Phytoplankton response to climatic and anthropogenic influences in the north-eastern Adriatic during the last four decades

A significantly lower Po River outflow in the 2000–2009 period, and altered circulation, was accompanied by a change in salinity and nutrient budget of the entire northern Adriatic. A four-decadal data set was analysed to gain a better perspective of phytoplankton driving pressures in the northern Adriatic. An observed regime shift in the system had altered the phytoplankton abundance, community composition and seasonal cycle. Appearance and frequency alterations of some prominent taxa (e.g. Pseudo-nitzschia delicatissima group and Pseudo-nitzschia seriata group) were detected. The identified changes highlight the importance of long-term observations for the understanding of the natural temporal variability in phytoplankton communities. We presume that such shifts in the community composition and abundance reflect on the entire Adriatic.