Epiplanktonske zajednice u južnom Jadranu: višestruke trofičke razine na transektima jug – sjever i obala-otvoreno more

The epiplankton community was investigated during Meduza cruises along south - north and offshore – inshore transects in the middle and southern Adriatic in spring 2002. The diel and vertical distribution of heterotrophic bacteria, phytoplankton pigment composition, micro- and mesozooplankton were assessed. At most stations we observed a thermocline at approximately 20 m and a prominent chlorophyll a peak at about 70 m depth. The integrated phytoplankton and bacterial biomass were lower at the station in the central part of the southern Adriatic, and increased gradually towards middle Adriatic and towards coastal stations. Vertical profiles of both bacterial abundance and production showed a distinct peak in the surface layer. Bacterial abundance was high also in the layer of the deep chlorophyll a maximum. Higher bacterial production was associated with elevated abundance of pico- and nanoplankton feeding zooplankton indicating that bacterial populations were generally controlled by predation.Istraživanje površinskih zajednica planktona obavljena su u proljeće 2002. godine tijekom “Meduza” krstarenja srednjim i južnim Jadranom na transektima “jug-sjever” i “obala-otvoreno more”. Utvrđena je dnevna vertikalna raspodjela heterotrofnih bakterija, sastava pigmenata fitoplanktona, te mikrozooplanktona i mezozooplanktona. Na glavnini postaja nađena je termoklina na oko 20 m i izraženo visoke vrijednosti klorofila a na oko 70 m dubine. Intergrirana bakterijska i fitoplanktonska biomasa bila je manja na središnjoj postaji južnoga Jadrana, a postupno se povećavala prema postajama Palagruža i Jabučka kotlina kao i prema obalnim postajama. Vertikalna raspodjela bakterijske brojnosti i produkcije pokazala je izraziti maksimum u površinskom sloju. Bakterijska brojnost bila je velika u sloju dubokog maksimuma klorofila a. Veća bakterijska produkcija bila je u svezi s povišenom brojnošću zooplanktona koji se hrani piko i nanoplanktonom, što ukazuje da su veličine bakterijskih populacija generalno kontrolirane predacijom