THE RELATION BETWEEN BACTERIOPLANKTON AND PHYTOPLANKTON PRODUCTION INTHE MID ADRIATIC SEA

The ratio of bacterioplankton: phytoplankton production was studied on a monthly basis from January 1980 to September 1982 in the area of th e coastal and open mid Adriatic Sea. Bacterial production constituted significant percentages of phytoplankton production at both sites. Bac terioplankton production amounted to, on average, 9 to 28% of phytopla nkton production in the coastal sea upper layers, and 10 to 40% in the open sea. On some occasions, bacterioplankton production exceeded phy toplankton production. This occurred during the summer when bacteriopl ankton production was maximal and the phytoplankton bloom was declinin g in the surface as well as in deeper layers where primary production was very low due to poor light penetration. Our results suggest that b acterial biomass could be a significant source of carbon for higher tr ophic levels in the Adriatic, particularly in the oligotrophic open ar ea.