engleski

Variability in the bottom-up and top-down controls of bacteria on trophic and temporal scales in the middle Adriatic Sea

Variability in the bottom-up (BU) and top-down (TD) regulation of bacteria was analysed on trophic and temporal (seasonal and inter-annual) scales in the middle Adriatic Sea during one decade (1997-2006), using three empirical models. The analyses showed the tendency for bacteria to be TD controlled in oligotrophic open sea, and BU controlled in more eutrophic coastal sea. However, temporal variability in the BU and TD control was much stronger, and the periods of both strong BU and strong TD control were found at all studied stations, independently of their trophic status. Decomposition of time series was performed to identify seasonal and inter-annual changes in the relative importance of the BU and TD control of bacteria. At all stations, the BU control dominated during colder part of the year, whereas the TD control dominated during warmer part of the year. Non-seasonal fluctuations in relative importance of the BU and TD control of bacteria pointed to a few periods when one or another type of control was very strong. These periods coincided with some specific meteorological and hydrographical conditions (strong influence of North Adriatic Dense Water in 1997, strong Levantine Intermediate Water ingression in 2004 or extremely warm winter and the Po River runoff in 2000/01).

Bacteria; bottom-up; top-down; trophic scale; temporal scale; Adriatic Sea

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