engleski

Phytoplankton response to climatic and anthropogenic influence in the northern Adriatic during last four decades

Microphytoplankton as a primary producer plays a major role in the marine food web and can reflect the ecosystems response to long- and short-term changes of external pressures (mainly climatic and anthropogenic). Fluctuations of the phytoplankton community composition and abundance at the two stations in the northern Adriatic (RV001 and SJ107, 1 and 13 nautical miles off Rovinj, respectively) were investigated using four decades long data series. We analyzed the collected data identifying seasonal patterns, inter-annual variability and long-terms trends in composition and abundance of the total phytoplankton and more specifically, of the main functional phytoplankton groups. The regime shift analysis identified 1984, 1994 and 1999 as the years of changes in the phytoplankton community, this coincided with the detected changes in the ecosystem. Very high abundances characterized the period 1984 to 1994. In following years abundances decreased and, from 2000 onwards, stayed constantly low, even lower than at the beginning of the analyzed period (1972-1984). Differences in the species composition and seasonality were also observed during the study period. Alteration in appearance and frequency of some important taxa (e.g. Pseudo-nitzschia delicatissima complex and Pseudo-nitzschia seriata complex) has been documented. Identified changes highlighted the importance of the long-term observations for the understanding of natural temporal variability in phytoplankton communities. Such shifts in the community composition and abundance probably have important impact on the northern Adriatic ecosystem.

phytoplankton community composition; long time changes; regime shift

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