engleski

The existence of Synechococcus in deep water of Adriatic Sea

The picoplanktonic cyanobacteria Synechococcus represent an important part of the total photosynthetic biomass in the oceans. This obligate autotroph often dominates under oligotrophic conditions in warm water systems and in environments non-limited by light. Synechococcus abundance usually fluctuates from 10-2 to 10-5 cell ml-1 through eutrophic zone both of coastal and open ocean waters. All the studies on Synechococcus were restricted to the upper ocean to the depths less than 200 m. Our study discovers the presence of these cyanobacteria in deep Adriatic layers down to 1000 m. Their maximum abundance was found at 800 m and the large values were found throughout the whole water column. After two months the concentrations decreased to near-zero levels due to hostile environmental conditions (lack of light). The deep abundance maximum has been associated to the fast ventilation and renewal of deep Adriatic waters with the surface waters. This also introduces a new role of Synechococcus as a tracer for dense water dynamics.

water masses; physical and biogeochemical interactions; phytoplankton; deep recirculations; Adriatic Sea

ASLO = American Society of Limnology and oceanography