How deep is our current knowledge of microbial metabolism in the Mediterranean Sea?

Thanks to the availability of new experimental tools, and dedicated research programs, recent years have been characterised by signifcant changes in the understanding of the role of the dark ocean in the global Earth system and its biogeochemical cycles. In this short note, the Author analyses critically current knowledge of microbial processes in deep waters, reviewing the status of the art of microbial studies concerning the Mediterranean Sea biogeochemistry. In particular, the paper focuses on the patterns of microbial enzymatic hydrolysis as a key process in organic matter transformation, also in the light of recent changes occurred in water masses circulation.