Temporal and spatial variations in benthic nitrogen cycling in a temperate macro-tidal coastal ecosystem: Observation and modeling

We used field observations, laboratory measurements and a reactive transport model (RTM) to investigate temporal spatial variations in benthic nitrogen (N) cycling the eutrophic temperate macro-tidal Vilaine Bay (VB), France. A time series of flux pore-water profiles dissolved inorganic N (DIN: ammonium, nitrate, nitrite) organic (DON) was conducted at single station between April September 2015 (six times). investigation fluxes performed July 2016 this three other stations VB. All were accompanied by large panel physical, chemical biological descriptors water column. In 2015, ammonium monitoring varied 75 μmol m−2 h−1 spring less than 10 summer. The DON co-varied with fluxes, ranging from 100 zero summer 2016, phytoplankton bloom occurred as result reached higher values bottom hypoxia one measured station. Benthic nitrate nitrite −31 (towards sediments) 22 explained concentration nitrification rates. After fitting existing profiles, applied RTM correctly simulated DIN predicted that part deposited matter (OM) is remineralized aerobically sediment-water interface (SWI). overall results showed synthetic pattern VB, based on occurrence diatom blooms main source OM sediments. rapid decomposition material SWI releases amounts column rapidly consumes oxygen sediment surface. When occur summer, their can be followed hypoxia/anoxia water. are absent, weak mainly fed diffusion pore-water. By integrating present 3D ecological model, it should possible more accurately predict development