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Abstract
A synthesis of field data carried out in the Mediterranean Sea are presented, aimed at contributing to the knowledge of three prokaryotic-mediated processes and their implications on the Carbon cycle. The distribution of exoenzymatic activities, secondary production and respiration rates was studied together with the prokaryotic abundances. Particular attention was paid to the meso- and bathypelagic layers which play an important role in the Mediterranean carbon cycle. The study is noteworthy because of its large spatial scale spanning the entire Mediterranean Sea over 4 years. In addition, two Atlantic stations in front of the Gibraltar Strait were investigated. The longitudinal distribution of prokaryotic activities and abundance along the MED showed different trends along the depth-layers. In particular, higher exoenzymatic rates were detected in the Eastern basin compared to the Western one; carbon respiration rate showed patterns variable with the sampling periods in the epipelagic and bathypelagic layers, while a consistent Westwards decreasing trend at the mesopelagic layers occurred. Specific enzyme activities per cell showed high values in the deepest layers for leucine aminopeptidase. Comparison with Carbon respiration rate data collected before the 2000s showed changing patterns of microbial heterotrophic processes in the Mediterranean Sea.
Acknowledgments
We want to thank M. Dibitetto (CNR–DCSPI), M. Astraldi (CNR–ISMAR, La Spezia), L. Giuliano (CIESM), E. De Domenico (CONISMA–University of Messina) for allowing us to participate in MedGOOS, CIESM SUB 1/SUB 2, MedBio, FIRB-MIUR Cruises. The research was funded by: FIRB-MIUR Project ‘Biodiversity and organization of the communities in different environmental context’ and partially by University of Messina (PRA 2003 and 2004); by MedGOOS (Global Ocean Observing System for the Mediterranean), by VECTOR Project (VulnErabilità delle Coste e degli ecosistemi marini italiani ai cambiamenti climaTici e loro ruolO nei cicli del caRbonio mediterraneo) in the frame of the CARPEL–TRANSMED cruises. Again many thanks to the following colleagues of IAMC-UOS.ME: F. Soraci, F. Raffa and A. Cosenza for their valuable technical assistance and F. Genovese, P. De Francesco, M. Furnari for their prompt and friendly help in logistic support.