Hydrographicand bio-opticalcharacteristicsofthe Southern Adriatic Pit in the winter period

Stanice fitoplanktona se razlikuju veličinom, oblikom, po prisutnosti ili odsutnosti stanične stijenke, strukturama na površini stanice i u stanici i sadržajem pigmenata, te na osnovi tih svojstava vrste će različito apsorbirati, raspršiti i fluorescentno sjajiti svjetlost, što je temelj bio-optičke oceanografije. Provedeno je istraživanje 2015. i 2016. godine u južnom Jadranu sa ciljem utvrđivanja hidrografskih i bio-optičkih svojstava, te na temelju njih opisati procese primarne produkcije istraživanog područja. Uzastopne zime znatno su se razlikovale. 2015. godina obilježena je dubokim vertikalnim miješanjem do 500 m dubine, dok u 2016. godini duboka konvekcija nije bila prisutna. Intruzija je bila na dubini od 400 - 600 m što je prvi puta zabilježeno za Jadransko more i ukazuje na promjene u cirkulaciji koja je moguće posljedica klimatskih promjena. U obje godine zajednica mikrofitoplanktona je uglavnom bila sastavljena od dijatomeja, a zajednica nanofitoplanktona od kokolitoforida. Unutar zajednice pikofitoplanktona došlo je do promjene zajednice, što je također po prvi puta zabilježeno u Jadranskom moru. Bio-optički čimbenici u potpunosti su pratili tradicionalnim metodama analiziranu fitoplanktonsku zajednicu, ukazujući na biomasu i prostornu raspodjelu primarnih producenata, međutim bez jasnog ukazivanja na određene taksonomske kategorije fitoplanktona.Phytoplankton cells are highly diverse according to their size, shape, absence or presence of the cell wall, structures surrounding the cell or in the cell itself as well as with having diverse pigments. According to those characteristics, cells can absorb, scatter or fluorescent the light which is the base of the bio-optical oceanography. During winter of 2015 and 2016 two research campaigns were conducted in the southern Adriatic Sea. The aim of the research was to measure hydrographic and bio-optical properties of the area and according those results to get insight into the processes of primary production. The consecutive winters substantially differed: while 2015 was characterized by deep vertical mixing, chlorophyll a signal and viable phytoplankton cells detected up to 500m depth, 2016 exhibited much weaker vertical mixing, reaching only Chl a up to 200 m depth. Intrusion was detected in the 400-600m depth layer that has never been recorded before, and indicates a change in the circulation pattern in the Adriatic Sea that may be driven by climate changes. Microphytoplankton was composed mostly of diatoms, and nanophytoplakton of coccolithophorids in both investigated years. Picophytoplankton showed community shift that is also recorded for the first time in the Adriatic Sea. Bio-optical features were following the pattern of phytoplankton distribution, showing in detail the spatial distribution of primary producers in the area, but not recognizing the taxonomical composition of the phytoplankton community