Seasonal and interannual variations of phytoplankton in the Gulf of Venice (Northern Adriatic Sea)

Abstract

Spatial and temporal variations of phytoplankton community structure were studied in the Gulf of Venice (Northern Adriatic Sea) from February 1999 to December 2001 (INTERREG II, Italia-Slovenia project). Phytoplankton samples were collected, with a monthly frequency, at 11 stations in the basin. Abundance, biomass, and species composition were considered. Synthetic descriptors were used in order to evaluate the main succession pattern and to cluster communities that typify different hydrological conditions. A decreasing gradient of abundance and biomass was generally observed from west to east, passing from the land-influenced waters to offshore. The seasonal pattern and inter-annual variability of the main phytoplankton taxa are described and discussed in relation with the occurrence of a massive mucilage event and of a Po River flood.

NW Adriatic Sea biogeochemical variability in the last 20 years (1986–2005)

“…Besides, the slightly higher values of chlorophyll-a in the deepest layer at both stations are a clear indicator of photosynthetic activity of the bottom SL and thus water transparency. This leads us to consider the areas as trophically much similar than previously reported in literature (e.g., Alberighi et al, 1997;Pugnetti et al, 2003Pugnetti et al, , 2004Bernardi Aubry et al, 2006).…”

“…1). Many authors (e.g., Alberighi et al, 1997;Pugnetti et al, 2003Pugnetti et al, , 2004Bernardi Aubry et al, 2006) have classified E06 as a station that is influenced by the Po river run-off and characterized by meso-eutrophic waters, while they have represented C10 as a meso-oligotrophic station that is only partially influenced by the Po river discharge; the latter occurs particularly during intense stratification periods, when the Po plume eventually turns north-eastwards. In particular, whereas Alberighi et al (1997) referred to the two stations as trophically different, Pugnetti et al (2003) could not typify a significant difference in community composition, because a prevalence of tolerant species is observed in the whole area of the North Adriatic Sea.…”

Seasonal phytoplankton dynamics in the coastal waters of the north-eastern Adriatic Sea

“…In this study Skeletonema marinoi, was observed sporadically in the late winter period, and was related to nutrient rich waters. This species is a characteristic winter diatom of the north-western Adriatic (Bernardi Aubry et al, 2006;, and we found it thriving in waters under Po River influence (supplementary Fig 3).…”

“…Bernardi Aubry et al (2006) found that main phytoplankton seasonal pattern in the northern Adriatic did not change significantly among years. The seasonal absence of many species is explained by periodicity and rarity, and even though we do not record specimens, some might be present.…”

“…The Po River causes pronounced spatial variability of phytoplankton abundance and biomass in the Adriatic Sea, especially in the western coastal waters (Bernardi Aubry et al, 2006;Mangoni et al, 2008). Eastern coastal waters are less influenced by the Po River and more spatially homogenous.…”