engleski

Kaštela Bay and Stončica

Long-term fluctuation of bacteria and heterotrophic nanoplankton in the Adriatic Sea was studied. In coastal area, analysis of monthly means showed higher bacterial abundance throughout the wormer part of the year (May – October), with maximum mean value in October. Bacterial production showed higher mean value in March, and during summer (June – August). Heterotrophic nanoplankton (HNAN) showed marked summer maxima (June – August). Annual mean values showed statistically significant decreasing trends for all parameters, and these trends were more expressed during the wormer part of the year. These results are typical for the Croatian coastal Adriatic Sea which is under the process of oligotrophication during last decade. In the open sea, bacterial abundance and production showed higher values during the colder part of the year (December – February), with May maximum in bacterial production. Higher values of Heterotrophic nanoplankton (HNAN) abundance were found in spring (March – May), summer (July – August) and autumn (October). Annual means showed strong negative trend in bacterial production, and decreasing tendency in bacterial and HNAN abundance which is not statistically significant (P>0.05). Annual means of studied parameters showed several maxima and minima, some of them coinciding with some specific meteorological and hydrographical conditions (for example, 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, Bacterial production, Heterotrophic nanoplankton, Adriatic Sea

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