EVIDENCE FOR ANAEROBIC BACTERIAL PROCESSES IN THE WATER COLUMN - DENITRIFICATION AND DISSIMILATORY NITRATE AMMONIFICATION IN THE NORTHWESTERN MEDITERRANEAN SEA

Bacterial anaerobic processes in particles in the water column of the northwestern Mediterranean Sea were investigated. Particles concentrat ed on a filter were incubated in oxygen-free sterile sea water. Result s demonstrated that there is a weak but almost constant expression of bacterial nitrate-dissimilation processes [denitrification and dissimi latory nitrate ammonification (DAP)] associated with particles. Both a ctivities were found from 30 m down to 615 m depth in coastal water of f Marseilles, France, in autumn and from 100 to 700 m depth in spring and autumn in coastal water off Nice. In summer when oligotrophic cond itions occurred, both activities were just detectable. In the other se asons, denitrification was the main process of nitrate dissimilation, with peak activity in autumn. This activity was associated with both l arge and small particles. In contrast, nitrate ammonification was asso ciated only with large particles that were located in the upper layer in autumn and spread throughout the water column in spring.