THE RELATION BETWEEN BACTERIOPLANKTON AND PHYTOPLANKTON PRODUCTION IN THE 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 the coastal and open mid Adriatic Sea. Bacterial production constituted significant percentages of phytoplankton production at both sites. Bacterioplankton production amounted to, on average, 9 to 28% of phytoplankton production in the coastal sea upper layers, and 10 to 40% in the open sea. On some occasions, bacterioplankton production exceeded phytoplankton production. This occurred during the summer when bacterioplankton production was maximal and the phytoplankton bloom was declining in the surface as well as in deeper layers where primary production was very low due to poor light penetration. Our results suggest that bacterial biomass could be a significant source of carbon for higher trophic levels in the Adriatic, particularly in the oligotrophic open area.