Determination of structure and functioning of the benthic community, pools and fluxes of N-compounds across sediment-water interface on the Concepcion shelf.

Determination of the structure and functioning of the benthic community, and pools and fluxes of N-compounds (ammonia, nitrate, nitrite) across the sediment-water interface in relation to local physical forcing, oxygen minimum, biological production cycles and sediment characteristics on the Concepcion shelf. 10 one-day oceanographic cruises were undertaken. These provided an adequate temporal resolution at the seasonal scale during the three years of the programme, as well as an adequate spatial scale that includes the bay of Concepcion and the adjacent shelf.

The study period coincided witht he onset and end of the 1997-98 El Nino. Several important chemical parameters and processes were measured and studied in order to estabish their contribution to organic mineralization and the potential effect on meiobenthic and macrobenthic communites. Chemical parameters in the water column (temperature, salinity, nutrient, oxygen) and in sediments (i.e. total organic carbon, total nitrogen, Chl-a redox, H2S, Fe2O, Mn4+, NO3-, NO2-, NH4+ pool sizes) were studied.