VARIABILITY OF ELECTRON TRANSPORT SYSTEM ACTIVITY IN THE WATER MASSES OF SOUTHERN ADRIATIC PIT IN THE PERIOD 1993-2008.

This study presents the temporal variability of respiratory rates assayed by microbial Electron Transport System activity (ETSa) in a deep convection site of Eastern Mediterranean Sea (the Southern Adriatic Pit). Our data, collected from 1993 to 2008 during several cruises in the context of various scientific projects (AM3, MATER, SINAPSI, VECTOR, SESAME), shed light on the seasonal variability of microbial respiration. Moreover, the binding of the oxidation of organic matter in the deep water with the formation or non-formation of deep water during these 15 years in the study area was investigated. In fact, in the years in which the deep water formation was documented, a supply of preformed C transported was observed within the deep water masses. Such C supply was reflected in a high oxidation of organic matter in the deep waters, that was not justified by the normal sink of organic matter conveyed by the Biological Pump. These findings are the starting point for the ADREX experiment in the frame of PERSEUS project.