PHYTOPLANKTON COMPOSITION AND LONG-TERM VARIATIONS IN TWO COASTAL AND OFFSHORE MARINE SITES (NORTHERN ADRIATIC SEA)

Two long term (1988-2019) data sets collected at a coastal and offshore stations located in the LTER Senigallia-Susak Transect were compared. The multivariate statistical analysis highlighted the role of the oceanographic conditions in discriminating the study areas. Environmental parameters at the coastal station was more variable and with a marked seasonality due to direct riverine inputs. Different mean annual cycles of physico-chemical parameters and of phytoplankton abundances were found, together with a different community composition. Higher mean abundances values and lower diversity were found at the coastal station, although the two stations were more similar in summer, due to the spreading southeastwards of riverine waters in stratified conditions. Graph network analysis highlighted that species not relevant following the IndVal were able to influence the overall community in both sites. The offshore community showed higher number of strong interactions among species than the coastal one.