Composition and annual cycle of phytoplankton assemblages in the northeastern Adriatic Sea

Abstract

Phytoplankton abundance and seasonality in the northeastern Adriatic Sea were directly related to the annual regime of the Po River discharge in the period , there was a shift in the timing of the annual Po River maximum discharge and of phytoplankton maxima from spring to autumn. In addition, the eastern coastal area was greatly influenced by oligotrophic karstic rivers and the Eastern Adriatic Current. Dominant phytoplankton taxa were defined on the basis of abundance and frequency of appearance. Such an approach may help in the comparison of phytoplankton communities within different environments. The dominant taxa were the diatoms Cerataulina pelagica, Chaetoceros socialis, Chaetoceros vixvisibilis and Pseudo-nitzschia spp., which appeared at maximum abundances )10 6 cells l -1 in more than 20% of samples. Among other phytoplankton, the most common was the coccolithophorid Emiliania huxleyi (maximum abundance of 2=10 5 cells l -1 in 50% of samples), and the dinoflagellate Prorocentrum minimum (maximum abundance of 3=10 5 cells l -1 in 12% of samples). The present state of the phytoplankton community may provide valuable information for evaluation of possible future environmental changes in the shallow Mediterranean ecosystem.

Spatial and seasonal variability of pico-, nano- and microphytoplankton at the bottom seawater in the north coast of Sfax, Eastern Mediterranean Sea

“…A rapid use of nutrients can be attributed to differences in cell size and species physiology, small-sized eukaryotes being better competitors for nutrient acquisition than larger phytoplankton cells (Fogg 1986;Stockner 1988). We recorded a spring prevalence of nanoeukaryotes also reported by Mozetič et al (2012) and Viličić et al (2009). Mozetič et al (2012) proposed that the absence of a top-down control allowed nanophytoplankton to burst out in spring, before being submitted to a more efficient predation.…”

Distribution of phytoplankton community in Kotor Bay (south-eastern Adriatic Sea)

“…Diatoms dominated throughout almost all of the investigated period and were most abundant in late winter-early spring, which has been previously recorded in the northern Adriatic Sea [11] and in the southwestern part of Adriatic [46]. Diatom domination in late winter-early spring most likely reflects their particular ability to survive relatively more turbulent conditions.…”

“…In the north-eastern Adriatic Sea, diatoms such as Cerataulina pelagica, Chaetoceros socialis, and Pseudo-nitzschia spp., often dominate the plankton community, as first noticed by Viličić et al [11]. In one part of this region (the Zrmanja estuary), oligothrophic conditions were most common, with diatoms dominating the community in early spring and dinoflagellates dominating in summer period [4].…”

Ecology and taxonomy of potentially toxic Pseudo-nitzschia species in Lim Bay (north-eastern Adriatic Sea)

“…The eastern Adriatic region is exposed to the north-westerly inflowing East Adriatic Current which brings highly saline and low-nutrient waters from the Ionian and Levantine Seas (Orlić et al, 2006). The Po river discharge and meteorological forcing are the main components triggering the alternation of stratification and mixing of the water column that strongly affects the annual dynamics of phytoplankton in the northern Adriatic (Revelante and Gilmartin, 1976;Viličić et al, 2009). Diatoms dominate the phytoplankton assemblages (both the microplankton and nanoplankton fractions) over the most of the year, while autotrophic and mixotrophic flagellates dominate in oligotrophic conditions in April-July .…”

“…Among the 32 species described in the literature so far, eleven are known to be toxic (Quiroga, 2006), producing domoic acid, a neurotoxic amino acid responsible for Amnesic Shellfish Poisoning (ASP) (Bates et al, 1998). In the Mediterranean basin, as well as in the Adriatic Sea, Pseudo-nitzschia is a persistent and dominant component of the phytoplankton assemblages (Socal et al, 1999;Orsini et al, 2002;Quiroga, 2006;Bosak et al, 2009;Viličić et al, 2009).…”