (SOD), inorganic carbon (DIC) and nitrogen and sediment features were measured in winter and summer 2007 on 22 shallow riverine wetlands in the Po River Plain (Northern Italy). Fluxes were determined from incubations of intact cores by measurement of concentration changes or isotope pairing in the case of denitrification. Sampled sites were eutrophic to hypertrophic; 10 were connected and 12 were isolated from the adjacent rivers, resulting in large differences in nitrate concentrations in the water column (from ＜5 to 1,133 μM). Benthic metabolism and denitrification rates were investigated by two overarching factors: season and hydrological connectivity. SOD and DIC fluxes resulted in respiratory quotients greater than one at most sampling sites. Sediment respiration was coupled to both ammonium efflux, which increased from winter to summer, and nitrate consumption, with higher rates in river-connected wetlands. Denitrification rates measured in river-connected wetlands (35-1,888 μmol N m^-2 h^-1) were up to two orders of magnitude higher than rates measured in isolated wetlands (2-231 μmol N m^-2 h^-1), suggesting a strong regulation of the process by nitrate availability. These rates were also significantly higher in summer (9-1,888 μmol N m^-2 h^-1) than in winter (2-365 μmol N m^-2 h^-1). Denitrification supported by water column nitrate (Dw) accounted for 60-100％ of total denitrification (Dtot); denitrification coupled to nitrification (DN) was probably controlled by limited oxygen availability within sediments. Denitrification efficiency, calculated as the ratio between N removal via denitrification and N regeneration, and the relative role of denitrification for organic matter oxidation, were high in connected wetlands but not in isolated sites. This study confirms the importance of restoring hydraulic connectivity of riverine wetlands for the maintenance of important biogeochemical functions such as nitrogen removal via denitrification.

Keywords: Denitrification; Benthic respiration; N-regeneration; Hydrological connectivity; Riverine wetlands』

Introduction
Materials and methods
　Study area
　Sampling program
　Sediment characteristics
　Dissolved oxygen, inorganic carbon and nutrient flux measurements
　Denitrification measurements
　Statistical analyses
Results
　General features of water column and surface sediments
　Benthic processes
　Denitrification rates
Discussion
　Denitrification in shallow eutrophic wetlands compared to other ecosystems and methodological considerations
　Regulation of denitrification　Denitrification efficiency in shallow eutrophic wetland sediments: N sink or sources?
　Benthic respiration and denitrification in shallow eutrophic wetlands
Concluding remarks
Acknowledgements
References