Attività e biomasse microbiche nelle acque superficiali del mar Ionio.

The aim of the study was to elucidate the microbial processes related to C and P biogeochemical cycles which occur at the surface layer (5-100 m) of the Ionian Sea during late autumn period. Two successive steps, concerning respectively the enzymatic hydrolysis of proteins, polysaccharides and organic phosphates and the incorporation of the released monomers into new microbial biomass were investigated, together with the abundance and biomass of total bacterioplankton and picophytoplankton and measurement of chlorophyll-a content as an index of phytoplankton biomass. Three main hydrological areas (Central Eastern -ICOr, Central- IC and Central-Western-Sicily Channel -ICOc-CS) with distinctive characteristics were identified by the analysis of 6 microbiological variables. ICOc-CS area was characterised by the highest values of microbial activity (production and decomposition) and consumption of inorganic phosphorus (Pi). IC area showed high potential mineralisation rates of organic phosphates and glycosides, while low total bacterioplankton and picophytoplankton abundances were found. In IC and ICOr areas, the high values of potentially mineralised Pi: consumed Pi ratio (59 and 250 respectively) provide the supply of Pi for further productive processes.