engleski

Deep water ventilation traced by Synechococcus cyanobacteria

Adriatic waters during the spring of 2006. The maximum abundance in early May was positioned at 800 m, being of order of the values referred for the surface waters in the Adriatic Sea. Both open-ocean convection (South Adriatic deep water generation) and shallow water intense cooling (North Adriatic dense water generation) were supposed to occur in winter of 2006 in the South Adriatic Pit and broad Northern Adriatic shelf, respectively. By using CTD, satellite and Synechoccocus abundance data during preconditioning and post-generation phases, these processes were successfully detected, explained and put in the context of the respective literature. The first process was responsible for bringing the cyanobacteria down to 600 m depth in the area of convection, and the second one triggered the downslope transport of the cyanobacteria to the very bottom of South Adriatic Pit. Also, the nature of the deep-convection process in the Adriatic, which lasts usually for a couple of days, enabled the estimation of Synechococcus loss rate characteristic time in the extremely hostile environment (no solar radiation), which is estimated to be of the order of one month. Last but not least, another important implication of this study is the persistence of phytoplankton at great depths and its relevance for the biogeochemical cycle.

deep water masses; biological tracer; Adriatic Sea

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